SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NWS LOS ANGELES/OXNARD CA
326 PM PST SUN NOV 18 2007
.SHORT TERM (TONIGHT-WEDNESDAY)...MARINE LAYER STUBBORN THIS
AFTERNOON AS EXPECTED. MOST BEACH AREAS STRUGGLED TO CLEAR THIS
AFTERNOON. MARINE LAYER WILL LIKELY RETURN TO MOST AREAS WHERE IT
WAS PRESENT LAST NIGHT. SOME CONCERN THAT THE MARINE LAYER MAY
THIN TONIGHT AS A MORE NORTHERLY GRADIENT IS PRESENT BEHIND A WEAK
BOUNDARY CURRENTLY PUSHING SOUTH DOWN THE COAST.
MARINE LAYER SHOULD RETREAT FROM MOST AREAS ON MONDAY NIGHT...LIKELY
REMAINING SOUTH OF POINT MUGU. IT IS POSSIBLE THAT THE STRATUS
COULD REFORM AT THE BEACHES NORTH OF POINT CONCEPTION...HOWEVER
NOT LIKELY AS INSTABILITY WITH THE SYSTEM ARRIVES AND COULD
DISRUPT THE MARINE INVERSION.
COLDER AIR REENFORCEMENT ARRIVES MONDAY NIGHT AS UPPER-LEVEL TROUGH
PUSHES INTO THE NORTHERN GREAT BASIN AND INTERMOUNTAIN REGION. A
SECONDARY BOUNDARY PUSHING SOUTH OVER THE STATE STILL BRINGS SOME
CONCERN FOR BREEZY CONDITIONS FOR SOUTHERN SANTA BARBARA COUNTY
AND THE ANTELOPE VALLEY MONDAY NIGHT. WEAK TO MODERATE THERMAL
GRADIENTS STILL DEVELOP BETWEEN THE CENTRAL VALLEY AND THE LEEWARD
SIDE...WITH ABOUT 15 TO 25 KNOTS OF WIND AT 850 MB. 12Z UKMET
STILL REMAINS QUITE STRONG RELATIVE TO ITS PAST RUNS...BUT
CONFIDENCE WOULD IMPROVE WITH BETTER MODEL AGREEMENT.
UNCERTAINTY STILL IN PLACE FOR MIDWEEK. UPPER-LEVEL SYSTEM PUSHES
INTO GREAT BASIN. THE MIDDLE-LEVEL COLD FRONT SAGS SOUTH THROUGH
UTAH AND NEVADA...THEN SEEMS TO DIE AND PUSH EAST. NAM-WRF SEEMS
TO PUSH A PIECE OF THE 700 MB FRONT INTO THE OWENS VALLEYS TUESDAY
NIGHT...BUT MODELS STILL STRUGGLE WITH MODELING THE LOWER AND
MIDDLE LEVELS WITH 18Z SOLUTIONS CONTINUING TO WEAKEN THE EVENT
FOR MIDWEEK. 18Z GFS SOLUTION IS SIGNIFICANTLY WEAKER THAN 12Z
SOLUTION...WITH NAM-WRF CONTINUING TO WEAKEN THE SYSTEM. THE
EUROPEAN MODEL SOLUTIONS CONTINUE TO STRUGGLE AS WELL. MODELS DO
AGREE THAT THE FLOW PATTERN DOES BECOME NORTHEASTERLY...BUT THE
QUESTION IS THE STRENGTH AND TIMING AT THIS TIME. ONE THING THAT
IS CERTAIN IS THAT COOLER CONDITIONS WILL DEVELOP OVER THE
AREA...WITH POSSIBLE FROST OR FREEZE CONDITIONS DEVELOPING TUESDAY
NIGHT AND/OR WEDNESDAY NIGHT IN THE ANTELOPE VALLEY.
.LONG TERM (THANKSGIVING DAY-SUNDAY)...MODELS SEEMING TO BE MORE
EXCITED ABOUT A SECOND SYSTEM DROPPING SOUTH OF CANADA INTO THE
GREAT BASIN AND PUSHING WEST INTO SOUTHEASTERN CALIFORNIA. GOOD
AGREEMENT DOES EXIST WITH GFS AND ECMWF ABOUT THE MOVEMENT OF THE
UPPER LEVEL SYSTEM THAT COULD PRODUCE A MODERATE TO STRONG EVENT
OVER THE HOLIDAY WEEKEND...HOWEVER WITH MODEL PERFORMANCE SO
POORLY LATELY...LITTLE CONFIDENCE SHOULD BE PLACED IN THE STRENGTH
AND TIMING OF THE EVENT AT THIS TIME.
&&
.AVIATION...18/1818Z...STRATUS SLOWING BURNING OFF TO THE COAST
THIS MORNING. LATEST AMDAR SOUNDINGS INDICATE MARINE INVERSION
AROUND 1400 FEET THIS MORNING. EXPECT THE STRATUS TO BURN OFF WELL
THIS AFTERNOON...WITH ONLY SOME MVFR VSBYS LINGERING ACROSS THE
COASTAL/VALLEY TERMINALS. FOR TONIGHT...ONSHORE FLOW IS FORECAST
TO BE STRONGER AND THE MARINE LAYER SHOULD DEEPEN SOMEWHAT.
SO...WILL EXPECT THE STRATUS/FOG TO RETURN TO THE COASTAL AND
VALLEY TAFS OVERNIGHT...WITH CIG AND VSBYS VERY SIMILAR TO LAST
NIGHT AND THIS MORNING.
KLAX...MVFR VSBYS TIL AROUND 22Z WHEN WEAK SEA BREEZE KICKS IN.
STRATUS/FOG EXPECTED TO RETURN AROUND 04Z THIS EVENING...WITH
IFR CIGS/VSBYS EXPECTED OVERNIGHT. OVERALL...MODERATE CONFIDENCE
IN 18Z TAF.
KBUR...EXPECT MVFR VSBYS THROUGH THE EVENING. OVERNIGHT...STRATUS
AND FOG SHOULD RETURN...AROUND THE 07Z TIME FRAME. WHEN STRATUS
DOES MOVE IN...IFR/LIFR CIGS AND VSBYS ARE EXPECTED. OVERALL...
MODERATE CONFIDENCE IN 18Z TAF.
&&
.LOX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
PUBLIC...HALL
AVIATION...RAT
WWW.WEATHER.GOV/LOSANGELES
AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
200 PM PST SAT NOV 17 2007
.SYNOPSIS...
THE MARINE LAYER AND WEAK ONSHORE FLOW WILL BRING COASTAL LOW CLOUDS
AND FOG DURING THE NIGHTS AND MORNINGS THROUGH MONDAY. A COOLER AIR
MASS WILL COVER THE REGION TUESDAY. DRY AND COOL OFFSHORE FLOW WILL
INCREASE WEDNESDAY AND BECOME STRONG BY FRIDAY.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
THE LOW CLOUDS CLEARED AT THE COAST TODAY AND THE MARINE LAYER WILL
BE MORE SHALLOW IN RESPONSE TO A SLIGHT HEIGHT RISE TONIGHT AND SUN.
THIS WILL MEAN THE LOW CLOUDS WILL BE SLIGHTLY LESS EXTENSIVE ON SUN
AND IT WILL BE WARMER AS WELL. A TROUGH OF LOW PRESSURE MOVES
THROUGH TO THE NORTH ON MON AND TUE...BRIEFLY STRENGTHENING THE
ONSHORE FLOW HERE IN SOCAL AND EXPANDING THE MARINE LAYER. NORTHERLY
GRADIENTS RESULT FROM THIS SYSTEM AS IT MOVES INTO THE WESTERN U.S.
INTERIOR TUE...BUT THE STEEP PRESSURE AND THERMAL GRADIENTS ARE MUCH
TOO FAR NORTH FOR MUCH IF ANY IMPACT ON SOCAL. THE GRADIENTS GET A
LITTLE CLOSER AND TIGHTEN UP WED AND THU...BUT STILL NOT IN OPTIMUIM
POSITION FOR REALLY STRONG WINDS. THERE WILL BE AN INCREASED FIRE
POTENTIAL WED AND THU WITH MODERATE OFFSHORE WINDS...STRONG IN THE
FAVORED SPOTS...ALONG WITH DRIER AIR. AN ARCTIC AIR MASS MOVES
SOUTHWARD OUT OF CANADA TO STRENGTHEN THIS OFFSHORE PATTERN FRI AND
SAT GIVING US WHAT LOOKS LIKE OUR BEST CHANCE AT WIDESPREAD STRONG
OFFSHORE WINDS. THE BIGGER STORY MAY BE THE COLD. GIVEN THE VAGARIES
OF THE MODEL SOLUTIONS AND THE TREND OF BACKING OFF THE STRENGTH AND
TIMING OF OFFSHORE FLOW A FEW DAYS OUT...ALL WE CAN SAY IS THIS IS
OUR BEST GUESS FOR NOW. AND STAY TUNED.
&&
.AVIATION...
172015Z...LATE MORNING MDCRS SOUNDINGS INDICATE THE MARINE LAYER
DEPTH HAD LOWERED TO AROUND 2000 FEET FROM THIS MORNING. LITTLE
CHANGE IS EXPECTED IN THE DEPTH THROUGH SUNDAY. STRATUS...WITH BASES
AROUND 1500 FEET MSL...OVER THE COASTAL WATERS SHOULD PUSH BACK
ONSHORE BY SUNSET AND INLAND DURING THE EVENING REACHING THE FAR
INLAND VALLEY AREAS BY MIDNIGHT. EXPECT LIFR CONDITIONS NEAR KONT
AFTER MIDNIGHT AS WELL. STRATUS SHOULD BREAK UP BETWEEN 17Z AND 19Z
ON SUNDAY.
ABOVE THE MARINE LAYER...VFR CONDITIONS WITH CIRRUS ABOVE FL250 AND
UNRESTRICTED VISIBILITIES THROUGH SUNDAY.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
PUBLIC...MM
AVIATION/MARINE...HORTON
AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
900 AM PST SAT NOV 17 2007
.SYNOPSIS...
THE MARINE LAYER AND WEAK ONSHORE FLOW WILL BRING COASTAL LOW CLOUDS
AND FOG DURING THE NIGHTS AND MORNINGS INTO EARLY NEXT WEEK. WEAK TO
LOCALLY MODERATE OFFSHORE FLOW IS EXPECTED TUESDAY THROUGH
THANKSGIVING WITH STRONGER OFFSHORE FLOW POSSIBLE FRIDAY AND
SATURDAY.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
THE BASE OF THE MARINE INVERSION INCREASED TO ABOUT 2500 FEET
OVERNIGHT. THE LOW CLOUDS COVERED MOST OF THE COASTAL BASIN AND
PATCHY DENSE FOG WAS OBSERVED AT ABOUT THE 1500-2500 FOOT ELEVATION.
THE STRONGER ONSHORE FLOW IS RESPONSIBLE FOR THE MORE EXTENSIVE
STRATUS CLOUDS. HEIGHTS RISE TONIGHT AND SUN AND THE MARINE LAYER
SHOULD GET MORE SHALLOW AND SLIGHTLY LESS EXTENSIVE. SUN WILL BE
WARMER AS WELL EXCEPT RIGHT AT THE COAST WHERE LITTLE SUNSHINE IS
EXPECTED. A TROUGH OF LOW PRESSURE MOVES THROUGH THE NORTHWEST ON
MON...BRIEFLY STRENGTHENING THE ONSHORE FLOW HERE IN SOCAL AND
EXPANDING THE MARINE LAYER. NORTHERLY GRADIENTS RESULT FROM THIS
SYSTEM AS IT MOVES INTO THE WESTERN U.S. INTERIOR MON NIGHT...BUT
THE STEEP PRESSURE AND THERMAL GRADIENTS ARE MUCH TOO FAR NORTH FOR
MUCH IF ANY IMPACT ON SOCAL. THE GRADIENTS GET A LITTLE CLOSER WED
AND THU...BUT STILL NOT IN FAVORABLE POSITION. THERE WILL BE AN
INCREASED FIRE POTENTIAL WITH SOME PEDESTRIAN WINDS ESPECIALLY IN
THE FAVORED SPOTS...ALONG WITH DRIER AIR. AN ARCTIC AIR MASS MOVES
SOUTHWARD OUT OF CANADA TO STRENGTHEN THIS OFFSHORE PATTERN NEXT FRI
AND SAT GIVING US WHAT LOOKS LIKE OUR BEST CHANCE AT STRONG OFFSHORE
WINDS. THE BIGGER STORY MAY BE THE COLD. GIVEN THE VAGARIES OF THE
MODEL SOLUTIONS AND THE TREND OF BACKING OFF THE STRENGTH AND TIMING
OF OFFSHORE FLOW A FEW DAYS OUT...ALL WE CAN SAY IS THIS IS OUR BEST
GUESS FOR NOW. AND STAY TUNED.
