AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
600 PM PDT WED MAR 18 2009
.SYNOPSIS...HIGH PRESSURE WILL KEEP THE WEATHER FAIR AND MILD
THROUGH THURSDAY EXCEPT FOR COASTAL LOW CLOUDS AND FOG MAINLY DURING
THE NIGHTS AND MORNINGS. LOW PRESSURE WILL BRING COOLER WEATHER WITH
WIND...CLOUDS AND A CHANCE OF SHOWERS OVER THE WEEKEND.
&&
.DISCUSSION...FOR SOUTHWEST CALIFORNIA INCLUDING SAN DIEGO...
ORANGE...SOUTHWEST SAN BERNARDINO AND WEST RIVERSIDE COUNTIES.
SKIES REMAIN CLEAR TODAY EXCEPT FOR AREAS OF FOG ON THE COAST. THE
COASTAL FOG PATTERN WILL BE MUCH THE SAME TONIGHT...EXCEPT WITH
EARLIER ONSET. DENSE FOG MAY BECOME WIDESPREAD NEAR THE COAST
TONIGHT. ON THURSDAY A WEAK SHORTWAVE WILL MOVE INTO SOCAL AND START
THE COOLING TREND INLAND. IT WILL ALSO DEEPEN THE MARINE LAYER
THURSDAY NIGHT AND FRIDAY MORNING. THEN OUR ATTENTION TURNS TO THE
DEEP LOW PRESSURE TROUGH OVER THE WEEKEND. IT WILL INITIALLY DEEPEN
THE MARINE LAYER FURTHER ON SATURDAY MORNING...THEN IT WILL BUST UP
THE INVERSION SATURDAY AFTERNOON. THE TROUGH WILL ALSO TIGHTEN
THE SURFACE PRESSURE GRADIENTS AND INCREASE THE WINDS ALOFT SATURDAY
AFTERNOON...TRANSLATING INTO QUITE WINDY WEATHER ESPECIALLY IN THE
MOUNTAINS AND DESERTS. ENOUGH ENERGY AND RISING MOTION WILL SQUEEZE
OUT SOME SHOWERS FROM THE MARGINAL MOISTURE FIELD SUNDAY
MORNING...BUT NOT IN THE LOWER DESERT. THAT WILL MEAN A BIT OF SNOW
IN THE MOUNTAINS TOO. IT WILL BE COOL AND BLUSTERY LATER SATURDAY
THROUGH SUNDAY MORNING...AND IT WILL BE SUNDAY NIGHT BEFORE THE
WINDS CALM DOWN. THE SYSTEM MOVES OUT LATE SUNDAY...BUT SHORTWAVES
IN THE WESTERN INTERIOR MONDAY AND TUESDAY WILL PREVENT A HIGH
PRESSURE RIDGE FROM BUILDING VERY RAPIDLY...AND SLOW DOWN THE
WARMING TREND. EVENTUALLY THE RIDGE APPEARS TO PREVAIL AND BY
WEDNESDAY TEMPERATURES SHOULD BE BACK TO NEAR NORMAL.
&&
.AVIATION...
181930Z...LATE MORNING MDCRS SOUNDINGS INDICATE THE MARINE LAYER
DEPTH WAS AROUND 800 FEET. LITTLE CHANGE IS EXPECTED IN THE MARINE
LAYER DEPTH THROUGH THURSDAY. SOME DEEPENING IS EXPECTED THURSDAY
NIGHT INTO FRIDAY MORNING. AREAS OF STRATUS/FOG ALONG THE IMMEDIATE
COAST COULD IMPACT THE COASTAL AIRPORTS SUCH AS KSAN...KCRQ AND AT
ANY TIME AFTER SUNSET BUT MORE LIKELY BETWEEN MIDNIGHT AND SUNRISE
ON THURSDAY. KSNA COULD RECEIVE LIFR CONDITIONS BEFORE
SUNRISE...ALSO. STRATUS/FOG SHOULD BREAK UP ON THURSDAY BETWEEN 16Z
AND 18Z.
ABOVE THE MARINE LAYER...A MOSTLY CLEAR SKY WITH UNRESTRICTED
VISIBILITIES IS EXPECTED THROUGH THURSDAY. HORTON
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
DENSE FOG ADVISORY FOR THE COASTAL AREAS AND SAN DIEGO INLAND
VALLEYS TONIGHT UNTIL 10 AM PDT THURSDAY MORNING.
&&
$$
PUBLIC...MM/ATKIN
AVIATION...HORTON
AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
200 PM PDT WED MAR 18 2009
.SYNOPSIS...HIGH PRESSURE WILL KEEP THE WEATHER FAIR AND MILD
THROUGH THURSDAY EXCEPT FOR COASTAL LOW CLOUDS AND FOG MAINLY DURING
THE NIGHTS AND MORNINGS. LOW PRESSURE WILL BRING COOLER WEATHER WITH
WIND...CLOUDS AND A CHANCE OF SHOWERS OVER THE WEEKEND.
&&
.DISCUSSION...FOR SOUTHWEST CALIFORNIA INCLUDING SAN DIEGO...
ORANGE...SOUTHWEST SAN BERNARDINO AND WEST RIVERSIDE COUNTIES.
