AREA FORECAST DISCUSSION
NWS UPTON NY
1108 PM EST SUN DEC 30 2007
.SYNOPSIS...
LOW PRESSURE ALONG THE VIRGINIA COAST WILL PASS SOUTHEAST OF LONG
ISLAND OVERNIGHT...BEFORE DEPARTING BY EARLY MONDAY AFTERNOON.
WEAK HIGH PRESSURE THEN QUICKLY PASSES TO THE SOUTH OF THE AREA.
A POTENT ALBERTA CLIPPER SYSTEM WILL MOVE ACROSS THE REGION ON
TUESDAY...USHERING BITTERLY COLD AIR BEHIND IT AS CANADIAN HIGH
PRESSURE BUILDS INTO THE REGION. DRY WEATHER IS THEN EXPECTED INTO
THE WEEKEND.
&&
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
DRY SLOT HAD WORKED ITS WAY INTO THE AREA...WITH EARLIER SNOW/SLEET
WELL NORTH/WEST OF NYC CHANGING TO FREEZING DRIZZLE AS WE LOSE MID
LEVEL MOISTURE AND AS TEMPS ALOFT WARM ABOVE FREEZING. SURFACE
TEMPERATURES FARTHER SOUTH/EAST HAVE REMAINED ABOVE FREEZING...WITH
PRECIPITATION PRIMARILY RAIN. LIGHT NORTHERLY FLOW OVER SOUTHERN CT
SHOULD ALLOW TEMPS TO DROP TO AT OR JUST BELOW FREEZING OVER MOST
INTERIOR SECTIONS AS WELL...WITH PRECIP CHANGING OVER TO LIGHT
FREEZING DRIZZLE/SLEET THERE AS WELL.
BAND OF HEAVIER PRECIP ORGANIZING OVER EASTERN PA MAY YET PIVOT
EASTWARD INTO THE AREA...IN TANDEM WITH COLDER AIR MOVING BACK INTO
THE AREA ON THE BACK SIDE OF LOW PRESSURE MOVING FROM THE VA COAST
TO SE OF MONTAUK OVERNIGHT...WITH A CHANGE BACK TO MOSTLY SNOW IN
ORANGE/PUTNAM/W PASSAIC COUNTIES AFTER MIDNIGHT...AND SNOW/SLEET
ELSEWHERE LATE. HAVE KEPT WINTER WX ADVISORY UP WHERE IT WAS ALREADY
POSTED...BUT HAVE CUT ACCUMULATIONS TO 2-4 INCHES FOR
ORANGE/PUTNAM/W PASSAIC AND 1-3 ELSEWHERE...WITH ADDED MENTION OF
SOME ICING.
AS THE LOW PASSES SE OF LONG ISLAND LATE TONIGHT...NORTHWEST WINDS
WILL PICK UP ACROSS THE AREA. ENOUGH COLD AIR WILL FILTER DOWN INTO
THE AREA TO TURN PRECIP OVER TO SNOW/SLEET IN THE COUNTIES JUST
SOUTH OF THE ADVISORY AREA INCLUDING PORTIONS OF NYC...AND A COATING
TO AN INCH OF SNOW MAY STILL BE POSSIBLE.
HAVE GONE WITH SLIGHTLY WARMER MINS IN MOST PLACES PER OBS AND BLEND
OF NAM 2M/MAV TEMPS UNDER CUT A COUPLE OF DEGREES...WITH MID 30S
ACROSS LONG ISLAND AND LOWER 30S ELSEWHERE.
&&
.SHORT TERM /6 AM MONDAY MORNING THROUGH TUESDAY NIGHT/...
PRECIP WILL WIND DOWN AS A PERIOD OF SNOW BEFORE TAPERING OFF WITH
MINOR ADDITIONAL ACCUMULATIONS. SKIES CLEAR OUT DURING THE AFTERNOON
AS HIGH PRES MOVES INTO THE MID-ATLANTIC BY MIDDAY...THEN OFFSHORE
MON NIGHT. A CLIPPER SYSTEM WILL MOVE ACROSS THE REGION ON TUE...
MOVING OFFSHORE BY TUE NIGHT. WILL CONTINUE TO CARRY LIKELY
POPS...AS THERE WEREN/T ANY MAJOR CHANGES THAT WERE NEEDED TO BE
MADE TO THE PREVIOUS FCST. MODELS SEEM TO HAVE A GOOD HANDLE ON
THIS UPCOMING SYSTEM. TEMPS WILL BE COLD ENOUGH TO SUPPORT SNOW
THE THE NORTH...AND WARM ENOUGH FOR RAIN TO THE SOUTH. PRECIP WILL
TAPER OFF AS ALL SNOW TUE NIGHT. WINTER WEATHER ADVISORIES MAY
HAVE TO BE POSTED FOR ORANGE/PUTNAM/NORTHERN FAIRFIELD COUNTIES
FOR TUE...AS OVER 3" SNOW COULD ACCUMULATE...BUT WILL WAIT FOR
FCST TO BE REFINED.
&&
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
AS THE STORM HEADS OUT FARTHER INTO THE CANADIAN MARITIMES ON
WED...THE TRAILING H5 TROUGH AXIS PASSES EAST. H8 FLOW IS WEAKLY
CYCLONIC...SO MOST OF THE AREA SHOULD REMAIN DRY BUT WITH ABUNDANT
INSTABILITY STRATOCU. EASTERN SECTIONS COULD SEE SOME SNOW SHOWERS
AS DEEPER MOISTURE WRAPS AROUND THE BACK SIDE OF THE DEPARTING LOW.
TEMPERATURES WILL BE ON THE COLD SIDE...DROPPING TO AROUND -12C TO
-14C AT 925 MB IN THE AFTERNOON. IT MIGHT BE A DAY WHERE HIGHS OCCUR
IN THE MORNING...PROBABLY REACHING ONLY 25-30. GUSTY NORTHWEST WINDS
WILL MAKE IT FEEL EVEN COLDER...WITH WIND CHILLS DROPPING TO AROUND
ZERO LATE WED NIGHT IN NYC....AND -5 TO -10 IN SOME INLAND SPOTS.
RIDGING AT THE SURFACE AND ALOFT BEGINS TO BUILD IN ON THU. IT WILL
BE MOSTLY SUNNY...BUT STILL COLDER THAN NORMAL. LOW LEVEL
THICKNESSES SUPPORT EVEN COLDER HIGH TEMPS THAN THOSE OF WED...
REMAINING IN THE 20S THROUGHOUT.