&&
.AVIATION...
171545Z...THE 12Z NKX SOUNDING AND MDCRS SOUNDINGS INDICATE THE
MARINE LAYER DEPTH OVER THE AREA WAS BETWEEN 2000 AND 2500 FEET.
SOME LOWERING OF THE MARINE LAYER TO AROUND 1800 FEET IS EXPECTED
THROUGH TONIGHT. STRATUS WITH BASES AROUND 1500 FEET MSL EXTENDS
INLAND INTO THE INLAND VALLEY AREAS. EXPECT THE STRATUS/FOG OVER THE
INLAND AREAS TO BREAK UP BETWEEN 16Z AND 17Z AND THE COASTAL AREAS
BETWEEN 17Z AND 19Z. STRATUS SHOULD PUSH BACK ONTO THE COAST BY
SUNSET AND INLAND DURING THE EVENING REACHING THE INLAND VALLEY
AREAS BY MIDNIGHT. SOME LIFR CONDITONS ARE EXPECTED OVER THE MESAS
AND INLAND AREAS BEFORE SUNRISE SUNDAY MORNING.
ABOVE THE MARINE LAYER...VFR CONDITIONS ARE EXPECTED THROUGH SUNDAY
WITH SOME CIRRUS ABOVE FL250 AND UNRESTRICTED VISIBILITIES. HORTON
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
HIGH SURF ADVISORY UNTIL 2 AM PST SUNDAY FOR ORANGE COUNTY
COASTAL AREAS-SAN DIEGO COUNTY COASTAL AREAS.
&&
$$
PUBLIC...MM
AVIATION/MARINE...HORTON
AREA FORECAST DISCUSSION
NWS BALTIMORE MD/WASHINGTON DC
220 PM EST SAT NOV 17 2007
.SYNOPSIS...
A WEAK CLIPPER SYSTEM WILL MOVE THROUGH THE MID ATLANTIC REGION
TONIGHT. THIS SYSTEM WILL BRING THE GREATEST CHANCES OF LIGHT
PRECIPITATION TO THE NORTHERN POTOMAC HIGHLANDS AND ALONG THE
MASON DIXON LINE. HIGH PRESSURE WILL BUILD BACK OVER THE REGION ON
SUNDAY...AND CONTINUE THROUGH MID WEEK. THE NEXT FRONTAL BOUNDARY
IS EXPECTED DURING THE LATTER HALF OF NEXT WEEK.
&&
.NEAR TERM /THROUGH TONIGHT/...
WATER VAPOR LOOP SHOWS A WAVE DIVING SOUTHEAST ACROSS THE MIDWEST IN
ADVANCE OF A SECOND WAVE SAGGING SOUTH INTO THE UPPER GREAT LAKES.
AN UPPER LOW IS SHEARING NORTHEAST ACROSS THE PLAINS. ACARS
400-250MB WIND OBSERVATIONS SHOW A 90-110KT NORTHWESTERLY JET
EXTENDS SOUTHEAST FROM THE LOWER GREAT LAKES TO THE MID ATLANTIC
WHERE PHASING OCCURS WITH A 70-90KT WESTERLY JET THAT EXTENDS EAST
FROM THE PLAINS. 12Z SURFACE ANALYSIS PLACED A 1009MB CYCLONE NEAR
DAVENPORT IOWA...ALONG A COLD FRONT SAGGING SOUTHEAST ACROSS THE
GREAT LAKES. A 1023MB ANTICYCLONE DOMINATES THE SOUTHEAST
CONUS...WITH A TROUGH IN THE LEE OF THE CENTRAL APPALACHIANS.
LIGHT PRECIPITATION EXPECTED TO SPREAD EAST AND AFFECT MAINLY THE
MOUNTAINS AND COMMUNITIES NORTH OF THE PENNSYLVANIA STATE LINE
TONIGHT. 12Z OPERATIONAL MODELS/09Z SREF/AND SIMULATED REFLECTIVITY
FROM THE LWX WRF-ARW...NCEP WRF-NMM...NSSL WRF-ARW ALL ON THE SAME
TRACK.
SATURATED LAYER SHOULD CONTAIN MAINLY SUPERCOOLED WATER
DROPLETS...ESPECIALLY SOUTHEAST OF THE MOUNTAINS AND PENNSYLVANIA
BORDER...WHICH WOULD INDICATE A LIQUID DOMINATE PRECIPITATION TYPE.
THIS IS ALSO SUPPORTED BY THE 09Z SREF PTYPE ALGORITHMS. A FEW
FLAKES MAY MIX IN ACROSS THE HIGHER TERRAIN...BUT LOW LEVEL
TEMPERATURES SHOULD TEMPER ACCUMULATIONS.
&&
.SHORT TERM /SUNDAY/...
EXPECT SCENARIO OUTLINED ABOVE TO CONTINUE THROUGH MUCH OF SUNDAY AS
THE GREAT LAKES WAVE IS SLOW TO APPROACH THE REGION FROM THE
NORTHWEST.
CLOUD/PRECIPITATION BOUNDARY ACROSS THE FORECAST AREA EXPECTED TO
LEAD TO A TEMPERATURE GRADIENT FROM THE LOWER 60S CENTRAL VIRGINIA
TO MID 40S HIGHER TERRAIN OF NORTHERN MARYLAND.
NAM HOLDS ONTO THE CYCLONE INLAND LONGER THAN GFS...SIDED WITH GFS
TRANSITIONING ENERGY TO THE COASTLINE DUE TO THE NAM BIAS. LARGEST
IMPLICATION IS WITH REGARD TO WINDS.
&&
.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
CLIPPER SYSTEM WILL HAVE MOVED OFFSHORE BY SUNDAY EVENING. STILL
EXPECT SOME PRECIPITATION WRAPPED AROUND THE LOW SUNDAY NIGHT WITH
AID FROM ANOTHER UPPER LEVEL FEATURE WHOSE IMPACT WILL MAINLY BE
FELT TO OUR NORTH. AS THE BOUNDARY LAYER COOLS...EXPECT P-TYPE TO
TRANSITION FROM RAIN TO SNOW MAINLY NORTHWEST OF BWI/DC. EVEN WITH
SUCH A TRANSITION...QPF WILL BE LIGHT AND THERE WILL BE LITTLE OR NO
SNOW ACCUMULATION.
HIGH PRESSURE BUILDS ACROSS THE REGION MONDAY...THEN MOVES EAST OF
THE AREA TUESDAY. SOUTHERLY FLOW TUESDAY AND WEDNESDAY WILL WARM
TEMPERATURES ABOVE CLIMO. HOWEVER...WARM ADVECTION WILL ALSO LEAD TO
MORE CLOUDS AND INCREASING CHANCES OF RAIN. BEST WARM ADVECTION WILL
OCCUR TO OUR NORTH AND WEST SO BEST CHANCES OF RAIN INITIALLY WILL
BE TO THE NORTH AND WEST. THESE CHANCES EXPAND ACROSS THE REST OF
THE CWA WEDNESDAY NIGHT INTO THURSDAY AS A STRONG COLD FRONT
APPROACHES AND THEN MOVES ACROSS THE REGION.
COLD FRONTAL PASSAGE WILL LEAD TO COOLER CONDITIONS BY
FRIDAY...ALONG WITH GUSTY WINDS. MOST OF ANY LINGERING PRECIPITATION
WOULD BE IN OUR WESTERN CWA FROM AN UPSLOPE COMPONENT TO THE WIND.
HIGH PRESSURE RETURNS FOR SATURDAY.
&&
.AVIATION /19Z SATURDAY THROUGH THURSDAY/...
NEXT CYCLONE ADVANCES FROM THE MIDWEST INTO THE MID ATLANTIC
THROUGH SUNDAY...BRINGING MID LEVEL CLOUDS WHICH WILL TEND TO
THICKEN AND LOWER (REMAINING VFR) TONIGHT. SHOWER ACTIVITY EXPECTED
TO FOCUS ALONG THE MOUNTAINS AND NORTH OF TERMINALS IN PENNSYLVANIA
TONIGHT AND TOMORROW PER 12Z NAM/GFS AND 09Z SREF.
CEILINGS MAY FALL INTO MVFR OR IFR CATEGORIES (BEGINNING NEAR THE
PENNSYLVANIA BORDER AND DEVELOPING SOUTHEAST TOWARD METRO HUBS) LATE
TOMORROW AFTERNOON BEHIND THE CYCLONE AS ADVERTISED BY 09Z SREF AND
GFS/NAM BUFKIT FORECAST SOUNDINGS.
THERE IS A CHANCE FOR IFR CIGS SUNDAY NIGHT INTO EARLY
MONDAY...OTHERWISE NO SIGNIFICANT WEATHER IS EXPECTED UNTIL LATE
NEXT WEEK AS A COLD FRONT MOVES ACROSS THE AREA.
&&
.MARINE...
ETA/GFS MOS AND 12Z KLWX WRF-ARW SUGGEST SSW WINDS 10-15KTS TONIGHT.
WINDS EXPECTED TO VEER TO NORTHEAST NORTH OF THOMAS POINT TOMORROW
AS A CYCLONE MOVES ACROSS THE MID ATLANTIC.
A NORTHERLY SURGE MAY LEAD TO SMALL CRAFT ADVISORY CONDITIONS MAINLY
ON THE CHESAPEAKE BAY MONDAY. A STRONG COLD FRONT WILL ALSO BRING
POSSIBLE SMALL CRAFT ADVISORY CONDITIONS TOWARD THE END OF THE WEEK.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...NONE.
&&
$$
SYNOPSIS...PELOQUIN
NEAR TERM...ROGOWSKI
SHORT TERM...ROGOWSKI
LONG TERM...PELOQUIN
AVIATION...ROGOWSKI/PELOQUIN
MARINE...ROGOWSKI/PELOQUIN
AREA FORECAST DISCUSSION
NWS BALTIMORE MD/WASHINGTON DC
905 AM EST SAT NOV 17 2007
.SYNOPSIS...
A WEAK CLIPPER SYSTEM WILL MOVE THROUGH THE MID ATLANTIC REGION
THIS AFTERNOON AND TONIGHT. THIS SYSTEM WILL BRING THE GREATEST
CHANCES OF LIGHT PRECIPITATION TO THE NORTHERN POTOMAC HIGHLANDS
AND ALONG THE MASON DIXON LINE. HIGH PRESSURE WILL BUILD BACK OVER
THE REGION ON SUNDAY...AND CONTINUE THROUGH MID WEEK. THE NEXT
FRONTAL BOUNDARY IS EXPECTED DURING THE LATTER HALF OF NEXT WEEK.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
WATER VAPOR LOOP SHOWS A WAVE DIVING SOUTHEAST ACROSS THE MIDWEST IN
ADVANCE OF A SECOND WAVE SAGGING SOUTH INTO THE UPPER GREAT LAKES.
AN UPPER LOW IS SHEARING NORTHEAST ACROSS THE PLAINS. ACARS
400-250MB WIND OBSERVATIONS SHOW A 90-110KT NORTHWESTERLY JET
EXTENDS SOUTHEAST FROM THE LOWER GREAT LAKES TO THE MID ATLANTIC
WHERE PHASING OCCURS WITH A 70-90KT WESTERLY JET THAT EXTENDS EAST
FROM THE PLAINS. 12Z SURFACE ANALYSIS PLACED A 1009MB CYCLONE NEAR
DAVENPORT IOWA...ALONG A COLD FRONT SAGGING SOUTHEAST ACROSS THE
GREAT LAKES. A 1023MB ANTICYCLONE DOMINATES THE SOUTHEAST
CONUS...WITH A TROUGH IN THE LEE OF THE CENTRAL APPALACHIANS.
EXPECT MID LEVEL CLOUDS TO ERODE ACROSS CENTRAL VIRGINIA IN THE WAKE
OF A WEAK SHORT WAVE WHICH PASSED OVERHEAD LAST NIGHT. MID LEVEL
MOISTURE WILL REMAIN IN PLACE FURTHER NORTH CLOSER TO THE
PENNSYLVANIA BORDER IN ADVANCE OF THE NEXT WAVE APPROACHING FROM THE
MIDWEST. BY THE END OF THE AFTERNOON...OPERATIONAL MODELS/03Z
SREF/SIMULATED REFLECTIVITY FROM LWX WRF-ARW/NCEP WRF-NMM AND
NSSL WRF-ARW ALL SUGGEST A SLIGHT CHANCE OF LIGHT RAIN ACROSS THE
PAN HANDLES OF MARYLAND AND WEST VIRGINIA. SOME LIGHT SNOW MAY MIX
IN WEST OF THE ALLEGHENY FRONT...BUT TEMPERATURES EXPECTED TO
PRECLUDE ACCUMULATION.