SKIES REMAIN CLEAR TODAY EXCEPT FOR AREAS OF FOG ON THE COAST. THE
COASTAL FOG PATTERN WILL BE MUCH THE SAME TONIGHT...EXCEPT WITH
EARLIER ONSET. DENSE FOG MAY BECOME WIDESPREAD NEAR THE COAST
TONIGHT. ON THURSDAY A WEAK SHORTWAVE WILL MOVE INTO SOCAL AND START
THE COOLING TREND INLAND. IT WILL ALSO DEEPEN THE MARINE LAYER
THURSDAY NIGHT AND FRIDAY MORNING. THEN OUR ATTENTION TURNS TO THE
DEEP LOW PRESSURE TROUGH OVER THE WEEKEND. IT WILL INITIALLY DEEPEN
THE MARINE LAYER FURTHER ON SATURDAY MORNING...THEN IT WILL BUST UP
THE INVERSION SATURDAY AFTERNOON. THE TROUGH WILL ALSO TIGHTEN
THE SURFACE PRESSURE GRADIENTS AND INCREASE THE WINDS ALOFT SATURDAY
AFTERNOON...TRANSLATING INTO QUITE WINDY WEATHER ESPECIALLY IN THE
MOUNTAINS AND DESERTS. ENOUGH ENERGY AND RISING MOTION WILL SQUEEZE
OUT SOME SHOWERS FROM THE MARGINAL MOISTURE FIELD SUNDAY
MORNING...BUT NOT IN THE LOWER DESERT. THAT WILL MEAN A BIT OF SNOW
IN THE MOUNTAINS TOO. IT WILL BE COOL AND BLUSTERY LATER SATURDAY
THROUGH SUNDAY MORNING...AND IT WILL BE SUNDAY NIGHT BEFORE THE
WINDS CALM DOWN. THE SYSTEM MOVES OUT LATE SUNDAY...BUT SHORTWAVES
IN THE WESTERN INTERIOR MONDAY AND TUESDAY WILL PREVENT A HIGH
PRESSURE RIDGE FROM BUILDING VERY RAPIDLY...AND SLOW DOWN THE
WARMING TREND. EVENTUALLY THE RIDGE APPEARS TO PREVAIL AND BY
WEDNESDAY TEMPERATURES SHOULD BE BACK TO NEAR NORMAL.
&&
.AVIATION...
181930Z...LATE MORNING MDCRS SOUNDINGS INDICATE THE MARINE LAYER
DEPTH WAS AROUND 800 FEET. LITTLE CHANGE IS EXPECTED IN THE MARINE
LAYER DEPTH THROUGH THURSDAY. SOME DEEPENING IS EXPECTED THURSDAY
NIGHT INTO FRIDAY MORNING. AREAS OF STRATUS/FOG ALONG THE IMMEDIATE
COAST COULD IMPACT THE COASTAL AIRPORTS SUCH AS KSAN...KCRQ AND AT
ANY TIME AFTER SUNSET BUT MORE LIKELY BETWEEN MIDNIGHT AND SUNRISE
ON THURSDAY. KSNA COULD RECEIVE LIFR CONDITIONS BEFORE
SUNRISE...ALSO. STRATUS/FOG SHOULD BREAK UP ON THURSDAY BETWEEN 16Z
AND 18Z.
ABOVE THE MARINE LAYER...A MOSTLY CLEAR SKY WITH UNRESTRICTED
VISIBILITIES IS EXPECTED THROUGH THURSDAY. HORTON
&&
.SGX WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
PUBLIC...MM
AVIATION...HORTON
AREA FORECAST DISCUSSION
NWS COLUMBIA SC
533 AM EDT TUE MAR 17 2009
.SYNOPSIS...
HIGH PRESSURE WILL BUILD INTO THE REGION TODAY THROUGH WEDNESDAY.
A COLD FRONT WILL MOVE THROUGH THE AREA THURSDAY WITH A SLIGHT
CHANCE OF SHOWERS.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
DRY AIR PENETRATED WELL INTO THE CAE CWA BY 5 AM THIS MORNING.
IN ADDITION...WINDS HAVE BECOME NORTHWEST 4-5 MPH. THIS HELPED TO
BREAK UP THE LOW CLOUDS AND FOG. CONSEQUENTLY...CAE CANCELLED THE
DENSE FOG ADVISORY. UPDATED PRODUCTS TO FOLLOW VERY SOON.
PREVIOUS DISCUSSION:
RECENT RAINFALL AND A SATURATED ATMOSPHERE WILL COMBINE TO
PRODUCE DENSE FOG OVER THE AREA THIS MORNING. THERE IS A DENSE FOG
ADVISORY OUT UNTIL 9 AM. DRIER AIR IS EXPECTED TO FILTER INTO THE
REGION AROUND 8 AM AND COULD ACTUALLY BREAK UP THE FOG BEFORE 9
AM. BUT FOR TIME BEING WILL KEEP ADVISORY OUT UNTIL 9 AM.
OTHERWISE HIGH PRESSURE WILL BUILD OVER THE AREA LATER THIS
MORNING AND TODAY. THIS WILL BRING IN DRIER AIR. IT WILL BE WARMER
WITH SUNSHINE THIS AFTERNOON AND HIGHS IN THE MID TO UPPER 60S.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY/...
IN GOOD AGREEMENT WITH MODELS SHOWING HIGH PRESSURE OVER THE AREA
TONIGHT AND WEDNESDAY. HIGH SHIFTS TO THE EAST WEDNESDAY NIGHT AS
A COLD FRONT HEADS TOWARD THE REGION THURSDAY. LIMITED MOISTURE
WITH SYSTEM BUT STILL ENOUGH TO KEEP THE SLIGHT CHANCE OF SHOWERS
ON THURSDAY. WARMER AHEAD OF FRONT WITH HIGHS IN THE LOWER 70S
WEDNESDAY AND LOWER TO MID 7OS THURSDAY. NIGHTTIME LOWS IN THE 40S.
&&
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
GFS AND ECMWF IN GOOD AGREEMENT SHOWING UPPER TROUGH MOVING TO
EAST THURSDAY NIGHT AND FRIDAY AND HIGH PRESSURE WITH COOLER
TEMPERATURES FRIDAY AND SATURDAY. HIGHS IN THE 60S FRIDAY AND
SATURDAY. OVERNIGHT LOWS CHILLY IN THE 30S FRIDAY NIGHT AND
SATURDAY NIGHT. THERE MAY BE SOME CONCERNS FOR SOME FROST FRIDAY
NIGHT AND SATURDAY BUT LOW TEMPERATURES ARE EXPECTED TO REMAIN
ABOVE FREEZING. UPPER HIGH STRENGTHENS SUNDAY AND MONDAY WILL A
GRADUAL WARMING TREND. HIGHS UPPER 60S SUNDAY AND LOWER 70S
MONDAY. LOWS SUNDAY NIGHT UPPER 30S TO LOWER 40S.
&&
.AVIATION /10Z TUESDAY THROUGH SATURDAY/...
