SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NWS LOS ANGELES/OXNARD CA
915 AM PDT SUN MAY 11 2008
.SHORT TERM (TODAY THROUGH TUESDAY)...
STRATUS ALREADY STARTING TO BREAK UP ALONG THE CENTRAL COAST THIS
MORNING...BUT A RATHER SOLID LAYER PERSISTS JUST OFF THEIR IMMEDIATE
COAST...AS WELL AS BLANKETING THE ENTIRE COASTAL AND VALLEY AREAS
SOUTH OF PT CONCEPTION. LATEST AIRCRAFT SOUNDINGS SHOW THE MARINE
LAYER NEAR 2800 FT AT LAX...AND WITH RATHER LOW CEILINGS FOR THIS
DEEP OF A MARINE LAYER...THE STRATUS LAYER LOOKS PRETTY THICK. THIS
THICK LAYER...WHEN COUPLED WITH A STRENGTHENING ONSHORE GRAD...HAS
TO SUGGEST A RATHER TOUGH CLEARING DAY. NOT ONLY THAT...BUT THE
STRENGTHENING GRADS WILL HELP THE STRATUS PUSH EVEN DEEPER INLAND
INTO THE AFTERNOON...AND EXPECTING THE COASTAL SLOPES AND SANTA
CLARITA VALLEY TO BE COVERED BY NOON. A SIMILAR IF NOT MORE
BLANKETED DAY IS EXPECTED FOR MON. UPDATED THE FORECAST TO ADD SOME
PESSIMISM IN THIS REGARD.
TEMPS LOOK GOOD OVERALL...WITH A FEW DEGREES OF COOLING EXPECTED
TODAY AND AGAIN ON MON ACROSS THE BOARD. THANKS CAN BE GIVEN TO THE
INCREASED CLOUD COVERAGE AND LOWER THICKS FROM A LOW CURRENTLY OVER
WASHINGTON THAT CONTINUES TO SAG SOUTHWARD. A MODERATE ONSHORE WIND
DAY IS EXPECTED. ALTHOUGH NO WIND ADVISORIES ARE ANTICIPATED AT THIS
TIME...IT SHOULD GET BREEZY IN THE ANTELOPE VALLEY. MON LOOKS A BIT
WINDIER...AND ADVISORIES ARE NOT OUT OF THE QUESTION IN THE ANTELOPE
VALLEY...AND TO A LESSER EXTENT THE CENTRAL COAST AND SANTA CLARITA
VALLEY.
...FROM PREVIOUS DISCUSSION...
BY MONDAY NIGHT/TUESDAY...MARINE LAYER SHOULD BE LESS IN DEPTH AND
AREAL COVERAGE AS SOME NORTHERLY FLOW IS INDICATED BY 00Z MODELS.
SO...BY TUESDAY AFTERNOON...SKIES SHOULD BE SUNNY FOR ALL AREAS.
.LONG TERM (TUESDAY NIGHT THROUGH SATURDAY)...EXTENDED MODELS
CONTINUE TO ADVERTISE A VERY WARM AND DRY PATTERN FOR THE AREA
THROUGH THE PERIOD. BOTH THE GFS/ECMWF HANDLES THE UPPER HIGH
OVER THE WEST COAST VERY WELL. THE DIFFERENCES BETWEEN THE GFS
AND ECMWF CONTINUE TO BE WITH THE TROUGH OVER THE CENTRAL STATES.
THE GFS KEEPS THE TROUGH OVER NEW MEXICO/WESTERN TEXAS WHILE THE
ECMWF IS MORE PROGRESSIVE WITH THE TROUGH. ADMITTEDLY THE LOCATION
OF THE UPPER TROUGH WILL HAVE SOME INFLUENCE ON THE OVERALL
PATTERN...BUT EITHER WAY...IT STILL WILL BE A VERY WARM FEW DAYS
LATER IN THE WEEK DUE TO VARYING DEGREES OF OFFSHORE FLOW.
LOCAL TEMP STUDY GUIDANCE DEFINITELY SUPPORTS POTENTIAL FOR
SIGNIFICANTLY WARM TEMPS DURING THE PERIOD...ESPECIALLY WEDNESDAY
AND THURSDAY. HAVE BUMPED UP PREVIOUS SHIFT`S TEMPS FOR WEDNESDAY
AND THURSDAY. HOWEVER...IF MODEL TRENDS CONTINUE IN THE SAME VEIN
COASTAL/VALLEY TEMPS WILL BE SEVERAL DEGREES THAN FORECASTED THIS
MORNING. SO...SITUATION WILL HAVE TO BE MONITORED CLOSELY.
BY FRIDAY/SATURDAY...THE OFFSHORE GRADIENTS START TO WEAKEN AS
THE UPPER HIGH WEAKENS. SO...WILL EXPECT SOME COOLER TEMPS NEXT
WEEKEND...BUT STILL WARMER THAN NORMAL CONDITIONS THROUGH THE
PERIOD.
&&
.AVIATION...11/1230Z.
STRATUS WDSPRD IN CSTL AND VLYS THIS MORNING. WITH INCREASING
ONSHORE GRADS...CIGS WILL LIKELY BE SLOW TO CLEAR IN THE
VALLEYS...AND PROBABLY WILL NOT CLEAR NEAR THE COAST.
KLAX...MVFR CIGS THIS MORNING. DO NOT EXPECT CIGS TO SCATTER
OUT THIS AFTERNOON. CONFIDENCE IS LOW TO MODERATE. TYPICAL
SEABREEZE NEAR 10 KT THIS AFTERNOON.
KBUR...EXPECT IFR CIGS TO BECOME MVFR BY MID OR LATE MORNING.
CIGS SHOULD SCATTER OUT AROUND 21Z OR 22Z. CONFIDENCE ON CLEARING
IS LOW TO MODERATE. NO WIND ISSUES WITH TYPICAL S TO SE WINDS AROUND
10 KT THIS AFTERNOON.
&&
.LOX WATCHES/WARNINGS/ADVISORIES...
SMALL CRAFT ADVISORY (SEE LAXCWFLOX).
&&
$$
PUBLIC...KITTELL/THOMPSON
AVIATION...BRUNO
WWW.WEATHER.GOV/LOSANGELES
AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
900 AM PDT SUN MAY 11 2008
.SYNOPSIS...
A TROUGH OF LOW PRESSURE MOVING THROUGH THE PACIFIC NORTHWEST TODAY
AND GREAT BASIN MONDAY WILL BRING STRONGER ONSHORE FLOW...A DEEPER
MARINE LAYER...AND COOLER WEATHER THROUGH MONDAY. THIS TROUGH WILL
ALSO BRING STRONGER ONSHORE WINDS FOR THE MOUNTAINS AND DESERTS
MONDAY AFTERNOON AND EVENING. FOR TUESDAY THROUGH THE END OF THE
WEEK...STRONG HIGH PRESSURE WILL BUILD ALONG THE WEST COAST WITH
DRIER AND MUCH WARMER WEATHER FOR WEDNESDAY INTO THE WEEKEND.
DAYTIME TEMPERATURES WILL RISE TO WELL ABOVE SEASONAL AVERAGES.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
LOW CLOUDS WILL CLEAR TO THE COAST THIS MORNING AND THE AFTERNOON
WILL BE SUNNY IN MOST SPOTS. THE APPROACHING UPPER LEVEL LOW FROM
THE NORTHWEST WILL DEEPEN THE MARINE LAYER TONIGHT AND MON ALLOWING
THE CLOUDS TO BE MORE PERSISTENT IN THE COASTAL BASIN. THERE WILL BE
PATCHY DRIZZLE UNDER THE CLOUDS AS WELL AS FOG ON THE COASTAL MTN
SLOPES. THIS TROUGH WILL ALSO CRANK UP WINDS IN THE MTNS AND DESERTS
MON AFTERNOON AND EVE. AS THE LOW MOVES EASTWARD TUE THE WEATHER
WILL TREND FROM DEEP MARINE LAYER TO CLEARER AND WARMER. A STRONG
UPPER HIGH WILL NOSE IN FROM THE PACIFIC AND WILL STRENGTHEN AND
AMPLIFY ALONG THE WEST COAST WED INTO THE WEEKEND. THIS WILL SQUASH
THE MARINE LAYER DOWN TO ALMOST NOTHING...AND IF ANY COASTAL CLOUDS
ARE LEFT OVER...A TOUCH OF OFFSHORE FLOW SHOULD FINISH THEM BY THU
OR FRI. MUCH HIGHER DAYTIME TEMPS WILL BE THE BIG STORY. THE HIGH
BEGINS TO BREAK DOWN OVER THE WEEKEND AND TEMPS WILL BEGIN TO TREND
BACK TOWARD NORMAL.
&&
.AVIATION...
111430Z...THE 12Z NKX SOUNDING AS WELL AS MDCRS SOUNDINGS NEAR KSAN
AND KLAX SHOW THE MARINE LAYER DEPTH TO BE NEAR 2800 FEET THIS
MORNING. THE MARINE LAYER SHOULD DEEPEN TO 3500 TO 4000 FEET TONIGHT.
STRATUS WITH BASES BETWEEN 1500 AND 2000 FEET MSL EXTENDS INLAND
OVER THE INLAND VALLEY AREAS. EXPECT THE STRATUS OVER THE INLAND
AREAS TO BEGIN TO BURN OFF BETWEEN 15Z AND 16Z AND THE COASTAL AREAS
BETWEEN 17Z AND 19Z. STRATUS SHOULD RETURN TO THE COASTAL AREAS BY
SUNSET AND PUSH INLAND DURING THE EVENING REACHING THE FAR INLAND
VALLEY AREAS BY MIDNIGHT. SOME BREAKUP OF THE STRATUS IS EXPECTED ON
MONDAY OVER THE INLAND AREAS BUT THE COASTAL AREAS SHOULD NOT HAVE
MUCH BREAK UP OF THE STRATUS ON MONDAY.
ABOVE THE MARINE LAYER INCLUDING THE MOUNTAINS AND DESERTS...MOSTLY
CLEAR WITH UNRESTRICTED VISIBILITIES WILL CONTINUE THROUGH MONDAY.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
PUBLIC...MM
AVIATION/MARINE...HORTON
SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION...UPDATED
NWS LOS ANGELES/OXNARD CA
530 AM PDT SUN MAY 11 2008
UPDATED AVIATION SECTION
.SHORT TERM (TODAY THROUGH TUESDAY)...LATEST SATELLITE SHOWS STRATUS
AND FOG FILLING IN OVER THE COASTAL WATERS AND ACROSS THE COASTAL
PLAIN. LATEST AMDAR SOUNDINGS INDICATE MARINE INVERSION DEPTH AROUND
1200 FT. SO...WITH GOOD ONSHORE PUSH...WILL EXPECT AT LEAST AREAS OF
STRATUS/FOG INTO THE COASTAL VALLEYS THIS MORNING. GIVEN THE CURRENT
DEPTH OF THE MARINE LAYER...WOULD EXPECT PRETTY GOOD CLEARING THIS
AFTERNOON. HOWEVER...CONFIDENCE IN GOOD CLEARING IS ONLY MODERATE AT
BEST. SO...WILL INDICATE PARTLY CLOUDY SKIES IN THE AFTERNOON FOR
COASTAL/VALLEY AREAS SOUTH OF PT CONCEPTION. OTHER THAN THE MARINE
LAYER...SKIES WILL BE SUNNY ACROSS THE AREA TODAY.
FOR TONIGHT/MONDAY...WILL EXPECT VERY SIMILAR MARINE LAYER CONDITIONS
ALTHOUGH WILL NOT ANTICIPATE ANY STRATUS INTO THE SALINAS RIVER
VALLEY. ONCE AGAIN...WILL GO WITH PARTLY CLOUDY SKIES MONDAY
AFTERNOON FOR COASTAL/VALLEY AREAS SOUTH OF PT CONCEPTION GIVEN
FORECASTED STRONG ONSHORE GRADIENTS.
BY MONDAY NIGHT/TUESDAY...MARINE LAYER SHOULD BE LESS IN DEPTH AND
AREAL COVERAGE AS SOME NORTHERLY FLOW IS INDICATED BY 00Z MODELS.
SO...BY TUESDAY AFTERNOON...SKIES SHOULD BE SUNNY FOR ALL AREAS.
AS FOR TEMPS...WILL EXPECT CONTINUED COOL CONDITIONS TODAY AND
MONDAY WITH MARINE LAYER PRESENCE AND ONSHORE FLOW. BY TUESDAY...
TEMPS SHOULD START TO RECOVER AS MARINE INFLUENCE DECREASES AND
ONSHORE FLOW DIMINISHES.
WITH THE GOOD ONSHORE GRADIENTS TODAY AND MONDAY...SOME GUSTY
AFTERNOON/EVENING WINDS WILL CONTINUE ACROSS THE MOUNTAINS AND
ANTELOPE VALLEY. WINDS COULD APPROACH ADVISORY LEVELS ACROSS THE
ANTELOPE VALLEY. HOWEVER...CONFIDENCE IN ADVISORY LEVEL WINDS IS
LOW...SO WILL KEEP WINDS JUST BELOW ADVISORY LEVELS.
.LONG TERM (TUESDAY NIGHT THROUGH SATURDAY)...EXTENDED MODELS
CONTINUE TO ADVERTISE A VERY WARM AND DRY PATTERN FOR THE AREA
THROUGH THE PERIOD. BOTH THE GFS/ECMWF HANDLES THE UPPER HIGH
OVER THE WEST COAST VERY WELL. THE DIFFERENCES BETWEEN THE GFS
AND ECMWF CONTINUE TO BE WITH THE TROUGH OVER THE CENTRAL STATES.
THE GFS KEEPS THE TROUGH OVER NEW MEXICO/WESTERN TEXAS WHILE THE
ECMWF IS MORE PROGRESSIVE WITH THE TROUGH. ADMITTEDLY THE LOCATION
OF THE UPPER TROUGH WILL HAVE SOME INFLUENCE ON THE OVERALL
PATTERN...BUT EITHER WAY...IT STILL WILL BE A VERY WARM FEW DAYS
LATER IN THE WEEK DUE TO VARYING DEGREES OF OFFSHORE FLOW.
LOCAL TEMP STUDY GUIDANCE DEFINITELY SUPPORTS POTENTIAL FOR
SIGNIFICANTLY WARM TEMPS DURING THE PERIOD...ESPECIALLY WEDNESDAY
AND THURSDAY. HAVE BUMPED UP PREVIOUS SHIFT`S TEMPS FOR WEDNESDAY
AND THURSDAY. HOWEVER...IF MODEL TRENDS CONTINUE IN THE SAME VEIN
COASTAL/VALLEY TEMPS WILL BE SEVERAL DEGREES THAN FORECASTED THIS
MORNING. SO...SITUATION WILL HAVE TO BE MONITORED CLOSELY.
BY FRIDAY/SATURDAY...THE OFFSHORE GRADIENTS START TO WEAKEN AS
THE UPPER HIGH WEAKENS. SO...WILL EXPECT SOME COOLER TEMPS NEXT
WEEKEND...BUT STILL WARMER THAN NORMAL CONDITIONS THROUGH THE
PERIOD.
&&
.AVIATION...11/1230Z.
STRATUS WDSPRD IN CSTL AND VLYS THIS MORNING. WITH INCREASING
ONSHORE GRADS...CIGS WILL LIKELY BE SLOW TO CLEAR IN THE
VALLEYS...AND PROBABLY WILL NOT CLEAR NEAR THE COAST.
KLAX...MVFR CIGS THIS MORNING. DO NOT EXPECT CIGS TO SCATTER
OUT THIS AFTERNOON. CONFIDENCE IS LOW TO MODERATE. TYPICAL
SEABREEZE NEAR 10 KT THIS AFTERNOON.
KBUR...EXPECT IFR CIGS TO BECOME MVFR BY MID OR LATE MORNING.
CIGS SHOULD SCATTER OUT AROUND 21Z OR 22Z. CONFIDENCE ON CLEARING
IS LOW TO MODERATE. NO WIND ISSUES WITH TYPICAL S TO SE WINDS AROUND
10 KT THIS AFTERNOON.
&&
.LOX WATCHES/WARNINGS/ADVISORIES...
SMALL CRAFT ADVISORY (SEE LAXCWFLOX).
&&
$$
PUBLIC...THOMPSON
AVIATION...BRUNO
WWW.WEATHER.GOV/LOSANGELES
SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NWS LOS ANGELES/OXNARD CA
300 AM PDT SUN MAY 11 2008
.SHORT TERM (TODAY THROUGH TUESDAY)...LATEST SATELLITE SHOWS STRATUS
AND FOG FILLING IN OVER THE COASTAL WATERS AND ACROSS THE COASTAL
PLAIN. LATEST AMDAR SOUNDINGS INDICATE MARINE INVERSION DEPTH AROUND
1200 FT. SO...WITH GOOD ONSHORE PUSH...WILL EXPECT AT LEAST AREAS OF
STRATUS/FOG INTO THE COASTAL VALLEYS THIS MORNING. GIVEN THE CURRENT
DEPTH OF THE MARINE LAYER...WOULD EXPECT PRETTY GOOD CLEARING THIS
AFTERNOON. HOWEVER...CONFIDENCE IN GOOD CLEARING IS ONLY MODERATE AT
BEST. SO...WILL INDICATE PARTLY CLOUDY SKIES IN THE AFTERNOON FOR
COASTAL/VALLEY AREAS SOUTH OF PT CONCEPTION. OTHER THAN THE MARINE
LAYER...SKIES WILL BE SUNNY ACROSS THE AREA TODAY.
FOR TONIGHT/MONDAY...WILL EXPECT VERY SIMILAR MARINE LAYER CONDITIONS
ALTHOUGH WILL NOT ANTICIPATE ANY STRATUS INTO THE SALINAS RIVER
VALLEY. ONCE AGAIN...WILL GO WITH PARTLY CLOUDY SKIES MONDAY
AFTERNOON FOR COASTAL/VALLEY AREAS SOUTH OF PT CONCEPTION GIVEN
FORECASTED STRONG ONSHORE GRADIENTS.
BY MONDAY NIGHT/TUESDAY...MARINE LAYER SHOULD BE LESS IN DEPTH AND
AREAL COVERAGE AS SOME NORTHERLY FLOW IS INDICATED BY 00Z MODELS.
SO...BY TUESDAY AFTERNOON...SKIES SHOULD BE SUNNY FOR ALL AREAS.
AS FOR TEMPS...WILL EXPECT CONTINUED COOL CONDITIONS TODAY AND
MONDAY WITH MARINE LAYER PRESENCE AND ONSHORE FLOW. BY TUESDAY...
TEMPS SHOULD START TO RECOVER AS MARINE INFLUENCE DECREASES AND
ONSHORE FLOW DIMINISHES.
WITH THE GOOD ONSHORE GRADIENTS TODAY AND MONDAY...SOME GUSTY
AFTERNOON/EVENING WINDS WILL CONTINUE ACROSS THE MOUNTAINS AND
ANTELOPE VALLEY. WINDS COULD APPROACH ADVISORY LEVELS ACROSS THE
ANTELOPE VALLEY. HOWEVER...CONFIDENCE IN ADVISORY LEVEL WINDS IS
LOW...SO WILL KEEP WINDS JUST BELOW ADVISORY LEVELS.
.LONG TERM (TUESDAY NIGHT THROUGH SATURDAY)...EXTENDED MODELS
CONTINUE TO ADVERTISE A VERY WARM AND DRY PATTERN FOR THE AREA
THROUGH THE PERIOD. BOTH THE GFS/ECMWF HANDLES THE UPPER HIGH
OVER THE WEST COAST VERY WELL. THE DIFFERENCES BETWEEN THE GFS
AND ECMWF CONTINUE TO BE WITH THE TROUGH OVER THE CENTRAL STATES.
THE GFS KEEPS THE TROUGH OVER NEW MEXICO/WESTERN TEXAS WHILE THE
ECMWF IS MORE PROGRESSIVE WITH THE TROUGH. ADMITTEDLY THE LOCATION
OF THE UPPER TROUGH WILL HAVE SOME INFLUENCE ON THE OVERALL
PATTERN...BUT EITHER WAY...IT STILL WILL BE A VERY WARM FEW DAYS
LATER IN THE WEEK DUE TO VARYING DEGREES OF OFFSHORE FLOW.
LOCAL TEMP STUDY GUIDANCE DEFINITELY SUPPORTS POTENTIAL FOR
SIGNIFICANTLY WARM TEMPS DURING THE PERIOD...ESPECIALLY WEDNESDAY
AND THURSDAY. HAVE BUMPED UP PREVIOUS SHIFT`S TEMPS FOR WEDNESDAY
AND THURSDAY. HOWEVER...IF MODEL TRENDS CONTINUE IN THE SAME VEIN
COASTAL/VALLEY TEMPS WILL BE SEVERAL DEGREES THAN FORECASTED THIS
MORNING. SO...SITUATION WILL HAVE TO BE MONITORED CLOSELY.
BY FRIDAY/SATURDAY...THE OFFSHORE GRADIENTS START TO WEAKEN AS
THE UPPER HIGH WEAKENS. SO...WILL EXPECT SOME COOLER TEMPS NEXT
WEEKEND...BUT STILL WARMER THAN NORMAL CONDITIONS THROUGH THE
PERIOD.
&&
.AVIATION...11/1130Z.
WILL BE UPDATED SHORTLY.
&&
.LOX WATCHES/WARNINGS/ADVISORIES...
SMALL CRAFT ADVISORY (SEE LAXCWFLOX).
&&
$$
PUBLIC...THOMPSON
AVIATION...BRUNO
WWW.WEATHER.GOV/LOSANGELES
AREA FORECAST DISCUSSION
NWS MOUNT HOLLY NJ
1050 AM EDT SUN MAY 11 2008
.SYNOPSIS...