AS FOR TEMPERATURES...USED 00Z NGM MOS AS A STARTING POINT AND
TWEAKED DOWN ESPECIALLY ACROSS THE NORTH DUE TO THE EXPECTED SKY
COVER.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SUNDAY/...
THE CLIPPER SYSTEM WILL COME THROUGH TONIGHT. THE GFS AND NAM HAVE
BOTH MOVED BACK THE ONSET OF PRECIP UNTIL AFTER 00Z...AND BOTH
MODELS KEEP THE BULK OF THE PRECIP NORTH OF THE MASON DIXON LINE.
THE 21Z SREFS ARE IN AGREEMENT. SO...HAVE TAILORED POPS ACCORDINGLY.
THE GREATEST CHANCES OF PRECIP REMAIN IN THE POTOMAC HIGHLANDS AND
ALONG THE MASON DIXON LINE.
PTYPE WILL BE AN ISSUE IN AREAS WEST OF THE BLUE RIDGE. THE
HIGHLANDS SHOULD HAVE A SNOW-RAIN MIX EARLY...THEN A SWITCH TO ALL
SNOW AFTER MIDNIGHT. CENTRAL MARYLAND AND EXTREME EASTERN PANHANDLE
OF WEST VIRGINIA SHOULD HAVE MOSTLY RAIN...POSSIBLY MIXING WITH
SNOW AFTER MIDNIGHT. FOR AREAS EAST OF THE BLUE RIDGE WITH
POPS...ALL RAIN.
POPULATED MIN TEMPS WITH MOSGUIDE...ADJUSTING UPWARDS A FEW DEGREES
FOR THE COLD BIAS.
&&
.LONG TERM /SUNDAY THROUGH FRIDAY/...
THE LAST WAVE OF THE UPPER TROF WILL SLOWLY EXIT THE REGION OFF THE
NORTHEAST COAST EARLY MONDAY. GFS/NAM AGREE THAT THE LOW WILL CLOSE
OFF THE MEAN MID LEVEL FLOW AND DEEPEN...DRIFTING SE OFF CAPE COD
MID MONDAY. THE SFC LOW WILL ALSO STRENGTHEN...WITH PRONOUNCED
NORTHERLY CHANNELING ACROSS THE BAY AND NEARBY LAND AREAS STARTING
LATE SUNDAY NIGHT. THIS WILL PRODUCE SCA WINDS OVER THE BAY FOR MUCH
OF THE OVERNIGHT HRS AND INTO MONDAY AFTN. MEANWHILE...NAM HOLDS A
FAIRLY SHALLOW BUT DECENT LAYER OF LOW LEVEL MOISTURE ACROSS THE
MASON/DIXON LINE LATE SUN NIGHT. BEFORE THE LOW STRENGTHENS OFF THE
COAST AND WINDS INCREASE OVER THE BAY...LOW CIGS AND VSBYS MAY BE
PRESENT WITH THIS MEANDERING AREA OF HIGHER RH/S AND SCATTERED
PRECIP.
A WEAK RIDGE OF HIGH PRESSURE WILL TILT ACROSS THE EASTERN SEABOARD
TUES INTO EARLY WED. THE SFC HIGH WILL ALLOW TEMPS TO REBOUND
SLIGHTLY INTO THE U50S/L60S TUES/WED. TWO AREAS OF DEEPENING UPPER
TROF REGIONS WILL DEVELOP ACROSS THE NORTHERN PLAINS LATE TUES. THE
NORTHERN WAVE WILL PUSH A LONG POTENT COLD FRONT ACROSS THE GREAT
LAKES REGION ON WED. THE FRONT IS EXPECTED TO REACH THE CENTRAL
APPALACHIANS OVERNIGHT WED INTO EARLY THURS...THOU THE NORTHERN
STREAM OF THE UPPER JET AND THE STRONGEST FORCING FROM THE MID LEVEL
TROF WILL SLIDE ACROSS THE ST. LAWRENCE INLET. THE COLD FRONT WILL
MOST LIKELY DISSIPATE AS IT CROSS THE HIGHER TERRAIN EARLY
THURS...BUT ONLY IN TERMS OF PRECIPITATION. STRONG NW FLOW AND
COOLER TEMPS WILL BE PRESENT FOR THE END OF NEXT WEEK WITH A
LONGWAVE TYPE PATTERN TO THE MAIN UPPER TROF...WHICH CONTINUES TO
SLIDE WEAK BANDS OF UPPER ENERGY ACROSS THE GREAT LAKES REGION INTO
NEXT WEEKEND.
&&
.AVIATION /14Z SATURDAY THROUGH WEDNESDAY/...
NEXT CYCLONE ADVANCES FROM THE MIDWEST INTO THE MID ATLANTIC
THROUGH SUNDAY...BRINGING MID LEVEL CLOUDS WHICH WILL TEND TO
THICKEN AND LOWER (REMAINING VFR) TONIGHT. SHOWER ACTIVITY EXPECTED
TO FOCUS ALONG THE MOUNTAINS AND NORTH OF TERMINALS IN PENNSYLVANIA
PER 06Z NAM/GFS AND 03Z SREF.
AN AREA OF LOW LEVEL MOISTURE WILL PERSIST SUNDAY NIGHT INTO
MONDAY...WITH POSSIBLE WIDESPREAD LOW CIGS/VSBYS OVERNIGHT.
CONDITIONS SHOULD IMPROVE CLOSER TO THE BAY...WITH A STRONG
NORTHERLY WIND DEVELOPING FROM AN OFFSHORE LOW. A COLD FRONT WILL
REACH THE AREA LATE WED/EARLY THURS. AFTER THE FRONT PASSES...GUSTY
NW WINDS ARE EXPECTED TO REMAIN OVER THE REGION THRU THE END OF NEXT
WEEK.
&&
.MARINE...
ETA/GFS MOS AND 09Z KLWX WRF-ARW SUGGEST WINDS AROUND 10KT BACK FROM
WESTERLY TO SOUTHERLY THIS AFTERNOON IN ADVANCE OF AN APPROACHING
WEAK CYCLONE FROM THE MIDWEST.
SCA CONDITIONS DEVELOPING LATE SUNDAY WITH STRENGTHENING LOW OFF THE
ATLANTIC COAST. NORTHERLY WINDS WILL CONTINUE TO CHANNEL THRU MIDDAY
MONDAY AND DECREASE INTO THE MIDDLE OF NEXT WEEK. A STRONG COLD
FRONT WILL SLIDE ACROSS THE BAY ON THURS...WITH ANOTHER BURST OF
SUSTAINED NW WINDS BEHIND THE FRONT.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...NONE.
&&
$$
SYNOPSIS...LISTEMAA
NEAR TERM...ROGOWSKI
SHORT TERM...LISTEMAA
LONG TERM...SCHOOR
AVIATION...ROGOWSKI/SCHOOR
MARINE...ROGOWSKI/SCHOOR
AREA FORECAST DISCUSSION...CORRECTED
NWS MARQUETTE MI
430 PM EST SAT NOV 17 2007
.SHORT TERM (TONIGHT AND SUN)...
MAIN FCST ISSUES ARE CLOUDS AND MIN TEMPS TONIGHT.
WATER VAPOR IMAGERY AND RUC ANALYSIS SHOW NW FLOW CONTINUING ACROSS
THE UPPER GREAT LAKES BTWN A RIDGE OVER THE ROCKIES AND A TROF OVER
SE CANADA. A WEAK SHORTWAVE WAS DROPPING ACROSS THE UPPER LAKES.
AT THE SFC...HIGH PRES WAS LOCATED OVER NRN ONTARIO...NOT FAR FROM
PICKLE LAKE. LES OFF LAKE SUPERIOR HAS BEEN GRADUALLY DIMINISHING
TODAY WITH MOST OF THE PCPN NOT MUCH MORE THAN FLURRIES NOW.
DIMINISHING TREND IS A RESULT OF 2 MAIN FACTORS. WITH APPROACHING
SFC HIGH...LOW-LEVEL WINDS ARE BECOMING INCREASINGLY ANTICYCLONIC...
AND SECONDLY...INVERSION IS BEGINNING TO LOWER DUE TO SUBSIDENCE
BEHIND PASSING SHORTWAVE. AT CWPL...00Z SOUNDING SHOWED INVERSION
BASED AT 8KFT MSL WHILE 12Z SOUNDING SHOWED IT AT ONLY 4KFT MSL.
EARLY AFTN TAMDAR SOUNDINGS SHOWED INVERSION AROUND 4KFT NEAR CYQT
AND 5-5.5KFT NEAR KCMX/KSAW.
WITH STEADILY LOWERING INVERSION AND WITH LOW-LEVEL WINDS ONLY
BECOMING MORE ANTICYCLONIC AS SFC HIGH DRIFTS ACROSS THE UPPER GREAT
LAKES TONIGHT...WILL ONLY CARRY A MENTION OF FLURRIES NEAR LAKE
SUPERIOR FOR NE TO E FLOW FAVORED AREAS. FLURRIES WILL END DURING
THE OVERNIGHT PERIOD. NEXT QUESTION IS CLOUD COVER WHICH WILL HAVE A
MAJOR IMPACT ON MIN TEMPS. HAVE TRIED TO DEPICT SHIFTING LAKE EFFECT
CLOUD PATTERN BASED ON VEERING LOW-LEVEL WINDS AS HIGH PRES MOVES
OVER THE AREA. THUS...EXPECT CLOUDS OVER THE E AND SRN FCST AREA TO
SCATTER OUT FIRST WITH THE AREA FROM THE HURON MOUNTAINS ACROSS THE
KEWEENAW PENINSULA LAST (LATE TONIGHT). ASSUMING THERE IS AT LEAST A
FEW HRS OF CLR/PARTLY CLOUDY SKIES...RADIATIONAL COOLING WILL BE
ENHANCED BY THE DRY COLUMN (PRECIPITABLE WATER ONLY AROUND 0.2
INCHES OR ABOUT 50PCT OF NORMAL). WILL THUS CONTINUE ALONG THE LINES
OF THE PREVIOUS FCST WITH MINS GENERALLY BLO MOS GUIDANCE. LOWEST
MINS WILL PROBABLY OCCUR IN THE SNOW COVERED AREA AROUND CHAMPION.
LOWS MAY DIP JUST BLO 10F THERE.
LAKE EFFECT CLOUDS MAY STILL BE AN ISSUE SUN...BUT THIS TIME OFF
LAKE MI. AS WINDS VEER AROUND TO THE SE THEN S...WOULD NOT BE
SURPRISED TO SOME LAKE EFFECT CLOUDS SHIFT N INTO PARTS OF CNTRL
UPPER MI FOR PART OF SUN MORNING/EARLY AFTN. WITH THE EXCEPTION OF
THAT POTENTIAL...THE DAY SHOULD BEGIN MOSTLY SUNNY ACROSS THE FCST
AREA. NEXT SHORTWAVE WILL BE MOVING E ACROSS SRN SASKATCHEWAN/SRN
MANITOBA SUN AFTN. STRENGTHENING WAA PATTERN AHEAD OF THIS SYSTEM
WILL LEAD TO FAIRLY STRONG MID LEVEL ISENTROPIC ASCENT (290 TO 300K
SFCS) SPREADING TOWARD UPPER MI IN THE AFTN. THUS...LOOK FOR THE
TYPICAL INCREASE AND LOWERING OF HIGH/MID CLOUDS FROM W TO E SUN
AFTN AND NIGHT. SUFFICIENT MOISTENING FOR PCPN LOOKS TO HOLD OFF
UNTIL SUN EVENING OVER THE FAR W NEAR KIWD...BUT WILL KEEP A MENTION
OF CHC POPS OVER FAR WRN LAKE SUPERIOR LATE IN THE AFTN.
.LONG TERM...(SUNDAY NIGHT THROUGH SATURDAY)
MAIN FCST CONCERNS SHIFT FROM PCPN CHANCES/TYPE SUN NIGHT INTO MON
TO PCPN AND LAKE EFFECT POTENTIAL AS A MID LEVEL TROUGH MOVES
THROUGH THE CNTRL CONUS.
SUNDAY NIGHT INTO MON...THE FCST LEANS MORE TOWARD THE GFS WHICH WAS
SUPPORTED BY THE UKMET/ECMWF.