UPDATE...
CURRENT OBS INDICATE LOW LEVEL WINDS HIGHER THAN PREVIOUS THOUGHT.
LATEST ACARS SOUNDING SHOWING WEAKENING OF LOW LEVEL INVERSION. CIGS
ARE GRADUALLY IMPROVING...AND VSBYS AT ALL TAF SITES CURRENTLY AOA
5SM. HAVE AMENDED TAFS.
PREVIOUS DISCUSSION...
MAIN RAIN AREA SLOWLY SHIFTING OUT OF THE FORECAST AREA...BUT
SHALLOW LOW LEVEL WEDGE REMAINS. CONFIDENCE OF LOW LIFR TO IFR CIGS
PERSISTING THROUGH AT LEAST MID MORNING IS HIGH.
HOWEVER...CONFIDENCE IN VSBYS IS LOW. ALONG WITH VAPOR IMAGERY
INDICATING DRYING ALOFT....LIGHT SURFACE WINDS AND MOISTURE RICH LOW
LEVELS WOULD ALLOW VSBYS TO FALL. HOWEVER...IT HAS NOT FORMED YET.
MOST REGIONAL ASOS/AWOS SITES CURRENTLY INDICATING A NORTH WIND
AROUND 3 TO 5 MPH. IT IS POSSIBLE THAT DUE TO A LITTLE WIND...VSBYS
MAY NOT DECLINE AS MUCH AS PREVIOUSLY EXPECTED. LATEST LAMP GUIDANCE
CONTINUES TO INDICATE DENSE FOG DEVELOPMENT HOWEVER. WILL CONTINUE
TO MONITOR AND MAY HAVE TO AMEND FOR LESS PESSIMISTIC VSBYS. GRADUAL
IMPROVEMENT EXPECTED TUESDAY. VFR GENERALLY EXPECTED TUESDAY
AFTERNOON.
EXTENDED AVIATION OUTLOOK...LIGHT WINDS AND CLEAR SKIES EXPECTED
TUESDAY NIGHT WHICH COULD ALLOW RADIATION FOG TO DEVELOP.
OTHERWISE...VFR CONDITIONS EXPECTED WED. A FRONT WILL MOVE THROUGH
THE REGION LATE THURSDAY. VFR EXPECTED FRI/SAT.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
SC...NONE.
GA...NONE.
&&
$$
SYNOPSIS...07
NEAR TERM...07
SHORT TERM...07
LONG TERM...07
AVIATION...31
AREA FORECAST DISCUSSION
NWS COLUMBIA SC
126 AM EDT TUE MAR 17 2009
.SYNOPSIS...
LOW CLOUDS...RAIN...AND FOG ALL EXPECTED TO MOVE OUT OF THE REGION
BY TUESDAY. DRY HIGH PRESSURE WILL BUILD INTO THE REGION THROUGH
THE MIDDLE OF THE WEEK...WITH PLEASANT TEMPERATURES FORECAST.
ANOTHER FRONTAL SYSTEM WILL APPROACH AND MOVE THROUGH THE AREA BY
THE MIDDLE OF THE WEEK.
&&
.NEAR TERM /UNTIL 7 AM THIS MORNING/...
RAIN AREA GRADUALLY SHIFTING OUT OF THE FORECAST AREA. LOW CLOUDS
WILL PERSIST THROUGH THE NIGHT AND AREAS OF FOG EXPECTED TO
DEVELOP. DENSE FOG ADVISORY IS IN PLACE UNTIL 9AM.
&&
.SHORT TERM /7 AM THIS MORNING THROUGH WEDNESDAY NIGHT/...
AFTER DEALING WITH THE FOG POTENTIAL EARLY TUESDAY...SUNSHINE
ACTUALLY EXPECTED TO BE SEEN ACROSS THE FORECAST AREA THROUGH
WEDNESDAY. DRY WEATHER THROUGH THAT TIME. WITH THE SUNSHINE
EXPECTED...TEMPERATURES WILL RISE BACK TO NEAR NORMAL FOR THIS
TIME OF THE YEAR WITH HIGH READINGS INTO THE 70S ONCE AGAIN. LOW
TEMPERATURES IN THE 40S.
&&
.LONG TERM /THURSDAY THROUGH MONDAY/...
MODELS SHOWING ANOTHER FRONT/RAIN POTENTIAL MOVING THROUGH THE
AREA IN THE THURSDAY/FRIDAY TIME FRAME. TEMPS COOL BACK DOWN INTO
THE LOWER 60S BEHIND THE FRONT. RAIN CHANCES RIGHT NOW REMAIN ON
THE LOW SIDE...WITH SLIGHT CHANCE TO CHANCE EXPECTED. HIGH
PRESSURE SETTLES IN BOTH AT THE SURFACE AND ALOFT INTO THE
WEEKEND. UPPER WINDS REMAIN OUT OF THE WEST/NORTHWEST BEHIND THIS
SYSTEM...SO DRY HIGH BEHIND THE FRONT.
&&
.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
MAIN RAIN AREA SLOWLY SHIFTING OUT OF THE FORECAST AREA...BUT
SHALLOW LOW LEVEL WEDGE REMAINS. VAPOR IMAGERY INDICATING DRYING
ALOFT. ACARS AND MODEL SOUNDINGS INDICATE SOME WIND INCREASE
AROUND 1500 TO 2000 FEET...BUT THIS IS WELL ABOVE SHALLOW STABLE
LAYER AND STRATUS. LIGHT SURFACE WINDS AND MOISTURE RICH LOW
LEVELS SHOULD ALLOW CIGS/VSBYS TO FALL...AND WILL EXPECT DENSE FOG
DEVELOPMENT. LAMP AND MOS GUIDANCE INDICATE SUCH. GRADUAL
IMPROVEMENT IN VSBYS EXPECTED TUESDAY MID MORNING...BUT LOW LEVEL
CLOUDS COULD LINGER FOR A WHILE AND WILL INDICATE SLOW IMPROVEMENT
IN CIGS. VFR GENERALLY EXPECTED TUESDAY AFTERNOON.