WEAK HIGH PRESSURE OVER THE AREA EARLY THIS MORNING WILL RECEDE
EAST. COMPLEX LOW PRESSURE WILL APPROACH FROM THE WEST TODAY,
CONSOLIDATE OFF THE NORTHERN MID-ATLANTIC COAST EARLY ON MONDAY,
AND THEN MOVE SLOWLY OUT TO SEA. HIGH PRESSURE IS FORECAST TO
BUILD INTO OUR REGION FROM THE WEST FOR THE MID-WEEK PERIOD.
A COLD FRONT IS EXPECTED TO FOLLOW FOR FRIDAY NIGHT.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
HAVE MADE SOME MINOR ADJUSTMENTS TO CLOUD COVER AND POPS (LOWER
ACROSS THE NORTH) BASED ON CURRENT RADAR AND SATELLITE IMAGERY AND THE
BEGINNINGS OF THE 12Z MODEL DATA. ALL IN ALL, CURRENT FCST LOOKS
GOOD.
AFTER A SUNNY START TO THE DAY, CLOUDS SHOULD BEGIN TO INVADE FROM
THE WEST AND SOUTHWEST. THE GFS AND THE ECMWF ARE A BIT QUICKER TO
BRING PRECIPITATION INTO THE AREA THAN THE NAM. INITIALLY, WE`RE
DEALING WITH ISENT LIFT PRECIP AT AROUND I300.
THE SYSTEM RESPONSIBLE, AS NOTED IN PREVIOUS DISCUSSIONS, IS A
VIGOROUS MID LEVEL TROF THAT IS IN THE PROCESS OF CUTTING OFF AS A
STRONG UPPER LEVEL JET DROPS INTO ITS BASE. THE MID LEVEL LOW WILL
BE MOVING INTO THE UPPER OHIO RIVER VALLEY BY THE END OF THE DAY,
AND IT WILL BEGIN TO TRANSFER ENERGY AT THE SURFACE FROM A
PRIMARY LOW NEAR THE PARENT MID LEVEL SYSTEM TO A SECONDARY LOW
OVER VIRGINIA.
WE HAVE MAINTAINED CONTINUITY ON TEMPERATURES. WINDS ARE EXPECTED
TO BEGIN TO PICK UP OUT OF THE EAST OR SOUTHEAST DURING THE
AFTERNOON, WHICH MAKES CONTINUITY SEEM LIKE A GOOD IDEA, AND THE
FIRST CHANCE OF PRECIP SHOULD BE LATER IN THE AFTERNOON OVER THE
SOUTHWESTERN PART OF THE FORECAST AREA.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH TUESDAY/...
THE SYSTEM WILL GENERATE A FAIRLY STRONG WIND FIELD, CARRY GOOD
MID AND UPPER LEVEL DYNAMICS, GENERATE GOOD LOWER LEVEL
FRONTOGENESIS, AND PERHAPS CARRY WITH IT SOME ELEVATED
INSTABILITY. THE STRONG AND FAIRLY DEEP WINDS ABOVE THE SURFACE
AND OFF THE OCEAN SHOULD CARRY AS MUCH ATLANTIC MOISTURE AS IS
POSSIBLE, ALTHOUGH, AGAIN, WE HAVE A HARD TIME SEEING VERY HIGH H8
DEWPOINTS IN OUR REGION IN THE MORE MOIST GFS. THE GFS CARRIES 5 DEG
C VALUES AS FAR NORTH AS ABOUT PHL AND CARRIES 8 DEG C VALUES INTO
OUR FAR SOUTHERN ZONES. FURTHER TO THE NORTH, MORE REMOVED FROM
THE SYSTEM, H8 DEW POINTS ARE EVEN LOWER.
WITHOUT THE POSSIBILITY OF SOME CONVECTION, WHICH IS DEPICTED /AS
ELEVATED CONVECTION/ A BIT MORE EMPHATICALLY IN THE GFS THAN THE
NAM, WE WOULD BE TEMPTED TO UNDERCUT MODEL QPF A BIT AS THE MODELS
HAVE A HIGH BIAS IN NON- CONVECTIVE EVENTS. HOWEVER, IT IS THE
FEAR OF ELEVATED CONVECTION THAT KEPT US FROM DOING THAT. THAT
MAKES FOR SOME RESPECTABLE PRECIPITATION AMOUNTS OVER ABOUT THE
SOUTHERN HALF TO TWO-THIRDS OF THE AREA. WE INCLUDE A HYDRO
SECTION BELOW.
THE WIND FIELDS SHOW A CONSIDERABLE AMOUNT OF SHEAR, AND WE HOPE
WE ARE CORRECT THAT ANY CONVECTION WOULD BE ALOFT. THAT IS WHAT
THE SURFACE-BASED STABILITY PROGS SHOW, AND THAT IS HOW SPC AND WE
ARE PLAYING IT.
WINDS ALSO WILL BEGIN STRENGTHEN SUFFICIENTLY, FIRST OUT OF THE
EAST TO SOUTHEAST TONIGHT, THEN OUT OF THE NORTHEAST ON MONDAY, TO
CAUSE SOME TIDAL CONCERNS AS NOTED BELOW. IT IS POSSIBLE, AFTER
THE TRANSFERENCE OF ENERGY AT THE SURFACE IS COMPLETE, THAT THE
SYSTEM WOULD WIND UP ENOUGH ON MONDAY TO EVENTUALLY CAUSE US TO
ISSUE A WIND ADVISORY, AT LEAST ALONG THE COAST, BUT BUFKIT FROM
THE GFS LOOKS MARGINAL AND WE HAVE PASSED ON THAT FOR THE TIME
BEING.
THE CONSOLIDATED SYSTEM EXITS SLOWLY ON MONDAY, PERHAPS A BIT TOO
SLOWLY AS DEPICTED BY THE NAM, AND THE BULK OF THE SIGNIFICANT
PRECIPITATION SHOULD BE OVER WITH BEFORE EVENING. STABILITY PROGS,
AT THE SURFACE AND ALOFT, INDICATE THAT THE THREAT OF CONVECTION
MAY BE OVER WITH EARLY ON MONDAY, AND WE`RE NOT CARRYING ANY
MENTION OF THUNDER AFTER TONIGHT FOR NOW.
GRADUAL IMPROVEMENT IS FORECAST OVER LAND ON MONDAY NIGHT AND
TUESDAY. AGAIN, CONTINUITY ON TEMPERATURES WAS MOSTLY ACCEPTED.
WE DID ACTUALLY LOWER THE MONDAY MAXES OVER ALL BUT THE FAR
SOUTHERN ZONES. SOUNDINGS FROM THIS RUN DON`T SHOW ANY PRECIP TYPE
CONCERNS, BUT WE`LL CONTINUE TO WATCH THAT.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
AT MID WEEK, WE ARE EXPECTING TO SEE THE UPPER LOW TAKING ITS TIME
MOVING OUT TO SEA. MEANWHILE, AN UPPER RIDGE AXIS IS FORECAST TO
EXTEND FROM THE GULF COAST UP INTO THE GREAT LAKES REGION ON TUESDAY
NIGHT. AS THE LOW DRIFTS EASTWARD, SO WILL THE RIDGE. THE RIDGE
AXIS IS EXPECTED TO PASS OVER OUR REGION FROM WEDNESDAY NIGHT INTO
THURSDAY.
AN UPPER LEVEL TROUGH IS FORECAST TO DIG INTO THE EASTERN STATES ON
FRIDAY AND SATURDAY. A SURFACE COLD FRONT, ASSOCIATED WITH THE
UPPER TROUGH, SHOULD PASS THROUGH OUR REGION ON FRIDAY NIGHT.
&&
.AVIATION /15Z SUNDAY THROUGH THURSDAY/...
WEAK HIGH PRESSURE OVER THE AREA WILL MOVE OFFSHORE THIS MORNING.
LIGHT WEST WINDS...OR CALM WINDS...WERE ALLOWING FOR SOME
RADIATIONAL COOLING EARLY THIS MORNING, AND FOG HAS WAFTED IN AND
OUT AT KRDG. A COUPLE OF OTHER PLACES MAY HAVE SOME BRIEF IFR
VISIBILITIES IN FOG, OTHERWISE CIRRUS WILL BE INCREASING FROM THE
WEST-SOUTHWEST AS THE MORNING WEARS ON.
LOW PRESSURE WILL APPROACH FROM THE OHIO VALLEY TODAY AND WEAKEN AS
SECONDARY DEVELOPMENT TAKES PLACES ALONG THE VIRGINIA CAPES LATE
TODAY AND EARLY TONIGHT. WITH THE DEVELOPING ONSHORE FLOW AND INFLUX
OF MID AND THEN LOW LEVEL MOISTURE, CEILINGS WILL GRADUALLY LOWER TO
MARGINAL VFR LATER THIS AFTERNOON, WITH RAIN DEVELOPING AS THE
COLUMN MOISTENS LATE TODAY OR MORE LIKELY THIS EVENING, PROBABLY
FROM WEST-SOUTHWEST TO EAST-NORTHEAST.
LIGHT WINDS (WITH A WESTERLY COMPONENT) EARLY THIS MORNING WILL BACK
AROUND TO EAST OR EAST-SOUTHEAST AND STRENGTHEN AS THE STORM SYSTEM
NEARS. AN INCREASING PRESSURE GRADIENT MAY BECOME TIGHT ENOUGH TO
ALLOW FOR GUSTS TO OCCUR FROM ABOUT MID AFTERNOON ON, ESPECIALLY
FROM KPHL SOUTH AND EAST. A WIND SHEAR REMARK WAS ADDED LATE IN THE
TAF VALID PERIOD AS LOW LEVEL WINDS WILL BE SCREAMING OUT OF THE
EAST. SURFACE WINDS WILL BE GUSTY, BUT IT WAS FELT THAT A POINTER TO
45 TO 50 KNOT WINDS JUST OFF THE SURFACE WOULD BE BENEFICIAL.
OUTLOOK...
CONDITIONS WILL BE MARGINAL VFR IN STRATUS, WITH RAIN HEAVY AT TIMES
AND FOG TONIGHT INTO MONDAY AS THE STORM IMPACTS THE REGION.
WIDESPREAD RAIN AND GUSTY WINDS WILL NEGATIVELY IMPACT AIRCRAFT
OPERATIONS SIGNIFICANTLY MONDAY. GRADUAL IMPROVEMENT IS EXPECTED
LATE MONDAY NIGHT AND ESPECIALLY TUESDAY, BUT LINGERING NEGATIVE
IMPACTS ARE LIKELY EVEN TUESDAY. HIGH PRESSURE IS FORECAST TO RETURN
WEDNESDAY, HOWEVER A COLD FRONT MAY APPROACH FROM THE WEST THURSDAY
WITH A CHANCE OF SHOWERS.
&&
.MARINE...
STRENGTHENING LOW PRESSURE APPROACHING FROM THE OHIO VALLEY TODAY
WILL SHIFT ITS ENERGY TO THE VIRGINIA CAPES EARLY TONIGHT, WITH A
GOOD OLD FASHIONED (MAY?) NOR`EASTER ON OUR HANDS. IT LOOKS LIKE A
PRETTY GOOD BLOW WITH GOOD WAVE ACTION (OVER 10 FEET MONDAY AND
MONDAY NIGHT), SO ANY SUNDAY PARTY BOATERS SHOULD PLAN ON RETURNING
THIS AFTERNOON OR EARLY TONIGHT. MODEL OUTPUT LENT CONFIDENCE TO THE
FORECAST, AS MODELS WERE CONSISTENT FROM PREVIOUS RUNS AND THERE WAS
LITTLE SPREAD IN MODEL SOLUTIONS.
FIRST, UPPER DELAWARE BAY: WINDS MAY GUSTS AT TIMES TO 35 KNOTS
TONIGHT INTO TUESDAY, BUT ON THE WHOLE IT WAS THOUGHT THAT THIS
WOULD BE A MINORITY OF THE TIME, SO THE SMALL CRAFT ADVISORY WAS
LEFT INTACT AND EXTENDED THROUGH 10Z TUESDAY.
THE INHERITED GALE WARNING ON THE SOUTHERN OCEAN WATERS WAS ALSO
CONTINUED, AND LIKEWISE EXTENDED THROUGH 10Z TUESDAY (OUR 4TH
PERIOD). HOWEVER, WE DID BACK UP THE STARTING TIME A COUPLE OF HOURS
FROM 22Z TODAY TO 00Z MONDAY.
THE NORTHERN OCEAN WATERS WERE ALSO BROUGHT INTO A GALE WARNING AT
THIS TIME, AS THE TIGHTEST GRADIENT APPEARS TO SHIFT TO THE NORTH
TONIGHT AND LINGER MONDAY. SO, THE STARTING TIME WAS A FEW HOURS
AFTER THE SOUTHERN WATERS, ALLOWING FOR SOME TIME FOR THE GRADIENT
TO BECOME COMPRESSED FURTHER NORTH. THIS TOO WILL EXTEND THROUGH 10Z
TUESDAY.
WAVES IN THE 8 TO 12 FOOT RANGE ON THE OCEAN WERE PRETTY MUCH
CONTINUED, ALTHOUGH WAVEWATCH HAD A LITTLE HIGHER SOLUTION FOR A FEW
TIME PERIODS MONDAY.
FOR THE OUTLOOK, HIGH PRESSURE SHOULD FOLLOW FOR THE MIDDLE OF THE
COMING WEEK, HOWEVER A COLD FRONT IS LIKELY TO APPROACH THURSDAY.
&&
.HYDROLOGY...
WE ARE EXPECTING AROUND AN INCH OR SO OF RAINFALL JUST NORTH OF
THE ELEVATED CONVECTION AREA, WHICH IS TO SAY FROM NORTH OF
READING TO NORTH OF TRENTON AND JUST NORTH OF INTERSTATE 195. AS
WE MOVE FURTHER SOUTH, THE THREAT OF ELEVATED CONVECTION AND THE
AMOUNT OF AVAILABLE MOISTURE INCREASES. WE COULD EASILY SEE AREAS
WITH IN EXCESS OF TWO INCHES OVER MUCH OF THE DELMARVA AND FAR
SOUTHERN NEW JERSEY, BUT BASED ON HEADWATER GUIDANCE /FFH/ AND
FLASH FLOOD /FFG/, THESE AMOUNTS WOULDN`T CAUSE ANYTHING OTHER
THAN POOR-DRAINAGE OR ROADWAY FLOODING. THE AREA OF CONCERN IS
FAR SOUTHEASTERN PENNSYLVANIA, NORTHERN DELAWARE AND NORTHEAST
MARYLAND, WHERE FFH AND/OR FFG VALUES WOULD BE WITHIN REACH ONCE
WE APPROACH TWO INCHES. WE THEREFORE HAVE ISSUED A FLOOD WATCH.
&&
.TIDES/COASTAL FLOODING...
THE DECISION WAS MADE TO ISSUE A COASTAL FLOOD ADVISORY FOR
WIDESPREAD MINOR TIDAL FLOODING FOR THE HIGH TIDE CYCLE LATE TONIGHT
ON THE OCEAN FRONT (AND ADJACENT BACK BAYS), AND ALSO TO ISSUE A
COASTAL FLOOD WATCH FOR THE SAME AREAS FOR MONDAY AND MONDAY NIGHT
AS SURGE GUIDANCE PAINTS SIGNIFICANT TIDE DEPARTURES. ITS POSSIBLE
THAT LINGERING EFFECTS WILL OCCUR TUESDAY AS WELL, BUT SINCE THAT`S
WAY OUT ON THE TIME HORIZON, THAT CAN BE LEFT FOR A LATER DAY.
AS THE DEVELOPING LOW PRESSURE AREA APPROACHES THIS AFTERNOON AND
AFFECTS THE AREA TONIGHT THROUGH TUESDAY, BOTH THE NGM AND AVIATION
STORM SURGE GUIDANCE SHOW PRONOUNCED POSITIVE ANOMALIES, ESPECIALLY
MONDAY AND MONDAY NIGHT. STARTING OFF TONIGHT, ONLY MINOR TIDAL
FLOODING IS FORESEEN FOR TONIGHT, BUT SINCE CONFIDENCE IS HIGH THAT
IT WILL BE WIDESPREAD (AS MODELS HAVE BEEN CONSISTENT RUN-TO-RUN AND
MODEL-TO-MODEL), IT WAS THOUGHT TO ISSUE THE ADVISORY NOW SO AS TO
PROVIDE GOOD LEAD TIME.
AN ADVISORY IS ALSO LIKELY TO BE NEEDED FOR DELAWARE BAY AND THE
TIDAL PORTIONS OF THE DELAWARE RIVER MONDAY (MORNING), BUT THAT CAN
BE ADDRESSED BY LATER SHIFTS.
THE AFTERNOON HIGH TIDE CYCLE ON THE OCEAN FRONT IS THE LOWER OF THE
TWO DAILY HIGH TIDES, WHICH MAY BE SOMEWHAT OF A SAVING FACTOR
MONDAY; HOWEVER, SOME FORECASTS FOR MONDAY NIGHT ARE A BIT LOWER
THAN THEY WERE FOR MONDAY AFTERNOON, ALTHOUGH ITS NOT CLEAR WHY THIS
WOULD BE SO AS THE WINDS SHOULD STILL BE FROM A FAVORABLE NORTHEAST
DIRECTION AND STILL QUITE STRONG. LATER MODEL RUNS MAY SHOW EQUAL
ANOMALIES, SO THE DECISION WAS MADE THAT MONDAY NIGHT MAY HAVE ONLY
SLIGHTLY LESS OR EVEN THE SAME EFFECTS AS MONDAY, AND A WATCH WOULD
BE WARRANTED FOR BOTH TIME FRAMES SINCE THERE COULD BE AREAS OF
MODERATE TIDAL FLOODING. AS INFORMATION CRYSTALLIZES LATER TODAY AND
TONIGHT, PERHAPS THE WATCH COULD BE TRANSFORMED INTO AN ADVISORY IF
WATCH/WARNING CRITERIA NO LONGER APPEAR TO BE MET. OR, HEY, MAYBE A
WARNING WILL BE NEEDED.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...FLOOD WATCH FROM LATE TONIGHT THROUGH MONDAY AFTERNOON FOR
PAZ067-070-071.
NJ...COASTAL FLOOD WATCH FROM MONDAY AFTERNOON THROUGH LATE MONDAY
NIGHT FOR NJZ012>014-020-022>027.
COASTAL FLOOD ADVISORY FROM MIDNIGHT TONIGHT TO 5 AM EDT
MONDAY FOR NJZ012>014-020-022>027.
DE...COASTAL FLOOD WATCH FROM MONDAY AFTERNOON THROUGH LATE MONDAY
NIGHT FOR DEZ003-004.
COASTAL FLOOD ADVISORY FROM MIDNIGHT TONIGHT TO 5 AM EDT
MONDAY FOR DEZ003-004.
FLOOD WATCH FROM LATE TONIGHT THROUGH MONDAY AFTERNOON FOR
DEZ001.
MD...FLOOD WATCH FROM LATE TONIGHT THROUGH MONDAY AFTERNOON FOR
MDZ008.
MARINE...GALE WARNING FROM 8 PM THIS EVENING TO 6 AM EDT TUESDAY FOR
ANZ431-452>455.
GALE WARNING FROM 11 PM THIS EVENING TO 6 AM EDT TUESDAY FOR
ANZ450-451.
SMALL CRAFT ADVISORY FROM 8 PM THIS EVENING TO 6 AM EDT
TUESDAY FOR ANZ430.
&&
$$
SYNOPSIS...DELISI
NEAR TERM...DELISI/NIERENBERG
SHORT TERM...DELISI
LONG TERM...IOVINO
AVIATION.../
MARINE.../
HYDROLOGY...DELISI
TIDES/COASTAL FLOODING.../
AREA FORECAST DISCUSSION
NWS MOUNT HOLLY NJ
452 AM EDT SUN MAY 11 2008
.SYNOPSIS...
WEAK HIGH PRESSURE OVER THE AREA EARLY THIS MORNING WILL RECEDE
EAST. COMPLEX LOW PRESSURE WILL APPROACH FROM THE WEST TODAY,
CONSOLIDATE OFF THE NORTHERN MID-ATLANTIC COAST EARLY ON MONDAY,
AND THEN MOVE SLOWLY OUT TO SEA. HIGH PRESSURE IS FORECAST TO
BUILD INTO OUR REGION FROM THE WEST FOR THE MID-WEEK PERIOD.
A COLD FRONT IS EXPECTED TO FOLLOW FOR FRIDAY NIGHT.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
AFTER A SUNNY START TO THE DAY, CLOUDS SHOULD BEGIN TO INVADE FROM
THE WEST AND SOUTHWEST. THE GFS AND THE ECMWF ARE A BIT QUICKER TO
BRING PRECIPITATION INTO THE AREA THAN THE NAM. INITIALLY, WE`RE
DEALING WITH ISENT LIFT PRECIP AT AROUND I300.
THE SYSTEM RESPONSIBLE, AS NOTED IN PREVIOUS DISCUSSIONS, IS A
VIGOROUS MID LEVEL TROF THAT IS IN THE PROCESS OF CUTTING OFF AS A
STRONG UPPER LEVEL JET DROPS INTO ITS BASE. THE MID LEVEL LOW WILL
BE MOVING INTO THE UPPER OHIO RIVER VALLEY BY THE END OF THE DAY,
AND IT WILL BEGIN TO TRANSFER ENERGY AT THE SURFACE FROM A
PRIMARY LOW NEAR THE PARENT MID LEVEL SYSTEM TO A SECONDARY LOW
OVER VIRGINIA.