THE DYNAMIC PACIFIC SHORTWAVE TROUGH AND 150 KT 300 MB JET MOVES
QUICKLY THROUGH THROUGH SRN CANADA NEAR THE US/CAN BORDER. MODERATE
TO STRONG 700-300 MB QVECTOR CONV....UPPER LEVEL DIV ASSOCIATED WITH
THE LEFT EXIT OF THE JET STAY JUST A BIT NORTH OF THE CWA. EVEN
THROUGH THE AIRMASS STARTS OUT FAIRLY DRY...A STRONG BAND 290K-295
ISENTROPIC ASCENT WITH 50-60KT INFLOW OF 4 G/KG MOISTURE...POPS WERE
RAISED OVER THE CWA. WITH A RELATIVELY BRIEF PERIOD OF STRONGEST
UPWARD MOTION...OVERALL PCPN AMOUNTS SHOULD BE LIGHT...GENERALLY A
TENTH OF AN INCH OR LESS. EXPECT THAT THE MAJORITY OF PCPN WILL FALL
AS SNOW...GIVEN GFS/NAM TEMP PROFILES DURING THE PERIOD OF MAX LIFT.
WITH THE STRONG WAA PATTERN BRINGING SFC-850 MB JUST ABOVE
0C(1000-850 MB THICKNESS AOA 1310 M)...A MIX WITH RAIN FROM LATE SUN
NIGHT INTO MON MAY OCCUR AS THE PCPN DIMINISHES. WITH STRONG MID
LEVEL DRYING MOVING IN OVER THE LOWER LEVEL MOIST LAYER...CANNOT
RULE OUT SOME DZ OR EVEN FZDZ IF SOME COLDER SFC TEMPS LINGER BUT
WILL NOT ADD MENTION NOW GIVEN REMAINING UNCERTAINTY ON DETAILS WITH
BOTH PCPN AND AMOUNT OF LOW LEVEL MOISTURE.
MON AFTERNOON INTO MON NIGHT...EXPECT PCPN TO END AS WEAK MID LEVEL
AND SFC RIDGING PREVAIL. A SLIGHT CHANCE FOR RAIN OR SNOW WAS
MENTIONED LATE MON NIGHT AS MID LEVEL FGEN AND SOME LIGHT PCPN COULD
SPREAD FROM THE NRN PLAINS INTO THE WRN PORTION OF THE CWA.
TUE THROUGH THU...THE 00Z ECMWF AND GFS WERE IN GOOD AGREEMENT INTO
EARLY WED WITH THE FIRST ELONGATED SFC WAVE MOVING THROUGH THE ERN
GREAT LAKES IN SW FLOW PATTERN AHEAD OF THE WRN CONUS TROUGH. MID
LEVEL FGEN IN SW MID/UPPER LEVEL FLOW PATTERN WOULD SUPPORT
POTENTIAL FOR PCPN BANDS INTO THE WRN LAKES. GFS/ECMWF LOW LEVEL
TEMP SUGGEST PCPN WOULD BE MAINLY RAIN OR A MIX OF RAIN/SNOW EARLY
TUE WITH COOLING BY LATE IN THE DAY RESULTING IN A CHANGEOVER TO
SNOW LATE TUE INTO TUE NIGHT.
THE MODELS THEN DIVERGE IN HANDLING ORIENTATION OF THE LONG WAVE
TROUGH AND AMOUNT OF SHORTWAVE ENERGY MOVING TOWARD THE GREAT LAKES.
THE 00Z/12Z ECMWF TAKES A FAST WEAKER LOW THROUGH THE ERN OH VALLEY
THU WHILE THE 12Z GFS SHOWS A STRONGER LOW NEAR DTW(12Z THU) AND THE
12Z UKMET PLACES THE LOW FARTHEST WEST(OVER WRN LOWER MI). THE FCST
LEANED MORE TOWARD A BLEND OF THE 06Z GFS AND 12Z ENS
MEAN...SUPPORTED BY THE 12Z CANADIAN GLBL GEM...WHICH TAKES THE LOW
TOWARD THE ERN LAKES. THIS WOULD FAVOR MAINLY LAKE EFFECT SHSN FOR
NRLY FLOW FAVORED LOCATIONS WED NIGHT THROUGH THU WITH MAINLY LIGHT
AMOUNTS. HOWEVER LARGE UNCERTAINTY REMAINS GIVEN THE TREND WITH THE
12Z GFS AND ENSEMBLES WHICH WOULD PLACE THE CWA IN THE AREA OF MORE
WIDESPREAD MODERATE SNOW WITH SIGNIFICANT LAKE ENHANCEMENT. WITH LOW
CONFIDENCE IN EVOLUTION OF THE SYSTEM...HEAVY SNOW POTENTIAL WAS NOT
HIGHLIGHTED IN THE HWO AT THIS POINT.
FRI-SAT...MODELS SHOW 850 MB TEMPS REMAINING COLD ENOUGH...FROM -10C
TO -15C FOR CONTINUES LES. WINDS ARE EXPECTED TO BACK TO MORE WRLY
AND POSSIBLY SW BY SAT.
&&
.AVIATION (FOR THE 18Z TAF ISSUANCE)...
HIGH PRES BUILDING SE ACROSS NRN ONTARIO THIS AFTN WILL SETTLE OVER
UPPER MI TONIGHT AND THEN QUICKLY SHIFT E SUN. CHILLY NNE FLOW
ACROSS LAKE SUPERIOR WILL CONTINUE TO GENERATE -SHSN/FLURRIES INTO
THE EVENING HRS BEFORE THE HIGH SETTLES OVER THE AREA. WHILE VIS
WILL BE IN THE VFR RANGE WITH FLURRIES...VIS MAY DROP BRIEFLY AT
TIMES TO MVFR IN -SHSN FOR THE NEXT FEW HRS. MEANWHILE...EXPECT CIGS
TO FLUCTUATE BTWN ABOUT 2.5KFT AND 4KFT THRU THE AFTN INTO THE
EVENING. AS THE HIGH SETTLES OVER UPPER MI TONIGHT...EXPECT CLOUDS
TO SCATTER OUT OR CLEAR AT KCMX AND KSAW LATE IN THE NIGHT. WHILE
KCMX SHOULD THEN REMAIN CLEAR THRU SUN MORNING...DEVELOPING SSE
WINDS MAY RESULT IN LAKE EFFECT CLOUDS (MVFR CIGS) FROM LAKE MI
SPREADING TO KSAW LATE SUN MORNING.
&&
.MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)...
MAIN FCST ISSUE IS THE GALE POTENTIAL SUN NIGHT/MON. HIGH PRES
MOVING ACROSS THE UPPER GREAT LAKES TONIGHT...BRINGING DIMINISHING
WINDS...WILL MOVE TO NEW ENGLAND BY SUN NIGHT AS IT STRENGTHENS.
TIGHTENING PRES GRADIENT BTWN THE DEPARTING HIGH AND LOW PRES MOVING
ACROSS SCNTRL CANADA WILL BRING INCREASING SRLY WINDS SUN. THE
SOUTHERLY WINDS WILL INCREASE FURTHER SUN NIGHT AS THE LOW MOVES TO
NRN ONTARIO. 35 KT GALES APPEAR LIKELY ACROSS MUCH OF THE LAKE...AND
WILL PROBABLY SEE FREQUENT GUSTS TO AROUND 40 KT OVER THE EASTERN
PORTION LATE SUN NIGHT/MON MORNING. AS IS TYPICAL FOR SRLY WINDS...
THE AREA AROUND GRAND MARAIS AT THE E END OF PICTURED ROCKS NATIONAL
LAKESHORE WILL PROBABLY SEE SOME OF THE STRONGEST WINDS. WINDS WILL
SLOWLY DIMINISH MON...WITH GALES ENDING BY EARLY AFTN AS LOW PRES
WEAKENS AND MOVES TO JAMES BAY. AFTER A PERIOD OF LIGHTER WINDS MON
NIGHT INTO TUE...WINDS WILL AGAIN INCREASE TUE NIGHT/WED AS LOW PRES
MOVES NE TOWARD THE LOWER GREAT LAKES.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...NONE
&&
$$
SHORT TERM...ROLFSON
LONG TERM...JLB
AVIATION/MARINE...ROLFSON
AREA FORECAST DISCUSSION...UPDATED
NWS MARQUETTE MI
1237 PM EST SAT NOV 17 2007
UPDATED AVIATION SECTION FOR 18Z TAF ISSUANCE
.DISCUSSION (ISSUED AT 345 AM EST)...
00Z RAOBS/LATEST WV IMAGERY AND RUC ANALYSIS SHOW NW FLOW ALF OVER
THE UPR GRT LKS ON WRN FLANK OF UPR TROF IN SE CAN AND E OF RDGING
THE ROCKIES BLDG INTO THE WRN PLAINS. SHRTWV EMBEDDED IN NW FLOW
OVER NW ONTARIO IS APRCHG NW LK SUP...AND DPVA/H85-5 QVECTOR CNVGC/
H85-7 FGEN IN ADVANCE OF THIS FEATURE IS CAUSING SOME -SN OVER
MAINLY THE SRN TIER ZNS. BUT GENERAL DRYNESS SHOWN ON THE 00Z INL/
GRB RAOBS AND 03Z TAMDAR SDNG FM CIU IS LIMITING THE COVG/INTENSITY
OF THIS PCPN. WITH LGT WINDS ALG WEAK SFC-H85 TROF PRESSING ACRS LK
SUP IN ADVANCE OF SHRTWV...LES HAS BEEN NEGLIGIBLE AS WELL. BUT MQT
88D SHOWING INCRSG RETURNS NR THE NCNTRL SHORE WITH SLOWLY INCRSG N
WINDS OVER THE OPEN WATERS OF LK SUP ADVECTING COLDER AIR TO THE N
(00Z H85 TEMP -13C AT YPL VS -5C AT GRB) AND BAND OF CLD ASSOCIATED
WITH TROF/ANOTHER AXIS OF H85-7 FGEN MOVING S ACRS LK SUP. SFC DWPT
DEPRESSIONS... 16F AT YQT AND 9F AT YGQ) SUG AIRMASS JUST N OF LK IS
STILL RATHER DRY. BUT 00Z YPL SDNG SHOWS A RELATIVELY DEEP MOIST LYR
UP TO HI INVRN BASE ARND H75 WITH H85 DEWPT DEPRESSION OF 0C. LAST
SFC OB FM YPL AT 02Z SHOWED DEWPT DEPRESSION OF ONLY 3F. SOME LGT
SN/FLURRIES FALLING IN THAT AREA ARND H85 THERMAL TROF. FARTHER
NW...SFC HI PRES BLDG INTO FAR NW ONTARIO. YYQ SDNG IS RATHER
DRY/STABLE WITH PWAT AT 0.14 INCH.
FCST CONCERNS THIS PACKAGE ARE LES TRENDS/AMTS INTO THIS EVNG...THEN
TEMPS LATER TNGT THRU SUN. FOCUS FOR LATE SUN/MON TURNS TO TIMING/
IMPACT OF SHRTWV IN THE NE PACIFIC EMBEDDED IN STRG WLY FLOW AIMED
AT THE PAC NW.
FOR TDAY...SHRTWV OVER ONTARIO PROGGED TO SLIDE ACRS LK SUP AND INTO
UPR MI BY 00Z SUN WHILE SFC HI CENTER TRAILING THIS SYS FCST TO
SETTLE TO JUST N OF INL. LGT SN OVER THE SRN TIER WL DIMINISH BY
FCST ISSUANCE AS H85-7 FGEN AXIS/SOMEWHAT DEEPER MSTR IMPACTING THAT
AREA NOW PUSHES TO THE SE. BUT EXPECT SOME INTENSIFICATION OF SN NR
LK SUP TEMPORARILY EARLY THIS MRNG WITH ARRIVAL OF AXIS OF THICKER
SC/H85-7 FGEN ASSOCIATED WITH SFC-H85 TROF AND COLDER H85 AIR BEHIND
THIS FEATURE. ANY INTENSIFICATION SHOULD BE RELATIVELY MINOR THOUGH
WITH NR SFC DRY AIR/HIER DWPT DEPRESSIONS FOLLOWING CLOSELY BEHIND
THE TROF. ALTHOUGH ADVECTION OF MORE FVRBL AIRMASS SHOWN ON THE 00Z
YPL SDNG MAY REINVIGORATE THE LES A BIT DURING THE DAY...ESPECIALLY
IN AREAS FVRD BY FCST NNE FLOW...INCRSG H85-5 QVECTOR DVGC/H7
SUBSIDENCE/LARGER SCALE ACYC FLOW WITH WEAK H95 CNVGC/SINKING INVRN
HGT ESPECIALLY AFT 18Z TO 3-4K FT BY 00Z AS SHOWN ON NAM/GFS FCST
SDNGS (LOWEST OVER THE W CLOSEST TO SFC RDG AXIS) WL KEEP LES AMTS
IN CHECK. GOING FCST LES TRENDS/AMTS AOB 1 INCH AT MOST SPOTS SEEM
TO BE IN GOOD ORDER AND IN LTL NEED OF CHG.