EXTENDED AVIATION OUTLOOK...LIGHT WINDS AND CLEAR SKIES EXPECTED
TUESDAY NIGHT WHICH COULD ALLOW RADIATION FOG TO DEVELOP.
OTHERWISE...VFR CONDITIONMS EXPECTED WED. A FRONT WILL MOVE
THROUGH THE REGION LATE THURSDAY. VFR EXPECTED FRI/SAT.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
SC...DENSE FOG ADVISORY UNTIL 9 AM EDT THIS MORNING FOR SCZ015-016-
018-020>022-025>031-035>038-041.
GA...DENSE FOG ADVISORY UNTIL 9 AM EDT THIS MORNING FOR GAZ040-
063>065-077.
&&
$$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
650 AM CDT TUE MAR 17 2009
.DISCUSSION...
305 AM...MAIN CONCERNS THIS PERIOD ARE WINDS/TEMPS TODAY THEN
FROPA TIMING ALONG WITH PRECIP CHANCES AND TEMP TRENDS BEHIND THE
FRONT WEDNESDAY.
MODELS HAVE BEEN QUITE CONSISTENT FOR DAYS NOW WITH A TIGHTENING
PRESSURE GRADIENT ACROSS THE REGION TODAY. IN ADDITION...MIXING IN
THE LOW LEVELS WILL ALLOW FOR SOME HIGHER GUSTS. GUIDANCE HAS ALSO
BEEN STEADILY INCREASING WIND SPEEDS EACH RUN. DEPENDING ON THE
MODEL...LOW LEVELS MIX AS HIGH AS 900MB LATER THIS AFTERNOON WHERE
WINDS ARE 25-30KTS...THUS GUSTS 30-35 MPH CERTAINLY POSSIBLE. WITH
PLENTY OF SUNSHINE AND STRONG WAA ALONG WITH THE WELL MIXED LOW
LEVELS...EXPECT LOWER 70S FOR HIGHS ON TRACK AND COULD SEE A FEW
LOCATIONS IN THE MID 70S. WIND DIRECTION FROM THE SOUTHWEST SO NO
LAKE COOLING TODAY.
COLD FRONT SLOWLY SAGGING SOUTH ACROSS THE DAKOTAS EARLY THIS
MORNING AND SHOULD MAKE IT TO SOUTHERN WISCONSIN BY EARLY THIS
EVENING PUSHING SOUTH ACROSS NORTHERN ILLINOIS OVERNIGHT TO ABOUT
I-80 BY DAYBREAK WEDNESDAY. WHILE THERE ISN/T A SIGNIFICANT AMOUNT
OF COLDER AIR BEHIND THIS FRONT...ONCE IT MAKES IT TO LAKE
MICHIGAN WITH THE COLD SFC TEMPS...COULD SEE SOME ACCELERATION
DOWN THE WEST SIDE OF THE LAKE LATE THIS EVENING. ANY PRECIP WILL
BE LIGHT THRU MORNING AND WILL MAINTAIN LOW CHANCE POPS ACROSS THE
NORTH AFTER MIDNIGHT. COULD ALSO BE SOME FOG/HAZE ESPECIALLY NEAR
THE LAKE.
THE FRONT CONTINUES TO SLOWLY MOVE SOUTH ACROSS CENTRAL IL AND
CENTRAL INDIANA DURING THE DAY WEDNESDAY. WITH NORTHERLY FLOW OFF
THE LAKE...EXPECT TEMPS TO REMAIN IN THE 40S BEHIND THE FRONT.
WITH SOME CLEARING IN THE AFTERNOON...TEMPS MAY REBOUND A BIT FOR
A LATE AFTERNOON HIGH BUT HAVE GENERALLY FOLLOWED THE NAM 3HR
TEMP TRENDS WHICH SHOW A MUCH COLDER...THOUGH NEAR/ABOVE NORMAL
WEDNESDAY.
BEST CHANCES OF PRECIP WILL BE ACROSS THE CENTRAL/SOUTHERN PART OF
THE CWA AS A WEAK SHORTWAVE RIDES NORTHEAST ALONG THE FRONT AND
STRENGTHENS SOME DURING THE DAY. ELEVATED INSTABILITY LOOKS
LIMITED/MARGINAL. COULD BE A RUMBLE OR TWO OF THUNDER ESPECIALLY
ACROSS THE SOUTHEAST CWA BUT NO MENTION FROM THIS DISTANCE. QPF
AMOUNTS LOOK TO BE ON THE LIGHT SIDE...WITH BASIN AVERAGES OF ONLY
A QUARTER INCH...MAYBE LESS SO ON GOING RIVER FLOODING SHOULDN/T
BE AFFECTED TOO MUCH.
WINDS TURN NORTHEAST OFF THE LAKE THURSDAY AFTERNOON AND DESPITE
SOME SUN...COULD BE A RATHER CHILLY THURSDAY AFTERNOON ACROSS
NORTHEAST IL. SEE ALSO CLIMATE AND FIRE WEATHER DISCUSSIONS
BELOW. CMS
&&
.AVIATION...DISCUSSION REGARDING 12Z TAFS...
650 AM CDT
LITTLE CHG TO PREVIOUS FCST. LATEST SATLT TRENDS SHOW SOME MID/HIGH
LVL CLOUDINESS THAT DVLPD EARLIER ACROSS NRN IA/SRN MN AT NOSE OF
STGR LLVL FLOW CONTINUES TO ERODE AS IT APCHS MS RVR SO WILL
CONTINUE WITH CLR FCST.
CONDITIONS EXPECTED TO REMAIN VFR THRU 06Z WED...THOUGH APCHG COLD
FRONT TONIGHT WILL BE PRECEDED BY INCR IN CLOUDINESS. COMBINATION
OF RETREATING HIGH PRES OVR ERN U.S. AND DEEP LOW MOVG EWD ACROSS
NRN ONTARIO WILL RESULT IN INCREASING GRADIENT ACROSS REGION TODAY.