WE HAVE MAINTAINED CONTINUITY ON TEMPERATURES. WINDS ARE EXPECTED
TO BEGIN TO PICK UP OUT OF THE EAST OR SOUTHEAST DURING THE
AFTERNOON, WHICH MAKES CONTINUITY SEEM LIKE A GOOD IDEA, AND THE
FIRST CHANCE OF PRECIP SHOULD BE LATER IN THE AFTERNOON OVER THE
SOUTHWESTERN PART OF THE FORECAST AREA.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH TUESDAY/...
THE SYSTEM WILL GENERATE A FAIRLY STRONG WIND FIELD, CARRY GOOD
MID AND UPPER LEVEL DYNAMICS, GENERATE GOOD LOWER LEVEL
FRONTOGENESIS, AND PERHAPS CARRY WITH IT SOME ELEVATED
INSTABILITY. THE STRONG AND FAIRLY DEEP WINDS ABOVE THE SURFACE
AND OFF THE OCEAN SHOULD CARRY AS MUCH ATLANTIC MOISTURE AS IS
POSSIBLE, ALTHOUGH, AGAIN, WE HAVE A HARD TIME SEEING VERY HIGH H8
DEWPOINTS IN OUR REGION IN THE MORE MOIST GFS. THE GFS CARRIES 5 DEG
C VALUES AS FAR NORTH AS ABOUT PHL AND CARRIES 8 DEG C VALUES INTO
OUR FAR SOUTHERN ZONES. FURTHER TO THE NORTH, MORE REMOVED FROM
THE SYSTEM, H8 DEW POINTS ARE EVEN LOWER.
WITHOUT THE POSSIBILITY OF SOME CONVECTION, WHICH IS DEPICTED /AS
ELEVATED CONVECTION/ A BIT MORE EMPHATICALLY IN THE GFS THAN THE
NAM, WE WOULD BE TEMPTED TO UNDERCUT MODEL QPF A BIT AS THE MODELS
HAVE A HIGH BIAS IN NON- CONVECTIVE EVENTS. HOWEVER, IT IS THE
FEAR OF ELEVATED CONVECTION THAT KEPT US FROM DOING THAT. THAT
MAKES FOR SOME RESPECTABLE PRECIPITATION AMOUNTS OVER ABOUT THE
SOUTHERN HALF TO TWO-THIRDS OF THE AREA. WE INCLUDE A HYDRO
SECTION BELOW.
THE WIND FIELDS SHOW A CONSIDERABLE AMOUNT OF SHEAR, AND WE HOPE
WE ARE CORRECT THAT ANY CONVECTION WOULD BE ALOFT. THAT IS WHAT
THE SURFACE-BASED STABILITY PROGS SHOW, AND THAT IS HOW SPC AND WE
ARE PLAYING IT.
WINDS ALSO WILL BEGIN STRENGTHEN SUFFICIENTLY, FIRST OUT OF THE
EAST TO SOUTHEAST TONIGHT, THEN OUT OF THE NORTHEAST ON MONDAY, TO
CAUSE SOME TIDAL CONCERNS AS NOTED BELOW. IT IS POSSIBLE, AFTER
THE TRANSFERRENCE OF ENERGY AT THE SURFACE IS COMPLETE, THAT THE
SYSTEM WOULD WIND UP ENOUGH ON MONDAY TO EVENTUALLY CAUSE US TO
ISSUE A WIND ADVISORY, AT LEAST ALONG THE COAST, BUT BUFKIT FROM
THE GFS LOOKS MARGINAL AND WE HAVE PASSED ON THAT FOR THE TIME
BEING.
THE CONSOLIDATED SYSTEM EXITS SLOWLY ON MONDAY, PERHAPS A BIT TOO
SLOWLY AS DEPICTED BY THE NAM, AND THE BULK OF THE SIGNIFICANT
PRECIPITATION SHOULD BE OVER WITH BEFORE EVENING. STABILITY PROGS,
AT THE SURFACE AND ALOFT, INDICATE THAT THE THREAT OF CONVECTION
MAY BE OVER WITH EARLY ON MONDAY, AND WE`RE NOT CARRYING ANY
MENTION OF THUNDER AFTER TONIGHT FOR NOW.
GRADUAL IMPROVEMENT IS FORECAST OVER LAND ON MONDAY NIGHT AND
TUESDAY. AGAIN, CONTINUITY ON TEMPERATURES WAS MOSTLY ACCEPTED.
WE DID ACTUALLY LOWER THE MONDAY MAXES OVER ALL BUT THE FAR
SOUTHERN ZONES. SOUNDINGS FROM THIS RUN DON`T SHOW ANY PRECIP TYPE
CONCERNS, BUT WE`LL CONTINUE TO WATCH THAT.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
AT MID WEEK, WE ARE EXPECTING TO SEE THE UPPER LOW TAKING ITS TIME
MOVING OUT TO SEA. MEANWHILE, AN UPPER RIDGE AXIS IS FORECAST TO
EXTEND FROM THE GULF COAST UP INTO THE GREAT LAKES REGION ON TUESDAY
NIGHT. AS THE LOW DRIFTS EASTWARD, SO WILL THE RIDGE. THE RIDGE
AXIS IS EXPECTED TO PASS OVER OUR REGION FROM WEDNESDAY NIGHT INTO
THURSDAY.
AN UPPER LEVEL TROUGH IS FORECAST TO DIG INTO THE EASTERN STATES ON
FRIDAY AND SATURDAY. A SURFACE COLD FRONT, ASSOCIATED WITH THE
UPPER TROUGH, SHOULD PASS THROUGH OUR REGION ON FRIDAY NIGHT.
&&
.AVIATION /08Z SUNDAY THROUGH THURSDAY/...
WEAK HIGH PRESSURE OVER THE AREA WILL MOVE OFFSHORE THIS MORNING.
LIGHT WEST WINDS...OR CALM WINDS...WERE ALLOWING FOR SOME
RADIATIONAL COOLING EARLY THIS MORNING, AND FOG HAS WAFTED IN AND
OUT AT KRDG. A COUPLE OF OTHER PLACES MAY HAVE SOME BRIEF IFR
VISIBILITIES IN FOG, OTHERWISE CIRRUS WILL BE INCREASING FROM THE
WEST-SOUTHWEST AS THE MORNING WEARS ON.
LOW PRESSURE WILL APPROACH FROM THE OHIO VALLEY TODAY AND WEAKEN AS
SECONDARY DEVELOPMENT TAKES PLACES ALONG THE VIRGINIA CAPES LATE
TODAY AND EARLY TONIGHT. WITH THE DEVELOPING ONSHORE FLOW AND INFLUX
OF MID AND THEN LOW LEVEL MOISTURE, CEILINGS WILL GRADUALLY LOWER TO
MARGINAL VFR LATER THIS AFTERNOON, WITH RAIN DEVELOPING AS THE
COLUMN MOISTENS LATE TODAY OR MORE LIKELY THIS EVENING, PROBABLY
FROM WEST-SOUTHWEST TO EAST-NORTHEAST.
LIGHT WINDS (WITH A WESTERLY COMPONENT) EARLY THIS MORNING WILL BACK
AROUND TO EAST OR EAST-SOUTHEAST AND STRENGTHEN AS THE STORM SYSTEM
NEARS. AN INCREASING PRESSURE GRADIENT MAY BECOME TIGHT ENOUGH TO
ALLOW FOR GUSTS TO OCCUR FROM ABOUT MID AFTERNOON ON, ESPECIALLY
FROM KPHL SOUTH AND EAST. A WIND SHEAR REMARK WAS ADDED LATE IN THE
TAF VALID PERIOD AS LOW LEVEL WINDS WILL BE SCREAMING OUT OF THE
EAST. SURFACE WINDS WILL BE GUSTY, BUT IT WAS FELT THAT A POINTER TO
45 TO 50 KNOT WINDS JUST OFF THE SURFACE WOULD BE BENEFICIAL.
OUTLOOK...
CONDITIONS WILL BE MARGINAL VFR IN STRATUS, WITH RAIN HEAVY AT TIMES
AND FOG TONIGHT INTO MONDAY AS THE STORM IMPACTS THE REGION.
WIDESPREAD RAIN AND GUSTY WINDS WILL NEGATIVELY IMPACT AIRCRAFT
OPERATIONS SIGNIFICANTLY MONDAY. GRADUAL IMPROVEMENT IS EXPECTED
LATE MONDAY NIGHT AND ESPECIALLY TUESDAY, BUT LINGERING NEGATIVE
IMPACTS ARE LIKELY EVEN TUESDAY. HIGH PRESSURE IS FORECAST TO RETURN
WEDNESDAY, HOWEVER A COLD FRONT MAY APPROACH FROM THE WEST THURSDAY
WITH A CHANCE OF SHOWERS.
&&
.MARINE...
STRENGTHENING LOW PRESSURE APPROACHING FROM THE OHIO VALLEY TODAY
WILL SHIFT ITS ENERGY TO THE VIRGINIA CAPES EARLY TONIGHT, WITH A
GOOD OLD FASHIONED (MAY?) NOR`EASTER ON OUR HANDS. IT LOOKS LIKE A
PRETTY GOOD BLOW WITH GOOD WAVE ACTION (OVER 10 FEET MONDAY AND
MONDAY NIGHT), SO ANY SUNDAY PARTY BOATERS SHOULD PLAN ON RETURNING
THIS AFTERNOON OR EARLY TONIGHT. MODEL OUTPUT LENT CONFIDENCE TO THE
FORECAST, AS MODELS WERE CONSISTENT FROM PREVIOUS RUNS AND THERE WAS
LITTLE SPREAD IN MODEL SOLUTIONS.
FIRST, UPPER DELAWARE BAY: WINDS MAY GUSTS AT TIMES TO 35 KNOTS
TONIGHT INTO TUESDAY, BUT ON THE WHOLE IT WAS THOUGHT THAT THIS
WOULD BE A MINORITY OF THE TIME, SO THE SMALL CRAFT ADVISORY WAS
LEFT INTACT AND EXTENDED THROUGH 10Z TUESDAY.
THE INHERITED GALE WARNING ON THE SOUTHERN OCEAN WATERS WAS ALSO
CONTINUED, AND LIKEWISE EXTENDED THROUGH 10Z TUESDAY (OUR 4TH
PERIOD). HOWEVER, WE DID BACK UP THE STARTING TIME A COUPLE OF HOURS
FROM 22Z TODAY TO 00Z MONDAY.
THE NORTHERN OCEAN WATERS WERE ALSO BROUGHT INTO A GALE WARNING AT
THIS TIME, AS THE TIGHTEST GRADIENT APPEARS TO SHIFT TO THE NORTH
TONIGHT AND LINGER MONDAY. SO, THE STARTING TIME WAS A FEW HOURS
AFTER THE SOUTHERN WATERS, ALLOWING FOR SOME TIME FOR THE GRADIENT
TO BECOME COMPRESSED FURTHER NORTH. THIS TOO WILL EXTEND THROUGH 10Z
TUESDAY.
WAVES IN THE 8 TO 12 FOOT RANGE ON THE OCEAN WERE PRETTY MUCH
CONTINUED, ALTHOUGH WAVEWATCH HAD A LITTLE HIGHER SOLUTION FOR A FEW
TIME PERIODS MONDAY.
FOR THE OUTLOOK, HIGH PRESSURE SHOULD FOLLOW FOR THE MIDDLE OF THE
COMING WEEK, HOWEVER A COLD FRONT IS LIKELY TO APPROACH THURSDAY.
&&
.HYDROLOGY...
WE ARE EXPECTING AROUND AN INCH OR SO OF RAINFALL JUST NORTH OF
THE ELEVATED CONVECTION AREA, WHICH IS TO SAY FROM NORTH OF
READING TO NORTH OF TRENTON AND JUST NORTH OF INTERSTATE 195. AS
WE MOVE FURTHER SOUTH, THE THREAT OF ELEVATED CONVECTION AND THE
AMOUNT OF AVAILABLE MOISTURE INCREASES. WE COULD EASILY SEE AREAS
WITH IN EXCESS OF TWO INCHES OVER MUCH OF THE DELMARVA AND FAR
SOUTHERN NEW JERSEY, BUT BASED ON HEADWATER GUIDANCE /FFH/ AND
FLASH FLOOD /FFG/, THESE AMOUNTS WOULDN`T CAUSE ANYTHING OTHER
THAN POOR-DRAINAGE OR ROADWAY FLOODING. THE AREA OF CONCERN IS
FAR SOUTHEASTERN PENNSYLVANIA, NORTHERN DELAWARE AND NORTHEAST
MARYLAND, WHERE FFH AND/OR FFG VALUES WOULD BE WITHIN REACH ONCE
WE APPROACH TWO INCHES. WE THEREFORE HAVE ISSUED A FLOOD WATCH.
&&
.TIDES/COASTAL FLOODING...
THE DECISION WAS MADE TO ISSUE A COASTAL FLOOD ADVISORY FOR
WIDESPREAD MINOR TIDAL FLOODING FOR THE HIGH TIDE CYCLE LATE TONIGHT
ON THE OCEAN FRONT (AND ADJACENT BACK BAYS), AND ALSO TO ISSUE A
COASTAL FLOOD WATCH FOR THE SAME AREAS FOR MONDAY AND MONDAY NIGHT
AS SURGE GUIDANCE PAINTS SIGNIFICANT TIDE DEPARTURES. ITS POSSIBLE
THAT LINGERING EFFECTS WILL OCCUR TUESDAY AS WELL, BUT SINCE THAT`S
WAY OUT ON THE TIME HORIZON, THAT CAN BE LEFT FOR A LATER DAY.
AS THE DEVELOPING LOW PRESSURE AREA APPROACHES THIS AFTERNOON AND
AFFECTS THE AREA TONIGHT THROUGH TUESDAY, BOTH THE NGM AND AVIATION
STORM SURGE GUIDANCE SHOW PRONOUNCED POSITIVE ANOMALIES, ESPECIALLY
MONDAY AND MONDAY NIGHT. STARTING OFF TONIGHT, ONLY MINOR TIDAL
FLOODING IS FORESEEN FOR TONIGHT, BUT SINCE CONFIDENCE IS HIGH THAT
IT WILL BE WIDESPREAD (AS MODELS HAVE BEEN CONSISTENT RUN-TO-RUN AND
MODEL-TO-MODEL), IT WAS THOUGHT TO ISSUE THE ADVISORY NOW SO AS TO
PROVIDE GOOD LEAD TIME.
AN ADVISORY IS ALSO LIKELY TO BE NEEDED FOR DELAWARE BAY AND THE
TIDAL PORTIONS OF THE DELAWARE RIVER MONDAY (MORNING), BUT THAT CAN
BE ADDRESSED BY LATER SHIFTS.
THE AFTERNOON HIGH TIDE CYCLE ON THE OCEAN FRONT IS THE LOWER OF THE
TWO DAILY HIGH TIDES, WHICH MAY BE SOMEWHAT OF A SAVING FACTOR
MONDAY; HOWEVER, SOME FORECASTS FOR MONDAY NIGHT ARE A BIT LOWER
THAN THEY WERE FOR MONDAY AFTERNOON, ALTHOUGH ITS NOT CLEAR WHY THIS
WOULD BE SO AS THE WINDS SHOULD STILL BE FROM A FAVORABLE NORTHEAST
DIRECTION AND STILL QUITE STRONG. LATER MODEL RUNS MAY SHOW EQUAL
ANOMALIES, SO THE DECISION WAS MADE THAT MONDAY NIGHT MAY HAVE ONLY
SLIGHTLY LESS OR EVEN THE SAME EFFECTS AS MONDAY, AND A WATCH WOULD
BE WARRANTED FOR BOTH TIME FRAMES SINCE THERE COULD BE AREAS OF
MODERATE TIDAL FLOODING. AS INFORMATION CRYSTALLIZES LATER TODAY AND
TONIGHT, PERHAPS THE WATCH COULD BE TRANSFORMED INTO AN ADVISORY IF
WATCH/WARNING CRITERIA NO LONGER APPEAR TO BE MET. OR, HEY, MAYBE A
WARNING WILL BE NEEDED.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...FLOOD WATCH FROM LATE TONIGHT THROUGH MONDAY AFTERNOON FOR
PAZ067-070-071.
NJ...COASTAL FLOOD WATCH FROM MONDAY AFTERNOON THROUGH LATE MONDAY
NIGHT FOR NJZ012>014-020-022>027.
COASTAL FLOOD ADVISORY FROM MIDNIGHT TONIGHT TO 5 AM EDT
MONDAY FOR NJZ012>014-020-022>027.
DE...COASTAL FLOOD WATCH FROM MONDAY AFTERNOON THROUGH LATE MONDAY
NIGHT FOR DEZ003-004.
COASTAL FLOOD ADVISORY FROM MIDNIGHT TONIGHT TO 5 AM EDT
MONDAY FOR DEZ003-004.
FLOOD WATCH FROM LATE TONIGHT THROUGH MONDAY AFTERNOON FOR
DEZ001.
MD...FLOOD WATCH FROM LATE TONIGHT THROUGH MONDAY AFTERNOON FOR
MDZ008.
MARINE...GALE WARNING FROM 8 PM THIS EVENING TO 6 AM EDT TUESDAY FOR
ANZ431-452>455.
GALE WARNING FROM 11 PM THIS EVENING TO 6 AM EDT TUESDAY FOR
ANZ450-451.
SMALL CRAFT ADVISORY FROM 8 PM THIS EVENING TO 6 AM EDT
TUESDAY FOR ANZ430.
&&
$$
SYNOPSIS...DELISI
NEAR TERM...DELISI
SHORT TERM...DELISI
LONG TERM...IOVINO
AVIATION...
MARINE...
HYDROLOGY...DELISI
TIDES/COASTAL FLOODING...
AREA FORECAST DISCUSSION
NWS BALTIMORE MD/WASHINGTON DC
1026 AM EDT SUN MAY 11 2008
.SYNOPSIS...
HIGH PRESSURE WILL MOVE OFF THE MID-ATLANTIC COAST EARLY THIS
AFTERNOON ALLOWING FOR A POTENT STORM SYSTEM TO APPROACH FROM THE
OHIO VALLEY. THIS SYSTEM WILL PASS THROUGH OUR REGION OVERNIGHT
AND IT WILL SLOWLY MOVE OFF THE MID-ATLANTIC COAST MONDAY.
SIGNIFICANT RAINFALL IS EXPECTED FROM THIS STORM SYSTEM WITH THE
HEAVIEST RAIN EXPECTED LATER THIS AFTERNOON THROUGH TONIGHT. HIGH
PRESSURE WILL SLOWLY BUILD IN BEHIND THIS STORM FOR TUESDAY AND
WEDNESDAY.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
WATER VAPOR LOOP SHOWS A VIGOROUS UPPER LOW TRANSLATING EAST OVER
THE MIDWEST. A DRY SLOT IS INTRUDING OVER THE TENNESSEE VALLEY. ACARS
400-250MB WIND OBSERVATIONS SHOW A 110-150KT CYCLICALLY CURVED JET
FROM THE PLAINS INTO THE CENTRAL APPALACHIANS. 11Z SURFACE ANALYSIS
PLACED A 985MB OCCLUDED CYCLONE IN EAST CENTRAL ILLINOIS. THE
OCCLUDED BOUNDARY EXTENDED SOUTHEAST INTO NORTHERN ALABAMA...WITH A
COLD FRONT CONTINUING SOUTHWEST ACROSS SOUTHERN TEXAS. A
WARM/STATIONARY BOUNDARY STRETCHED EAST FROM CENTRAL ALABAMA
THROUGH SOUTHERN GEORGIA. RIDGING IS OCCURRING EAST OF THE
APPALACHIANS WITH A COASTAL BOUNDARY BEGINNING TO DEVELOP ALONG THE
EASTERN CAROLINAS. A PRE-FRONTAL TROUGH WAS NOTED 50-100 MILES AHEAD
OF THE OCCLUDED BOUNDARY.
FORECAST TIMING REMAINS ON TRACK. AS THE UPPER LEVEL RIDGE MOVES
TO THE EAST AND HEIGHTS FALL...LOWER LEVEL ISENTROPIC LIFT WILL
INCREASE ABOVE THE BOUNDARY WELL SOUTH ACROSS THE EASTERN GULF
STATES. THIS WILL BE AIDED AS CONVECTION MOVES OFF THE SOUTHEAST
CONUS COAST...AND SOUTHERLY FLOW RECOVERY INCREASES FOR THE
REMAINDER OF THE DAY.
STRONG CONVECTION ALONG THE UPPER LOW SHOULD WEAKEN AS IT MOVES
ACROSS THE MOUNTAINS DURING THE LATE AFTERNOON...AS STABILITY
INCREASES TO THE NORTHEAST ACROSS THE REGION. HAVE HOWEVER UPDATED
THE EVENING FORECAST WITH FURTHER DISCUSSION BELOW.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM MONDAY/...
UPDATED THE FORECAST TO ADD THUNDER IN FOR THE SOUTHERN ZONES.
SURFACE INSTABILITY SHOULD REMAIN WELL SOUTH OF THE AREA GIVEN THE
FORECAST TRACK OF THE TRIPLE POINT LOW. THERE IS CURRENTLY UPSTREAM
CONVECTION ALONG THE UPPER LOW. 03Z SREF INDICATES 50 PERCENT OR
GREATER PROBABILITY OF MUCAPE (MOST-UNSTABLE) ACROSS SOUTHERN ZONES
THIS EVENING AND EARLY TONIGHT. ANY CONVECTION OF COURSE WILL
ALSO SERVE TO INCREASE RAIN RATES FOR INCREASED FLOOD THREAT.
AS THE PRIMARY LOW PRESSURE SYSTEM MOVES INTO THE OHIO
VALLEY...IT BEGINS TO TRANSFER ITS ENERGY TO A DEVELOPING LOW
CENTER OVER SE VIRGINIA. THE SECONDARY LOW PRESSURE IS EXPECTED TO
MOVE UP THE CHESAPEAKE BAY OVERNIGHT.