WITH INCRSG LARGER SCALE DNVA/H85-5 QVECTOR DVGC/HGT RISES/H7
SUBSIDENCE IN THE WAKE OF SHRTWV TNGT...DRY HI PRES FCST TO BLD ACRS
THE CWA AFT 06Z. EXPECT ANY LINGERING FLURRIES NEAR LK SUP TO
PERSIST LONGEST OVER THE NCNTRL IN UPSLOPE NNE FLOW TO THE SE OF THE
HI CENTER BEFORE PASSAGE OF HI CENTER OVERNGT TURNS FLOW OFFSHORE
AFT 06Z. PROSPECT OF CLRG SKIES/LGT WINDS/FCST PWAT TO ARND 0.15
INCH SUGS THE COLDEST NGT OF THE SEASON MAY BE IN STORE FOR MUCH OF
THE FA...WITH THE LOWEST READINGS AWAY FM THE MODERATING INFLUENCE
OF THE LKS. ALTHOUGH RETURN SLY FLOW DVLPG LATE OVER THE W MAY CHECK
THE DIURNAL TEMP FALL...WL FCST LO TEMPS BLO MOS GUIDANCE AT MOST
SPOTS WITH NEAR IDEAL RADIATION HEAT LOSS EXPECTED.
SUN WL AT LEAST START ON THE MOSUNNY SIDE WITH HI PRES CENTERED JUST
TO THE E OF ANJ AT 12Z SUN. BUT AS FLOW ALF BECOMES MORE ZONAL IN
ADVANCE OF PACIFIC SHRTWV PLOWING ACRS SRN CAN AND SFC WINDS TURN SW
BTWN DEPARTING SFC HI AND ACCOMPANYING SFC LO PRES OVER SCNTRL CAN
SETTING UP ISENTROPIC LIFT ON THE GFS FCST 290K SFC...EXPECT AN
INCRS IN MID/HI CLD LATE OVER THE W. ALTHOUGH UKMET SHOWS SIMILAR
MID LVL MOISTENING...PREFER THE DRIER GFS FCST (DRY THRU 00Z MON VS
UKMET WHICH GENERATES SOME PCPN AS FAR E AS THE WRN ZNS) DUE TO
ANTECEDENT DRY AIRMASS AND ABSENCE OF SHARPER H85-5 QVECTOR CNVGC/
UPR DVGC. WL MAINTAIN SCHC POPS ONLY OVER FAR WRN LK SUP NEAR TO
WHERE GFS SHOWS PCPN ARRIVING ARND 00Z. OTRW...MIXING TO H875 ON GFS
FCST SDNGS YIELDS HI TEMPS JUST A FEW DEGREES UNDER GOING FCST.
ON SUN NGT...FAVORED GFS/UKMET/CNDN MODELS SHOW PACIFIC SHRTWV/SFC
LO MOVING INTO NW ONTARIO BY 12Z MON. SINCE THE SHRTWV/SHARPEST
DPVA/DEEP QVECTOR CNVGC/UPR DVGC ON CYC SIDE OF SUPPORTING JET AXIS
LOOK TO REMAIN TO THE N...SUSPECT PCPN OVER THE LAND FA WL BE ON THE
LGT SIDE...ESPECIALLY SINCE STRENGTHENING SW FLOW APPEARS TO TAP
ONLY MARGINALLY MOIST AIR. GFS SHOWS ONLY NARROW BAND OF H7 SPECIFIC
HUMIDITY AOA 3G/KG RETURNING N INTO THE UPR LKS...WITH MODEL FCST
SDNGS NEVER SHOWING DEEP SATURATION FOR ANY SGNFT LENGTH OF TIME.
LIKE GFS MOS IDEA OF POPS RANGING FM 10-20 OR SO OVER THE SCNTRL TO
40 AT CMX. THE DRY AIR SHOULD ENSURE THAT WHATEVER PCPN DOES FALL WL
BE IN THE FORM OF SN PER WBLB ON FCST SDNGS...EXCEPT PERHAPS OVER
THE FAR W LATE. BUT BEST ASCENT MIGHT BE PAST THERE AT THAT POINT
WITH AXIS OF HIER SPECIFIC HUMIDITY OFF TO THE E BY THEN. MOST SGNFT
IMPACT OF THIS SYS ON SUN NGT WL BE WINDS ESPECIALLY OVER LK SUP...
WHERE GFS FCST SDNGS SHOW SSW 35KT WINDS WITHIN MIXED LYR BLO WAD
INVRN. THESE STRONG WINDS/CLD COVER WL MITIGATE DIURNAL TEMP DROP IN
FACE OF EVAPORATIVE COOLING.
ALTHOUGH THERE MAY BE A BREAK AFT INITIAL BAND OF OVERRNG PCPN ON
SUN NGT...GFS/UKMET SHOW ANOTHER ROUND OF PCPN BREAKING OUT ON MON
(WHICH WOULD BE IN THE FORM OF RA) IN PERSISTENT ISENTROPIC LIFT N
OF WARM FNT EXTENDING E FM SFC LO IN THE NORTHERN PLAINS INTO NRN
WI. ON THE OTHER HAND...CNDN/ECMWF MODELS SHOW ATTENDANT COLD FNT TO
THE SW OF LO TRACKING THRU ONTARIO PASSAING ACRS THE CWA DURING THE
DAY...WITH DRYING FCST IN THE AFTN. CONSIDERING THE MAJOR
DISCREPANCIES BTWN THESE TWO CAMPS...OPTED TO LEAVE GOING FCST AS IS
ON MON IN AGREEMENT WITH GFS/UKMET GUIDANCE.
COORDINATED WITH APX/GRB.
&&
.AVIATION (FOR THE 18Z TAF ISSUANCE)...
HIGH PRES BUILDING SE ACROSS NRN ONTARIO THIS AFTN WILL SETTLE OVER
UPPER MI TONIGHT AND THEN QUICKLY SHIFT E SUN. CHILLY NNE FLOW
ACROSS LAKE SUPERIOR WILL CONTINUE TO GENERATE -SHSN/FLURRIES INTO
THE EVENING HRS BEFORE THE HIGH SETTLES OVER THE AREA. WHILE VIS
WILL BE IN THE VFR RANGE WITH FLURRIES...VIS MAY DROP BRIEFLY AT
TIMES TO MVFR IN -SHSN FOR THE NEXT FEW HRS. MEANWHILE...EXPECT CIGS
TO FLUCTUATE BTWN ABOUT 2.5KFT AND 4KFT THRU THE AFTN INTO THE
EVENING. AS THE HIGH SETTLES OVER UPPER MI TONIGHT...EXPECT CLOUDS
TO SCATTER OUT OR CLEAR AT KCMX AND KSAW LATE IN THE NIGHT. WHILE
KCMX SHOULD THEN REMAIN CLEAR THRU SUN MORNING...DEVELOPING SSE
WINDS MAY RESULT IN LAKE EFFECT CLOUDS (MVFR CIGS) FROM LAKE MI
SPREADING TO KSAW LATE SUN MORNING.
&&
.MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)...
WINDS OF 15 TO 25 KT ARE POSSIBLE THIS MORNING AS HIGH PRESSURE OVER
NORTHERN MANITOBA BUILDS SOUTH TOWARDS LAKE SUPERIOR. EXPECT WINDS
TO DROP OFF TONIGHT AS THE HIGH CROSSES. ON SUNDAY...LOOK FOR WINDS
TO SHIFT TO THE SOUTH AND PICK UP AGAIN AS THE HIGH SHIFTS OFF INTO
QUEBEC...WITH 25 KT WINDS POSSIBLE ACROSS MUCH OF THE LAKE BY LATE
IN THE DAY. THE SOUTHERLY WINDS WILL INCREASE FURTHER SUN NIGHT AS
LOW PRESSURE IN SW MANITOBA MOVES INTO WESTERN ONTARIO. 35 KT GALES
SEEM LIKELY ACROSS MUCH OF THE LAKE...AND PROBABLY 40 KT OVER THE
EASTERN PORTION. WINDS WILL SLOWLY DIMINISH ON MONDAY...WITH ANY
GALES ENDING BY EARLY IN THE AFTERNOON...THANKS TO THE SURFACE LOW
WEAKENING AND LIFTING INTO FAR NORTHERN ONTARIO. LOOK FOR WINDS TO
SHIFT TO THE WEST LATE MONDAY AND NW MONDAY NIGHT WHILE DIMINISHING
BELOW 20 KT...DUE TO THE COLD FRONT ASSOCIATED WITH THE LOW CROSSING
LAKE SUPERIOR. THIS FRONT WILL STALL IN SOUTHERN LOWER MICHIGAN TUE
MORNING WHILE HIGH PRESSURE BEGINS BUILDING SOUTH OUT OF CANADA. A
SURFACE LOW IS EXPECTED TO RIDE UP ALONG THE FRONT LATE TUE...
CAUSING NORTHERLY WINDS TO INCREASE TO 15 TO 25 KT ON LAKE SUPERIOR
TUE NIGHT. WINDS WILL SLOWLY DIMINISH ON WEDNESDAY AS THE LOW HEADS
TOWARDS NEW ENGLAND AND THE AFOREMENTIONED HIGH BUILDS IN.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...NONE
&&
$$
DISCUSSION...KC
AVIATION...ROLFSON
MARINE...AJ
AREA FORECAST DISCUSSION...UPDATED
NWS MARQUETTE MI
634 AM EST SAT NOV 17 2007
UPDATED AVIATION SECTION FOR 12Z TAF ISSUANCE
.DISCUSSION...
00Z RAOBS/LATEST WV IMAGERY AND RUC ANALYSIS SHOW NW FLOW ALF OVER
THE UPR GRT LKS ON WRN FLANK OF UPR TROF IN SE CAN AND E OF RDGING
THE ROCKIES BLDG INTO THE WRN PLAINS. SHRTWV EMBEDDED IN NW FLOW
OVER NW ONTARIO IS APRCHG NW LK SUP...AND DPVA/H85-5 QVECTOR CNVGC/
H85-7 FGEN IN ADVANCE OF THIS FEATURE IS CAUSING SOME -SN OVER
MAINLY THE SRN TIER ZNS. BUT GENERAL DRYNESS SHOWN ON THE 00Z INL/
GRB RAOBS AND 03Z TAMDAR SDNG FM CIU IS LIMITING THE COVG/INTENSITY
OF THIS PCPN. WITH LGT WINDS ALG WEAK SFC-H85 TROF PRESSING ACRS LK
SUP IN ADVANCE OF SHRTWV...LES HAS BEEN NEGLIGIBLE AS WELL. BUT MQT
88D SHOWING INCRSG RETURNS NR THE NCNTRL SHORE WITH SLOWLY INCRSG N
WINDS OVER THE OPEN WATERS OF LK SUP ADVECTING COLDER AIR TO THE N
(00Z H85 TEMP -13C AT YPL VS -5C AT GRB) AND BAND OF CLD ASSOCIATED
WITH TROF/ANOTHER AXIS OF H85-7 FGEN MOVING S ACRS LK SUP. SFC DWPT
DEPRESSIONS... 16F AT YQT AND 9F AT YGQ) SUG AIRMASS JUST N OF LK IS
STILL RATHER DRY. BUT 00Z YPL SDNG SHOWS A RELATIVELY DEEP MOIST LYR
UP TO HI INVRN BASE ARND H75 WITH H85 DEWPT DEPRESSION OF 0C. LAST
SFC OB FM YPL AT 02Z SHOWED DEWPT DEPRESSION OF ONLY 3F. SOME LGT
SN/FLURRIES FALLING IN THAT AREA ARND H85 THERMAL TROF. FARTHER
NW...SFC HI PRES BLDG INTO FAR NW ONTARIO. YYQ SDNG IS RATHER
DRY/STABLE WITH PWAT AT 0.14 INCH.
FCST CONCERNS THIS PACKAGE ARE LES TRENDS/AMTS INTO THIS EVNG...THEN
TEMPS LATER TNGT THRU SUN. FOCUS FOR LATE SUN/MON TURNS TO TIMING/
IMPACT OF SHRTWV IN THE NE PACIFIC EMBEDDED IN STRG WLY FLOW AIMED
AT THE PAC NW.