WIND PROFILER DATA SHOWS LLVL WINDS ALREADY UP TO 45 KTS AT 012
ACROSS NWRN MO AND EARLY MORNING ACARS SOUNDING FROM RFD AND ORD
SHOW SWLY WINDS AOA 30 KTS AT ABOUT THE SAME ALTITUDE.
FCST SOUNDINGS ALSO ADVERTISING A DEEP MIXED LYR DVLPG FROM SFC TO
NR 6 THSD FT DURG AFTN SO SLY WINDS AOB 10 KTS THRU MID MRNG WILL BE
QUICKLY INCRG TO NR 20 KTS AS SFC WARMS. FQT GUSTS TO NR
30 KTS CAN BE EXPECTED THRU AFTN. GUSTS TO DIMINISH QUICKLY ERLY
THIS EVENING AS SFC COOLS AND FRONTAL TROUGH APCHS.
AS TAIL END OF DEEP UPR SYS OVR CANADA MOVES ACROSS UPR MS VLY LATE
THIS AFT AND THIS EVENING...MID LVL CLOUDINESS WILL BCM MORE
EXTENSIVE. HOWEVER...WITH FLOW OFF GLFMEX BLOCKED BY HIGH PRESS
RIDGE...SFC/LLVL DEW POINTS TO REMAIN RELATIVELY LOW SO CIGS AND VIS
SHOULD RMN VFR TIL SFC FROPA LATE TNGT.
MERZLOCK
&&
.MARINE...
240 AM CDT
A LARGE RIDGE OF HIGH PRESSURE WILL REMAIN OVER THE
EASTERN U.S. WHILE A LOW OVER NORTHWEST ONTARIO DEEPENS AS IT MOVES
TO LABRADOR BY WEDNESDAY MORNING. A COLD FRONT TRAILING SOUTHWARD
FROM THIS LOW WILL MOVE DOWN LAKE MICHIGAN LATE THIS AFTERNOON AND
TONIGHT. BEHIND THIS FRONT...A HIGH PRESSURE OVER ALBERTA WILL
SETTLE SOUTHEASTWARD ACROSS THE WESTERN GREAT LAKES BY EARLY FRIDAY.
THIS SCENARIO WILL CAUSE A TIGHTENING SOUTH TO SOUTHWEST GRADIENT
TO DEVELOP TODAY. HOWEVER...SINCE THE LAKE IS STILL QUITE
COLD...STRONGER WINDS ARE EXPECTED TO RIDE UP OVER THE COLD MARINE
LAYER. STRONGEST WINDS WILL ACTUALLY OCCUR OVER THE WINDWARD
NEARSHORE WATERS LATE THIS MORNING AND THIS AFTERNOON. AS A
RESULT...A SMALL CRAFT ADVISORY WILL REMAIN IN EFFECT FOR THE
ILLINOIS AND INDIANA WATERS.
IN THE WAKE OF THE COLD FRONT TONIGHT...ONLY A BRIEF AND FAIRLY WEAK
PUSH OF COLD AIR IS EXPECTED AS WINDS TURN TO A NORTHERLY COMPONENT
BY EARLY WEDNESDAY.
MERZLOCK
&&
.FIRE WEATHER...
305 AM...NO HEADLINES THIS MORNING BUT AM CONCERNED THAT GUIDANCE
DEWPOINTS ARE TOO HIGH...GENERALLY IN THE MID 40S DURING THE
AFTERNOON. GIVEN HOW WELL THE LOW LEVELS WILL LIKELY MIX BY THIS
AFTERNOON...PERHAPS UP TO 900MB IF THE NAM SOUNDINGS VERIFY...
COULD EASILY SEE DEWPOINTS DIP INTO THE UPPER 30S. BUT CONFIDENCE
IS NOT TOO HIGH. HAVE SHAVED 3-5 DEGREES OFF DEWPOINTS WHICH
YIELDS AROUND 40 OR SO THRU THE AFTERNOON. WITH HIGHS REACHING THE
LOWER 70S...MAYBE A FEW MID 70S...THIS CORRESPONDS TO MIN RH
VALUES OF 30 PERCENT DURING THE MID AFTERNOON. LOCAL CRITERIA ARE
25 PERCENT OR LOWER RH...SFC WINDS 20+ MPH AND 10 HR FUELS AT 8
PERCENT OR LESS. WHILE MIN RH VALUES APPEAR...AT THIS POINT...TO
REMAIN ABOVE 25 PERCENT...WINDS WILL CERTAINLY MAKE 20+ MPH. 10 HR
FUEL MOISTURE THE MOST DIFFICULT TO FORECAST. WHILE SOIL/GROUND
CONDITIONS REMAIN WET/MOIST...10 HR FUEL MOISTURE ON MONDAY WAS
GENERALLY 7-10 PERCENT ACROSS THE AREA AND GOING BACK TO 8 PERCENT
OR LESS THIS AFTERNOON SEEMS POSSIBLE...ESPECIALLY UNDER MOSTLY
SUNNY SKIES. SO AS NOTED AT THE BEGINNING WILL HOLD OFF ON ANY
HEADLINES THIS MORNING...BUT DEWPOINTS/RH WILL NEED TO BE
MONITORED THRU THE DAY. CMS
&&
.CLIMATE...
305 AM...NEAR RECORD HIGHS ARE POSSIBLE TODAY WITH A RECORD OF 74
IN 1894 AT ORD AND ALSO 74 IN RFD SET JUST A FEW YEARS AGO IN
2003. NORMAL HIGHS FOR MARCH 17TH ARE ONLY 47 AT ORD AND 46 AT
RFD. LINK ON OUR WEBPAGE HAS MANY STATS FOR MARCH 17TH... ST.
PATRICK`S DAY...AND INTERESTING TO NOTE IN CHICAGO ONLY 11 TIMES
IN 136 YEARS OF RECORDS HAS THE HIGH TEMPERATURE ON MARCH 17TH
REACHED 60 OR HIGHER...INDICATING JUST HOW RARE THESE TEMPS ARE IN
MID MARCH. CURRENTLY FORECASTING A HIGH OF 72 AT ORD AND 73 AT RFD
SO MAY COME CLOSE TO TYING ONE OR BOTH. CMS
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
LMZ745...NOON TUESDAY TO 8 PM TUESDAY.