AS THE DIFFLUENCE ALOFT MOVES EASTWARD...HELPING TO CREATE STRONG
LIFT...THE HEAVY RAINFALL IS EXPECTED TO BEGIN SPREADING EAST OF THE
BLUE RIDGE MOUNTAINS. BY THIS TIME...PW WATER VALUES ARE NEAR 2
STANDARD DEVIATIONS ABOVE NORMAL FOR THIS TIME OF YEAR AS MOISTURE
IS TRANSPORTED FROM THE GULF OF MEXICO AND FROM THE ATLANTIC
OCEAN. THE EASTERLY FLOW WILL ALSO HELP TO INCREASE UPSLOPE ALONG
THE BLUE RIDGE MOUNTAINS.
AREAS MAINLY ALONG AND EAST OF THE BLUE RIDGE MOUNTAINS RECEIVED
ANYWHERE FROM ONE TO THREE INCHES OF RAINFALL WITH THE THU/FRI
SYSTEM. FLASH FLOOD GUIDANCE VALUES ARE PARTICULARLY LOW IN THIS
AREA...WITH VALUES AROUND/BELOW AN INCH FOR 6 HOUR TOTALS FOR THE
METRO BALTIMORE AND DC AREAS. 6 HOUR VALUES FOR THE SUBURBS ARE
UNDER/AROUND 2 INCHES. THIS AREA IS THE MOST VULNERABLE FOR FLOODING
WITH THE SUNDAY NIGHT/MONDAY SYSTEM. RAINFALL TOTALS OF TWO TO THREE
INCHES WILL BE LIKELY IN THE AREA...WHERE SOILS REMAIN SATURATED.
WEST OF THE BLUE RIDGE...6 HOUR FFG RANGES FROM TWO TO THREE INCHES.
THIS SYSTEM IS EXPECTED TO PRODUCE ONE TO THREE INCHES OF RAINFALL
IN THIS AREA. BELIEVE THE EARLIER START TIME FOR THE SW PORTION OF
THE CWFA STILL LOOKS GOOD. WILL BE MAKING NO CHANGES TO THE FLOOD
HEADLINE.
THIS SYSTEM WILL HAVE THE POTENTIAL TO PRODUCE RIVER FLOODING AND
FLOODING OF STREAMS/CREEKS IN THE URBAN CORRIDOR. SOILS...ESPECIALLY
EAST OF THE BLUE RIDGE...REMAIN SATURATED AND ANY ADDITIONAL
RAINFALL WILL ONLY CREATE RUN OFF.
&&
.LONG TERM /MONDAY THROUGH SATURDAY/...
THE STRONG COASTAL STORM WILL SLOWLY MOVE OFF THE DELMARVA PENINSULA
MONDAY MORNING AND OUT TO SEA DURING THE AFTERNOON. DESPITE THE FACT
THAT THE LOW WILL BE SLOWLY MOVING AWAY FROM THE REGION...PLENTY OF
MOISTURE FROM THE ATLANTIC WILL RAP AROUND THE LOW KEEPING CLOUDS
ALONG WITH MORE RAIN ACROSS MOST OF THE REGION. STRONG PRESSURE
GRADIENT BETWEEN THIS STORM AND HIGHER PRESSURE TO THE WEST WILL
BRING BREEZY CONDITIONS. THIS COMBINED WITH THE CLOUDS AND RAIN WILL
MAKE IT FEEL CHILLY. WITH A STRONG NORTHERLY FLOW IN PLACE...MAX
TEMPERATURES WILL ONLY RANGE FROM THE MID 40S IN THE POTOMAC
HIGHLANDS TO THE LOWER 50S IN THE WASHINGTON AND BALTIMORE
AREAS...TO THE LOWER 60S ACROSS PORTIONS OF CENTRAL VIRGINIA. THIS
IS ABOUT 15 TO 20 DEGREES BELOW CLIMO.
HIGH PRESSURE WILL SLOWLY BUILD TOWARDS THE REGION MONDAY NIGHT AND
TUESDAY BRINGING A RETURN OF DRIER CONDITIONS AND MORE SUNSHINE FOR
TUESDAY. MAX TEMPERATURES TUESDAY WILL BE MUCH CLOSER TO CLIMO
THANKS TO THE SUNSHINE. HIGH PRESSURE WILL SLOWLY DRIFT OFF THE
MID-ATLANTIC COAST WEDNESDAY AND THE NEXT COLD FRONT WILL APPROACH
FOR THURSDAY. STILL SOME UNCERTAINTY AS TO EXACTLY HOW THIS WILL
PLAY OUT GIVEN THE FACT IT IS STILL SEVERAL DAYS AWAY.
HOWEVER...MOST GUIDANCE IS IN AGREEMENT THAT THE FRONT STALLS OVER
THE CWA THURSDAY AND A WAVE OF LOW PRESSURE DEVELOPS ALONG THE FRONT
AND PASSES THROUGH THURSDAY NIGHT INTO FRIDAY. LEFT CHANCE POPS IN
FOR THE LATTER PART OF THE WEEK INTO EARLY NEXT WEEKEND.
&&
.AVIATION /14Z SUNDAY THROUGH THURSDAY/...
SUB VFR CONDITIONS EXPECTED BY THE MID AFTERNOON AT THE KCHO AND
KMRB TERMINALS...AND BY LATE AFTERNOON AT THE REMAINDER OF THE
TERMINAL SITES. CIGS ARE EXPECTED TO REMAIN AT IFR CONDITIONS
OVERNIGHT IN THE HEAVIEST RAIN.
A WIND SHIFT IS EXPECTED LATE TONIGHT AS STRONG LOW PRESSURE MOVES
ACROSS THE MID ATLANTIC.
MVFR/IFR CIGS AND VSBYS EXPECTED MONDAY BEHIND THE STORM SYSTEM
ALONG WITH PERIODS OF RAIN. N/NW WIND GUSTS AROUND 30 KT ARE
POSSIBLE ESPECIALLY DURING THE LATE MORNING AND AFTERNOON HOURS. A
RETURN OF VFR CONDITIONS ARE EXPECTED MONDAY NIGHT AS HIGH PRESSURE
BUILDS CLOSER TO THE TERMINALS.
VFR CONDITIONS WILL PERSIST THROUGH WEDNESDAY. THE NEXT SYSTEM WILL
BRING A CHANCE FOR PRECIPITATION ALONG WITH MVFR/IFR CIGS AND VSBYS
WEDNESDAY NIGHT AND THURSDAY.
&&
.MARINE...
WILL NOT BE CHANGING THE HEADLINES ALREADY IN EFFECT FOR THE TIDAL
POTOMAC AND MARYLAND PORTION OF THE CHESAPEAKE BAY FOR THE NEAR TERM
AND SHORT TERM PERIODS. BUFKIT SOUNDINGS AND LOCAL WRF MODEL
SUPPORT AN INCREASING GRADIENT THIS AFTERNOON...WITH GUSTS UP TO
25 KT LIKELY. AS THE STRONG LOW PRESSURE APPROACHES FROM THE SW
AND MOVES OVER THE CHESAPEAKE BAY...GALE CONDITIONS WILL OCCUR.
GUSTS TO 35 KT WILL BE LIKELY.
A STRONG STORM SYSTEM OVER THE WATERS EARLY MONDAY WILL SLOWLY MOVE
OFF THE MID-ATLANTIC COAST BY MONDAY NIGHT. GUSTY N/NE WINDS WILL
SHIFT TO THE N/NW BEHIND THIS STORM SYSTEM. A GALE WARNING IS IN
EFFECT THROUGH MONDAY FOR THE LOWER TIDAL POTOMAC AND CHESAPEAKE
BAY. A SMALL CRAFT ADVISORY IS IN EFFECT FOR THE UPPER TIDAL POTOMAC
THROUGH MONDAY.
A SMALL CRAFT ADVISORY WILL LIKELY HAVE TO BE ADDED FOR MONDAY NIGHT
AND TUESDAY FOR THE TIDAL POTOMAC AND CHESAPEAKE BAY. HIGH PRESSURE
WILL BUILD OVER THE WATERS TUESDAY NIGHT AND WEDNESDAY ALLOWING FOR
WINDS TO DIMINISH.
&&
.TIDES/COASTAL FLOODING...
WATER LEVELS ARE STILL RUNNING ABOUT A FOOT ABOVE NORMAL. WATER
LEVEL DEPARTURES ARE EXPECTED TO INCREASE TO 1 TO 2 FEET ABOVE
ASTRONOMICAL PREDICATIONS THROUGH MONDAY AS STRONG LOW PRESSURE
MOVES ACROSS THE CHESAPEAKE BAY. HAVE ISSUED A COASTAL FLOOD
ADVISORY ALONG THE WESTERN SHORE OF THE CHESAPEAKE BAY WHERE THE STRONGEST
AND MOST PERSISTENT FAVARABLE SOUTHEASTELY FETCH WILL TRAP
WATER...DESPITE BEING AT A QUARTER MOON.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...FLOOD WATCH FROM 6 PM EDT THIS EVENING THROUGH MONDAY
AFTERNOON FOR DCZ001.
MD...FLOOD WATCH FROM 2 PM EDT THIS AFTERNOON THROUGH MONDAY
MORNING FOR MDZ003-501-502.
FLOOD WATCH FROM 6 PM EDT THIS EVENING THROUGH MONDAY
AFTERNOON FOR MDZ004>007-009>011-013-014-016>018.
COASTAL FLOOD ADVISORY UNTIL 10 AM EDT MONDAY FOR MDZ007-011-
014-017-018.
VA...FLOOD WATCH FROM 2 PM EDT THIS AFTERNOON THROUGH MONDAY
MORNING FOR VAZ021-025>031-036>040-050-051-056.
FLOOD WATCH FROM 6 PM EDT THIS EVENING THROUGH MONDAY
AFTERNOON FOR VAZ041-042-052>055-057.
WV...FLOOD WATCH FROM 2 PM EDT THIS AFTERNOON THROUGH MONDAY
MORNING FOR WVZ050>055-501>504.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EDT THIS AFTERNOON FOR
ANZ530>534-537.
GALE WARNING FROM 6 PM THIS EVENING TO 6 PM EDT MONDAY FOR
ANZ530>534-537.
SMALL CRAFT ADVISORY UNTIL 6 PM EDT MONDAY FOR ANZ535-536.
&&
$$
SYNOPSIS...LASORSA
NEAR TERM...ROGOWSKI
SHORT TERM...ROGOWSKI/LISTEMAA
LONG TERM...LASORSA
AVIATION...ROGOWSKI/LISTEMAA/LASORSA
MARINE...ROGOWSKI/LISTEMAA/LASORSA
TIDES/COASTAL FLOODING...ROGOWSKI
AREA FORECAST DISCUSSION...UPDATED
NWS MARQUETTE MI
808 PM EDT MON MAY 12 2008
UPDATED FOR 00Z AVIATION DISCUSSION
.SYNOPSIS...
WATER VAPOR IMAGERY AND RUC ANALYSIS SHOW AN UNSEASONABLY DEEP
MIDLEVEL LOW JUST OFF THE COAST OF THE MID ATLANTIC STATES...A RIDGE
OVER THE MISSISSIPPI VALLEY AND A TROF OVER THE NRN ROCKIES. PER 12Z
RAOBS...STRONG WAA/ISENTROPIC ASCENT PATTERN AHEAD OF THE NRN
ROCKIES TROF IS PRODUCING CONSIDERABLE MID/HIGH CLOUDS ACROSS THE
DAKOTAS/MN. REGIONAL RADARS SHOW RETURNS ACROSS ND/NRN MN...BUT SO
FAR...NOT TOO MUCH PCPN IS REACHING THE GROUND. MOST OF THE OBS
INDICATING PCPN ARE ACROSS FAR NRN MN WHERE SATURATION OF THE DRY
LOW-LEVELS CAN BE ACHIEVED.
&&
.SHORT TERM...
AREA OF STRONG WAA/ISENTROPIC ASCENT AS VIEWED ON THE 300K SFC WILL
SLIDE E ACROSS THE FCST AREA THIS EVENING AND THEN TEND TO LIFT NE
OVERNIGHT. AFTN TAMDAR SOUNDINGS FROM KSAW/KCMX SHOW QUITE A BIT OF
DRY AIR AT THE LOW-MID LEVELS...SUGGESTING IT SHOULD BE DIFFICULT TO
GET PCPN TO REACH THE GROUND. HOWEVER...GIVEN STRENGTH OF ASCENT
WITH 30-40KT WINDS ORIENTED NEARLY PERPENDICULAR TO ISOBARS...PCPN
CAN`T BE SIMPLY RULED OUT DUE TO WHAT LOOKS LIKE TOO MUCH DRY AIR AT
THE LWR LEVELS. LATEST RADAR IMAGERY SHOWS RETURNS ORGANIZING INTO
BANDS WITH THE NRN BAND ACROSS FAR NRN MN PRODUCING PCPN THAT IS
REACHING THE GROUND. WITH NAM/GFS GENERALLY SHOWING AN AREA OF
STRONGER ISENTROPIC ASCENT TO PUSH ACROSS WRN UPPER MI THIS
EVENING...IT IS THE SECOND BAND OF RADAR RETURNS CURRENTLY ACROSS
CNTRL MN INTO FAR NW WI THAT MAY DEVELOP SUFFICIENTLY TO RESULT IN
SOME -SHRA/SPRINKLES. FOR NOW...HAVE INCLUDED SLIGHT CHC POPS DURING
THE EVENING OVER ROUGHLY THE W 1/3RD OF UPPER MI. ONCE THAT PCPN
EXITS...DON`T EXPECT ANY ADDITIONAL PCPN UNTIL THE SHORTWAVE TROF
CURRENTLY OVER THE NRN ROCKIES APPROACHES TUE AFTN.
CONSENSUS OF 12Z MODEL GUIDANCE SUGGESTS GFS IS A LITTLE TOO FAST
WITH PROGRESSION OF SHORTWAVE TROF AND ASSOCIATED SFC LOW/COLD FRONT
TUE. HAVE THUS LEANED TOWARD THE NAM FOR THE DETAILS WHICH IS VERY
SIMLAR TO THE REGIONAL CANADIAN. AS SHORTWAVE TROF MOVES ACROSS THE
DAKOTAS TO MN BY TUE EVENING...A WELL-DEFINED SW-NE UPPER JET STREAK
ON THE FRONT SIDE OF THE TROF SHIFTS E...PLACING RIGHT ENTRANCE
UPPER DIVERGENCE OVER WRN UPPER MI DURING THE AFTN. AS THE FORCING
ACTS ON AXIS OF PRECIPITABLE WATER IN EXCESS OF 1 INCH LIFTING INTO
THE AREA...-SHRA INTENSITY/COVERAGE SHOULD IMPROVE WITH TIME. AFTER
A DRY MORNING...WILL TAKE SLIGHT CHC POPS OVER THE FAR W EARLY IN
THE AFTN INTO THE LIKELY CATEGORY BY MID/LATE AFTN. OPTED TO ONLY
BRING SLIGHT CHC POPS AS FAR E AS ABOUT IN KMQT/KIMT BY 00Z WED IN
LIGHT OF THE PREFERRED NAM/REGIONAL CANADIAN SOLUTIONS. EVEN THAT
MAY BE A BIT TOO FAR E. DEPENDING ON AMOUNT OF HEATING AND MIXING
DEPTH...IT SHOULD BE BREEZY DAY WITH 30-35KT AVBL TO BE MIXED DOWN.
SHOULD SEE SOME GUSTS IN THE 30-35MPH RANGE IN THE AREAS THAT
TYPICALLY SEE HIGHER WINDS IN SRLY FLOW (KSAW/KERY/GRAND MARAIS FOR
EXAMPLE). IF MORE HEATING OCCURS THAN CURRENTLY EXPECTED...WINDS
WILL BE A BIT STRONGER.
&&
.LONG TERM (TUESDAY NIGHT THROUGH MONDAY)...
MUCH OF THIS PERIOD WILL BE DOMINATED BY A 500MB LOW PRESSURE SYSTEM
ORIENTED NEAR THE GREAT LAKES AND CENTRAL ONTARIO. STILL...BELIEVE
THAT THERE WILL BE MORE VARIABILITY THAN A SINGLE PARTLY CLOUDY
VALUE IN THE SKY COVER FOR DAYS 2 THROUGH 6...WITH LONG TERM
FORECAST GUIDANCE IN RELATIVELY GOOD SHAPE AND TRANSIENT SYSTEMS.
THE GFS SOLUTION WAS CONSIDERED AN OUTLIER FOR MUCH OF THIS
PERIOD...MAINLY THURSDAY ON...WITH ITS HANDLING OF THE MAIN
FEATURES.
BY 00Z WEDNESDAY...A COLD FRONT WILL BE KNOCKING AT OUR DOORSTEP.
THE EXACT TRACK OF THE NORTHERN MOST SURFACE LOW IS STILL A LITTLE
FUZZY...WITH THE NAM AND GFS BEING THE NORTHERN MOST SOLUTIONS AND
NO FORECAST SOLUTION BEING TOO FAR OFF. KEPT THE SLIGHT CHANCE OF
THUNDERSTORMS OVER THE CENTRAL AND EASTERN CWA. EXPECT THE COLD
FRONT TO SWEEP ACROSS THE CWA OVERNIGHT AND JUST TO THE EAST BY 15Z
WEDNESDAY. THIS SHOULD SHUT OFF MUCH OF THE PRECIPITATION...EXCEPT
FOR SOME POTENTIALLY LINGERING SHOWERS OR DRIZZLE ACTIVITY FAR WEST
WEDNESDAY PRIOR TO 18Z WEDNESDAY BEING HINTED AT BY BOTH THE GFS AND
ECMWF.
KEPT DRY WEATHER GOING A FEW HOURS LONGER...BEFORE ITS
REINTRODUCTION LATE THURSDAY NIGHT IN RESPONSE TO 500MB TROUGH
ROTATING THROUGH THE MEAN FLOW AND A WEAK COLD FRONT AT THE
SURFACE. WITH THE CENTER OF THE 500MB LOW OVER SW HUDSON
BAY...ADDITIONAL WAVES ARE EXPECTED TO ROTATE AROUND AND INTO THE
CWA FROM THE NW. THIS WILL KEEP UNSETTLED WEATHER IN THE FORECAST
THROUGH THE WEEKEND WITH THE CONTINUATION OF BELOW NORMAL
TEMPERATURES AND ABOVE NORMAL PRECIPITATION. THE EXACT TIMING OF
WAVES WILL LEAD TO A MODERATE CONFIDENCE LEVEL AT THIS TIME.
UTILIZED HPC GUIDANCE HEAVILY FOR DAYS 4/FRIDAY THROUGH 7/MONDAY
WHICH WAS MAINLY THE 00Z ECMWF WITH A FEW TWEAKS DUE TO UNCERTAINTY.
&&
.AVIATION (FOR THE 00Z TAF ISSUANCE)...
EXPECT VFR CONDITIONS TO PREVAIL AT KCMX/KSAW TONIGHT INTO EARLY TUE
AFTERNOON. MID CLOUDS HAVE SPREAD ACROSS THE AREA THIS EVENING IN A
STRONG WAA REGIME AS CLOUD BASES HAVE GENERALLY BEEN NO LOWER THAN
6KFT TONIGHT. THERE WAS A BRIEF SHRA AT KCMX WHICH LOWERED CIGS TO
2500 FT AND VSBY TO 5SM IN THE PAST HR...BUT CONDITIONS HAVE SINCE
POPPED BACK UP TO VFR AS SHRA PASSED TO THE NORTH. EXPECT GUSTY
WINDS TO DEVELOP TUE AHEAD OF APPROACHING LOW PRES. AS IS
TYPICAL...WINDS WILL BE STRONGER AT KSAW THAN KCMX IN SRLY FLOW.
WINDS SHOULD BEGIN GUSTING UPWARDS OF 25KT AT KSAW BY LATE MORNING.
MAY SEE EVEN HIGHER GUSTS DURING THE AFTN. AS COLD FRONT APPROACHES
WITH PLAINS SYSTEM...LOOK FOR RAIN TO BEGIN AT KCMX AROUND 20Z AND
OCCASIONALLY LOWER CIGS/VSBYS TO MVFR TOWARD EVENING.
&&
.MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)...
AS A HIGH PRES RIDGE OVER THE WRN GREAT LAKES SHIFTS E TONIGHT AND
LOW PRES DEVELOPS OVER MN...EXPECT ERLY WINDS TO VEER SE DURING THE
NIGHT. NE WINDS DURING THE EVENING OVER FAR WRN LAKE SUPERIOR WILL
LIKELY REACH THE 20-30KT RANGE. AS THE RIDGE SHIFTS TO THE LOWER
LAKES BY TUE EVENING AND THE LOW PRES LIFTS INTO ONTARIO TUE NIGHT...
S WINDS MAY INCREASE TO NEAR 30KT OVER ERN LAKE SUPERIOR TUE. STABLE
AIRMASS WITH WAA OVERTOP CHILLY MARINE LAYER SHOULD WORK TO KEEP
WINDS BELOW GALE. AS THE LOW CONTINUES NE TO JAMES BAY...LOOK FOR
WINDS TO SHIFT W...GENERALLY IN THE 20-25KT RANGE LATE TUE
NIGHT/WED. A HIGH PRES RIDGE WILL THEN BUILD INTO THE GREAT LAKES
THU...BRINGING A RETURN TO LIGHT WINDS. AS THE RIDGE GRADUALLY SINKS
S TO THE OHIO VALLEY FRI...A LOW PRES SYSTEM WILL TRACK SE FROM
CENTRAL CANADA INTO ONTARIO. THIS LOW WILL DROP INTO THE GREAT LAKES
REGION SAT...BRINGING THE POTENTIAL FOR 20-30KT NW WINDS.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
SYNOPSIS/SHORT TERM...ROLFSON
LONG TERM...KF
AVIATION...VOSS
MARINE...ROLFSON
AREA FORECAST DISCUSSION
NWS DETROIT/PONTIAC MI
747 PM EDT MON MAY 12 2008
.AVIATION...