THE CENTER OF THE HIGH WILL MOVE OFF THE MID ATLANTIC COAST ON
FRI...WITH A DEVELOPING RETURN FLOW. MODERATION WILL BE SLOWER THAN
MOS SUGGESTS ON FRI...WITH HIGHS IN THE 30S THROUGHOUT...BUT SHOULD
KICK IN FOR SAT/SUN WITH HIGHS IN THE 40S...PERHAPS NEARING 50 IN
NYC METRO ON SUN. A WARM FRONT PASSING TO THE NORTH/WEST COULD BRING
THICKENING HIGH/MID LEVEL CLOUDS SAT NIGHT AND SUN...BUT LOW LEVELS
WILL REMAIN QUITE DRY...SO NO PRECIP EXPECTED. NEXT CHANCE OF PRECIP
APPEARS TO BE LATE SUN NIGHT WITH THE APPROACH OF A COLD FRONT.
TEMPS SHOULD RUN AT LEAST SEVERAL DEGREES WARMER THAN MOS WITH
SOUTHERLY FLOW AND CLOUD COVER...MAKING FOR AN ALL RAIN EVENT
SUN NIGHT.
&&
.AVIATION /04Z MONDAY THROUGH FRIDAY/...
CONDITIONS SHOULD DROP TO MVFR BY 01Z OR 02Z ACROSS WESTERN
TERMINALS...02Z TO 03Z AT KISP...KBDR AND KGON. IFR/LIFR TO FOLLOW
BETWEEN 03Z AND 06Z. LATEST ACARS SOUNDINGS ACROSS NYC INDICATE
THAT THE GFS IS VERIFYING BETTER THAN THE NAM. THE WARM NOSE IN
THE NAM IS ABOUT 2 DEGREES TOO HIGH AT 800 MB. THE RUC IS VERIFIES
EVEN BETTER...BUT THIS IS TO BE EXPECTED SINCE IT USES ACARS
SOUNDINGS IN IT.
-SN IS EXPECTED TO BE THE DOMINANT P-TYPE AT
KSWF BUT MAY BRIEFLY MIX WITH -IP AT TIMES THROUGH 09Z. LOOKING
UPSTREAM...KMPO (AND KDXR) HAVE CHANGED TO FZRA OVER THE LAST
HOUR. THIS IS BOTHERSOME AND INDICATES THAT WARMER AIR IS MOVING
IN ALOFT. RUC INDICATES ABOUT A 3 HOUR PERIOD OF A WARM NOSE AT
KSWF BETWEEN 04Z AND 07Z WHICH IS WHEN THERE COULD BE SOME IP
MIXING IN...BUT IF THE WARM LAYER IS LARGER THAN THE PROFILE
INDICATES WE COULD BE LOOKING AT PRECIP CHANGING TO FZRA. NOT
CONFIDENT ENOUGH THAT THIS WILL OCCUR...SO HAVE NOT INCLUDED IN
THE TAF.
KJFK...KLGA...KEWR...KTEB AND KISP SHOULD ALL REMAIN RAIN
FOR THE MAJORITY OF THE EVENT...BUT COULD CHANGE OVER TO -SN AT
THE END (BETWEEN 09Z AND 12Z).
SO ACCORDING TO THE RUC...THE REMAINING TERMINALS (KBDR...KGON
AND KHPN)...WHICH WERE THE TOUGH ONES SINCE THEY REMAIN THE
CLOSEST TO THE RAIN/SNOW LINE...ALL REMAIN -RA FOR MAJORITY OF THE
EVENT AS WELL POSSIBLY CHANGING TO -SN AT THE END TOO.
E/NE WINDS WILL GRADUALLY BACK TO THE N THEN NW AS THE COASTAL LOW
PASSES TO THE SOUTH AND EAST LATE TONIGHT/EARLY MON MORNING.
PRECIP SHOULD TAPER OFF FROM SW TO NE BETWEEN 12Z AND 15Z AND IT
MAY NEED TO BE EXTENDED AN HOUR OR TWO LONGER THAN WHAT IS IN THE
00Z TAFS...BUT WILL WATCH RADAR AND ADJUST ACCORDINGLY.
VFR CONDITIONS RETURN TO ALL TERMINALS BETWEEN 14Z AND 16Z WITH
ONLY GUSTY NW WINDS TO CONTEND WITH. SUSTAINED WINDS SHOULD RANGE
BETWEEN 12 AND 17KT WITH GUSTS BETWEEN 25 AND 30 KT.
OUTLOOK FOR 00Z TUESDAY THROUGH THURSDAY...VFR REMAINS THROUGH
MONDAY NIGHT. SUB-VFR CONDITIONS ARE AGAIN LIKELY TUESDAY AND
TUESDAY EVENING AS AN ALBERTA CLIPPER LOW AND COLD FRONT PASS
ACROSS THE AREA. RAIN NEAR THE COAST...RAIN/SNOW INTERIOR. THIS
WILL BE FOLLOWED BY GUSTY W-NW FLOW LATER TUE NIGHT THROUGH THU AS
THE OFFSHORE LOW INTENSIFIES AND DRAWS DOWN ARCTIC AIR. LIGHT SNOW
SHOWERS OR FLURRIES WILL BE POSSIBLE ON WEDNESDAY...OTHERWISE DRY.
&&
.MARINE...
TODAY THROUGH TUESDAY NIGHT...
SCA DELAYED FOR THE SOUND/HARBOR/BAYS UNTIL WINDS PICK UP ON THE
BACK SIDE OF THE DEPARTING COASTAL LOW. OTHERWISE...SCA UP FOR THE
OCEAN AS WIND GUSTS WILL BE OVER 25 KT...WITH SEAS 4-6 FT. AFTER THE
LOW DEPARTS ON MON...WEAK HIGH PRES WILL BUILD TO THE SOUTH. WITH A
SHOT OF CAA...AND A TIGHT PRESSURE GRADIENT ON THE WATERS...THERE
COULD BE OCNL GALE FORCE GUSTS DURING MON AFTERNOON. WILL CARRY
STRONG SCA FOR NOW...AND LET MID SHIFT DECIDE IF GALES WILL BE MORE
PREVALENT. FLAGS COME DOWN FROM WEST TO EAST MON EVENING...ENDING ON
ALL WATERS BY MIDNIGHT. TRANQUIL CONDITIONS THEN EXPECTED THROUGH
MIDDAY TUE. ANOTHER SYSTEM WILL BRING AT LEAST SCA CONDITIONS WITH
GALES POSSIBLE ONCE AGAIN. DUE TO STRONGER CAA AND A STRONGER
GRADIENT...THINK THERE WILL BE A BETTER CHANCE FOR GALES LATE TUE.
WEDNESDAY THROUGH FRIDAY NIGHT...
A STRONG PRESSURE GRADIENT AND LOW LEVEL CAA/INSTABILITY WILL
COMBINE TO PRODUCE NW GALES ON THE OCEAN WED THROUGH THU MORNING...