&&
$$
AREA FORECAST DISCUSSION
NWS SALT LAKE CITY UT
338 PM MDT WED MAR 18 2009
.SYNOPSIS...A MILD WESTERLY FLOW ALOFT TONIGHT WILL TURN TO THE
SOUTHWEST AS HIGH PRESSURE BUILDS EAST OF UTAH. A WEAK WEATHER
SYSTEM WILL CROSS THE AREA THURSDAY NIGHT AND FRIDAY. A MUCH
COLDER STORM SYSTEM WILL REACH UTAH LATE IN THE WEEKEND.
&&
.DISCUSSION...WATER VAPOR LOOP SHOWS AN UPPER LOW OVER THE GULF OF
ALASKA. FLAT RIDGING WAS DOMINATING OVER THE SOUTHWEST CONUS...WITH
THE NEXT DISTURBANCE APPROACHING 135W/35N. ACARS 400-250MB WIND
OBSERVATIONS REVEAL A CYCLONICALLY CURVED 90-130KT JET FROM THE
PACIFIC NORTHWEST INTO THE UPPER GREAT LAKES. 12Z 700MB ANALYSIS
PLACED A BAROCLINIC ZONE BETWEEN THE GREAT BASIN AND THE PACIFIC
NORTHWEST. WESTERLY FLOW ON THE COLD SIDE WAS PARALLEL TO THE FRONT.
-16C WAS LOCATED OVER BRITISH COLOMBIA...WITH +3 TO +6C OVER THE
DESERT SOUTHWEST. LOCALLY...COLD ADVECTION WAS IN PLACE WITH -1C AT
KSLC AND -2C UPSTREAM AT KLKN.
12Z KSLC RAOB INDICATES NEARLY NEUTRAL ADVECTION ABOVE 700MB...AND
3-5C OF COOLING BELOW 700MB DURING THE PAST 24 HOURS. A FRONTAL
INVERSION WAS LOCATED AT ABOUT 845MB. THE PRECIPITABLE WATER VALUE
DURING THE PAST 24 HOURS HAS BEEN STEADY AT FOUR TENTHS OF AN INCH.
SHALLOW COLD FRONT REMAINS SOUTH OF THE FORECAST AREA TONIGHT. WITH
MAINLY CLEAR SKIES...LIGHT WINDS AND RELATIVELY DRY LOWER
LEVELS...ANTICIPATE ANOTHER NIGHT OF COOL TEMPERATURES. FOR TONIGHTS
LOWS...BEGAN WITH THE OBSERVED VALUES EARLY THIS MORNING AND BLENDED
WITH THIS MORNINGS GFS BASED GUIDANCE TO ACCOUNT FOR RECENT TRENDS.
THE FRONT SHOULD LIFT NORTHWARD THROUGH THE LATE WORK WEEK AHEAD OF
THE PACIFIC SYSTEM....ALLOWING BETTER MIXING ESPECIALLY ACROSS
SOUTHERN AND CENTRAL UTAH. EXPECT MID AND UPPER LEVEL CLOUDS WILL
INCREASE AHEAD OF THE NEXT SYSTEM.
THE PACIFIC SYSTEM WHICH SHEARED NORTHEAST YESTERDAY IS STILL ON
TRACK TO WEAKEN AS IT PASSES OVER THE GREAT BASIN FRIDAY. WHILE
DYNAMICS LOOK MEAGER...BLENDED PRECIPITABLE WATER LOOP SHOWS GOOD
TELECONNECTIONS TO TROPICAL MOISTURE. THIS MAY BRING AN OPPORTUNITY
FOR CONVECTION ESPECIALLY TO NORTHWEST UTAH FRIDAY INTO SATURDAY
WHERE THE 09Z SHORT RANGE ENSEMBLES INDICATE A GOOD CHANCE OF
NEGATIVE LIFTED INDEX VALUES AND MUCAPE GREATER THAN 250 J/KG.
GFS AND EUROPEAN ARE COMING INTO LINE FOR A SUNDAY FRONTAL PASSAGE.
EXPECT WINDS TO BECOME GUSTY OUT OF THE SOUTH SATURDAY AS THE
PRESSURE GRADIENT TIGHTENS UP...THROUGH SUNDAY MORNING AS FLOW AT
700MB INCREASES TO 50KTS. AS A RESULT...WENT WELL ABOVE GUIDANCE FOR
LOW TEMPERATURES SATURDAY NIGHT. TEMPERATURES SUNDAY ARE FAIRLY
UNCERTAIN AS THEY HIGHLY DEPEND ON THE TIMING OF THE FRONTAL
PASSAGE. KEPT MENTION OF THUNDER WITH THE FRONTAL PASSAGE SUNDAY
GIVEN THE BUILDING INSTABILITY AHEAD OF THE COLD AIR PUSH.
BOTH THE EUROPEAN AND GFS HAVE CONTINUED THEIR RUN-TO-RUN TREND
WARMER AT 700MB AND 500MB AS THE SYSTEM MOVES INTO THE GREAT BASIN.
THE COLD FRONT IS THEREFORE NOT AS SHARP AS IT COULD BE. THE COLDER
AIR WILL DRIBBLE INTO THE REGION ON NORTH-NORTHWESTERLY FLOW ALOFT
MONDAY NIGHT...WITH SNOW LEVELS LOWERING FROM THE BENCHES TOWARD THE
VALLEY FLOOR. BECAUSE THE 12Z GFS FORECAST SOUNDINGS ARE RATHER WARM
IN THE BOUNDARY LAYER....KEPT VALLEYS AS A RAIN/SNOW MIX SUNDAY
NIGHT. OTHER FACTORS WHICH WILL PLAY A ROLE IN LIMITING
ACCUMULATIONS ACROSS THE LOWER LEVELS INCLUDE THE WARM GROUND DUE TO
THE RECENT WARMTH...PLUS THE RELATIVELY HIGH SUN ANGLE DURING THE
DAYLIGHT HOURS.