STRATO CU DECK OVER SOUTHEAST MICHIGAN LOOKS LIKE IT WILL HOLD INTO
THIS EVENING AS THE SUN SETS. SOME BREAKS IN THE CLOUDS CAN BE SEEN
ACROSS THE NORTHERN THUMB AND THE HI RES NAM DEPICTS CLOUDS SLOWLY
SLIDING TO THE CENTRAL PART OF THE STATE AS LOW LEVEL WINDS VEER TO
THE EAST...BEFORE FINALLY SCATTERING OUT. SURFACE WINDS WILL
ACTUALLY BE QUITE LIGHT OVERNIGHT WHICH WILL SUPPORT SOME PATCHY FOG
AS THE SURFACE HIGH BUILDS AND DEWPOINTS LINGER IN THE 40S AFTER MIDNIGHT.
HOWEVER...SKIES WILL BE SLOWER TO CLEAR THAN EARLIER ANTICIPATED
WITH HIGH CLOUDS STARTING TO INCREASE AGAIN BY LATE TONIGHT...SO
HAVE TRENDED TOWARDS SLIGHTLY LESS BR/PATCHY FOG TOWARDS DAWN.
GOOD AVIATION CONDITIONS ARE EXPECTED ON TUESDAY WITH A SCATTERED
VFR DECK AND AND SOUTHERLY WINDS OF 8-14 KNOTS.
&&
.PREV DISCUSSION...ISSUED 325 PM EDT MON MAY 12 2008
SHORT TERM...TONIGHT
THE SURFACE RIDGE AXIS CURRENTLY ACROSS THE WESTERN GREAT LAKES IS
FORECAST TO TRACK ACROSS EASTERN MICHIGAN OVERNIGHT AS THE UPPER
RIDGE AMPLIFIES ACROSS LOWER MI. A 1746Z TAMDAR SOUNDING OUT OF DTW
SHOWED A NEARLY SATURATED LAYER FROM 900-800MB. A BKN TO OVC STRATO
CU FIELD HAS THEREFORE BEEN VERY PERSISTENT THIS AFTERNOON. BOUNDARY
LAYER CONVERGENCE ALONG A LINGERING SURFACE TROUGH EXTENDING FROM
LAKE ST CLAIR UP THROUGH THE THUMB HAS ACTUALLY BEEN SUSTAINING SOME
AREAS OF DRIZZLE ACROSS THE EASTERN HALF OF THE FORECAST AREA. THIS
CONVERGENCE SHOULD PERSIST FOR A FEW MORE HOURS BEFORE WEAKENING.
NORTHEASTERLY FLOW OFF LAKE HURON HAS BEEN KEEPING TEMPS STUCK IN
THE 40S ACROSS THE EASTERN THUMB. MEANWHILE...SOME PEAKS OF SUN HAVE
BEEN OCCURRING ACROSS THE FAR WESTERN SECTIONS OF THE FORECAST
AREA...CLOSER TO THE SURFACE RIDGE WHICH HAS ALLOWED TEMPS TO RISE
INTO THE MID TO UPPER 50S. THE CLOUDS ARE EXPECTED TO DIMINISH
DURING THE COURSE OF THE EVENING AS THE LOW LEVEL FLOW BECOMES MORE
ANTICYCLONIC AND DAYTIME HEATING WANES.
EXPECT SKIES TO BECOME MOSTLY CLEAR OVERNIGHT WITH WINDS BECOMING
LIGHT. WITH DEWPOINTS REMAINING IN THE 40S...CONDITIONS WILL BECOME
FAVORABLE FOR THE DEVELOPMENT OF SOME RADIATIONAL FOG AS MIN TEMPS
DROP DOWN TO AROUND 40. THE FOG POTENTIAL ACTUALLY LOOKS THE BEST
ACROSS THE THUMB REGION WHERE TEMP/DEWPOINT SPREADS ARE QUITE LOW.
THE MAIN LIMITING FACTOR WILL BE AN INCREASE IN THE SOUTHEASTERLY
GRADIENT LATE TONIGHT. SO WILL CARRY A MENTION OF JUST AREAS OR
PATCHY FOG OVERNIGHT.
LONG TERM...TUESDAY THROUGH NEXT MONDAY
SURFACE HIGH PRESSURE WILL MOVE TO OUR EAST ON TUESDAY AND START A
WELCOME WARMING TREND COMPARED TO THE LAST COUPLE OF DAYS. EVEN
AREAS CLOSER TO THE LAKES, EXCEPT POSSIBLY RIGHT NEAR THE SHORELINE,
WILL BE NOTICEABLY WARMER DESPITE AN ONSHORE SE WIND COMPONENT.
INLAND AREAS WILL MAKE A RUN AT LOWER 70S WITH THE HELP OF SUNSHINE
ONLY DISRUPTED BY SOME PATCHES OF HIGH CLOUDS AT TIMES. THESE CLOUDS
WILL MAKE IT INTO THE AREA AS DEBRIS FROM UPSTREAM CONVECTION
ASSOCIATED WITH THE NEXT SYSTEM DEVELOPING IN THE PLAINS. SOUTHERLY
FLOW AHEAD OF THIS FRONTAL SYSTEM WILL KEEP TEMPERATURES MILD
TUESDAY NIGHT WITH THE HELP OF THICKENING HIGH CLOUDS.
THE 12Z MODEL DATA INDICATES LOW LEVEL MOISTURE TRANSPORT RAMPING UP
CONSIDERABLY WITH THE LOW LEVEL JET LATER TUESDAY NIGHT. THIS LOOKS
GOOD JUDGING BY THE SURFACE PRESSURE PATTERN THAT SUGGESTS AN OPEN
SUPPLY OF GULF MOISTURE AVAILABLE TO THE FLOW. THIS MOISTURE WILL
HELP BOOST CONVECTIVE POTENTIAL WITH DEWPOINT SHOWN TO INCREASE UP
TO 10C NEAR 850 MB AS THE LOW LEVEL MOISTURE AXIS BUILDS INTO THE
REGION. ELEVATED INSTABILITY IS USUALLY ENHANCED BY NOCTURNAL LOW
LEVEL MOISTURE TRANSPORT COUPLED WITH DIURNAL COOLING NEAR THE TOP
OF THE TROPOSPHERE. AS A QUICK MEASURE OF ELEVATED INSTABILITY,
THE MODELS SHOW JUST MARGINALLY BELOW ZERO 850 MB LIFTED INDEX
BUT HAVE A GOOD HANDLE ON THE EXPECTED PATTERN OF SHOWERS AND
STORMS AHEAD OF THE COLD FRONT BY SUNRISE WEDNESDAY MORNING. THE
ADDITIONAL FORCING OF THE UPPER WAVE AND COLD FRONT DURING THE
DAYTIME ON WEDNESDAY FURTHER SUPPORTS CATEGORICAL POPS THAT WERE
ADDED IN OUR FORECAST CYCLE FROM EARLY THIS MORNING. SURFACE BASED
INSTABILITY IN BOTH THE GFS AND NAM IS QUITE MINIMAL WITH BARELY
ANY CAPE INDICATED IN THE DATA. THIS SEEMS REASONABLE AS THERE
WILL BE LITTLE OPPORTUNITY FOR AIR MASS RECOVERY BEFORE THE
FRONTAL PASSAGE. EVEN MODEST UPWARD ADJUSTMENTS SUPPORT JUST A
CHANCE OF THUNDERSTORMS WITH LITTLE OR NO WINDOW FOR SEVERE
WEATHER.
TIMING ON THE FRONTAL PASSAGE REMAINS FAST ENOUGH TO SCOUR THE
PRECIPITATION FROM OUR AREA STARTING WEDNESDAY NIGHT. THE CLEARING
TREND WILL ALSO BE PRONOUNCED DURING THE EVENING AS HIGH PRESSURE
BUILDS INTO THE REGION UNDER WEAK SUBSIDENCE ALOFT. THIS WILL
PRESENT RESPECTABLE RADIATIONAL COOLING TO CONSIDER FOR LOW
TEMPERATURES. A FEW UPPER 30S FOR OVERNIGHT LOWS WILL BE POSSIBLE
IN THE TYPICALLY COLDER LOCATIONS IN SE MICHIGAN, WHICH IS ON THE
LOW END OF THE LATEST TEMPERATURE GUIDANCE. COOL BUT DRY
CONDITIONS WILL THEN LAST THROUGH FRIDAY AS SE MICHIGAN WILL BE IN
BETWEEN SYSTEMS TO THE NORTH AND TO THE WEST IN A POSITIVELY
TILTED SPLIT FLOW UPPER LEVEL PATTERN. MODEL SOLUTIONS ALONG THESE
LINES HAVE BEEN MORE CONSISTENT OVER THE LAST FEW RUNS. WEAK SHORT
WAVE RIDGING OVER LOWER MICHIGAN WILL BE A RESULT OF RENEWED
HEIGHT FALLS OVER CENTRAL CANADA AND THE TRAILING SOUTHERN STREAM
TROUGH OVER THE SW STATES.
THERE IS VERY LITTLE CHANGE IN THE OUTLOOK FOR NEXT WEEKEND INTO
EARLY NEXT WEEK, OTHER THAN EVEN BETTER MODEL AGREEMENT ON THE LARGE
SCALE UPPER AIR PATTERN. THE LATEST GLOBAL MODELS CONTINUE TO
ADVERTISE A LARGE UPPER LOW OVER THE EASTERN HALF OF THE COUNTRY,
CENTERED OVER JAMES BAY, AND AS THE WESTERN PART OF A MATURE OMEGA
BLOCK OVER THE NORTHERN ATLANTIC. HIGHLY AMPLIFIED FLOW THEN EXTENDS
WESTWARD THROUGH THE NORTH PACIFIC. COLD AND DEEP NW FLOW AND A
SERIES OF SHORT WAVES FROM CENTRAL CANADA WILL KEEP UNSETTLED
CONDITIONS OVER THE GREAT LAKES WITH A CHANCE OF SHOWERS EACH DAY
AND BELOW NORMAL TEMPERATURES THROUGH EARLY NEXT WEEK.
MARINE...
WINDS WILL CONTINUE TO DECREASE THIS EVENING AS HIGH PRESSURE
ADVANCES INTO THE REGION. THE HIGH WILL MOVE TO THE EAST ON TUESDAY
AS A FRONTAL BOUNDARY MOVES INTO THE WESTERN GREAT LAKES. THIS FRONT
WILL TRACK ACROSS THE EASTERN GREAT LAKES WEDNESDAY AFTERNOON.
SOUTH-SOUTHEASTERLY WINDS WILL INCREASE BEGINNING TUES AFTERNOON
WITH THE APPROACH OF THIS FRONT. BY WEDNESDAY MORNING...WIND GUSTS
ARE EXPECTED TO RANGE FROM 20 TO 25 KNOTS ACROSS THE NEARSHORE
WATERS...WITH GUSTS APPROACHING 30 KNOTS ACROSS THE OPEN WATERS OF
LAKE HURON.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...NONE.
&&
$$
AVIATION.....KEC
SHORT TERM...SC
LONG TERM....BT
MARINE.......SC
YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE
AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
428 PM EDT MON MAY 12 2008
.SYNOPSIS...
WATER VAPOR IMAGERY AND RUC ANALYSIS SHOW AN UNSEASONABLY DEEP
MIDLEVEL LOW JUST OFF THE COAST OF THE MID ATLANTIC STATES...A RIDGE
OVER THE MISSISSIPPI VALLEY AND A TROF OVER THE NRN ROCKIES. PER 12Z
RAOBS...STRONG WAA/ISENTROPIC ASCENT PATTERN AHEAD OF THE NRN
ROCKIES TROF IS PRODUCING CONSIDERABLE MID/HIGH CLOUDS ACROSS THE
DAKOTAS/MN. REGIONAL RADARS SHOW RETURNS ACROSS ND/NRN MN...BUT SO
FAR...NOT TOO MUCH PCPN IS REACHING THE GROUND. MOST OF THE OBS
INDICATING PCPN ARE ACROSS FAR NRN MN WHERE SATURATION OF THE DRY
LOW-LEVELS CAN BE ACHIEVED.
&&
.SHORT TERM...
AREA OF STRONG WAA/ISENTROPIC ASCENT AS VIEWED ON THE 300K SFC WILL
SLIDE E ACROSS THE FCST AREA THIS EVENING AND THEN TEND TO LIFT NE
OVERNIGHT. AFTN TAMDAR SOUNDINGS FROM KSAW/KCMX SHOW QUITE A BIT OF
DRY AIR AT THE LOW-MID LEVELS...SUGGESTING IT SHOULD BE DIFFICULT TO
GET PCPN TO REACH THE GROUND. HOWEVER...GIVEN STRENGTH OF ASCENT
WITH 30-40KT WINDS ORIENTED NEARLY PERPENDICULAR TO ISOBARS...PCPN
CAN`T BE SIMPLY RULED OUT DUE TO WHAT LOOKS LIKE TOO MUCH DRY AIR AT
THE LWR LEVELS. LATEST RADAR IMAGERY SHOWS RETURNS ORGANIZING INTO
BANDS WITH THE NRN BAND ACROSS FAR NRN MN PRODUCING PCPN THAT IS
REACHING THE GROUND. WITH NAM/GFS GENERALLY SHOWING AN AREA OF
STRONGER ISENTROPIC ASCENT TO PUSH ACROSS WRN UPPER MI THIS
EVENING...IT IS THE SECOND BAND OF RADAR RETURNS CURRENTLY ACROSS
CNTRL MN INTO FAR NW WI THAT MAY DEVELOP SUFFICIENTLY TO RESULT IN
SOME -SHRA/SPRINKLES. FOR NOW...HAVE INCLUDED SLIGHT CHC POPS DURING
THE EVENING OVER ROUGHLY THE W 1/3RD OF UPPER MI. ONCE THAT PCPN
EXITS...DON`T EXPECT ANY ADDITIONAL PCPN UNTIL THE SHORTWAVE TROF
CURRENTLY OVER THE NRN ROCKIES APPROACHES TUE AFTN.
CONSENSUS OF 12Z MODEL GUIDANCE SUGGESTS GFS IS A LITTLE TOO FAST
WITH PROGRESSION OF SHORTWAVE TROF AND ASSOCIATED SFC LOW/COLD FRONT
TUE. HAVE THUS LEANED TOWARD THE NAM FOR THE DETAILS WHICH IS VERY
SIMLAR TO THE REGIONAL CANADIAN. AS SHORTWAVE TROF MOVES ACROSS THE
DAKOTAS TO MN BY TUE EVENING...A WELL-DEFINED SW-NE UPPER JET STREAK
ON THE FRONT SIDE OF THE TROF SHIFTS E...PLACING RIGHT ENTRANCE
UPPER DIVERGENCE OVER WRN UPPER MI DURING THE AFTN. AS THE FORCING
ACTS ON AXIS OF PRECIPITABLE WATER IN EXCESS OF 1 INCH LIFTING INTO
THE AREA...-SHRA INTENSITY/COVERAGE SHOULD IMPROVE WITH TIME. AFTER
A DRY MORNING...WILL TAKE SLIGHT CHC POPS OVER THE FAR W EARLY IN
THE AFTN INTO THE LIKELY CATEGORY BY MID/LATE AFTN. OPTED TO ONLY
BRING SLIGHT CHC POPS AS FAR E AS ABOUT IN KMQT/KIMT BY 00Z WED IN
LIGHT OF THE PREFERRED NAM/REGIONAL CANADIAN SOLUTIONS. EVEN THAT
MAY BE A BIT TOO FAR E. DEPENDING ON AMOUNT OF HEATING AND MIXING
DEPTH...IT SHOULD BE BREEZY DAY WITH 30-35KT AVBL TO BE MIXED DOWN.
SHOULD SEE SOME GUSTS IN THE 30-35MPH RANGE IN THE AREAS THAT
TYPICALLY SEE HIGHER WINDS IN SRLY FLOW (KSAW/KERY/GRAND MARAIS FOR
EXAMPLE). IF MORE HEATING OCCURS THAN CURRENTLY EXPECTED...WINDS
WILL BE A BIT STRONGER.
&&
.LONG TERM (TUESDAY NIGHT THROUGH MONDAY)...
MUCH OF THIS PERIOD WILL BE DOMINATED BY A 500MB LOW PRESSURE SYSTEM
ORIENTED NEAR THE GREAT LAKES AND CENTRAL ONTARIO. STILL...BELIEVE
THAT THERE WILL BE MORE VARIABILITY THAN A SINGLE PARTLY CLOUDY
VALUE IN THE SKY COVER FOR DAYS 2 THROUGH 6...WITH LONG TERM
FORECAST GUIDANCE IN RELATIVELY GOOD SHAPE AND TRANSIENT SYSTEMS.
THE GFS SOLUTION WAS CONSIDERED AN OUTLIER FOR MUCH OF THIS
PERIOD...MAINLY THURSDAY ON...WITH ITS HANDLING OF THE MAIN
FEATURES.
BY 00Z WEDNESDAY...A COLD FRONT WILL BE KNOCKING AT OUR DOORSTEP.
THE EXACT TRACK OF THE NORTHERN MOST SURFACE LOW IS STILL A LITTLE
FUZZY...WITH THE NAM AND GFS BEING THE NORTHERN MOST SOLUTIONS AND
NO FORECAST SOLUTION BEING TOO FAR OFF. KEPT THE SLIGHT CHANCE OF
THUNDERSTORMS OVER THE CENTRAL AND EASTERN CWA. EXPECT THE COLD
FRONT TO SWEEP ACROSS THE CWA OVERNIGHT AND JUST TO THE EAST BY 15Z
WEDNESDAY. THIS SHOULD SHUT OFF MUCH OF THE PRECIPITATION...EXCEPT
FOR SOME POTENTIALLY LINGERING SHOWERS OR DRIZZLE ACTIVITY FAR WEST
WEDNESDAY PRIOR TO 18Z WEDNESDAY BEING HINTED AT BY BOTH THE GFS AND
ECMWF.
KEPT DRY WEATHER GOING A FEW HOURS LONGER...BEFORE ITS
REINTRODUCTION LATE THURSDAY NIGHT IN RESPONSE TO 500MB TROUGH
ROTATING THROUGH THE MEAN FLOW AND A WEAK COLD FRONT AT THE
SURFACE. WITH THE CENTER OF THE 500MB LOW OVER SW HUDSON
BAY...ADDITIONAL WAVES ARE EXPECTED TO ROTATE AROUND AND INTO THE
CWA FROM THE NW. THIS WILL KEEP UNSETTLED WEATHER IN THE FORECAST
THROUGH THE WEEKEND WITH THE CONTINUATION OF BELOW NORMAL
TEMPERATURES AND ABOVE NORMAL PRECIPITATION. THE EXACT TIMING OF
WAVES WILL LEAD TO A MODERATE CONFIDENCE LEVEL AT THIS TIME.
UTILIZED HPC GUIDANCE HEAVILY FOR DAYS 4/FRIDAY THROUGH 7/MONDAY
WHICH WAS MAINLY THE 00Z ECMWF WITH A FEW TWEAKS DUE TO UNCERTAINTY.
&&
.AVIATION (FOR THE 18Z TAF ISSUANCE)...
EXPECT VFR CONDITIONS TO PREVAIL AT KCMX/KSAW THRU THIS FCST PERIOD.
HIGH AND THEN MID CLOUDS WILL BE SPREADING ACROSS THE AREA THIS AFTN
AND EVENING UNDER DEVELOPING STRONG WAA REGIME...BUT CLOUD BASES
SHOULD NOT FALL ANY LOWER THAN ABOUT 7KFT TONIGHT. DESPITE DRY
LOW-LEVELS...THE STRONG WAA MAY PRODUCE A FEW -SHRA/SPRINKLES
TONIGHT. IF ANY PCPN OCCURS...KCMX WOULD BE MORE LIKELY TO SEE IT
(VIS SHOULD REMAIN VFR). GUSTY WINDS WILL DEVELOP TUE AHEAD OF
APPROACHING LOW PRES. AS IS TYPICAL...WINDS WILL BE STRONGER AT KSAW
THAN KCMX IN SRLY FLOW. WINDS SHOULD BEGIN GUSTING UPWARDS OF 25KT
AT KSAW BY LATE MORNING. MAY SEE EVEN HIGHER GUSTS DURING THE AFTN.
&&
.MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)...
AS A HIGH PRES RIDGE OVER THE WRN GREAT LAKES SHIFTS E TONIGHT AND
LOW PRES DEVELOPS OVER MN...EXPECT ERLY WINDS TO VEER SE DURING THE
NIGHT. NE WINDS DURING THE EVENING OVER FAR WRN LAKE SUPERIOR WILL
LIKELY REACH THE 20-30KT RANGE. AS THE RIDGE SHIFTS TO THE LOWER
LAKES BY TUE EVENING AND THE LOW PRES LIFTS INTO ONTARIO TUE NIGHT...