AND SCA CONDITIONS ELSEWHERE. SCA CONDITIONS ON THE OCEAN SHOULD
COME TO AN END LATE THU NIGHT AS HIGH PRESSURE BUILDS OVER THE
WATERS...BUT COULD RETURN TO THE EASTERN OCEAN WATERS FRI NIGHT VIA
A STRENGTHENING WSW FLOW AS THE CORE OF THE HIGH PASSES OFF THE MID
ATLANTIC COAST.
&&
.HYDROLOGY...
COASTAL LOW IS EXPECTED TO PRODUCE 1/2 TO 2/3 INCH QPF THROUGH MON
MORNING. ANOTHER SYSTEM ON TUE COULD PRODUCE UP TO 1/2 INCH QPF.
&&
.EQUIPMENT...
KOKX WSR-88D IS FULLY OPERATIONAL...THOUGH A SOFTWARE/HARDWARE ISSUE
WITH OUR AWIPS HAS CAUSED INTERRUPTIONS OF EXTERNAL DISSEMINATION.
PLEASE CONTACT US IF YOU NOTICE THAT KOKX RADAR IS NOT AVAILABLE.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...WINTER WEATHER ADVISORY UNTIL 9 AM EST MONDAY FOR CTZ005>008.
NY...WINTER WEATHER ADVISORY UNTIL 9 AM EST MONDAY FOR NYZ067>070.
NJ...WINTER WEATHER ADVISORY UNTIL 9 AM EST MONDAY FOR NJZ002.
MARINE...SMALL CRAFT ADVISORY FROM 11 AM TO 6 PM EST MONDAY FOR
ANZ330-335-338-340-345.
SMALL CRAFT ADVISORY UNTIL MIDNIGHT EST MONDAY NIGHT FOR
ANZ350-353.
SMALL CRAFT ADVISORY UNTIL 6 PM EST MONDAY FOR ANZ355.
&&
$$
SYNOPSIS...BG/MPS
NEAR TERM...BG
SHORT TERM...MPS
LONG TERM...BG
AVIATION...AL
MARINE...BG/MPS
HYDROLOGY...BG/MPS
AREA FORECAST DISCUSSION
NWS UPTON NY
841 PM EST SUN DEC 30 2007
.SYNOPSIS...
LOW PRESSURE WILL APPROACH FROM THE MID-ATLANTIC...PASSING SOUTH AND
EAST OF LONG ISLAND DURING THE OVERNIGHT BEFORE DEPARTING BY EARLY
MONDAY AFTERNOON. WEAK HIGH PRESSURE THEN QUICKLY PASSES TO THE
SOUTH OF THE AREA. A CLIPPER SYSTEM WILL MOVE ACROSS THE REGION ON
TUESDAY...USHERING BITTERLY COLD AIR BEHIND IT AS CANADIAN HIGH
PRESSURE BUILDS INTO THE REGION. DRY WEATHER IS THEN EXPECTED INTO
THE WEEKEND.
&&
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
MODELS COMING INTO FAIR AGREEMENT REGARDING THE STORM SYSTEM
CURRENTLY STRENGTHENING OVER THE SOUTHEAST. THE LOW WILL FIND ITSELF
JUST OVER THE DELMARVA AREA BY 00Z...RAPIDLY DEEPENING FROM ABOUT
1010 MB TO 1003 MB AS IT MOVES NORTHEAST TO A POINT ABOUT 100 MILES
SOUTH AND EAST OF KMTP TOWARDS DAYBREAK.
MAIN ISSUE IS GOING TO BE PTYPE. BASED ON NAM AND GFS BUFKIT
SOUNDINGS...LOOKS LIKE A FAIR AMOUNT OF WARM AIR WILL OVERSPREAD THE
MIDDLE LAYERS OF THE ATMOSPHERE ACROSS THE REGION...MAINLY KEEPING
PRECIP IN THE FORM OF RAIN FOR SOUTHERN LOCATIONS...MIXING WITH
SLEET AFTER MIDNIGHT. FURTHER TO THE NORTH...PTYPE MAY START OUT AS
A PERIOD OF RAIN BEFORE MIXING WITH AND CHANGING TO SNOW THIS
EVENING. WILL ALSO SEE SLEET MIXING WITH THE SNOW DURING THE
OVERNIGHT. THESE SIGNATURES WERE INDICATED ON BOTH NAM AND GFS
BUFKIT SOUNDINGS. CHANGES WERE NOT NEEDED FOR THE WINTER WEATHER
ADVISORY...AS 3-5" OF SNOW/SLEET WILL FALL ACROSS INTERIOR PORTIONS
OF THE LOWER HUDSON VALLEY AND INTERIOR PORTIONS OF SOUTHERN CT.
THERE MAY BE A THIN SWATH OF 1" TO MAYBE 2" ACROSS SOUTHERN PORTIONS
OF THE LOWER HUDSON VALLEY AND INTO NORTHERN PORTIONS OF NORTHEAST
NJ. NYC/LONG ISLAND AND IMMEDIATE COASTAL LOCALES ARE EXPECTED TO
PICK UP LESS THAN AN INCH OF SLUSHY ACCUMULATION...AND MAINLY ON
COLDER AND GRASSY SURFACES. WILL HAVE TO MONITOR NORTHERN AND
WESTERN PORTIONS OF ORANGE COUNTY. QPF WAS A BIT HIGHER THAN
PREVIOUSLY FCST. STILL THINK THERE WILL BE ENOUGH WARM AIR ALOFT TO
CAP ACCUMULATIONS AT 5"...BUT NAM/GFS BUFKIT DATA DID INDICATE THAT
UP TO 6" OF SNOW COULD ACCUMULATE. EVENING SHIFT WILL HAVE TO
MONITOR TO DETERMINE IF A WARNING IS NEEDED IF MORE THAN 6" WOULD
ACCUMULATE. IT/S CLOSE...BUT WILL HOLD AT A WINTER WEATHER
ADVISORY WITH THIS PACKAGE.
TOWARDS DAYBREAK...AS THE LOW MOVES TOWARDS THE GULF OF MAINE...
NORTHWEST WINDS WILL PICK UP ACROSS THE AREA. ENOUGH COLD AIR WILL
MIX DOWN TO THE AREA TO TURN PRECIP OVER TO SNOW BEFORE ENDING.
WITH 1/2" TO 3/4" QPF EXPECTED...WILL HAVE TO ALSO MONITOR FOR ANY
LOCALIZED URBAN FLOODING PROBLEMS WHERE PRECIP REMAINS MAINLY RAIN
THROUGH A GOOD PORTION OF THE NIGHT.
USED A BLEND OF MAV/MET/FWC MOS GUIDANCE TO GET LOWS IN THE LOW-MID
30S ACROSS SOUTHERN PORTIONS OF THE CWA AND UPPER 20S ACROSS THE
INTERIOR.