THE NORTHERN AND CENTRAL MOUNTAINS HOWEVER SHOULD FAIR
WELL...ALTHOUGH FAVORED SLOPES WILL VARY FROM SOUTHWEST EARLY DURING
THE STORM TO NORTHWEST MONDAY NIGHT BEFORE SWITCHING TO NORTH
TUESDAY. LIQUID EQUIVALENT TOTALS SHOULD RANGE FROM A HALF INCH TO
AN INCH.
HEADING INTO THE MIDWEEK...THE GFS AND EUROPEAN DIVERGE...WITH
RIDGING ADVERTISED BY THE GFS AND THE NEXT POTENT STORM DIVING
SOUTHEAST FROM BRITISH COLUMBIA BY THE EUROPEAN. WITH THE LACK OF
CONFIDENCE WENT WITH POPS CLOSE TO CLIMATOLOGY.
&&
.AVIATION...WINDS ARE EXPECTED TO REMAIN NORTHERLY THROUGH THIS
EVENINGS PUSH...WITH NORMAL SOUTHEASTERLY DRAINAGE WINDS DEVELOPING
AROUND 03Z. VFR CONDITIONS WILL PREVAIL WITH MOSTLY CLEAR SKIES.
&&
.SLC WATCHES/WARNINGS/ADVISORIES...
UT...NONE.
WY...NONE.
&&
$$
PUBLIC...ROGOWSKI
AVIATION...MERRILL
FOR MORE INFORMATION FROM NOAA/S NATIONAL WEATHER SERVICE VISIT...
HTTP://WEATHER.GOV/SALTLAKECITY (ALL LOWER CASE)
TO THE TEXT PRODUCTS AS WELL. PREVIOUS FORECAST DISCUSSION FOLLOWS...
THE LATEST ECMWF/GFS MODELS ARE IN GENERAL AGREEMENT THAT HEIGHTS
WILL BEGIN TO SLOWLY RISE ACROSS THE INTERIOR WEST LATE
WEDNESDAY/THURSDAY. THIS RISE WILL COME AHEAD OF A DEEPENING AND
RATHER COLD UPPER TROUGH FORMING OVER THE ERN PACIFIC. THE FIRST
THREAT FOR ANY PRECIP WILL COME FRIDAY WHEN THE RIDGE SHIFTS OFF TO
THE EAST AND A COUPLE OF RATHER WEAK SHORTWAVES EJECTING E-NE
THROUGH THE BASIN. DYNAMIC LIFT/THERMAL ADVECTION WILL BE ON THE
WEAK SIDE...BUT THE MOISTURE TAPPED BY THESE FEATURES WILL IMPROVE
THE CHANCE FOR LIGHT PRECIP DURING THE DAY.
THE MAJOR COLD ERN PACIFIC TROUGH STILL PLAGUED BY SIGNIFICANT
TIMING DIFFERENCES BETWEEN THE FASTER GFS AND SLOWER ECMWF. BOTH
MODELS ARE SHOWING A FAIRLY HIGH-AMPLITUDE PATTERN DEVELOPING ACROSS
NORTH AMERICA THROUGH THE ERN PACIFIC. THIS SOLUTION WOULD SUGGEST
SLOWER EASTWARD PROGRESSION WHICH WOULD FALL MORE IN LINE WITH THE
ECMWF. WILL KEEP SATURDAY ON THE DRIER/WARMER SIDE TO GO ALONG WITH
THE ECMWF...THEN BRING MUCH COLDER TEMPS AND WIDESPREAD PRECIP TO
THE AREA LATE SUNDAY/MONDAY. TUESDAY STILL A BIG QUESTION FOR NOW AS
THE TROUGH IN THE ECMWF EVOLVES INTO A TIGHTLY WOUND CLOSED LOW AS
IT EXITS INTO THE PLAINS STATES. WRAPAROUND PRECIP COULD BE AN ISSUE
ON TUESDAY...BUT FOR NOW WILL KEEP POPS CLOSER TO CLIMATOLOGY OWING
TO THE UNCERTAINTY OF THE PATTERN EVOLUTION.
&&
.AVIATION...LIGHT NORTHERLY WINDS WILL CONTINUE AT THE SLC TERMINAL
WILL BECOME A BIT STRONGER AFTER 17Z AS THE LAKE BREEZE REINFORCES
THE NORTHERLY WINDS. OTHERWISE...ANY CEILINGS THAT DEVELOP THROUGHOUT
THE DAY ARE EXPECTED TO REMAIN ABOVE 7000 FEET AGL.
&&
.SLC WATCHES/WARNINGS/ADVISORIES...
UT...NONE.
WY...NONE.
&&
$$
PUBLIC...ROGOWSKI/CONGER
AVIATION...KRUSE
FOR MORE INFORMATION FROM NOAA/S NATIONAL WEATHER SERVICE VISIT...
HTTP://WEATHER.GOV/SALTLAKECITY (ALL LOWER CASE)
AREA FORECAST DISCUSSION
NWS SEATTLE WA
415 AM PDT TUE MAR 17 2009
.SYNOPSIS...COOL SHOWERY WEATHER WILL CONTINUE ACROSS WESTERN
WASHINGTON TODAY AS AN UPPER TROUGH REMAINS OVER THE REGION. SHOWERS
WILL DECREASE TONIGHT AS A WARM FRONT APPROACHES THE AREA. RAIN WILL
INCREASE WEDNESDAY OVER THE NORTH PORTION OF THE AREA AS A WARM
FRONT SAGS SOUTH. WET WEATHER WILL CONTINUE WEDNESDAY NIGHT THROUGH
THURSDAY NIGHT AS THE COLD FRONT MOVES SLOWLY THROUGH. THE UPPER
TROUGH OFFSHORE WILL KEEP THE WEATHER WET AND UNSETTLED AS IT MOVES
INLAND THIS WEEKEND.