S WINDS MAY INCREASE TO NEAR 30KT OVER ERN LAKE SUPERIOR TUE. STABLE
AIRMASS WITH WAA OVERTOP CHILLY MARINE LAYER SHOULD WORK TO KEEP
WINDS BELOW GALE. AS THE LOW CONTINUES NE TO JAMES BAY...LOOK FOR
WINDS TO SHIFT W...GENERALLY IN THE 20-25KT RANGE LATE TUE
NIGHT/WED. A HIGH PRES RIDGE WILL THEN BUILD INTO THE GREAT LAKES
THU...BRINGING A RETURN TO LIGHT WINDS. AS THE RIDGE GRADUALLY SINKS
S TO THE OHIO VALLEY FRI...A LOW PRES SYSTEM WILL TRACK SE FROM
CENTRAL CANADA INTO ONTARIO. THIS LOW WILL DROP INTO THE GREAT LAKES
REGION SAT...BRINGING THE POTENTIAL FOR 20-30KT NW WINDS.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
SYNOPSIS/SHORT TERM...ROLFSON
LONG TERM...KF
AVIATION...ROLFSON
MARINE...ROLFSON
AREA FORECAST DISCUSSION
NWS DETROIT/PONTIAC MI
325 PM EDT MON MAY 12 2008
.SHORT TERM...TONIGHT
THE SURFACE RIDGE AXIS CURRENTLY ACROSS THE WESTERN GREAT LAKES IS
FORECAST TO TRACK ACROSS EASTERN MICHIGAN OVERNIGHT AS THE UPPER
RIDGE AMPLIFIES ACROSS LOWER MI. A 1746Z TAMDAR SOUNDING OUT OF DTW
SHOWED A NEARLY SATURATED LAYER FROM 900-800MB. A BKN TO OVC STRATO
CU FIELD HAS THEREFORE BEEN VERY PERSISTENT THIS AFTERNOON. BOUNDARY
LAYER CONVERGENCE ALONG A LINGERING SURFACE TROUGH EXTENDING FROM
LAKE ST CLAIR UP THROUGH THE THUMB HAS ACTUALLY BEEN SUSTAINING SOME
AREAS OF DRIZZLE ACROSS THE EASTERN HALF OF THE FORECAST AREA. THIS
CONVERGENCE SHOULD PERSIST FOR A FEW MORE HOURS BEFORE WEAKENING.
NORTHEASTERLY FLOW OFF LAKE HURON HAS BEEN KEEPING TEMPS STUCK IN
THE 40S ACROSS THE EASTERN THUMB. MEANWHILE...SOME PEAKS OF SUN HAVE
BEEN OCCURRING ACROSS THE FAR WESTERN SECTIONS OF THE FORECAST
AREA...CLOSER TO THE SURFACE RIDGE WHICH HAS ALLOWED TEMPS TO RISE
INTO THE MID TO UPPER 50S. THE CLOUDS ARE EXPECTED TO DIMINISH
DURING THE COURSE OF THE EVENING AS THE LOW LEVEL FLOW BECOMES MORE
ANTICYCLONIC AND DAYTIME HEATING WANES.
EXPECT SKIES TO BECOME MOSTLY CLEAR OVERNIGHT WITH WINDS BECOMING
LIGHT. WITH DEWPOINTS REMAINING IN THE 40S...CONDITIONS WILL BECOME
FAVORABLE FOR THE DEVELOPMENT OF SOME RADIATIONAL FOG AS MIN TEMPS
DROP DOWN TO AROUND 40. THE FOG POTENTIAL ACTUALLY LOOKS THE BEST
ACROSS THE THUMB REGION WHERE TEMP/DEWPOINT SPREADS ARE QUITE LOW.
THE MAIN LIMITING FACTOR WILL BE AN INCREASE IN THE SOUTHEASTERLY
GRADIENT LATE TONIGHT. SO WILL CARRY A MENTION OF JUST AREAS OR
PATCHY FOG OVERNIGHT.
&&
.LONG TERM...TUESDAY THROUGH NEXT MONDAY
SURFACE HIGH PRESSURE WILL MOVE TO OUR EAST ON TUESDAY AND START A
WELCOME WARMING TREND COMPARED TO THE LAST COUPLE OF DAYS. EVEN
AREAS CLOSER TO THE LAKES, EXCEPT POSSIBLY RIGHT NEAR THE SHORELINE,
WILL BE NOTICEABLY WARMER DESPITE AN ONSHORE SE WIND COMPONENT.
INLAND AREAS WILL MAKE A RUN AT LOWER 70S WITH THE HELP OF SUNSHINE
ONLY DISRUPTED BY SOME PATCHES OF HIGH CLOUDS AT TIMES. THESE CLOUDS
WILL MAKE IT INTO THE AREA AS DEBRIS FROM UPSTREAM CONVECTION
ASSOCIATED WITH THE NEXT SYSTEM DEVELOPING IN THE PLAINS. SOUTHERLY
FLOW AHEAD OF THIS FRONTAL SYSTEM WILL KEEP TEMPERATURES MILD
TUESDAY NIGHT WITH THE HELP OF THICKENING HIGH CLOUDS.
THE 12Z MODEL DATA INDICATES LOW LEVEL MOISTURE TRANSPORT RAMPING UP
CONSIDERABLY WITH THE LOW LEVEL JET LATER TUESDAY NIGHT. THIS LOOKS
GOOD JUDGING BY THE SURFACE PRESSURE PATTERN THAT SUGGESTS AN OPEN
SUPPLY OF GULF MOISTURE AVAILABLE TO THE FLOW. THIS MOISTURE WILL
HELP BOOST CONVECTIVE POTENTIAL WITH DEWPOINT SHOWN TO INCREASE UP
TO 10C NEAR 850 MB AS THE LOW LEVEL MOISTURE AXIS BUILDS INTO THE
REGION. ELEVATED INSTABILITY IS USUALLY ENHANCED BY NOCTURNAL LOW
LEVEL MOISTURE TRANSPORT COUPLED WITH DIURNAL COOLING NEAR THE TOP
OF THE TROPOSPHERE. AS A QUICK MEASURE OF ELEVATED INSTABILITY,
THE MODELS SHOW JUST MARGINALLY BELOW ZERO 850 MB LIFTED INDEX
BUT HAVE A GOOD HANDLE ON THE EXPECTED PATTERN OF SHOWERS AND
STORMS AHEAD OF THE COLD FRONT BY SUNRISE WEDNESDAY MORNING. THE
ADDITIONAL FORCING OF THE UPPER WAVE AND COLD FRONT DURING THE
DAYTIME ON WEDNESDAY FURTHER SUPPORTS CATEGORICAL POPS THAT WERE
ADDED IN OUR FORECAST CYCLE FROM EARLY THIS MORNING. SURFACE BASED
INSTABILITY IN BOTH THE GFS AND NAM IS QUITE MINIMAL WITH BARELY
ANY CAPE INDICATED IN THE DATA. THIS SEEMS REASONABLE AS THERE
WILL BE LITTLE OPPORTUNITY FOR AIR MASS RECOVERY BEFORE THE
FRONTAL PASSAGE. EVEN MODEST UPWARD ADJUSTMENTS SUPPORT JUST A
CHANCE OF THUNDERSTORMS WITH LITTLE OR NO WINDOW FOR SEVERE
WEATHER.
TIMING ON THE FRONTAL PASSAGE REMAINS FAST ENOUGH TO SCOUR THE
PRECIPITATION FROM OUR AREA STARTING WEDNESDAY NIGHT. THE CLEARING
TREND WILL ALSO BE PRONOUNCED DURING THE EVENING AS HIGH PRESSURE
BUILDS INTO THE REGION UNDER WEAK SUBSIDENCE ALOFT. THIS WILL
PRESENT RESPECTABLE RADIATIONAL COOLING TO CONSIDER FOR LOW
TEMPERATURES. A FEW UPPER 30S FOR OVERNIGHT LOWS WILL BE POSSIBLE
IN THE TYPICALLY COLDER LOCATIONS IN SE MICHIGAN, WHICH IS ON THE
LOW END OF THE LATEST TEMPERATURE GUIDANCE. COOL BUT DRY
CONDITIONS WILL THEN LAST THROUGH FRIDAY AS SE MICHIGAN WILL BE IN
BETWEEN SYSTEMS TO THE NORTH AND TO THE WEST IN A POSITIVELY
TILTED SPLIT FLOW UPPER LEVEL PATTERN. MODEL SOLUTIONS ALONG THESE
LINES HAVE BEEN MORE CONSISTENT OVER THE LAST FEW RUNS. WEAK SHORT
WAVE RIDGING OVER LOWER MICHIGAN WILL BE A RESULT OF RENEWED
HEIGHT FALLS OVER CENTRAL CANADA AND THE TRAILING SOUTHERN STREAM
TROUGH OVER THE SW STATES.
THERE IS VERY LITTLE CHANGE IN THE OUTLOOK FOR NEXT WEEKEND INTO
EARLY NEXT WEEK, OTHER THAN EVEN BETTER MODEL AGREEMENT ON THE LARGE
SCALE UPPER AIR PATTERN. THE LATEST GLOBAL MODELS CONTINUE TO
ADVERTISE A LARGE UPPER LOW OVER THE EASTERN HALF OF THE COUNTRY,
CENTERED OVER JAMES BAY, AND AS THE WESTERN PART OF A MATURE OMEGA
BLOCK OVER THE NORTHERN ATLANTIC. HIGHLY AMPLIFIED FLOW THEN EXTENDS
WESTWARD THROUGH THE NORTH PACIFIC. COLD AND DEEP NW FLOW AND A
SERIES OF SHORT WAVES FROM CENTRAL CANADA WILL KEEP UNSETTLED
CONDITIONS OVER THE GREAT LAKES WITH A CHANCE OF SHOWERS EACH DAY
AND BELOW NORMAL TEMPERATURES THROUGH EARLY NEXT WEEK.
&&
.MARINE...
WINDS WILL CONTINUE TO DECREASE THIS EVENING AS HIGH PRESSURE
ADVANCES INTO THE REGION. THE HIGH WILL MOVE TO THE EAST ON TUESDAY
AS A FRONTAL BOUNDARY MOVES INTO THE WESTERN GREAT LAKES. THIS FRONT
WILL TRACK ACROSS THE EASTERN GREAT LAKES WEDNESDAY AFTERNOON.
SOUTH-SOUTHEASTERLY WINDS WILL INCREASE BEGINNING TUES AFTERNOON
WITH THE APPROACH OF THIS FRONT. BY WEDNESDAY MORNING...WIND GUSTS
ARE EXPECTED TO RANGE FROM 20 TO 25 KNOTS ACROSS THE NEARSHORE
WATERS...WITH GUSTS APPROACHING 30 KNOTS ACROSS THE OPEN WATERS OF
LAKE HURON.
&&
.PREV DISCUSSION...ISSUED 109 PM EDT MON MAY 12 2008
AVIATION...
A 1613Z TAMDAR SOUNDING OUT OF DTW SHOWS THE MOIST LAYER TO BE
ROUGHLY 2500 FT THICK. THUS SUSPECT IT WILL TAKE INTO THE EVENING
/22Z TO 00Z/ BEFORE THE EXTENSIVE MVFR STRATO CU FIELD IS ABLE TO
MIX OUT. THE APPROACHING SURFACE RIDGE AND LOSS OF DAYTIME HEATING
WILL CONTRIBUTE TO THE DIMINISHING CLOUDS THIS EVENING. WITH A
NORTHERLY COMPONENT TO THE SURFACE WIND...THE CLOUDS MAY BE ABLE TO
MIX OUT A COUPLE HOURS EARLIER AT MBS DUE TO THE SLIGHT DOWNSLOPE
COMPONENT OFF THE HIGHER TERRAIN OF CENTRAL MI.
THE LATE CLEARING WILL LIMIT THE AMOUNT OF MIXING DURING THE
AFTERNOON...WHICH SHOULD KEEP SURFACE DEWPOINTS IN THE 40S AT THE
TERMINALS. THIS WILL SET THE STAGE FOR SOME RADIATIONAL FOG
DEVELOPMENT OVERNIGHT AS THE SURFACE RIDGE MOVES OVERHEAD. THUS WILL
INTRODUCE SOME IFR AND MVFR VISIBILITIES AT THE TERMINALS LATE
TONIGHT INTO EARLY TUES MORNING.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...NONE.
&&
$$
SHORT TERM...SC
LONG TERM....BT
MARINE.......SC
AVIATION.....SC
YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE
AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).
AREA FORECAST DISCUSSION
NWS DETROIT/PONTIAC MI
109 PM EDT MON MAY 12 2008
.AVIATION...
A 1613Z TAMDAR SOUNDING OUT OF DTW SHOWS THE MOIST LAYER TO BE
ROUGHLY 2500 FT THICK. THUS SUSPECT IT WILL TAKE INTO THE EVENING
/22Z TO 00Z/ BEFORE THE EXTENSIVE MVFR STRATO CU FIELD IS ABLE TO
MIX OUT. THE APPROACHING SURFACE RIDGE AND LOSS OF DAYTIME HEATING
WILL CONTRIBUTE TO THE DIMINISHING CLOUDS THIS EVENING. WITH A
NORTHERLY COMPONENT TO THE SURFACE WIND...THE CLOUDS MAY BE ABLE TO
MIX OUT A COUPLE HOURS EARLIER AT MBS DUE TO THE SLIGHT DOWNSLOPE
COMPONENT OFF THE HIGHER TERRAIN OF CENTRAL MI.
THE LATE CLEARING WILL LIMIT THE AMOUNT OF MIXING DURING THE
AFTERNOON...WHICH SHOULD KEEP SURFACE DEWPOINTS IN THE 40S AT THE
TERMINALS. THIS WILL SET THE STAGE FOR SOME RADIATIONAL FOG
DEVELOPMENT OVERNIGHT AS THE SURFACE RIDGE MOVES OVERHEAD. THUS WILL
INTRODUCE SOME IFR AND MVFR VISIBILITIES AT THE TERMINALS LATE
TONIGHT INTO EARLY TUES MORNING.
&&
.PREV DISCUSSION...ISSUED 1037 AM EDT MON MAY 12 2008
UPDATE...
MID LEVEL DEFORMATION ASSOCIATED WITH THE UPPER LOW NOW OVER THE
MID ATLANTIC APPEARS TO HAVE SHIFTED EAST OF THE FORECAST AREA.
LINGERING LOW LEVEL MOISTURE AND BOUNDARY LAYER CONVERGENCE
HOWEVER IS MAINTAINING AREAS OF DRIZZLE ACROSS THE EASTERN 2/3RDS
OF SE MI...WITH SOME LIGHT SHOWERS LINGERING ALONG THE ST CLAIR
RIVER. MODEL SOUNDINGS SHOW THE BOUNDARY LAYER DRYING OUT SLIGHTLY
OVER THE NEXT TWO TO THREE HOURS WHICH SHOULD BRING THE DRIZZLE TO
AN END. SOME BREAKS IN THE CLOUDS OVER THE WESTERN PORTIONS OF THE
FORECAST AREA THIS MORNING HAVE QUICKLY FILLED IN WITH A BKN TO
OVC CU FIELD. THE 12Z SOUNDINGS OUT OF BOTH GRB AND APX SHOWED AN
INVERSION BASED AROUND 1000 FT AGL. LINGERING LOW LEVEL MOISTURE
OVER SE MI SHOULD CONTINUE TO SUSTAIN DIURNALLY ENHANCED CLOUDS
WELL INTO THE AFTERNOON...WITH BASES SLOWLY LIFTING AS DAYTIME
HEATING MIXES OUT THE SHALLOW INVERSION. STILL EXPECT A CLEARING
TREND LATE IN THE AFTERNOON INTO THE EVENING AS THE LOW LEVEL FLOW
BECOMES MORE ANTICYCLONIC.
TEMPS HAVE BEEN RUNNING 2 TO 5 DEGREES BELOW GUIDANCE THIS
MORNING...WITH 10 AM TEMPS STILL IN THE UPPER 40S. WILL ONLY
LOWER THE FORECAST MAX TEMPS A COUPLE DEGREES THOUGH AS ANY LATE
AFTERNOON SUNSHINE WOULD CAUSE A SHARP RISE IN TEMPS.
PREV DISCUSSION...ISSUED 339 AM EDT MON MAY 12 2008
SHORT TERM...TODAY
OCCLUDED SFC CYCLONE CONTINUING TO FILL AS IT ROTATES EAST ACROSS
OHIO EARLY THIS MORNING. MID LEVEL DEFORMATION AXIS REMAINS DRAPED
ACROSS SOUTHEAST LOWER MICHIGAN...MAINTAINING A BROAD AREA OF LIGHT
RAIN OVER THE AREA. BACK EDGE OF THE DEFORMATION PER LATEST WATER
VAPOR IMAGERY MAKING VERY SLOW PROGRESS EAST OF THE LAKE MICHIGAN
SHORELINE...AND THUS WILL LIKELY MAINTAIN AN INFLUENCE LOCALLY
THROUGH AT LEAST MIDDAY. LIGHT RAIN WILL SLOWLY TAPER OFF FROM
WEST TO EAST THIS MORNING AS THE DEEPER MOISTURE STRIPS AWAY. MODEL
SOUNDINGS/RH FIELDS STILL INDICATE PLENTY OF RESIDUAL LOW LEVEL
MOISTURE INTO THE AFTERNOON...AND EXPECT ANY GOOD CLEARING TO HOLD
OFF UNTIL EARLY EVENING WHEN WEAK HIGH PRESSURE/UPPER RIDGING
BUILDS IN. THE LACK OF SOLAR HEATING AND SLIGHT COLD AIR ADVECTION
UNDER A PREDOMINANT NORTH-NORTHEAST LOW LEVEL GRADIENT WILL LEAD
TO ANOTHER SEASONABLY COOL DAY. BASED ON PROGGED 850MB/LOW LEVEL
THICKNESS TRENDS...WILL SEE READINGS AROUND 10 DEGREES BELOW
NORMAL...WITH HIGHS IN THE MID/UPPER 50S (COOLEST WITHIN PORT
HURON TO BAD AXE CORRIDOR).
LONG TERM...TONIGHT THROUGH NEXT SUNDAY
MID/UPPER LEVEL HEIGHTS ARE RISING IN EARNEST THIS MORNING ACROSS
THE GREAT PLAINS AS LATEST WATER VAPOR IMAGERY DEPICTS COUPLED PEAK
MOVEMENT OF THE THE NORTHERN AND SOUTHERN STREAMS. THIS UPPER LEVEL
RIDGING AND ASSOCIATED LARGE SCALE SUBSIDENCE/SURFACE RIDGING WILL
ARRIVE THIS EVENING...IN TIME TO CUT THE RIBBON ON THE LONG TERM.
WITH A DECREASED SKY FRACTION OVERNIGHT AND A WANING EASTERLY WIND
EXPECT CHILLY CONDITIONS BY MORNING WITH FAVORABLE RADIATIVE
COOLING CONDITIONS. LOWS TONIGHT ARE EXPECTED TO FALL INTO THE
LOWER 40S FOR THE HEAT ISLAND WITH UPPER 30S POSSIBLE OUTSIDE OF
THE METRO. CONTINUED QUIET ON TUESDAY AS THE HEART OF THE RIDGE
SHELTERS SOUTHEASTERN MICHIGAN THROUGHOUT THE DAY. HIGH CLOUDS IN
ADVANCE OF THE NEXT SYSTEM SHOULD WAIT UNTIL THE EVENING. WITH THE
EXPECTED SUNSHINE AND AMOUNT OF WAA...TUESDAY WILL BE THE MOST
FAVORABLE OF THE EARLY WEEK DAYS AS HIGHS CLIMB TO NEAR 70
(NORMAL).
THE WALL OF MOISTURE ON RETURN FLOW AND IN ADVANCE OF THE NEXT LARGE
UPPER LEVEL TROUGH WILL ARRIVE THE LATTER HALF OF TUESDAY NIGHT.
ISENTROPIC LIFT ON THE 295/305K SURFACE INCREASES AHEAD OF THE COLD
FRONT AS THE WEDGE OF INCREASED THETA E SWEEPS ACROSS. GIVEN THE
PROXIMITY OF THE LLJ AND THE QUALITY OF LOW TO MIDLEVEL FRONTAL
CONVERGENCE HAVE GONE AHEAD AND INCREASED POPS WEDNESDAY TO
CATEGORICAL. GIVEN TIME OF DAY CONSIDERATIONS....A LACK OF STEEP
MIDLEVEL LAPSE RATES (MODEL SOUNDINGS SHOWING A SATURATED/SCHEME
CONTAMINATED COLUMN) STILL WILL NOT INCLUDE THUNDER. IT APPEARS A
FEW TENTHS OF WIDESPREAD QPF IS IN THE OFFING MAINLY BEFORE 18Z.
THE COLD FRONT WILL PASS THROUGH THE CWA DURING THE LATE MORNING
AND EARLY AFTERNOON HOURS FORCING A QUICK DRYING TREND. WITH A
MIXED AND RELATIVELY MOIST BOUNDARY LAYER TUESDAY NIGHT RAISED
MINS A FULL CATEGORY ABOVE GUIDANCE/MID 50S. AN EARLY TO MIDDAY
FRONTAL PASSAGE SOCKED IN CLOUD COVER WILL KEEP HIGHS WEDNESDAY
TEMPERED IN THE MID 60S.
COLD...POLAR HIGH PRESSURE WILL INFLUENCE THE REGION IN THE WAKE OF
THE MIDWEEK SYSTEM. BEYOND THURSDAY...THE FORECAST BECOMES MUDDLED
AS AN UPPER LEVEL VORTEX REGAINS CONTROL OF NORTHERN
ONTARIO/QUEBEC. WITH THE GREAT LAKES UNDER A MERGED
NORTHERN/SOUTHERN STREAM JET...TIMING OF PRECIPITATION IS EXTREMELY
TENUOUS. LEFT AS INHERITED.
MARINE...
PRESSURE GRADIENT WILL RELAX TODAY AS A LOW PRESSURE SYSTEM
MOVES TOWARD THE EAST COAST...AND WEAK HIGH PRESSURE MOVES OVER THE
GREAT LAKES. THIS WILL BRING A GRADUAL REDUCTION IN WINDS AND WAVE
HEIGHTS THROUGH THE DAY. AS THE NORTHERLY WINDS VEER MORE TOWARD
THE EAST THIS EVENING...WAVES MAY RESPOND ACCORDINGLY TO THE LONG
FETCH OVER THE MICHIGAN WATERS OF LAKE ERIE. HOWEVER...WAVE HEIGHTS
LOOK TO REMAIN BELOW ADVISORY CRITERIA. HIGH PRESSURE SLIDING EAST
MONDAY NIGHT WILL RESULT IN A DEVELOPING SOUTHERLY WIND FOR TUESDAY.