&&
.SHORT TERM /6 AM MONDAY MORNING THROUGH TUESDAY NIGHT/...
PRECIP WILL WIND DOWN AS A PERIOD OF SNOW BEFORE TAPERING OFF WITH
MINOR ADDITIONAL ACCUMULATIONS. SKIES CLEAR OUT DURING THE AFTERNOON
AS HIGH PRES MOVES INTO THE MID-ATLANTIC BY MIDDAY...THEN OFFSHORE
MON NIGHT. A CLIPPER SYSTEM WILL MOVE ACROSS THE REGION ON TUE...
MOVING OFFSHORE BY TUE NIGHT. WILL CONTINUE TO CARRY LIKELY
POPS...AS THERE WEREN/T ANY MAJOR CHANGES THAT WERE NEEDED TO BE
MADE TO THE PREVIOUS FCST. MODELS SEEM TO HAVE A GOOD HANDLE ON
THIS UPCOMING SYSTEM. TEMPS WILL BE COLD ENOUGH TO SUPPORT SNOW
THE THE NORTH...AND WARM ENOUGH FOR RAIN TO THE SOUTH. PRECIP WILL
TAPER OFF AS ALL SNOW TUE NIGHT. WINTER WEATHER ADVISORIES MAY
HAVE TO BE POSTED FOR ORANGE/PUTNAM/NORTHERN FAIRFIELD COUNTIES
FOR TUE...AS OVER 3" SNOW COULD ACCUMULATE...BUT WILL WAIT FOR
FCST TO BE REFINED.
&&
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
AS THE STORM HEADS OUT FARTHER INTO THE CANADIAN MARITIMES ON
WED...THE TRAILING H5 TROUGH AXIS PASSES EAST. H8 FLOW IS WEAKLY
CYCLONIC...SO MOST OF THE AREA SHOULD REMAIN DRY BUT WITH ABUNDANT
INSTABILITY STRATOCU. EASTERN SECTIONS COULD SEE SOME SNOW SHOWERS
AS DEEPER MOISTURE WRAPS AROUND THE BACK SIDE OF THE DEPARTING LOW.
TEMPERATURES WILL BE ON THE COLD SIDE...DROPPING TO AROUND -12C TO
-14C AT 925 MB IN THE AFTERNOON. IT MIGHT BE A DAY WHERE HIGHS OCCUR
IN THE MORNING...PROBABLY REACHING ONLY 25-30. GUSTY NORTHWEST WINDS
WILL MAKE IT FEEL EVEN COLDER...WITH WIND CHILLS DROPPING TO AROUND
ZERO LATE WED NIGHT IN NYC....AND -5 TO -10 IN SOME INLAND SPOTS.
RIDGING AT THE SURFACE AND ALOFT BEGINS TO BUILD IN ON THU. IT WILL
BE MOSTLY SUNNY...BUT STILL COLDER THAN NORMAL. LOW LEVEL
THICKNESSES SUPPORT EVEN COLDER HIGH TEMPS THAN THOSE OF WED...
REMAINING IN THE 20S THROUGHOUT.
THE CENTER OF THE HIGH WILL MOVE OFF THE MID ATLANTIC COAST ON
FRI...WITH A DEVELOPING RETURN FLOW. MODERATION WILL BE SLOWER THAN
MOS SUGGESTS ON FRI...WITH HIGHS IN THE 30S THROUGHOUT...BUT SHOULD
KICK IN FOR SAT/SUN WITH HIGHS IN THE 40S...PERHAPS NEARING 50 IN
NYC METRO ON SUN. A WARM FRONT PASSING TO THE NORTH/WEST COULD BRING
THICKENING HIGH/MID LEVEL CLOUDS SAT NIGHT AND SUN...BUT LOW LEVELS
WILL REMAIN QUITE DRY...SO NO PRECIP EXPECTED. NEXT CHANCE OF PRECIP
APPEARS TO BE LATE SUN NIGHT WITH THE APPROACH OF A COLD FRONT.
TEMPS SHOULD RUN AT LEAST SEVERAL DEGREES WARMER THAN MOS WITH
SOUTHERLY FLOW AND CLOUD COVER...MAKING FOR AN ALL RAIN EVENT
SUN NIGHT.
&&
.AVIATION /00Z MONDAY THROUGH FRIDAY/...
CONDITIONS SHOULD DROP TO MVFR BY 01Z OR 02Z ACROSS WESTERN
TERMINALS...02Z TO 03Z AT KISP...KBDR AND KGON. IFR/LIFR TO FOLLOW
BETWEEN 03Z AND 06Z. LATEST ACARS SOUNDINGS ACROSS NYC INDICATE
THAT THE GFS IS VERIFYING BETTER THAN THE NAM. THE WARM NOSE IN
THE NAM IS ABOUT 2 DEGREES TOO HIGH AT 800 MB. THE RUC IS VERIFIES
EVEN BETTER...BUT THIS IS TO BE EXPECTED SINCE IT USES ACARS
SOUNDINGS IN IT.
-SN IS EXPECTED TO BE THE DOMINANT P-TYPE AT
KSWF BUT MAY BRIEFLY MIX WITH -IP AT TIMES THROUGH 09Z. LOOKING
UPSTREAM...KMPO (AND KDXR) HAVE CHANGED TO FZRA OVER THE LAST
HOUR. THIS IS BOTHERSOME AND INDICATES THAT WARMER AIR IS MOVING
IN ALOFT. RUC INDICATES ABOUT A 3 HOUR PERIOD OF A WARM NOSE AT
KSWF BETWEEN 04Z AND 07Z WHICH IS WHEN THERE COULD BE SOME IP
MIXING IN...BUT IF THE WARM LAYER IS LARGER THAN THE PROFILE
INDICATES WE COULD BE LOOKING AT PRECIP CHANGING TO FZRA. NOT
CONFIDENT ENOUGH THAT THIS WILL OCCUR...SO HAVE NOT INCLUDED IN
THE TAF.
KJFK...KLGA...KEWR...KTEB AND KISP SHOULD ALL REMAIN RAIN
FOR THE MAJORITY OF THE EVENT...BUT COULD CHANGE OVER TO -SN AT
THE END (BETWEEN 09Z AND 12Z).
SO ACCORDING TO THE RUC...THE REMAINING TERMINALS (KBDR...KGON
AND KHPN)...WHICH WERE THE TOUGH ONES SINCE THEY REMAIN THE
CLOSEST TO THE RAIN/SNOW LINE...ALL REMAIN -RA FOR MAJORITY OF THE
EVENT AS WELL POSSIBLY CHANGING TO -SN AT THE END TOO.