FOR TDAY...SHRTWV OVER ONTARIO PROGGED TO SLIDE ACRS LK SUP AND INTO
UPR MI BY 00Z SUN WHILE SFC HI CENTER TRAILING THIS SYS FCST TO
SETTLE TO JUST N OF INL. LGT SN OVER THE SRN TIER WL DIMINISH BY
FCST ISSUANCE AS H85-7 FGEN AXIS/SOMEWHAT DEEPER MSTR IMPACTING THAT
AREA NOW PUSHES TO THE SE. BUT EXPECT SOME INTENSIFICATION OF SN NR
LK SUP TEMPORARILY EARLY THIS MRNG WITH ARRIVAL OF AXIS OF THICKER
SC/H85-7 FGEN ASSOCIATED WITH SFC-H85 TROF AND COLDER H85 AIR BEHIND
THIS FEATURE. ANY INTENSIFICATION SHOULD BE RELATIVELY MINOR THOUGH
WITH NR SFC DRY AIR/HIER DWPT DEPRESSIONS FOLLOWING CLOSELY BEHIND
THE TROF. ALTHOUGH ADVECTION OF MORE FVRBL AIRMASS SHOWN ON THE 00Z
YPL SDNG MAY REINVIGORATE THE LES A BIT DURING THE DAY...ESPECIALLY
IN AREAS FVRD BY FCST NNE FLOW...INCRSG H85-5 QVECTOR DVGC/H7
SUBSIDENCE/LARGER SCALE ACYC FLOW WITH WEAK H95 CNVGC/SINKING INVRN
HGT ESPECIALLY AFT 18Z TO 3-4K FT BY 00Z AS SHOWN ON NAM/GFS FCST
SDNGS (LOWEST OVER THE W CLOSEST TO SFC RDG AXIS) WL KEEP LES AMTS
IN CHECK. GOING FCST LES TRENDS/AMTS AOB 1 INCH AT MOST SPOTS SEEM
TO BE IN GOOD ORDER AND IN LTL NEED OF CHG.
WITH INCRSG LARGER SCALE DNVA/H85-5 QVECTOR DVGC/HGT RISES/H7
SUBSIDENCE IN THE WAKE OF SHRTWV TNGT...DRY HI PRES FCST TO BLD ACRS
THE CWA AFT 06Z. EXPECT ANY LINGERING FLURRIES NEAR LK SUP TO
PERSIST LONGEST OVER THE NCNTRL IN UPSLOPE NNE FLOW TO THE SE OF THE
HI CENTER BEFORE PASSAGE OF HI CENTER OVERNGT TURNS FLOW OFFSHORE
AFT 06Z. PROSPECT OF CLRG SKIES/LGT WINDS/FCST PWAT TO ARND 0.15
INCH SUGS THE COLDEST NGT OF THE SEASON MAY BE IN STORE FOR MUCH OF
THE FA...WITH THE LOWEST READINGS AWAY FM THE MODERATING INFLUENCE
OF THE LKS. ALTHOUGH RETURN SLY FLOW DVLPG LATE OVER THE W MAY CHECK
THE DIURNAL TEMP FALL...WL FCST LO TEMPS BLO MOS GUIDANCE AT MOST
SPOTS WITH NEAR IDEAL RADIATION HEAT LOSS EXPECTED.
SUN WL AT LEAST START ON THE MOSUNNY SIDE WITH HI PRES CENTERED JUST
TO THE E OF ANJ AT 12Z SUN. BUT AS FLOW ALF BECOMES MORE ZONAL IN
ADVANCE OF PACIFIC SHRTWV PLOWING ACRS SRN CAN AND SFC WINDS TURN SW
BTWN DEPARTING SFC HI AND ACCOMPANYING SFC LO PRES OVER SCNTRL CAN
SETTING UP ISENTROPIC LIFT ON THE GFS FCST 290K SFC...EXPECT AN
INCRS IN MID/HI CLD LATE OVER THE W. ALTHOUGH UKMET SHOWS SIMILAR
MID LVL MOISTENING...PREFER THE DRIER GFS FCST (DRY THRU 00Z MON VS
UKMET WHICH GENERATES SOME PCPN AS FAR E AS THE WRN ZNS) DUE TO
ANTECEDENT DRY AIRMASS AND ABSENCE OF SHARPER H85-5 QVECTOR CNVGC/
UPR DVGC. WL MAINTAIN SCHC POPS ONLY OVER FAR WRN LK SUP NEAR TO
WHERE GFS SHOWS PCPN ARRIVING ARND 00Z. OTRW...MIXING TO H875 ON GFS
FCST SDNGS YIELDS HI TEMPS JUST A FEW DEGREES UNDER GOING FCST.
ON SUN NGT...FAVORED GFS/UKMET/CNDN MODELS SHOW PACIFIC SHRTWV/SFC
LO MOVING INTO NW ONTARIO BY 12Z MON. SINCE THE SHRTWV/SHARPEST
DPVA/DEEP QVECTOR CNVGC/UPR DVGC ON CYC SIDE OF SUPPORTING JET AXIS
LOOK TO REMAIN TO THE N...SUSPECT PCPN OVER THE LAND FA WL BE ON THE
LGT SIDE...ESPECIALLY SINCE STRENGTHENING SW FLOW APPEARS TO TAP
ONLY MARGINALLY MOIST AIR. GFS SHOWS ONLY NARROW BAND OF H7 SPECIFIC
HUMIDITY AOA 3G/KG RETURNING N INTO THE UPR LKS...WITH MODEL FCST
SDNGS NEVER SHOWING DEEP SATURATION FOR ANY SGNFT LENGTH OF TIME.
LIKE GFS MOS IDEA OF POPS RANGING FM 10-20 OR SO OVER THE SCNTRL TO
40 AT CMX. THE DRY AIR SHOULD ENSURE THAT WHATEVER PCPN DOES FALL WL
BE IN THE FORM OF SN PER WBLB ON FCST SDNGS...EXCEPT PERHAPS OVER
THE FAR W LATE. BUT BEST ASCENT MIGHT BE PAST THERE AT THAT POINT
WITH AXIS OF HIER SPECIFIC HUMIDITY OFF TO THE E BY THEN. MOST SGNFT
IMPACT OF THIS SYS ON SUN NGT WL BE WINDS ESPECIALLY OVER LK SUP...
WHERE GFS FCST SDNGS SHOW SSW 35KT WINDS WITHIN MIXED LYR BLO WAD
INVRN. THESE STRONG WINDS/CLD COVER WL MITIGATE DIURNAL TEMP DROP IN
FACE OF EVAPORATIVE COOLING.
ALTHOUGH THERE MAY BE A BREAK AFT INITIAL BAND OF OVERRNG PCPN ON
SUN NGT...GFS/UKMET SHOW ANOTHER ROUND OF PCPN BREAKING OUT ON MON
(WHICH WOULD BE IN THE FORM OF RA) IN PERSISTENT ISENTROPIC LIFT N
OF WARM FNT EXTENDING E FM SFC LO IN THE NORTHERN PLAINS INTO NRN
WI. ON THE OTHER HAND...CNDN/ECMWF MODELS SHOW ATTENDANT COLD FNT TO
THE SW OF LO TRACKING THRU ONTARIO PASSAING ACRS THE CWA DURING THE
DAY...WITH DRYING FCST IN THE AFTN. CONSIDERING THE MAJOR
DISCREPANCIES BTWN THESE TWO CAMPS...OPTED TO LEAVE GOING FCST AS IS
ON MON IN AGREEMENT WITH GFS/UKMET GUIDANCE.
COORDINATED WITH APX/GRB.
&&
.AVIATION (FOR THE 12Z TAF ISSUANCE)...
NORTH TO NORTHEAST LOW LEVEL FLOW IN ADVANCE OF COLD AND MOIST HIGH
PRESSURE DROPPING SOUTH THROUGH MANITOBA IS PUSHING A CONVERGENT
WEST TO EAST BAND OF LAKE EFFECT SNOW ACROSS SAW AS OF 1115Z. THIS
BAND OF SNOW IS WEAKENING AND SHOULD CONTINUE TO DO SO AS IT BECOMES
FURTHER REMOVED FROM THE HEAT SOURCE OF LAKE SUPERIOR. HOWEVER...
LIGHT LAKE EFFECT SNOW SHOWERS WILL PERSIST THROUGH THE DAY...MAINLY
AFFECTING SAW AS A NNE WIND AT CMX IS NOT AS FAVORABLE. IN
ADDITION...NNE WINDS COMBINED WITH CEILINGS NORTH OF LAKE SUPERIOR
IN THE MVFR CATEGORY SUGGESTS THAT SAW SHOULD BE ABLE TO HOLD ONTO
AN MVFR DECK...DESPITE ANY MIXING THAT MIGHT OCCUR FROM DAYTIME
HEATING. SNOW SHOWERS SHOULD END THIS EVENING AS THE HIGH PRESSURE
AREA BEGINS TO MOVE OVER UPPER MICHIGAN...BUT WITH THE HIGH COMES A
LOWERING INVERSION...WHICH WOULD HELP TO KEEP CEILING HEIGHTS WHERE
THEY ARE. MODELS SUGGEST ENOUGH DRY AIR WILL COME IN LATE IN
THE EVENING AT CMX AND AFTER MIDNIGHT AT SAW TO RESULT IN SOME
CLEARING...THOUGH NO SIGNIFICANT CLEARING IS EXPECTED UNTIL THE
GENERAL LOW LEVEL WINDS TURN SOUTH SUNDAY MORNING.
&&
.MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)...
WINDS OF 15 TO 25 KT ARE POSSIBLE THIS MORNING AS HIGH PRESSURE OVER
NORTHERN MANITOBA BUILDS SOUTH TOWARDS LAKE SUPERIOR. EXPECT WINDS
TO DROP OFF TONIGHT AS THE HIGH CROSSES. ON SUNDAY...LOOK FOR WINDS
TO SHIFT TO THE SOUTH AND PICK UP AGAIN AS THE HIGH SHIFTS OFF INTO
QUEBEC...WITH 25 KT WINDS POSSIBLE ACROSS MUCH OF THE LAKE BY LATE
IN THE DAY. THE SOUTHERLY WINDS WILL INCREASE FURTHER SUN NIGHT AS
LOW PRESSURE IN SW MANITOBA MOVES INTO WESTERN ONTARIO. 35 KT GALES
SEEM LIKELY ACROSS MUCH OF THE LAKE...AND PROBABLY 40 KT OVER THE
EASTERN PORTION. WINDS WILL SLOWLY DIMINISH ON MONDAY...WITH ANY
GALES ENDING BY EARLY IN THE AFTERNOON...THANKS TO THE SURFACE LOW
WEAKENING AND LIFTING INTO FAR NORTHERN ONTARIO. LOOK FOR WINDS TO
SHIFT TO THE WEST LATE MONDAY AND NW MONDAY NIGHT WHILE DIMINISHING
BELOW 20 KT...DUE TO THE COLD FRONT ASSOCIATED WITH THE LOW CROSSING
LAKE SUPERIOR. THIS FRONT WILL STALL IN SOUTHERN LOWER MICHIGAN TUE
MORNING WHILE HIGH PRESSURE BEGINS BUILDING SOUTH OUT OF CANADA. A
SURFACE LOW IS EXPECTED TO RIDE UP ALONG THE FRONT LATE TUE...
CAUSING NORTHERLY WINDS TO INCREASE TO 15 TO 25 KT ON LAKE SUPERIOR
TUE NIGHT. WINDS WILL SLOWLY DIMINISH ON WEDNESDAY AS THE LOW HEADS
TOWARDS NEW ENGLAND AND THE AFOREMENTIONED HIGH BUILDS IN.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...NONE
&&
$$
DISCUSSION...KC
AVIATION...AJ
MARINE...AJ
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
345 AM EST SAT NOV 17 2007
.DISCUSSION...
00Z RAOBS/LATEST WV IMAGERY AND RUC ANALYSIS SHOW NW FLOW ALF OVER
THE UPR GRT LKS ON WRN FLANK OF UPR TROF IN SE CAN AND E OF RDGING
THE ROCKIES BLDG INTO THE WRN PLAINS. SHRTWV EMBEDDED IN NW FLOW
OVER NW ONTARIO IS APRCHG NW LK SUP...AND DPVA/H85-5 QVECTOR CNVGC/
H85-7 FGEN IN ADVANCE OF THIS FEATURE IS CAUSING SOME -SN OVER
MAINLY THE SRN TIER ZNS. BUT GENERAL DRYNESS SHOWN ON THE 00Z INL/
GRB RAOBS AND 03Z TAMDAR SDNG FM CIU IS LIMITING THE COVG/INTENSITY
OF THIS PCPN. WITH LGT WINDS ALG WEAK SFC-H85 TROF PRESSING ACRS LK
SUP IN ADVANCE OF SHRTWV...LES HAS BEEN NEGLIGIBLE AS WELL. BUT MQT
88D SHOWING INCRSG RETURNS NR THE NCNTRL SHORE WITH SLOWLY INCRSG N
WINDS OVER THE OPEN WATERS OF LK SUP ADVECTING COLDER AIR TO THE N
(00Z H85 TEMP -13C AT YPL VS -5C AT GRB) AND BAND OF CLD ASSOCIATED
WITH TROF/ANOTHER AXIS OF H85-7 FGEN MOVING S ACRS LK SUP. SFC DWPT
DEPRESSIONS... 16F AT YQT AND 9F AT YGQ) SUG AIRMASS JUST N OF LK IS
STILL RATHER DRY. BUT 00Z YPL SDNG SHOWS A RELATIVELY DEEP MOIST LYR
UP TO HI INVRN BASE ARND H75 WITH H85 DEWPT DEPRESSION OF 0C. LAST
SFC OB FM YPL AT 02Z SHOWED DEWPT DEPRESSION OF ONLY 3F. SOME LGT
SN/FLURRIES FALLING IN THAT AREA ARND H85 THERMAL TROF. FARTHER
NW...SFC HI PRES BLDG INTO FAR NW ONTARIO. YYQ SDNG IS RATHER
DRY/STABLE WITH PWAT AT 0.14 INCH.