WINDS WILL STRENGTHEN TUESDAY NIGHT AND EARLY WEDNESDAY AS A COLD
FRONT MOVES THROUGH...WITH GUSTS UP TO 30 KNOTS OVER THE LAKE HURON
OPEN WATERS. THE LONGER FETCH MAY LEAD TO HIGHER WAVES OVER THE
OUTER SAGINAW BAY DURING THIS TIME.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...NONE.
&&
$$
AVIATION.....SC
UPDATE.......SC
SHORT TERM...MR
LONG TERM....CB
MARINE.......MR
YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE
AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).
AREA FORECAST DISCUSSION
NWS RALEIGH NC
735 PM EDT MON MAY 12 2008
.SYNOPSIS...A STRONG AREA OF LOW PRESSURE OFF THE DELMARVA COAST
WILL SLOWLY MOVE OFFSHORE TONIGHT. THIS WILL RESULT IN A DECREASE IN
CLOUDS AND WINDS AS THE NIGHT PROGRESSES. COOL HIGH PRESSURE WILL
BUILD INTO THE REGION TUESDAY... BRINGING MILD TEMPERATURES AND
ABUNDANT SUNSHINE.
&&
.NEAR TERM /THROUGH TUESDAY/...
AS OF 735 PM MONDAY...
CHANNELED VORTICITY AT H5 DIVING SOUTH ON THE BACK OF MATURE
OCCLUDED CYCLONE... WILL CONTINUE TO RESULT IN WEAK LIFT AND THREAT
FOR A FEW SHOWERS... WITH BANDS OF STRATOCUMULUS/NIMBOSTRATUS FOR
MUCH OF THE OVERNIGHT PERIOD (ESPECIALLY OVER THE EASTERN PIEDMONT
AND COASTAL PLAIN.
AN UPDATE HAS BEEN MADE TO THE FORECAST TO ACCOUNT FOR THE LIGHT
SHOWERS OVER THE NORTHERN PIEDMONT... MOVING QUICKLY SOUTH INTO THE
EASTERN PIEDMONT. A CHANCE POP FOR 0.01 QPF WILL BE FORECAST BETWEEN
800 PM AND 1000 PM... FROM NEAR ROXBORO THROUGH THE TRIANGLE TO NEAR
GOLDSBORO.
NO OTHER CHANGES AT THIS TIME.
&&
ABUNDANT STRATOCUMULUS ON THE BACKSIDE OF THE OCCLUDED CYCLONE OFF
THE DELMARVA COAST HAS GREATLY INHIBITED THE MIXING POTENTIAL TODAY.
AS A RESULT... TEMPS HAVE BEEN VERY SLOW TO CLIMB AND WINDS
GENERALLY HAVE NOT GUSTED NEAR AS HIGH AS THEY COULD UNDER BETTER
MIXING. AT TIMES WHEN THE SKIES HAVE SCATTERED SUFFICIENTLY... WE
HAVE SEEN PEAK WIND GUSTS OF 30-35 KT AT INT/GSO/FAY AND A FEW OTHER
SITES. HOWEVER... GUSTS GENERALLY HAVE BEEN BELOW 30 KT. IN
ADDITION... A 17Z RDU AMDAR SOUNDING SHOWS WINDS IN THE MIXED LAYER
HAVE DECREASED TO AROUND 30 KT. GIVEN THIS... HAVE DECIDED TO CANCEL
THE WIND ADVISORY EARLY. THERE WILL STILL BE OCCASIONAL GUSTS NEAR
OR JUST ABOVE 30 KT... PARTICULARLY IN AREAS THAT RECEIVE SOME SUN.
OTHERWISE... GUSTS SHOULD AVERAGE 20-25 KT FOR THE REST OF THE
AFTERNOON.
GUIDANCE IS IN GOOD AGREEMENT THAT THE DEEP LOW WILL MOVE FURTHER
OFFSHORE TONIGHT AS UPPER RIDGING TRIES TO BUILD IN FROM THE WEST.
WE SHOULD SEE A DECREASE IN CLOUD COVER TONIGHT AS WE LOSE THE STEEP
LOW LEVEL LAPSE RATES AND THE BEST 850-700 MB MOISTURE MOVES EAST OF
THE AREA. WINDS WILL ALSO SUBSIDE SOME AS THE PRESSURE GRADIENT
BEGINS TO RELAX. THERE APPEARS TO BE ENOUGH OF A GRADIENT IN THE
COASTAL PLAIN TO KEEP WINDS NEAR 10 KT FOR MUCH OF THE NIGHT...
WHILE IN THE WESTERN PIEDMONT... WINDS WILL LIKELY SETTLE CLOSER TO
5 KT BY EARLY MORNING. WHILE MOST OF THE AREA WILL REMAIN MIXED
OVERNIGHT... THE BEST COOLING POTENTIAL WILL BE IN THE WEST DUE TO
LIGHTER WINDS. 1000-850 MB THICKNESSES DROP TO NEAR 45M BELOW CLIMO
TOMORROW MORNING. THIS WOULD PLACE MOST OF THE AREA IN THE LOWER
40S. WILL FORECAST LOWS A LITTLE WARMER THAN THIS GIVEN THE STEADY
BREEZE OVERNIGHT. 44 WEST TO 47 EAST.
BY TOMORROW... THE UPPER LEVEL RIDGE AXIS WILL BE CENTERED ACROSS
THE GREAT LAKES DOWN TO THE NORTHERN GULF COAST. MEANWHILE... THE
DEEP TROUGH CONTINUES TO MOVE FURTHER OFFSHORE. THIS PLACES CENTRAL
NORTH CAROLINA INT A DEEP NORTHERLY FLOW THAT WILL USHER IN MUCH
DRIER AIR. A FANTASTIC DAY IS SETTING UP WITH SUNNY SKIES AND VERY
REASONABLE TEMPERATURES. LOW LEVEL THICKNESSES ARE STILL FORECAST TO
BE 20-30M BELOW NORMAL. WE WILL PROBABLY END UP A LITTLE WARMER THAN
THICKNESSES SUGGEST GIVEN DEEP MIXING UP TO 850 MB. LOCAL DRY
ADIABATIC TECHNIQUE YIELDS GENERALLY LOW 70S FOR THE FORECAST
AREA... WHICH IS ABOUT 5 DEGREES BELOW NORMAL. WINDS WILL BE A
LITTLE BREEZY FOR THE FIRST HALF OF THE DAY WITH 20-25 KT STILL
PRESENT IN THE MIXED LAYER. LIKELY TO SEE SOME GUSTS TO 20 KT AFTER
SUNRISE ONCE MIXING COMMENCES. WINDS SHOULD TAPER OFF IN THE
AFTERNOON AS WINDS ABOVE THE SURFACE DECREASE AND SFC HIGH PRESSURE
BUILDS OVERHEAD. -JFB/PWB
&&
.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
AS OF 230 PM MONDAY...
EXPECT CALM AND SEASONABLY COOL CONDITIONS TUESDAY NIGHT WITH BOTH
THE SURFACE HIGH AND MID LEVEL RIDGE AXIS OVERHEAD. WILL GO A BIT
UNDER MOS GUIDANCE LOWS... MAINLY 43-48. MINOR MID LEVEL
PERTURBATIONS ATTEMPT TO SCALE THE RIDGE LATE TUESDAY NIGHT THROUGH
WEDNESDAY BUT THESE WILL LIKELY BE THWARTED BY THE MID LEVEL RIDGE
WHICH RETAINS A SUFFICIENT AMPLITUDE TO HOLD ANY NOTABLE FORCING
MECHANISMS TO OUR NW THROUGH WEDNESDAY. BUT FORECAST SOUNDINGS DO
INDICATE INCREASING SATURATION ALOFT WITH CEILINGS LOWERING TO 12000
FT THROUGH THE DAY AND WEAK UPGLIDE OVER NW NC... AND THIS INCREASE
IN HIGH AND MID CLOUDS PRIMARILY IN THE NW CWA WILL BE REFLECTED IN
THE FORECAST. A DRY ADIABATIC THERMAL PROFILE THROUGH THE LOW LEVELS
SUPPORTS HIGHS OF 75-80 ON WEDNESDAY.
THE LARGE MID LEVEL VORTEX OVER THE NW ATLANTIC SHIFTS NORTHEASTWARD
WEDNESDAY/WEDNESDAY NIGHT IN RESPONSE TO A VORTICITY MAXIMUM
SWINGING AROUND THE BASE OF THE SEMI-PERMANENT HUDSON BAY VORTEX...
WHICH ALSO SERVES TO DAMPEN THE RIDGING OVER THE SOUTHEAST STATES AS
A COLD FRONT SLOWLY APPROACHES FROM THE NW. FORECAST DETAILS BECOME
PROBLEMATIC TO RESOLVE STARTING LATE WEDNESDAY INTO THURSDAY DUE TO
THE RAMPANT CONVECTIVE FEEDBACK PLAGUING BOTH THE NAM AND ESPECIALLY
IN THE GFS. A WEAK WARM FRONTAL FEATURE APPEARS TO SWEEP ENE THROUGH
NC LATE WEDNESDAY/WEDNESDAY NIGHT BUT WITH ONLY WEAK/ELEVATED
ENTROPIC UPGLIDE IN NW NC AND NO CONFIDENCE IN ANY MODELED MID
LEVEL PERTURBATION... WILL KEEP POPS AT JUST A SLIGHT CHANCE
WEDNESDAY NIGHT. EXPECT MILD LOWS OF 54-59 WITH CONSIDERABLE CLOUD
COVER.
THEN FOR THURSDAY... THE CLOSED MID LEVEL LOW OVER THE FAR SOUTHWEST
STATES STARTS TO LIFT OUT TO THE EAST. MODEL CONSENSUS OF IMPROVING
ISENTROPIC UPGLIDE AHEAD OF THE FRONT... INCREASINGLY CONFLUENT FLOW
IN THE LOW LEVELS... INCREASINGLY CYCLONIC MID LEVEL FLOW... THE
APPROACHING WARM FRONT FROM THE SSW... AND RISING PRECIPITABLE WATER
TO NEAR 175% OF NORMAL ALL NECESSITATE CHANCE POPS... HIGHER IN THE
S AND W AND LOWEST NE. EXPECT BELOW-NORMAL HIGHS OF 73-79. -GIH
&&
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
AS OF 310 PM MONDAY...
THE MEDIUM RANGE BEGINS WITH BROAD TROUGHING FROM THE HUDSON BAY
VORTEX THROUGH THE MIDWEST TO THE DESERT SOUTHWEST... AND FAST WSW
FLOW FROM THE CENTRAL/SRN PLAINS THROUGH THE CAROLINAS. THE ECMWF
AND GFS AGREE ON THE FRONT EXTENDING JUST NORTH AND WEST OF NC WITH
A LOW TRACKING INTO NE TN THEN NEAR THE NC/VA BORDER THURSDAY
NIGHT... ALTHOUGH THE GFS TAKES A MORE NORTHERLY TRACK ACROSS VA
WHILE THE ECMWF TRACK IS FARTHER SOUTH OVER NRN NC. WHILE THE ECMWF
IS GENERALLY PREFERRED OVER THE GFS DURING THE MEDIUM RANGE BASED ON
THE LATTER`S EARLIER CONVECTIVE FEEDBACK ISSUES... THE PRECISE
FRONTAL POSITION IS TOUGH TO PINPOINT AND IT MAY END UP FARTHER
NORTH LIKE THE GFS DEPICTS. EXPECT GOOD CHANCES FOR RAIN THURSDAY
NIGHT AS THE ECMWF SHOWS A 25-30 KT LOW LEVEL JET NOSING INTO NC
FROM THE SW. THE FRONT EASES TO OUR SOUTH ON FRIDAY AS MID LEVEL
SHORTWAVE TROUGHING SWINGS FROM NEBRASKA SE INTO THE LOWER
MISSISSIPPI VALLEY. HAVE HELD ONTO CHANCE POPS THROUGH FRIDAY WITH
MOSTLY CLOUDY SKIES. THE GFS PUSHES DRIER AND MORE STABLE AIR
SOUTHWARD INTO THE NORTHERN CWA... AND WHILE THIS MAY OR MAY NOT
OCCUR... HAVE GONE WITH SLIGHTLY LOWER POPS NORTH. THE
AFOREMENTIONED SHORTWAVE SWINGS THROUGH THE CAROLINAS FRIDAY NIGHT
AND THIS SHOULD PUSH THE FRONT FAR ENOUGH SOUTHEAST TO TAPER POPS
DOWN FRIDAY NIGHT THROUGH SATURDAY. EXPECT WELL BELOW NORMAL TEMPS
SATURDAY AS THICKNESSES DROP INTO THE 1350S.
SATURDAY NIGHT THROUGH MONDAY SHOULD BE RELATIVELY COOL FOR THIS
TIME OF YEAR GIVEN THE MEAN LARGE TROUGH THAT BECOMES ESTABLISHED
OVER EASTERN NORTH AMERICA. THE PERIODIC PASSAGE OF WEAK/FAST
SHORTWAVE TROUGHS DROPPING THROUGH THE MIDATLANTIC REGION SHOULD
KEEP SKIES AT LEAST PARTLY CLOUDY BUT THE LACK OF MOISTURE PRECLUDES
HAVING ANY POPS DURING THIS TIME. -GIH
&&
.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
AS OF 735 PM MONDAY...
VFR CONDITIONS EXPECTED THROUGH THE TAF PERIOD.
CHANNELED VORT ENERGY DIVING SOUTH ON THE BACK OF MATURE OCCLUDED
CYCLONE...WILL CONTINUE TO RESULT IN WEAK LIFT AND A CONTINUATION OF
BROKEN TO OVERCAST STRATOCUMULUS/NIMBOSTRATUS FOR MUCH OF THE
OVERNIGHT PERIOD... WITH A SCATTERING OUT OF THE LOW CLOUDS BETWEEN
09Z TO 12Z... AS DNVA OVERSPREADS THE AREA FROM THE NW...BEHIND
EXITING S/W ENERGY. -CBL
WINDS CONTINUE TO DIMINISH AS MIXED LAYER LOWERS WITH LOSS OF
HEATING. HOWEVER...A DECENT PRESSURE GRADIENT PERSISTS OVERNIGHT...
ESPECIALLY IN THE EAST TOWARD RWI. THIS WILL KEEP WINDS FROM GOING
COMPLETELY CALM OVERNIGHT... AVERAGING 5-10 KT AT INT/GSO/RDU/FAY
AND NEAR 10 KT MOST OF THE NIGHT AT RWI. WINDS WILL PICK BACK UP
AGAIN BY 14Z TUESDAY AS MIXING COMMENCES ONCE AGAIN. MIXED LAYER
WINDS STILL IN THE 20-25 KT RANGE... SO GUSTS OF 18-23 KT HAVE BEEN
INCLUDED IN THE TAFS... LOWEST GSO/INT AND HIGHEST FAY/RWI.
MVFR/IFR CONDITIONS IN SCATTERED SHOWERS AND THUNDERSTORMS ARE
POSSIBLE THURSDAY NIGHT INTO FRIDAY AHEAD OF THE NEXT FRONTAL
SYSTEM.-JFB
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...BLS
NEAR TERM...JFB/PWB
SHORT TERM...HARTFIELD
LONG TERM...HARTFIELD
AVIATION...CBL/JFB
AREA FORECAST DISCUSSION
NWS RALEIGH NC
315 PM EDT MON MAY 12 2008
.SYNOPSIS...A STRONG AREA OF LOW PRESSURE OFF THE DELMARVA COAST
WILL SLOWLY MOVE OFFSHORE TONIGHT. THIS WILL RESULT IN A DECREASE IN
CLOUDS AND WINDS AS THE NIGHT PROGRESSES. COOL HIGH PRESSURE BUILDS
INTO THE REGION TOMORROW... BRINGING ABOUT VERY COMFORTABLE
TEMPERATURES AND ABUNDANT SUNSHINE.
&&
.NEAR TERM /THROUGH TUESDAY/...
AS OF 245 PM MONDAY...
ABUNDANT STRATOCUMULUS ON THE BACKSIDE OF THE OCCLUDED CYCLONE OFF
THE DELMARVA COAST HAS GREATLY INHIBITED THE MIXING POTENTIAL TODAY.
AS A RESULT... TEMPS HAVE BEEN VERY SLOW TO CLIMB AND WINDS
GENERALLY HAVE NOT GUSTED NEAR AS HIGH AS THEY COULD UNDER BETTER
MIXING. AT TIMES WHEN THE SKIES HAVE SCATTERED SUFFICIENTLY... WE
HAVE SEEN PEAK WIND GUSTS OF 30-35 KT AT INT/GSO/FAY AND A FEW OTHER
SITES. HOWEVER... GUSTS GENERALLY HAVE BEEN BELOW 30 KT. IN
ADDITION... A 17Z RDU AMDAR SOUNDING SHOWS WINDS IN THE MIXED LAYER
HAVE DECREASED TO AROUND 30 KT. GIVEN THIS... HAVE DECIDED TO CANCEL
THE WIND ADVISORY EARLY. THERE WILL STILL BE OCCASIONAL GUSTS NEAR
OR JUST ABOVE 30 KT... PARTICULARLY IN AREAS THAT RECEIVE SOME SUN.
OTHERWISE... GUSTS SHOULD AVERAGE 20-25 KT FOR THE REST OF THE
AFTERNOON.
GUIDANCE IS IN GOOD AGREEMENT THAT THE DEEP LOW WILL MOVE FURTHER
OFFSHORE TONIGHT AS UPPER RIDGING TRIES TO BUILD IN FROM THE WEST.
WE SHOULD SEE A DECREASE IN CLOUD COVER TONIGHT AS WE LOSE THE STEEP
LOW LEVEL LAPSE RATES AND THE BEST 850-700 MB MOISTURE MOVES EAST OF
THE AREA. WINDS WILL ALSO SUBSIDE SOME AS THE PRESSURE GRADIENT
BEGINS TO RELAX. THERE APPEARS TO BE ENOUGH OF A GRADIENT IN THE
COASTAL PLAIN TO KEEP WINDS NEAR 10 KT FOR MUCH OF THE NIGHT...
WHILE IN THE WESTERN PIEDMONT... WINDS WILL LIKELY SETTLE CLOSER TO
5 KT BY EARLY MORNING. WHILE MOST OF THE AREA WILL REMAIN MIXED
OVERNIGHT... THE BEST COOLING POTENTIAL WILL BE IN THE WEST DUE TO
LIGHTER WINDS. 1000-850 MB THICKNESSES DROP TO NEAR 45M BELOW CLIMO
TOMORROW MORNING. THIS WOULD PLACE MOST OF THE AREA IN THE LOWER
40S. WILL FORECAST LOWS A LITTLE WARMER THAN THIS GIVEN THE STEADY
BREEZE OVERNIGHT. 44 WEST TO 47 EAST.
BY TOMORROW... THE UPPER LEVEL RIDGE AXIS WILL BE CENTERED ACROSS
THE GREAT LAKES DOWN TO THE NORTHERN GULF COAST. MEANWHILE... THE
DEEP TROUGH CONTINUES TO MOVE FURTHER OFFSHORE. THIS PLACES CENTRAL
NORTH CAROLINA INT A DEEP NORTHERLY FLOW THAT WILL USHER IN MUCH
DRIER AIR. A FANTASTIC DAY IS SETTING UP WITH SUNNY SKIES AND VERY
REASONABLE TEMPERATURES. LOW LEVEL THICKNESSES ARE STILL FORECAST TO
BE 20-30M BELOW NORMAL. WE WILL PROBABLY END UP A LITTLE WARMER THAN
THICKNESSES SUGGEST GIVEN DEEP MIXING UP TO 850 MB. LOCAL DRY
ADIABATIC TECHNIQUE YIELDS GENERALLY LOW 70S FOR THE FORECAST
AREA... WHICH IS ABOUT 5 DEGREES BELOW NORMAL. WINDS WILL BE A
LITTLE BREEZY FOR THE FIRST HALF OF THE DAY WITH 20-25 KT STILL
PRESENT IN THE MIXED LAYER. LIKELY TO SEE SOME GUSTS TO 20 KT AFTER
SUNRISE ONCE MIXING COMMENCES. WINDS SHOULD TAPER OFF IN THE
AFTERNOON AS WINDS ABOVE THE SURFACE DECREASE AND SFC HIGH PRESSURE
BUILDS OVERHEAD. -JFB
&&
.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
AS OF 230 PM MONDAY...
EXPECT CALM AND SEASONABLY COOL CONDITIONS TUESDAY NIGHT WITH BOTH
THE SURFACE HIGH AND MID LEVEL RIDGE AXIS OVERHEAD. WILL GO A BIT
UNDER MOS GUIDANCE LOWS... MAINLY 43-48. MINOR MID LEVEL
PERTURBATIONS ATTEMPT TO SCALE THE RIDGE LATE TUESDAY NIGHT THROUGH
WEDNESDAY BUT THESE WILL LIKELY BE THWARTED BY THE MID LEVEL RIDGE
WHICH RETAINS A SUFFICIENT AMPLITUDE TO HOLD ANY NOTABLE FORCING
MECHANISMS TO OUR NW THROUGH WEDNESDAY. BUT FORECAST SOUNDINGS DO
INDICATE INCREASING SATURATION ALOFT WITH CEILINGS LOWERING TO 12000
FT THROUGH THE DAY AND WEAK UPGLIDE OVER NW NC... AND THIS INCREASE
IN HIGH AND MID CLOUDS PRIMARILY IN THE NW CWA WILL BE REFLECTED IN
THE FORECAST. A DRY ADIABATIC THERMAL PROFILE THROUGH THE LOW LEVELS
SUPPORTS HIGHS OF 75-80 ON WEDNESDAY.