E/NE WINDS WILL GRADUALLY BACK TO THE N THEN NW AS THE COASTAL LOW
PASSES TO THE SOUTH AND EAST LATE TONIGHT/EARLY MON MORNING.
PRECIP SHOULD TAPER OFF FROM SW TO NE BETWEEN 12Z AND 15Z AND IT
MAY NEED TO BE EXTENDED AN HOUR OR TWO LONGER THAN WHAT IS IN THE
00Z TAFS...BUT WILL WATCH RADAR AND ADJUST ACCORDINGLY.
VFR CONDITIONS RETURN TO ALL TERMINALS BETWEEN 14Z AND 16Z WITH
ONLY GUSTY NW WINDS TO CONTEND WITH. SUSTAINED WINDS SHOULD RANGE
BETWEEN 12 AND 17KT WITH GUSTS BETWEEN 25 AND 30 KT.
OUTLOOK FOR 00Z TUESDAY THROUGH THURSDAY...VFR REMAINS THROUGH
MONDAY NIGHT. SUB-VFR CONDITIONS ARE AGAIN LIKELY TUESDAY AND
TUESDAY EVENING AS AN ALBERTA CLIPPER LOW AND COLD FRONT PASS
ACROSS THE AREA. RAIN NEAR THE COAST...RAIN/SNOW INTERIOR. THIS
WILL BE FOLLOWED BY GUSTY W-NW FLOW LATER TUE NIGHT THROUGH THU AS
THE OFFSHORE LOW INTENSIFIES AND DRAWS DOWN ARCTIC AIR. LIGHT SNOW
SHOWERS OR FLURRIES WILL BE POSSIBLE ON WEDNESDAY...OTHERWISE DRY.
&&
.MARINE...
TODAY THROUGH TUESDAY NIGHT...
SCA WILL BE UP FOR ALL WATERS STARTING THIS EVENING AS WIND GUSTS
WILL BE OVER 25 KT...AND WAVES WILL BUILD TO 4-6 FT ON THE OCEAN.
AFTER THE LOW DEPARTS ON MON...WEAK HIGH PRES WILL BUILD TO THE
SOUTH. WITH A SHOT OF CAA...AND A TIGHT GRADIENT ON THE WATERS...
THERE COULD BE OCNL GALE FORCE GUSTS DURING MON AFTERNOON. WILL
CARRY STRONGLY WORDED SCA FOR NOW...AND LET MID SHIFT DECIDE IF
GALES WILL BE MORE PREVALENT. THINK A GALE EVENT WILL BE MARGINAL
AT BEST. FLAGS COME DOWN FROM WEST TO EAST MON EVENING...ENDING ON
ALL WATERS BY MIDNIGHT. TRANQUIL CONDITIONS THEN EXPECTED THROUGH
MIDDAY TUE. ANOTHER SYSTEM WILL BRING AT LEAST SCA CONDITIONS WITH
GALES POSSIBLE ONCE AGAIN. DUE TO STRONGER CAA AND A STRONGER
GRADIENT...THINK THERE WILL BE A BETTER CHANCE FOR GALES LATE TUE
THAN LATE MON.
WEDNESDAY THROUGH FRIDAY NIGHT...
A STRONG PRESSURE GRADIENT AND LOW LEVEL CAA/INSTABILITY WILL
COMBINE TO PRODUCE NW GALES ON THE OCEAN WED THROUGH THU
MORNING...AND SCA CONDITIONS ELSEWHERE. SCA CONDITIONS ON THE
OCEAN SHOULD COME TO AN END LATE THU NIGHT AS HIGH PRESSURE BUILDS
OVER THE WATERS...BUT COULD RETURN TO THE EASTERN OCEAN WATERS FRI
NIGHT VIA A STRENGTHENING WSW FLOW AS THE CORE OF THE HIGH PASSES
OFF THE MID ATLANTIC COAST.
&&
.HYDROLOGY...
STORM SYSTEM TONIGHT IS EXPECTED TO PRODUCE 1/2 TO 3/4 INCH QPF
THROUGH MON MORNING. SNOW AND SNOW/SLEET IS EXPECTED INLAND...AND
RAIN THEN RAIN/SLEET/SNOW IS EXPECTED CLOSER TO THE COAST.
ANOTHER SYSTEM ON TUE COULD PRODUCE UP TO 1/2" QPF ACROSS THE
AREA.
&&
.EQUIPMENT...
KOKX WSR-88D IS FULLY OPERATIONAL...THOUGH A SOFTWARE/HARDWARE ISSUE
WITH OUR AWIPS HAS CAUSED INTERRUPTIONS OF EXTERNAL DISSEMINATION.
PLEASE CONTACT US IF YOU NOTICE THAT KOKX RADAR IS NOT AVAILABLE.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...WINTER WEATHER ADVISORY UNTIL 9 AM EST MONDAY FOR CTZ005>008.
NY...WINTER WEATHER ADVISORY UNTIL 9 AM EST MONDAY FOR NYZ067>070.
NJ...WINTER WEATHER ADVISORY UNTIL 9 AM EST MONDAY FOR NJZ002.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EST MONDAY FOR ANZ335-338-355.
SMALL CRAFT ADVISORY UNTIL 9 PM EST MONDAY FOR ANZ330-340-345.
SMALL CRAFT ADVISORY UNTIL 11 PM EST MONDAY FOR ANZ350-353.
&&
$$
SYNOPSIS...MPS
NEAR TERM...MPS
SHORT TERM...MPS
LONG TERM...BG
AVIATION...AL
MARINE...BG/MPS
HYDROLOGY...MPS
AREA FORECAST DISCUSSION
NWS GRAND RAPIDS MI
633 AM EST SAT DEC 29 2007
LATEST UPDATE...AVIATION...
.SYNOPSIS...(332 AM EST SAT DEC 29 2007)
LOW PRESSURE OVER LOWER MICHIGAN EARLY THIS MORNING WILL TRACK
NORTHEAST TO NORTHERN LAKE HURON. A QUIET WEEKEND IS EXPECTED WITH
MOSTLY CLOUDY SKIES AND PERHAPS A FEW FLURRIES. TEMPERATURES WILL BE
NEAR SEASONAL AVERAGES.
&&
.SHORT TERM...(332 AM EST SAT DEC 29 2007)
A WEAK SHORT WAVE IS MOVING THROUGH LOWER MICHIGAN EARLY THIS
MORNING. THIS HAS CAUSED THE RADAR TO LIGHT UP AGAIN ACROSS THE
CENTRAL CWA. CLOUD TOPS ARE COOLING TOO AND TAMDAR SOUNDINGS COUPLED
WITH RADAR SUGGEST THAT CLOUD TOPS ARE HITTING -14C...ENOUGH FOR
NUCLEATION. WILL KEEP THE MENTION OF SCT SHSN ACROSS THE CWA THIS
MORNING WITH HIGHEST POPS OVER THE CENTRAL PORTION.