FCST CONCERNS THIS PACKAGE ARE LES TRENDS/AMTS INTO THIS EVNG...THEN
TEMPS LATER TNGT THRU SUN. FOCUS FOR LATE SUN/MON TURNS TO TIMING/
IMPACT OF SHRTWV IN THE NE PACIFIC EMBEDDED IN STRG WLY FLOW AIMED
AT THE PAC NW.
FOR TDAY...SHRTWV OVER ONTARIO PROGGED TO SLIDE ACRS LK SUP AND INTO
UPR MI BY 00Z SUN WHILE SFC HI CENTER TRAILING THIS SYS FCST TO
SETTLE TO JUST N OF INL. LGT SN OVER THE SRN TIER WL DIMINISH BY
FCST ISSUANCE AS H85-7 FGEN AXIS/SOMEWHAT DEEPER MSTR IMPACTING THAT
AREA NOW PUSHES TO THE SE. BUT EXPECT SOME INTENSIFICATION OF SN NR
LK SUP TEMPORARILY EARLY THIS MRNG WITH ARRIVAL OF AXIS OF THICKER
SC/H85-7 FGEN ASSOCIATED WITH SFC-H85 TROF AND COLDER H85 AIR BEHIND
THIS FEATURE. ANY INTENSIFICATION SHOULD BE RELATIVELY MINOR THOUGH
WITH NR SFC DRY AIR/HIER DWPT DEPRESSIONS FOLLOWING CLOSELY BEHIND
THE TROF. ALTHOUGH ADVECTION OF MORE FVRBL AIRMASS SHOWN ON THE 00Z
YPL SDNG MAY REINVIGORATE THE LES A BIT DURING THE DAY...ESPECIALLY
IN AREAS FVRD BY FCST NNE FLOW...INCRSG H85-5 QVECTOR DVGC/H7
SUBSIDENCE/LARGER SCALE ACYC FLOW WITH WEAK H95 CNVGC/SINKING INVRN
HGT ESPECIALLY AFT 18Z TO 3-4K FT BY 00Z AS SHOWN ON NAM/GFS FCST
SDNGS (LOWEST OVER THE W CLOSEST TO SFC RDG AXIS) WL KEEP LES AMTS
IN CHECK. GOING FCST LES TRENDS/AMTS AOB 1 INCH AT MOST SPOTS SEEM
TO BE IN GOOD ORDER AND IN LTL NEED OF CHG.
WITH INCRSG LARGER SCALE DNVA/H85-5 QVECTOR DVGC/HGT RISES/H7
SUBSIDENCE IN THE WAKE OF SHRTWV TNGT...DRY HI PRES FCST TO BLD ACRS
THE CWA AFT 06Z. EXPECT ANY LINGERING FLURRIES NEAR LK SUP TO
PERSIST LONGEST OVER THE NCNTRL IN UPSLOPE NNE FLOW TO THE SE OF THE
HI CENTER BEFORE PASSAGE OF HI CENTER OVERNGT TURNS FLOW OFFSHORE
AFT 06Z. PROSPECT OF CLRG SKIES/LGT WINDS/FCST PWAT TO ARND 0.15
INCH SUGS THE COLDEST NGT OF THE SEASON MAY BE IN STORE FOR MUCH OF
THE FA...WITH THE LOWEST READINGS AWAY FM THE MODERATING INFLUENCE
OF THE LKS. ALTHOUGH RETURN SLY FLOW DVLPG LATE OVER THE W MAY CHECK
THE DIURNAL TEMP FALL...WL FCST LO TEMPS BLO MOS GUIDANCE AT MOST
SPOTS WITH NEAR IDEAL RADIATION HEAT LOSS EXPECTED.
SUN WL AT LEAST START ON THE MOSUNNY SIDE WITH HI PRES CENTERED JUST
TO THE E OF ANJ AT 12Z SUN. BUT AS FLOW ALF BECOMES MORE ZONAL IN
ADVANCE OF PACIFIC SHRTWV PLOWING ACRS SRN CAN AND SFC WINDS TURN SW
BTWN DEPARTING SFC HI AND ACCOMPANYING SFC LO PRES OVER SCNTRL CAN
SETTING UP ISENTROPIC LIFT ON THE GFS FCST 290K SFC...EXPECT AN
INCRS IN MID/HI CLD LATE OVER THE W. ALTHOUGH UKMET SHOWS SIMILAR
MID LVL MOISTENING...PREFER THE DRIER GFS FCST (DRY THRU 00Z MON VS
UKMET WHICH GENERATES SOME PCPN AS FAR E AS THE WRN ZNS) DUE TO
ANTECEDENT DRY AIRMASS AND ABSENCE OF SHARPER H85-5 QVECTOR CNVGC/
UPR DVGC. WL MAINTAIN SCHC POPS ONLY OVER FAR WRN LK SUP NEAR TO
WHERE GFS SHOWS PCPN ARRIVING ARND 00Z. OTRW...MIXING TO H875 ON GFS
FCST SDNGS YIELDS HI TEMPS JUST A FEW DEGREES UNDER GOING FCST.
ON SUN NGT...FAVORED GFS/UKMET/CNDN MODELS SHOW PACIFIC SHRTWV/SFC
LO MOVING INTO NW ONTARIO BY 12Z MON. SINCE THE SHRTWV/SHARPEST
DPVA/DEEP QVECTOR CNVGC/UPR DVGC ON CYC SIDE OF SUPPORTING JET AXIS
LOOK TO REMAIN TO THE N...SUSPECT PCPN OVER THE LAND FA WL BE ON THE
LGT SIDE...ESPECIALLY SINCE STRENGTHENING SW FLOW APPEARS TO TAP
ONLY MARGINALLY MOIST AIR. GFS SHOWS ONLY NARROW BAND OF H7 SPECIFIC
HUMIDITY AOA 3G/KG RETURNING N INTO THE UPR LKS...WITH MODEL FCST
SDNGS NEVER SHOWING DEEP SATURATION FOR ANY SGNFT LENGTH OF TIME.
LIKE GFS MOS IDEA OF POPS RANGING FM 10-20 OR SO OVER THE SCNTRL TO
40 AT CMX. THE DRY AIR SHOULD ENSURE THAT WHATEVER PCPN DOES FALL WL
BE IN THE FORM OF SN PER WBLB ON FCST SDNGS...EXCEPT PERHAPS OVER
THE FAR W LATE. BUT BEST ASCENT MIGHT BE PAST THERE AT THAT POINT
WITH AXIS OF HIER SPECIFIC HUMIDITY OFF TO THE E BY THEN. MOST SGNFT
IMPACT OF THIS SYS ON SUN NGT WL BE WINDS ESPECIALLY OVER LK SUP...
WHERE GFS FCST SDNGS SHOW SSW 35KT WINDS WITHIN MIXED LYR BLO WAD
INVRN. THESE STRONG WINDS/CLD COVER WL MITIGATE DIURNAL TEMP DROP IN
FACE OF EVAPORATIVE COOLING.
ALTHOUGH THERE MAY BE A BREAK AFT INITIAL BAND OF OVERRNG PCPN ON
SUN NGT...GFS/UKMET SHOW ANOTHER ROUND OF PCPN BREAKING OUT ON MON
(WHICH WOULD BE IN THE FORM OF RA) IN PERSISTENT ISENTROPIC LIFT N
OF WARM FNT EXTENDING E FM SFC LO IN THE NORTHERN PLAINS INTO NRN
WI. ON THE OTHER HAND...CNDN/ECMWF MODELS SHOW ATTENDANT COLD FNT TO
THE SW OF LO TRACKING THRU ONTARIO PASSAING ACRS THE CWA DURING THE
DAY...WITH DRYING FCST IN THE AFTN. CONSIDERING THE MAJOR
DISCREPANCIES BTWN THESE TWO CAMPS...OPTED TO LEAVE GOING FCST AS IS
ON MON IN AGREEMENT WITH GFS/UKMET GUIDANCE.
COORDINATED WITH APX/GRB.
&&
.AVIATION (FOR THE 06Z TAF ISSUANCE)...
HIGH PRESSURE OVER NRN MANITOBA WILL DRIFT TOWARD NRN ONTARIO LATE
TONIGHT AND SAT. AS A RESULT LOW-LEVEL WIND FLOW WILL BECOMING NNE
ACROSS LAKE SUPERIOR LATE TONIGHT THRU SAT MORNING. WITH THE
LOW-LEVEL AIRMASS COOLING UNDER THIS FLOW REGIME...LAKE EFFECT
CLOUDINESS AND SOME -SHSN/FLURRIES WILL DEVELOP TONIGHT AND CONTINUE
INTO SAT. DESPITE THE COOLER AIRMASS...FAIRLY DRY BOUNDARY LAYER
CONDITIONS SHOULD KEEP -SHSN SCT. EXPECT VFR VIS TO PREVAIL FOR THE
ENTIRE FCST PERIOD AT KCMX AND KSAW. WITH MORE FAVORABLE UPSLOPE
WIND...-SHSN WILL BE A BIT MORE FREQUENT AT KSAW...AND CIGS WILL
LIKELY DROP INTO THE HIGH MVFR RANGE ON SAT. EXPECT VFR CIGS AT
KCMX. WEAKENING NRLY FLOW AS THE HIGH PRESSURE RIDGE BUILDS OVER THE
AREA COULD RESULT IN SOME PARTIAL CLEARING BY LATE EVENING AT BOTH
TAF SITES.
&&
.MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)...
WINDS OF 15 TO 25 KT ARE POSSIBLE THIS MORNING AS HIGH PRESSURE OVER
NORTHERN MANITOBA BUILDS SOUTH TOWARDS LAKE SUPERIOR. EXPECT WINDS
TO DROP OFF TONIGHT AS THE HIGH CROSSES. ON SUNDAY...LOOK FOR WINDS
TO SHIFT TO THE SOUTH AND PICK UP AGAIN AS THE HIGH SHIFTS OFF INTO
QUEBEC...WITH 25 KT WINDS POSSIBLE ACROSS MUCH OF THE LAKE BY LATE
IN THE DAY. THE SOUTHERLY WINDS WILL INCREASE FURTHER SUN NIGHT AS
LOW PRESSURE IN SW MANITOBA MOVES INTO WESTERN ONTARIO. 35 KT GALES
SEEM LIKELY ACROSS MUCH OF THE LAKE...AND PROBABLY 40 KT OVER THE
EASTERN PORTION. WINDS WILL SLOWLY DIMINISH ON MONDAY...WITH ANY
GALES ENDING BY EARLY IN THE AFTERNOON...THANKS TO THE SURFACE LOW
WEAKENING AND LIFTING INTO FAR NORTHERN ONTARIO. LOOK FOR WINDS TO
SHIFT TO THE WEST LATE MONDAY AND NW MONDAY NIGHT WHILE DIMINISHING
BELOW 20 KT...DUE TO THE COLD FRONT ASSOCIATED WITH THE LOW CROSSING
LAKE SUPERIOR. THIS FRONT WILL STALL IN SOUTHERN LOWER MICHIGAN TUE
MORNING WHILE HIGH PRESSURE BEGINS BUILDING SOUTH OUT OF CANADA. A
SURFACE LOW IS EXPECTED TO RIDE UP ALONG THE FRONT LATE TUE...
CAUSING NORTHERLY WINDS TO INCREASE TO 15 TO 25 KT ON LAKE SUPERIOR
TUE NIGHT. WINDS WILL SLOWLY DIMINISH ON WEDNESDAY AS THE LOW HEADS
TOWARDS NEW ENGLAND AND THE AFOREMENTIONED HIGH BUILDS IN.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...NONE
&&
$$
DISCUSSION...KC
AVIATION...AJ
MARINE...AJ
AREA FORECAST DISCUSSION...UPDATED
NWS MARQUETTE MI
1221 AM EST SAT NOV 17 2007
UPDATED AVIATION SECTION FOR 06Z TAF ISSUANCE
.SHORT TERM (TONIGHT AND SAT)...