THE LARGE MID LEVEL VORTEX OVER THE NW ATLANTIC SHIFTS NORTHEASTWARD
WEDNESDAY/WEDNESDAY NIGHT IN RESPONSE TO A VORTICITY MAXIMUM
SWINGING AROUND THE BASE OF THE SEMI-PERMANENT HUDSON BAY VORTEX...
WHICH ALSO SERVES TO DAMPEN THE RIDGING OVER THE SOUTHEAST STATES AS
A COLD FRONT SLOWLY APPROACHES FROM THE NW. FORECAST DETAILS BECOME
PROBLEMATIC TO RESOLVE STARTING LATE WEDNESDAY INTO THURSDAY DUE TO
THE RAMPANT CONVECTIVE FEEDBACK PLAGUING BOTH THE NAM AND ESPECIALLY
IN THE GFS. A WEAK WARM FRONTAL FEATURE APPEARS TO SWEEP ENE THROUGH
NC LATE WEDNESDAY/WEDNESDAY NIGHT BUT WITH ONLY WEAK/ELEVATED
SENTROPIC UPGLIDE IN NW NC AND NO CONFIDENCE IN ANY MODELED MID
LEVEL PERTURBATION... WILL KEEP POPS AT JUST A SLIGHT CHANCE
WEDNESDAY NIGHT. EXPECT MILD LOWS OF 54-59 WITH CONSIDERABLE CLOUD
COVER.
THEN FOR THURSDAY... THE CLOSED MID LEVEL LOW OVER THE FAR SOUTHWEST
STATES STARTS TO LIFT OUT TO THE EAST. MODEL CONSENSUS OF IMPROVING
ISENTROPIC UPGLIDE AHEAD OF THE FRONT... INCREASINGLY CONFLUENT FLOW
IN THE LOW LEVELS... INCREASINGLY CYCLONIC MID LEVEL FLOW... THE
APPROACHING WARM FRONT FROM THE SSW... AND RISING PRECIPITABLE WATER
TO NEAR 175% OF NORMAL ALL NECESSITATE CHANCE POPS... HIGHER IN THE
S AND W AND LOWEST NE. EXPECT BELOW-NORMAL HIGHS OF 73-79. -GIH
&&
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
AS OF 310 PM MONDAY...
THE MEDIUM RANGE BEGINS WITH BROAD TROUGHING FROM THE HUDSON BAY
VORTEX THROUGH THE MIDWEST TO THE DESERT SOUTHWEST... AND FAST WSW
FLOW FROM THE CENTRAL/SRN PLAINS THROUGH THE CAROLINAS. THE ECMWF
AND GFS AGREE ON THE FRONT EXTENDING JUST NORTH AND WEST OF NC WITH
A LOW TRACKING INTO NE TN THEN NEAR THE NC/VA BORDER THURSDAY
NIGHT... ALTHOUGH THE GFS TAKES A MORE NORTHERLY TRACK ACROSS VA
WHILE THE ECMWF TRACK IS FARTHER SOUTH OVER NRN NC. WHILE THE ECMWF
IS GENERALLY PREFERRED OVER THE GFS DURING THE MEDIUM RANGE BASED ON
THE LATTER`S EARLIER CONVECTIVE FEEDBACK ISSUES... THE PRECISE
FRONTAL POSITION IS TOUGH TO PINPOINT AND IT MAY END UP FARTHER
NORTH LIKE THE GFS DEPICTS. EXPECT GOOD CHANCES FOR RAIN THURSDAY
NIGHT AS THE ECMWF SHOWS A 25-30 KT LOW LEVEL JET NOSING INTO NC
FROM THE SW. THE FRONT EASES TO OUR SOUTH ON FRIDAY AS MID LEVEL
SHORTWAVE TROUGHING SWINGS FROM NEBRASKA SE INTO THE LOWER
MISSISSIPPI VALLEY. HAVE HELD ONTO CHANCE POPS THROUGH FRIDAY WITH
MOSTLY CLOUDY SKIES. THE GFS PUSHES DRIER AND MORE STABLE AIR
SOUTHWARD INTO THE NORTHERN CWA... AND WHILE THIS MAY OR MAY NOT
OCCUR... HAVE GONE WITH SLIGHTLY LOWER POPS NORTH. THE
AFOREMENTIONED SHORTWAVE SWINGS THROUGH THE CAROLINAS FRIDAY NIGHT
AND THIS SHOULD PUSH THE FRONT FAR ENOUGH SOUTHEAST TO TAPER POPS
DOWN FRIDAY NIGHT THROUGH SATURDAY. EXPECT WELL BELOW NORMAL TEMPS
SATURDAY AS THICKNESSES DROP INTO THE 1350S.
SATURDAY NIGHT THROUGH MONDAY SHOULD BE RELATIVELY COOL FOR THIS
TIME OF YEAR GIVEN THE MEAN LARGE TROUGH THAT BECOMES ESTABLISHED
OVER EASTERN NORTH AMERICA. THE PERIODIC PASSAGE OF WEAK/FAST
SHORTWAVE TROUGHS DROPPING THROUGH THE MIDATLANTIC REGION SHOULD
KEEP SKIES AT LEAST PARTLY CLOUDY BUT THE LACK OF MOISTURE PRECLUDES
HAVING ANY POPS DURING THIS TIME. -GIH
&&
.AVIATION /19Z MONDAY THROUGH SATURDAY/...
AS OF 145 PM MONDAY...
VFR CONDITIONS EXPECTED THROUGH THE TAF PERIOD. STRONG NORTHWEST
WINDS WILL PERSIST THROUGH THE REST OF THE AFTERNOON AS A DEEP
CYCLONE OFF THE DELMARVA COAST ONLY GRADUALLY MOVES EAST. OCCASIONAL
GUSTS OF 30-35 KT POSSIBLE... BUT MOST GUSTS WILL BE IN THE 20-25KT
RANGE. THE HIGHER GUSTS WILL CAUSE SOME CROSSWIND IMPACTS AT THE
LOCAL TERMINALS. THE GUSTINESS WILL SUBSIDE THIS EVENING WITH THE
LOSS OF DEEP MIXING. A DECENT PRESSURE GRADIENT PERSISTS
OVERNIGHT... ESPECIALLY IN THE EAST TOWARD RWI. THIS WILL KEEP WINDS
FROM GOING COMPLETELY CALM OVERNIGHT... AVERAGING 5-10 KT AT
INT/GSO/RDU/FAY AND NEAR 10 KT MOST OF THE NIGHT AT RWI. WINDS WILL
PICK BACK UP AGAIN BY 14Z TUESDAY AS MIXING COMMENCES ONCE AGAIN.
MIXED LAYER WINDS STILL IN THE 20-25 KT RANGE... SO GUSTS OF 18-23
KT HAVE BEEN INCLUDED IN THE TAFS... LOWEST GSO/INT AND HIGHEST
FAY/RWI.
SCATTERED TO BROKEN STRATOCUMULUS WITH BASES OF 4-5 KFT WILL
DIMINISH TONIGHT AS THE BEST LOW LEVEL MOISTURE MOVES EAST OF THE
AREA. CLEAR SKIES ARE EXPECTED TOMORROW AS UPPER RIDGING BUILDS IN
FROM THE WEST AND A DEEP NORTHERLY FLOW THROUGH THE ATMOSPHERE
USHERS IN DRIER AIR.
MVFR/IFR CONDITIONS IN SCATTERED SHOWERS AND THUNDERSTORMS POSSIBLE
THURSDAY NIGHT INTO FRIDAY AHEAD OF THE NEXT FRONTAL SYSTEM.-JFB
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...BLS
NEAR TERM...JFB
SHORT TERM...HARTFIELD
LONG TERM...HARTFIELD
AVIATION...JFB
AREA FORECAST DISCUSSION
NWS SEATTLE WA
830 AM PDT SUN MAY 11 2008
.SYNOPSIS...A COOL UPPER TROUGH WILL PRODUCE SCATTERED SHOWERS AND
SUN BREAKS ACROSS WESTERN WASHINGTON TODAY. A WEAK RIDGE WILL BUILD
INTO THE AREA MONDAY FOR A GENERALLY DRY DAY...WITH MORNING CLOUDS
GIVING WAY TO SOME AFTERNOON SUNSHINE. A WARM FRONT WILL BRING A
CHANCE OF RAIN TUESDAY. A STRONG UPPER RIDGE WILL BUILD OVER THE
PACIFIC NORTHWEST FOR WARM SUNNY DAYS WEDNESDAY THROUGH FRIDAY.
&&
.SHORT TERM...COULD BE THE LAST DUSTING OF SNOW IN THE CASCADES DOWN
TO PASS LEVEL TODAY WITH A COOL UPPER LEVEL TROUGH OVER THE REGION
TODAY. A LITTLE NEW SNOW ON THE TREES ON THE PASS WEBCAMS...MAINLY
ABOVE 3000FT. AN ACARS FREEZING LEVEL OVER SEATTLE AT 8AM WAS
3200FT...WITH A 700MB TEMP OF -11C AND -29C AT 500MB. SO THERE IS
JUST A SLIGHT CHANCE OF A THUNDERSTORM TODAY IN THE UNSTABLE AIR
MASS...WILL WATCH THE RADAR ECHO TOPS TODAY. AT 8AM THE PSCZ ONLY
HAS SHOWERS WITH TOPS TO 10 OR 15KFT...BUT THE PSCZ WILL SHIFT SOUTH
INTO KING COUNTY BY AFTERNOON AND DAYTIME INSOLATION COULD HELP FIRE
OFF A THUNDERSTORM. WILL HANDLE THAT WITH A NOWCAST OR TWO LATER IF
IT HAPPENS. ZONE FORECASTS ARE IN THE BALLPARK WITH HIGHEST POPS IN
THE PSCZ/NORTH OF SEATTLE WITH SCATTERED SHOWERS ELSEWHERE. NOT MUCH
IN THE WAY OF SHOWERS OUTSIDE THE PSCZ...BUT THE HEATING OF THE DAY
SHOULD FIRE OFF SCATTERED SHOWERS JUST ABOUT ANYWHERE OUTSIDE THE
PSCZ IN THE AFTERNOON. THE NAM CONTINUES TO FORECAST DRY WEATHER
MONDAY AND MONDAY NIGHT AS A WEAK RIDGE BUILDS IN...AND A WARM FRONT
ON TUESDAY IS LOOKING INCREASINGLY WET IN THE MODELS SO WE PROBABLY
WILL NOT GET BY WITH JUST A BRUSH BY/CHANCE OF RAIN FORECAST FOR
THAT DAY. WILL PROBABLY MOVE THE POPS WAY UP FOR TUESDAY AND TUESDAY
NIGHT AND EVEN KEEP A CHANCE OF RAIN OR DRIZZLE IN THE FORECAST FOR
WEDNESDAY MORNING. SEEMS LATE IN THE YEAR FOR A WARM FRONT TO BE SO
WET...BUT THAT IS WHAT THE MODELS SHOW. I DO THINK THAT WITH HEIGHTS
RISING TO 580-585DAM WEDNESDAY AFTERNOON THAT THE PRECIP WILL DRY UP
AROUND NOON AND MAX TEMPS WILL SPIKE NICELY INTO THE LOWER TO MID
70S BEHIND THE WARM FRONT IN CLEARING SKIES WED AFTERNOON. 19
.LONG TERM...THE 06Z GFS KEEPS THE STRONG WARM UPPER RIDGE OVER THE
REGION THROUGH FRIDAY AND THEN WEAKENS IT AND SHIFTS IT INLAND
SUNDAY...WITH HEIGHTS FALLING TO ARND 576DAM SUNDAY. THAT SUGGESTS A
MARINE PUSH SATURDAY NIGHT. I EXPECT TO SHOW TWO VERY WARM DAYS
THURSDAY AND FRIDAY...THEN DROP TEMPS JUST A LITTLE SATURDAY...AND
FURTHER INTO SUNDAY AS IT BECOMES INCREASINGLY LIKELY THAT MARINE
AIR WILL HAVE COOLED OFF WRN WA. HAVE ALREADY STARTED TO PUSH THE
GRIDS THAT WAY SO ADJACENT OFFICES CAN SEE THAT...AND IF THE 12Z GFS
AND ECMWF AGREE MAY EVEN ADD FIVE DEGREES TO THE CURRENT MAX TEMP
FORECASTS FOR THU/FRI. 19
&&
.AVIATION....RADAR SHOWS THE PSCZ CURRENTLY LOCATED OVER SNOHOMISH
COUNTY WITH LITTLE MOVEMENT NOTED. MODELS SHIFT THE WLY 850 MB FLOW
MORE WNW-NW THROUGH THE DAY WHICH SHOULD ALLOW THE CONVERGENCE ZONE
TO SHIFT SLOWLY SWD...PROBABLY INTO NORTH KING COUNTY 18-20Z...AND
TO NEAR OR OVER THE KBFI/KSEA TERMINALS BY 22-24Z. THIS WILL CREATE
WIND SHIFT ISSUES AND TEMPO MVFR CONDS WITH HEAVIER RAIN BANDS. THE
PSCZ ZONE SHOULD WEAKEN AFTER MIDNIGHT BUT COULD LINGER NEAR THE
KBFI/KSEA TERMINALS OVERNIGHT. THE NEXT TAF ISSUANCE WILL REFLECT
THIS IDEA.
.SEA...THE PSCZ WILL LIKELY SAG SWD THROUGH THE DAY...REACHING THE
THE KSEA TERMINAL BETWEEN 22-24Z. SW WIND 6-10 KT....BECOMING
VARIABLE ARND 10 KT OR LESS 22Z...THEN N 4-8 KT AFTER 00Z. EXPECT
MVFR CONDS UNDER HEAVIER RAIN BANDS LATER TODAY AND TONIGHT. DTM
&&
.MARINE...SLY GRADIENTS OVER THE INLAND WATERS ARE WEAKENING THIS
MORNING...BUT MODERATELY STRONG ONSHORE FLOW WILL CONTINUE TO
PRODUCE WLY SMALL CRAFT WINDS THROUGH THE STRAIT TODAY. WILL DROP
ADVISORIES FOR ADMIRALTY/PUGET SOUND. SEAS WILL BE COMING UP TO 10
FEET OR SO ON THE COASTAL WATERS THIS AFTERNOON AS WINDS ARE
DECREASING. GRAYS HARBOR BAR CONDITIONS BECOMING ROUGH DURING THE
EBBS. DTM
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
.SMALL CRAFT ADVISORY FOR THE COAST...AND STRAIT OF JUAN DE FUCA.
.SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR.
$$
WEATHER.GOV/SEATTLE
AREA FORECAST DISCUSSION
NWS HONOLULU HI
950 AM HST MON MAY 12 2008
.SYNOPSIS...TRADE WINDS WILL CONTINUE TO WEAKEN...WITH LIGHT AND
VARIABLE WINDS PERSISTING OVER MOST AREAS FROM TUESDAY THROUGH
FRIDAY. WITH THE LIGHT WINDS...CLOUDS AND A FEW SHOWERS WILL DEVELOP
OVER THE INTERIOR AND UPSLOPE AREAS DURING THE AFTERNOONS AND
EVENINGS...WITH CLEAR AND COOL NIGHTS AND MORNINGS. EXPECT HAZY
CONDITIONS AS WELL...WITH VOLCANIC EMISSIONS FROM THE BIG ISLAND
STAGNATING OVER THE STATE.
&&
.DISCUSSION...CURRENTLY A 1028 MB HIGH IS LOCATED FAR NORTHEAST OF
THE STATE...WITH A RIDGE THAT EXTENDS WEST-SOUTHWEST FROM IT/S
CENTER...THAT IS CURRENTLY LOCATED ABOUT 325 MILES NORTH OF KAUAI.
DESPITE A MORNING QUIKSCAT PASS THAT INDICATES MODERATE TRADE WINDS
OVER ISLAND WATERS...WINDS OVER LAND HAVE TRENDED TOWARD BEING LIGHT
AND VARIABLE OVERNIGHT. A DEVELOPING 996 MB LOW IS LOCATED NEAR 39N
179W...AND IS FORECAST TO EXPLOSIVELY DEVELOP AND MOVE RAPIDLY
NORTHEAST OVER THE NEXT 24 HOURS. HIGH CLOUD MOTIONS OVER THE
TROPICAL CENTRAL NORTH PACIFIC HELP TO OUTLINE A BROAD TROPICAL
UPPER TROPOSPHERIC TROUGH /TUTT/ THAT IS EAST-WEST ORIENTED WITH ITS
AXIS SOUTH OF THE ISLANDS ALONG 15N. WITHIN THIS TROUGH A WEAK LOW
ALOFT IS EMBEDDED NEAR 23N 153W...MOVING SOUTHWARD NEAR 15 MPH.
ALTHOUGH ALREADY WEAKENING...TRADE WINDS WILL BE HERE TODAY
/BARELY/...AND GONE TOMORROW...TAKING THE REMAINDER OF THE WORK
WEEK OFF. THE SURFACE RIDGE WILL BE SHUNTED SOUTHWARD IN RESPONSE TO
THE UNSEASONABLY STRONG LOW DEVELOPING TO OUR NORTHWEST...AND IT/S
ASSOCIATED FRONT THAT WILL APPROACH FROM THE NORTHWEST. BY TUESDAY
AFTERNOON...THE RIDGE WILL BE ABOUT 100 MILES NORTH OF KAUAI...AND
WILL MOVE SOUTH TO THE BIG ISLAND BY WEDNESDAY...WHERE IT WILL
REMAIN UNTIL FRIDAY. WITH THE RIDGE IN THIS POSITION...MOST ISLANDS
WILL BE RULED BY A LAND/SEA BREEZE WIND REGIME. THIS WEATHER PATTERN
OF MOSTLY CLEAR AND COOL NIGHTS WITH CLOUDS AND SHOWERS DEVELOPING
UPSLOPE AND OVER INTERIOR AREAS DURING AFTERNOONS AND EVENINGS WILL
PREVAIL OVER MOST ISLANDS FROM TUESDAY THROUGH THURSDAY. KAUAI WILL
BE FAR ENOUGH NORTH OF THE RIDGE AXIS THAT IT WILL EXPERIENCE A
MODIFIED LAND/SEA BREEZE PATTERN...AS WEAKLY CONVERGENT LIGHT TO
MODERATE SOUTHWEST WINDS DRIVE THE DEVELOPMENT OF A FEW SHOWERS.
THE FRONT WILL STALL AND WEAKEN JUST TO THE NORTHWEST OF KAUAI ON
THURSDAY...BUT A SHORTWAVE DIGGING INTO THE LONGWAVE POSITION NORTH
OF THE ISLANDS ON FRIDAY WILL REACTIVATE THE BOUNDARY...KEEPING THE
SURFACE RIDGE OVER THE ISLANDS. AS THE BOUNDARY GRADUALLY DISSIPATES
THIS WEEKEND...THE HIGH PRESSURE RIDGE IS STILL EXPECTED TO SLOWLY
SHIFT NORTH OF THE ISLANDS SATURDAY AND SUNDAY...ALLOWING TRADE
WINDS...AS WELL AS MORE TYPICAL TRADE WIND WEATHER...TO RETURN.
THE UPPER LOW CURRENTLY EAST-NORTHEAST OF THE ISLANDS HAS LED TO A
WEAKENING OF THE SUBSIDENCE INVERSION...AS SEEN IN 12Z BALLOON
SOUNDINGS AND A 16Z AIRCRAFT SOUNDING OUT OF PHKO. THIS LOW ALOFT
WILL LINGER JUST EAST OF THE ISLANDS THROUGH TUESDAY BEFORE MOVING
NORTHEAST AND ALLOWING MID AND UPPER LEVEL RIDGING TO BUILD FROM THE
NORTHWEST...WHICH WILL RESULT IN A BREAKDOWN OF THE TUTT. THIS RIDGE
WILL SUPPORT A RELATIVELY STABLE AIR MASS...WITH RAINFALL AMOUNTS
ON THE LIGHTER SIDE. WITH THE LOW AROUND TODAY...HAVE ALLOWED FOR
THE DEVELOPMENT OF A FEW HEAVY SHOWERS OVER THE KONA SLOPES THIS
AFTERNOON. WILL WAIT TO SEE HOW THINGS GO TODAY BEFORE DOING THE
SAME FOR TOMORROW. OVERALL THOUGH...MOST AREAS WILL BE ON THE DRIER
SIDE THIS WEEK.
WITH THE RIDGE NEAR THE BIG ISLAND...EMISSIONS FROM PUU OO AND
HALEMAUMAU WILL STAGNATE NEAR THEIR SOURCES. HOWEVER...THE LIGHT
LOW-LEVEL SOUTHERLY WIND FLOW WILL ALSO SERVE TO SPREAD THE VOG TO
OTHER AREAS ON THE BIG ISLAND...AS WELL AS TO THE REST OF THE
ISLANDS...IN THE COMING DAYS.
&&
.MARINE...
THE EXPLOSIVELY DEVELOPING LOW PRESSURE SYSTEM TO THE NORTHWEST...
ALTHOUGH MOVING RAPIDLY NORTHEAST...WILL GENERATE SIGNIFICANT
NORTHWEST SWELL THAT WILL LIKELY BRING ADVISORY LEVEL SURF TO MOST
NORTH AND WEST FACING SHORES BY THURSDAY. THIS SWELL WILL GRADUALLY
SUBSIDE FRIDAY AND SATURDAY.
&&
.HFO WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
BIRCHARD
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