A BROAD UPPER TROUGH WILL GRADUALLY MOVE TOWARD MICHIGAN THIS
WEEKEND. NO MAJOR STORMS ARE IN THE OFFING. WEST BOUNDARY LAYER FLOW
AND H8 TEMPS AROUND -9C SHOULD CREATE SOME WEAK INSTABILITY OVER THE
LAKE. HOWEVER BUFKIT CLEARLY SHOWS THE SNOW GROWTH REGION
UNSATURATED THROUGH SUNDAY. THAT MEANS THAT WE/RE NOT LIKELY TO SEE
SHSN. PERHAPS SCT FLURRIES/DRIZZLE/FZDZ. ANY PCPN WE SEE WILL BE
VERY LIGHT. THE WEEKEND WILL BE MORE DRY THAN ANYTHING.
THE NEXT CHANCE AT ACCUMULATING SNOW WILL COME MONDAY AFTERNOON AS A
CLIPPER MOVES SOUTHEAST TOWARD THE LAKES. GFS ENSEMBLE MEAN IS
FARTHER NORTH THAN THE OPERATIONAL GFS. THE CANADIAN GEM TAKES THE
FARTHER NORTH APPROACH AND THE ECMWF SPLITS THE DIFFERENCE. AT THIS
POINT WE/LL INCREASE POPS TO LIKELY OVER THE NORTHERN CWA AND FINE
TUNE OVER THE WEEKEND.
&&
LONG TERM...(332 AM EST SAT DEC 29 2007)
WHILE I DID MAKE SOME RATHER MINOR CHANGES TO THE GRIDS FOR THE
PERIOD FROM MONDAY NIGHT THROUGH FRIDAY THE OVERALL PICTURE IS AS IT
HAS BEEN FOR THE PAST WEEK. THAT IS... A SHORTWAVE TROUGH ROTATES
THROUGH THE MEAN LONGWAVE TROUGH OVER THE CENTRAL U.S. EARLY IN THE
WEEK. THAT BRINGING DOWN SOME OF THE COLDEST AIR OF THE SEASON. IT
SHOULD BE NOTED THAT WHILE THIS IS COLD AIR...BY EARLY JANUARY
STANDARDS...IT IS NOT ALL THAT COLD ACTUALLY. THEN THE UPSTREAM
SHORTWAVE RIDGE ROTATES THROUGH THAT MEAN LONGWAVE TROUGH AND
FLATTENS IT BY THE END OF THE WEEK. THAT BRING IN PACIFIC AIR AND OF
COURSE THAT WOULD RESULT IN SOME SIGNIFICANT WARMING.
IF YOU REMEMBER MY MJO DISCUSSION FROM YESTERDAY...IT REMAINS TRUE
THAT I WOULD EXPECT SOUTHWEST MICHIGAN TO SEE AT LEAST A WEEK OF
WARMER THAN NORMAL TEMPERATURES. THAT WARM PERIOD WILL BE FOLLOWING
THE COLD PERIOD THAT WILL USHER IN 2008. THE REASON FOR THE COLD
WEATHER EARLY THIS COMING WEEK THAT WILL BE FOLLOWED BY A WARM UP...
IS RELATED TO ROSSBY WAVE DISPERSION FROM THE CONVECTIVE ACTIVITY IN
THE TROPICAL PACIFIC. WHETHER SOUTHWEST MICHIGAN IS WARM OR COLD IS
VERY MUCH RELATED TO WHERE THAT CONVECTIVE MAX IS AT ANY ONE TIME.
WHERE THE MAX TROPICAL PACIFIC CONVECTIVE ACTIVITY AREA IS FORCES
THE POSITION OF THE LONG WAVES IN THE EXTRATROPICS. IT`S ALSO THE
MOVEMENT OF THAT CONVECTION WITH TIME THAT MATTERS TO OUR LONGWAVE.
CURRENTLY IT IS HEADING EAST OF INDONESIA.
THE GFS FROM RUN TO RUN CHANGES WHEN THE WARM AIR COMES BACK IN.
YESTERDAY IT SLOWED THE WARM UP TILL FRIDAY... TONIGHTS RUN SPEEDS
THE WARM UP TO THURSDAY. I AM TOTALLY NOT ON THAT PAGE YET. THE
MODELS TEND TO BRING THE WARM TO FAST SO I WOULD WANT THREE DAYS IN
ROW THE THE SAME SOLUTION TO BELIEVE IT.
THE PRIMARY MESSAGE OF THE LONG RANGE PART OF THIS FORECAST IS LAKE
EFFECT SNOW TUESDAY INTO WEDNESDAY WITH SIGNIFICANT ACCUMULATIONS
MORE THAN POSSIBLE SOUTHWEST OF GRAND RAPIDS. THIS WOULD BE A
NORTHWEST FLOW SORT OF EVENT SO NOT ONLY WOULD OTTAWA... ALLEGAN...
VAN BUREN AND KALAMAZOO COUNTIES SEE SIGNIFICANT ACCUMULATIONS BUT
SO WOULD MASON AND LAKE COUNTIES. THIS WILL BE OUR NEXT FOCUS FOR
SIGNIFICANT SNOWFALL.
&&
.AVIATION...(633 AM EST SAT DEC 29 2007)
AS OF 630 AM THIS SATURDAY MORNING CEILINGS WERE MVFR ACROSS THE CWA
AND THERE WAS A DIMINISHING AREA OF SNOW FLURRIES FROM GRR EAST TO
NEAR LAN. WITH CONTINUED CAA AT LOW TO MID LEVELS MOST OF THIS
MORNING... I WOULD EXPECT THE MVFR CIGS TO CONTINUE THROUGH MOST OF
THE DAY. TONIGHT THE SHORTWAVE RIDGE MOVES THROUGH AND THAT WILL
TURN WINDS SOUTHERLY. DUE BOTH THE WARM ADVECTION AND THE MORE
SOUTHERLY WIND DIRECTION BELOW 3000 FT.... I ALLOWED THE LOWER
CLOUDS TO BREAK OUT AFTER 21Z ALONG THE I-94 TAF SITE AND AROUND 00Z
AT GRR AND LAN. MKG...BEING SO CLOSE TO THE LAKE MAY HAVE MVFR CIGS
THROUGH SUNDAY.
THERE IS NOT MUCH FORCING FOR PRECIPITATION SO I DID NOT INCLUDE IT
IN ANY OF THE TAFS SITES EXCEPT TO ALLOW THE CURRENT LAKE EFFECT
SNOW SHOWERS DO DIMINISH AND END BY 15Z.