MAIN FCST ISSUE IS LES POTENTIAL TONIGHT/SAT.
WATER VAPOR IMAGERY AND RUC ANALYSIS SHOW NW FLOW ACROSS THE UPPER
GREAT LAKES BTWN A DEEP TROF FROM HUDSON BAY TO NEW ENGLAND AND A
RIDGE OVER THE ROCKIES. WEAK SHORTWAVE WAS NOTED OVER NRN ONTARIO.
AT THE SFC...HIGH PRES WAS CENTERED OVER NRN MANITOBA AND THE GULF
COAST WHILE LOW PRES WAS JUST E OF MAINE AND A TROF EXTENDED SE
ACROSS THE DAKOTAS. LOCATED BTWN THESE PRES FEATURES...A COL AREA
WAS OVER UPPER MI/LAKE SUPERIOR...AND THUS LIGHT WINDS HAVE BEEN THE
RULE HERE TODAY. BAND OF LOW-MIDLEVEL FRONTOGENESIS FROM NRN MN
ACROSS NRN WI HAS BEEN GENERATING A BAND OF CLOUDS AND RADAR
RETURNS. NOT ALL OF THE PCPN ALOFT HAS BEEN REACHING THE GROUND...
BUT RECENT SFC OBS DO SHOW SOME FLURRIES/-SN STREAKING ALONG THE
MI/WI BORDER AREA. LES HAS BEEN NONEXISTENT OFF LAKE SUPERIOR TODAY.
EARLY AFTN TAMDAR SOUNDING FROM KCMX INDICATED 850MB TEMP AROUND
-9C. WITH WATER TEMP AROUND 6C...DELTA-T AROUND 15C IS SUFFICIENT
FOR LES...BUT THE DISORGANIZED WIND FIELD AND WELL-MIXED BOUNDARY
LAYER PER TAMDAR SOUNDING HAVE BEEN RESPONSIBLE FOR THE LACK OF LES.
THERE HASN`T BEEN MUCH IN THE WAY OF LAKE EFFECT CLOUDS EITHER.
EXPECT -SN/FLURRIES ALONG THE WI/MI BORDER TO BE OUT OF THE AREA BY
00Z. THEN ATTENTION TURNS TO LES. ALTHOUGH SHORTWAVE OVER NRN
ONTARIO WILL DROP S TO LAKE SUPERIOR LATE TONIGHT...DEEP LAYER
QVECTOR PROGS SHOW LITTLE/NO FORCING FOR UPWARD MOTION. MEANWHILE...
FCST SOUNDINGS (ESPECIALLY GFS) CONTINUE TO SHOW A WELL MIXED
BOUNDARY LAYER (INVERTED-V LOOK). UPSTREAM SFC DWPT DEPRESSIONS IN
ONTARIO TEND TO SUPPORT THE DRIER GFS LOOK. SO...AS WINDS BECOME NNE
DURING THE NIGHT AS NRN MANITOBA HIGH PRES BUILDS TOWARD NRN
ONTARIO...NOT EXPECTING LES TO AMOUNT TO MUCH DESPITE 850MB TEMPS
FALLING TO AROUND -12C BY MORNING PER PREFERRED COOLER GFS WHICH
ANALYZED 12Z RAOBS BETTER. MAY SEE A FEW FLURRIES DEVELOP E OF KMQT
EARLY THIS EVENING...BUT MORE LIKELY MID TO LATE EVENING THERE AND
ALSO OVER THE FAR W. DON`T REALLY EXPECT -SHSN TO DEVELOP NEAR THE
LAKE UNTIL AFTER MIDNIGHT WHEN NNE LOW-LEVEL FLOW STRENGTHENS. GIVEN
THE NEGATIVES DISCUSSED ABOVE...POPS WILL BE KEPT IN THE 30-40 RANGE
(HIGHEST NCNTRL DUE TO MORE DIRECT UPSLOPE)...AND ACCUMULATIONS
SHOULD BE LESS THAN 1 INCH.
CORE OF THE COLDEST 850MB AIR PASSES OVER THE AREA SAT MORNING
THRU EARLY AFTN. GIVEN THE WELL MIXED BOUNDARY LAYER APPEARANCE OF
THE FCST SOUNDINGS AND LOW-LEVEL FLOW TRENDING MORE ANTICYCLONIC
WITH HIGH PRES MOVING CLOSER...LES WILL CONTINUE TO BE KEPT IN
CHECK. MAX ACCUMULATIONS WILL BE OVER THE NCNTRL WITH MORE FAVORABLE
UPSLOPE...BUT EVEN THERE...ACCUMULATIONS SHOULD ONLY BE AROUND 1
INCH. COOLER ETA MOS TEMPS LOOK ACCEPTABLE FOR MAX TEMPS WITH CORE
OF COLDEST AIR PASSING OVER THE AREA.
.LONG TERM (SAT NIGHT THROUGH FRIDAY)...
SAT NIGHT THROUGH MON...SATURDAY NIGHT MAY BE THE COLDEST NIGHT OF
THE SEASON SO FAR FOR MANY LOCATIONS. WITH HIGH PRESSURE MOVING
THROUGH...WINDS SHOULD DROP AND SKIES SHOULD CLEAR. LOWS ACROSS THE
WESTERN HALF OF THE AREA SHOULD DROP INTO THE TEENS...WITH SINGLE
DIGITS POSSIBLE IN THE HIGHER TERRAIN. TEMPERATURES MAY REMAIN
CLOSER TO 20 IN THE EAST AS IT WILL TAKE LONGER FOR CLOUDS TO MOVE
OUT OF THE AREA. SUNDAY SHOULD BE QUIET WITH THE HIGH PUSHING
THROUGH AND TEMPERATURES NEAR NORMAL FOR THIS TIME OF YEAR. LOW
PRESSURE DEVELOPING OVER CENTRAL CANADA WILL MOVE INTO MANITOBA
SUNDAY NIGHT DRAGGING A WEAK COLD FRONT THROUGH THE AREA ON MONDAY.
STRONG SOUTHERLY WINDS WILL SWEEP WARM AIR IN AND RESULT IN A
POSSIBLE MIX OF RAIN AND SNOW EARLY IN THE DAY BEFORE SWITCHING TO
ALL RAIN BY AFTERNOON.
TUE THROUGH FRI...LOW CONFIDENCE THROUGH THIS PORTION OF THE
FORECAST PERIOD DUE TO LARGE DIFFERENCES BETWEEN MODELS. AS A
RESULT...MADE LITTLE CHANGE TO THE GOING FORECAST UNTIL SOME MODEL
CONSISTENCY BEGINS TO APPEAR. MOST MODELS DEVELOP A SECOND SURFACE
LOW ACROSS THE COLD FRONT OF THE PREVIOUS SYSTEM AND BRING THE
SURFACE LOW THROUGH UPPER MICHIGAN BY 12Z TUESDAY...WITH
PRECIPITATION WIDESPREAD ACROSS THE AREA. MODELS DIFFER QUITE A BIT
WITH LOW-LEVEL THICKNESSES DURING THIS TIME PERIOD. ECMWF HAS RAIN
MONDAY NIGHT...WITH COLDER AIR ADVECTING IN ON TUESDAY TO CHANGE
EVERYTHING OVER TO SNOW. GFS ALSO HAS RAIN MONDAY NIGHT...BUT IS A
BIT MORE DELAYED IN BRINGING THE COLDER AIR INTO THE REGION. STUCK
WITH GOING FORECAST OF RAIN MONDAY NIGHT...WITH A RAIN-SNOW MIX
DURING THE DAY ON TUESDAY. ALSO BROUGHT POPS INTO THE SOUTH ON
TUESDAY...AS PREVIOUS MODEL RUNS HAD INDICATED THIS WOULD BE MORE OF
A LAKE EFFECT EVENT CONTAINED TO THE SUPERIOR LAKESHORE. WITH LATEST
MODEL GUIDANCE SHOWING THE LOW BARRELING THROUGH THE AREA...EVERYONE
SHOULD SEE SOME SORT OF PRECIPITATION. ONCE COLDER AIR PUSHES INTO
THE AREA TUESDAY NIGHT...ONSHORE FLOW SHOULD PERSIST AND RESULT IN A
CHANCE OF SNOW ALONG LAKE SUPERIOR THROUGH MUCH OF THE REST OF THE
FORECAST PERIOD. MODELS HAVE SHOWN VARYING SOLUTIONS FOR A POTENTIAL
STORM AFFECTING THE REGION ON THANKSGIVING. WHILE THE ECMWF HAS KEPT
THIS STORM TO THE SOUTH OF THE AREA FOR SEVERAL MODEL RUNS...THE GFS
HAS INSISTED ON A MORE NORTHERLY TRACK ACROSS MICHIGAN. THE 12Z GFS
RUN HAS FINALLY GONE WITH A MORE SOUTHERLY ROUTE...MATCHING UP WITH
OTHER MODELS. AT THIS TIME...IT DOES NOT APPEAR THAT THE STORM WILL
END UP AFFECTING TRAVEL PLANS ACROSS UPPER MICHIGAN.
&&
.AVIATION (FOR THE 06Z TAF ISSUANCE)...
HIGH PRESSURE OVER NRN MANITOBA WILL DRIFT TOWARD NRN ONTARIO LATE
TONIGHT AND SAT. AS A RESULT LOW-LEVEL WIND FLOW WILL BECOMING NNE
ACROSS LAKE SUPERIOR LATE TONIGHT THRU SAT MORNING. WITH THE
LOW-LEVEL AIRMASS COOLING UNDER THIS FLOW REGIME...LAKE EFFECT
CLOUDINESS AND SOME -SHSN/FLURRIES WILL DEVELOP TONIGHT AND CONTINUE
INTO SAT. DESPITE THE COOLER AIRMASS...FAIRLY DRY BOUNDARY LAYER
CONDITIONS SHOULD KEEP -SHSN SCT. EXPECT VFR VIS TO PREVAIL FOR
THE ENTIRE FCST PERIOD AT KCMX AND KSAW. WITH MORE FAVORABLE UPSLOPE
WIND...-SHSN WILL BE A BIT MORE FREQUENT AT KSAW...AND CIGS WILL
LIKELY DROP INTO THE HIGH MVFR RANGE ON SAT. EXPECT VFR CIGS AT
KCMX. WEAKENING NRLY FLOW AS THE HIGH PRESSURE RIDGE BUILDS OVER THE
AREA COULD RESULT IN SOME PARTIAL CLEARING BY LATE EVENING AT BOTH
TAF SITES.
&&
.MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)...
OUTSIDE OF A PERIOD OF 15 TO 25 KT WINDS LATE TONIGHT THRU SAT
MORNING DUE TO HIGH PRES BUILDING SE TOWARD NORTHERN ONTARIO...
EXPECT WINDS BELOW 20 KT ACROSS ALL OF LAKE SUPERIOR THROUGH SUN
MORNING. ON SUN...WINDS WILL BEGIN INCREASING ACROSS ALL OF LAKE
SUPERIOR AS AFOREMENTIONED BUILDING HIGH PRES AREA HEADS TOWARD
NEW ENGLAND AND A SFC LOW TRACKS THRU SOUTH CENTRAL CANADA. WINDS
SHOULD APPROACH 25 KT BY LATE SUN. WINDS WILL CONTINUE TO INCREASE
SUN NIGHT AS THE SFC LOW MOVES TO NORTHERN ONTARIO. S GALES OF 35-40
KT WILL LIKELY DEVELOP LATE SUN NIGHT. THE HIGHEST WINDS SHOULD BE
CONFINED TO CENTRAL AND EASTERN LAKE SUPERIOR. AS THE LOW LIFTS
TOWARD JAMES BAY MON...WINDS WILL GRADUALLY RELAX W TO E. IT IS
POSSIBLE WIND GUSTS COULD APPROACH 45 KT FOR A BRIEF TIME MON
MORNING ON EASTERN LAKE SUPERIOR. A COLD FRONT ASSOCIATED WITH THE
LOW WILL CROSS LAKE SUPERIOR LATE MONDAY INTO MONDAY NIGHT...WITH
WINDS SHIFTING NW AND DIMINISHING TO BELOW 20 KT. WINDS MAY AGAIN
INCREASE TO 30 KT TUE/WED AS ANOTHER LOW PRES MOVES NE FROM THE
SOUTHERN PLAINS TO THE LWR GREAT LAKES.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...NONE
&&
$$
SHORT TERM...ROLFSON
LONG TERM...TAG
AVIATION...VOSS
MARINE...ROLFSON
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