&&
.SHORT TERM...MOIST SOUTHWEST FLOW CONTINUES ACROSS WESTERN
WASHINGTON THIS MORNING WITH A DEEP UPPER LEVEL TROUGH OFFSHORE AND
A STRONG ZONAL JET TO THE SOUTH ACROSS OREGON. NOTHING REAL
ORGANIZED OFFSHORE BUT THE AIR MASS REMAINS UNSTABLE THIS MORNING
WITH 500 MB TEMPERATURES OFF OF THE LAST ACARS SOUND STILL AROUND
-35C OVER THE AREA. SOME WEAK WARM ADVECTION THIS AFTERNOON AS THE
THE JET BEGINS TO SHIFT NORTH AHEAD OF AN APPROACHING WARM FRONT.
THIS WILL SIGNIFICANTLY DECREASE THE SHOWERS ACTIVITY LATER THIS
AFTERNOON INTO THIS EVENING. ACARS SOUNDING ALSO SHOWED SOUTHWEST
WINDS 30-35 KNOTS BETWEEN 850-700 MB SO WILL KEEP THE SNOW ADVISORY
GOING FOR THE MOUNTAINS INTO THE EARLY AFTERNOON HOURS. SOME CHANGES
IN THE FORECAST FOR WEDNESDAY. NEW 00Z MODEL RUNS ARE MUCH SLOWER
WITH THE APPROACH OF THE WARM FRONT FROM THE NORTHWEST. COLD UPPER
LEVEL LOW STILL IN PLACE OVER THE GULF OF ALASKA WITH THE JET
LIFTING NORTH INTO THE QUEEN CHARLOTTES/NORTHERN TIP OF VANCOUVER
ISLAND AREA WEDNESDAY MORNING. IN ADDITION WITH THE COLD TROUGH
SLOWLY DIGGING SOUTH OVER THE EASTERN PACIFIC SLOWING THE EASTWARD
MOVEMENT OF THE ASSOCIATED COLD FRONT WHICH WILL HELP KEEP THE WARM
FRONT TO THE NORTH. WITH THE 00Z RUNS BEING THE FIRST RUN IN THE
SHORT TERM TO SLOW DOWN THE PRECIPITATION WILL NOT COMPLETELY TAKE
THE RAIN OUT OF THE FORECAST FOR THE SOUTHERN PORTION OF WESTERN
WASHINGTON. WILL START SCALING BACK WITH JUST CHANCE POPS IN THE
MORNING THEN LIKELY POPS IN THE AFTERNOON. WARM FRONT NOT FAR ENOUGH
NORTH AT THIS POINT TO KEEP THE NORTHERN PORTION OF THE AREA DRY AND
WILL STAY WITH THE RAIN FORECAST FOR THE NORTHWEST INTERIOR AND
NORTH COAST. WILL WESTERN WASHINGTON IN THE WARM SECTOR WILL ADD A
COUPLE OF DEGREES TO THE MAX TEMPS ON WEDNESDAY WITH MOST PLACES
GETTING INTO THE 50S. COLD FRONT EVENTUALLY APPROACHES THE AREA
LATER WEDNESDAY INTO WEDNESDAY NIGHT. THE QUESTION NOW IS HOW LONG
WILL THE FRONT STALL OVER WESTERN WASHINGTON. WITH THE TROUGH
DIGGING OFFSHORE AT THIS POINT IT LOOKS LIKE THE FRONT COULD STALL
FOR AT LEAST 24 HOURS. WILL STAY WITH THE RAIN FORECAST FOR THURSDAY
INTO THURSDAY NIGHT. FELTON
.LONG TERM...GIVEN THE PATTERN THE EXTENDED MODELS ARE IN PRETTY
GOOD AGREEMENT THIS MORNING BUT THE RUN TO RUN CONSISTENCY IS
LACKING SOMEWHAT. THIS MORNING SOLUTION BRINGS THE FRONT THROUGH
SOMETIME ON FRIDAY WITH THE COLD UPPER LEVEL TROUGH OFFSHORE KEEPING
SHOWERS IN THE FORECAST INTO SUNDAY. BOTH THE EURO AND THE GFS BRING
THE TROUGH AXIS THROUGH THE AREA WITH A POSSIBLE BREAK BEFORE THE
NEXT SYSTEM ARRIVES. MODEL SOLUTION DIVERGE AT THIS POINT WITH THE
GFS BRINGING ANOTHER FRONT INTO THE AREA ON MONDAY WHILE THE EURO
HAS THE FRONT FURTHER TO THE NORTH AND STILL OFFSHORE MONDAY. NO
REASON TO GO WITH EITHER MODEL SOLUTION THAT FAR OUT AND WILL STAY
WITH THE CHANCE POPS ALREADY IN THE FORECAST. FELTON
&&
.AVIATION...SHOWERS AND ONSHORE FLOW CONTINUE WITH VARIABLE
CONDITIONS BUT GENERALLY VFR EXCEPT CIGS AND VSBY DROPPING W/ SCT
SHOWERS. CASCADES AND OLYMPICS MSTLY OBSCURED. LITTLE CHANGE TIL
EVENING WHEN THE SCATTERED SHOWERS TAPER OFF. 19
&&
.MARINE...UNSTABLE AIR MASS WITH BLUSTERY WINDS...ESPECIALLY NEAR
SHOWERS. LOW PRES IN NE PAC W/ HIGHER PRES BLDG OVER NRN CALIF THRU
WILL MAINTAIN SLY GRADIENTS FOR SMALL CRAFT WINDS AT TIMES ALL
WATERS...BUT MAINLY AS SHOWERS PASS BY. LATEST SPOT TO HAVE BRIEF
GALE FORCE WINDS WAS TATOOSH AT 2AM BUT THESE LOCALIZED GUSTY WINDS
ARE NOT PREDICTABLE AND HAVING THE SMALL CRAFT ADVISORY ALL WATERS
IS ABOUT AS GOOD AS YOU CAN DO IN A COOL UNSTABLE AIR MASS IN
ONSHORE FLOW. TYPICAL BLUSTERY MARCH WEATHER. 19
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...WINTER WEATHER ADVISORY OLYMPICS AND CASCADES UNTIL 2 PM.
PZ...SMALL CRAFT ADVISORY ALL WATERS.
SMALL CRAFT ADVISORY FOR ROUGH BAR CONDITIONS GRAYS HARBOR BAR.
$$
WWW.WEATHER.GOV/SEATTLE
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