&&
.MARINE...(332 AM EST SAT DEC 29 2007)
SMALL CRAFT ADVISORY IS IN PLACE AS MODERATELY STRONG WINDS
OVERNIGHT HAVE PUSHED WAVES ABOVE 4 FEET.
&&
.HYDROLOGY...(332 AM EST SAT DEC 29 2007)
WE DON/T ANTICIPATE MAY HYDRO PROBLEMS AS FRIDAY/S SYSTEM WAS
MAINLY SNOW. LIQUID EQUIVALENT NEAR 0.4 INCHES SHOULDN/T RESULT IN
HYDRO PROBLEMS. TEMPS IN THE 30S WILL PROMOTE A SLOW MELT.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...SMALL CRAFT ADVISORY ST JOE TO MANISTEE TONIGHT THROUGH
SATURDAY EVENING.
&&
$$
SYNOPSIS: 93
SHORT TERM: 93
LONG TERM: WDM
AVIATION: WDM
MARINE: 93
HYDROLOGY: 93
AREA FORECAST DISCUSSION
NWS GRAND RAPIDS MI
332 AM EST SAT DEC 29 2007
LATEST UPDATE...ALL BUT AVIATION...
.SYNOPSIS...(332 AM EST SAT DEC 29 2007)
LOW PRESSURE OVER LOWER MICHIGAN EARLY THIS MORNING WILL TRACK
NORTHEAST TO NORTHERN LAKE HURON. A QUIET WEEKEND IS EXPECTED WITH
MOSTLY CLOUDY SKIES AND PERHAPS A FEW FLURRIES. TEMPERATURES WILL BE
NEAR SEASONAL AVERAGES.
&&
.SHORT TERM...(332 AM EST SAT DEC 29 2007)
A WEAK SHORT WAVE IS MOVING THROUGH LOWER MICHIGAN EARLY THIS
MORNING. THIS HAS CAUSED THE RADAR TO LIGHT UP AGAIN ACROSS THE
CENTRAL CWA. CLOUD TOPS ARE COOLING TOO AND TAMDAR SOUNDINGS COUPLED
WITH RADAR SUGGEST THAT CLOUD TOPS ARE HITTING -14C...ENOUGH FOR
NUCLEATION. WILL KEEP THE MENTION OF SCT SHSN ACROSS THE CWA THIS
MORNING WITH HIGHEST POPS OVER THE CENTRAL PORTION.
A BROAD UPPER TROUGH WILL GRADUALLY MOVE TOWARD MICHIGAN THIS
WEEKEND. NO MAJOR STORMS ARE IN THE OFFING. WEST BOUNDARY LAYER FLOW
AND H8 TEMPS AROUND -9C SHOULD CREATE SOME WEAK INSTABILITY OVER THE
LAKE. HOWEVER BUFKIT CLEARLY SHOWS THE SNOW GROWTH REGION
UNSATURATED THROUGH SUNDAY. THAT MEANS THAT WE/RE NOT LIKELY TO SEE
SHSN. PERHAPS SCT FLURRIES/DRIZZLE/FZDZ. ANY PCPN WE SEE WILL BE
VERY LIGHT. THE WEEKEND WILL BE MORE DRY THAN ANYTHING.
THE NEXT CHANCE AT ACCUMULATING SNOW WILL COME MONDAY AFTERNOON AS A
CLIPPER MOVES SOUTHEAST TOWARD THE LAKES. GFS ENSEMBLE MEAN IS
FARTHER NORTH THAN THE OPERATIONAL GFS. THE CANADIAN GEM TAKES THE
FARTHER NORTH APPROACH AND THE ECMWF SPLITS THE DIFFERENCE. AT THIS
POINT WE/LL INCREASE POPS TO LIKELY OVER THE NORTHERN CWA AND FINE
TUNE OVER THE WEEKEND.
&&
LONG TERM...(332 AM EST SAT DEC 29 2007)
WHILE I DID MAKE SOME RATHER MINOR CHANGES TO THE GRIDS FOR THE
PERIOD FROM MONDAY NIGHT THROUGH FRIDAY THE OVERALL PICTURE IS AS IT
HAS BEEN FOR THE PAST WEEK. THAT IS... A SHORTWAVE TROUGH ROTATES
THROUGH THE MEAN LONGWAVE TROUGH OVER THE CENTRAL U.S. EARLY IN THE
WEEK. THAT BRINGING DOWN SOME OF THE COLDEST AIR OF THE SEASON. IT
SHOULD BE NOTED THAT WHILE THIS IS COLD AIR...BY EARLY JANUARY
STANDARDS...IT IS NOT ALL THAT COLD ACTUALLY. THEN THE UPSTREAM
SHORTWAVE RIDGE ROTATES THROUGH THAT MEAN LONGWAVE TROUGH AND
FLATTENS IT BY THE END OF THE WEEK. THAT BRING IN PACIFIC AIR AND OF
COURSE THAT WOULD RESULT IN SOME SIGNIFICANT WARMING.
IF YOU REMEMBER MY MJO DISCUSSION FROM YESTERDAY...IT REMAINS TRUE
THAT I WOULD EXPECT SOUTHWEST MICHIGAN TO SEE AT LEAST A WEEK OF
WARMER THAN NORMAL TEMPERATURES. THAT WARM PERIOD WILL BE FOLLOWING
THE COLD PERIOD THAT WILL USHER IN 2008. THE REASON FOR THE COLD
WEATHER EARLY THIS COMING WEEK THAT WILL BE FOLLOWED BY A WARM UP...
IS RELATED TO ROSSBY WAVE DISPERSION FROM THE CONVECTIVE ACTIVITY IN
THE TROPICAL PACIFIC. WHETHER SOUTHWEST MICHIGAN IS WARM OR COLD IS
VERY MUCH RELATED TO WHERE THAT CONVECTIVE MAX IS AT ANY ONE TIME.
WHERE THE MAX TROPICAL PACIFIC CONVECTIVE ACTIVITY AREA IS FORCES
THE POSITION OF THE LONG WAVES IN THE EXTRATROPICS. IT`S ALSO THE
MOVEMENT OF THAT CONVECTION WITH TIME THAT MATTERS TO OUR LONGWAVE.
CURRENTLY IT IS HEADING EAST OF INDONESIA.
THE GFS FROM RUN TO RUN CHANGES WHEN THE WARM AIR COMES BACK IN.
YESTERDAY IT SLOWED THE WARM UP TILL FRIDAY... TONIGHTS RUN SPEEDS
THE WARM UP TO THURSDAY. I AM TOTALLY NOT ON THAT PAGE YET. THE
MODELS TEND TO BRING THE WARM TO FAST SO I WOULD WANT THREE DAYS IN
ROW THE THE SAME SOLUTION TO BELIEVE IT.
THE PRIMARY MESSAGE OF THE LONG RANGE PART OF THIS FORECAST IS LAKE
EFFECT SNOW TUESDAY INTO WEDNESDAY WITH SIGNIFICANT ACCUMULATIONS
MORE THAN POSSIBLE SOUTHWEST OF GRAND RAPIDS. THIS WOULD BE A
NORTHWEST FLOW SORT OF EVENT SO NOT ONLY WOULD OTTAWA... ALLEGAN...
VAN BUREN AND KALAMAZOO COUNTIES SEE SIGNIFICANT ACCUMULATIONS BUT
SO WOULD MASON AND LAKE COUNTIES. THIS WILL BE OUR NEXT FOCUS FOR
SIGNIFICANT SNOWFALL.
&&
.AVIATION...(1155 PM EST FRI DEC 28 2007)
PRECIPITATION HAS SHIFTED WELL NORTH AND EAST OF THE TAF SITES AS OF
MIDNIGHT...WITH CHANCES ONLY FOR SOME LIGHT DRIZZLE OR FLURRIES
OVERNIGHT. DECIDED THE THREAT LOOKED TOO LOW TO INCLUDE IN THE TAFS.
CANNOT RULE OUT SOME LIGHT FREEZING DRIZZLE EITHER LATE
TONIGHT...BUT AGAIN...CHANCES SMALL AND DID NOT INCLUDE IN THE
FORECAST. VISIBILITIES SHOULD NOT BE RESTRICTED TONIGHT OR TOMORROW
IT APPEARS. CEILINGS WILL REMAIN IN THE MVFR CATEGORY THOUGH THE
NIGHT AND MUCH OF THE DAY TOMORROW WITH A PRETTY SOLID OVERCAST IN
PLACE IN THE WAKE OF THE DEPARTING SYSTEM. INDICATING IMPROVEMENT TO
VFR CEILINGS TOMORROW EVENING AS SURFACE RIDGING BUILDS INTO THE
AREA.
&&
.MARINE...(332 AM EST SAT DEC 29 2007)
SMALL CRAFT ADIVISORY IS IN PLACE AS MODERATELY STRONG WINDS
OVERNIGHT HAVE PUSHED WAVES ABOVE 4 FEET.
&&
.HYDROLOGY...(332 AM EST SAT DEC 29 2007)
WE DON/T ANTICIPATE MAY HYDRO PROBLEMS AS FRIDAY/S SYSTEM WAS
MAINLY SNOW. LIQUID EQUIVALENT NEAR 0.4 INCHES SHOULDN/T RESULT IN
HYDRO PROBLEMS. TEMPS IN THE 30S WILL PROMOTE A SLOW MELT.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...SMALL CRAFT ADVISORY ST JOE TO MANISTEE TONIGHT THROUGH
SATURDAY EVENING.
&&
$$
SYNOPSIS: 93
SHORT TERM: 93
LONG TERM: WDM
AVIATION: DUKE
MARINE: 93
HYDROLOGY: 93
AREA FORECAST DISCUSSION
NWS BUFFALO NY
721 AM EST SAT DEC 29 2007
.SYNOPSIS...
A POTENT AREA OF LOW PRESSURE MOVING THROUGH SOUTHERN QUEBEC WILL
BRING GUSTY WINDS TODAY ALONG WITH SLOWLY FALLING TEMPERATURES. IT
WILL BE A RELATIVELY DRY DAY HOWEVER WITH JUST A FEW LEFTOVER
FLURRIES AND SPRINKLES. TONIGHT A WESTERLY FLOW OF COLDER AIR WILL
DEVELOP AND SET THE STAGE FOR SOME MINOR LAKE EFFECT SNOW EAST OF
LAKES ERIE AND ONTARIO. THE LAKE SNOWS WILL DIMINISH QUICKLY SUNDAY
MORNING AS AN AREA OF HIGH PRESSURE BUILDS ACROSS THE REGION.
ANOTHER WEAK TROUGH OF LOW PRESSURE WILL CROSS THE EASTERN GREAT
LAKES SUNDAY NIGHT WITH A CHANCE OF A LITTLE LIGHT SNOW. ANOTHER
AREA OF LOW PRESSURE IS THEN FORECAST TO MOVE THROUGH THE GREAT
LAKES MONDAY NIGHT INTO TUESDAY AND BRING A MIX OF RAIN AND SNOW
MONDAY NIGHT CHANGING TO ALL SNOW FOR NEW YEARS DAY WITH GUSTY WINDS
AND FALLING TEMPERATURES.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
MOISTURE CHANNEL IMAGERY IS QUITE IMPRESSIVE EARLY THIS MORNING AS
WE WATCH A MID LATITUDE SYSTEM REACH MATURITY AND BEGIN TO OCCLUDE.
A STRONG MID LEVEL SPEED MAX ROTATING THROUGH THE BASE OF THE
DIGGING TROUGH AIDED IN ENHANCING PRECIP OVER CENTRAL AND EASTERN NY
AND EVEN PRODUCED A FEW WEAK THUNDERSTORMS ACROSS WESTERN NY FRIDAY
EVENING. THE STEADY RAINS ARE EXITING THE EASTERN EDGE OF THE CWA AT
08Z AND WILL BE GONE COMPLETELY BY 12Z. A SURFACE COLD FRONT IS
ENTERING WESTERN NY AT 08Z WITH WINDS SHIFTING TO THE SOUTHWEST AND
INCREASING DRAMATICALLY. PORT COLBURNE AND LONG POINT ARE GUSTING TO
42 KNOTS AND 45 KNOTS RESPECTIVELY AT 07Z...ALTHOUGH THESE ARE TWO
OF THE WINDIEST SPOTS IN THIS REGION WITH THEIR UN-OBSTRUCTED
EXPOSURE TO THE SOUTHWEST WINDS OFF LAKE ERIE.
MAIN CONCERN TODAY WILL BE THE GUSTY WINDS. A MODERATE SURFACE
PRESSURE GRADIENT WILL COUPLE WITH STEADY COLD AIR ADVECTION IN THE
BOUNDARY LAYER TO SUPPORT MIXING OF HIGHER MOMENTUMS ALOFT DOWN TO
THE SURFACE. STRONGEST GUSTS SHOULD BE THIS MORNING ACROSS WESTERN
NY AND MIDDAY TO EARLY AFTERNOON EAST OF LAKE ONTARIO COINCIDENT
WITH THE TIME OF STRONGEST 925MB WINDS /40 KNOTS/ AND THE BEST
AGEOSTROPHIC CONTRIBUTION FROM ISALLOBARIC PRESSURE RISES. EXPECT
STRONGEST GUSTS TO REMAIN JUST BELOW ADVISORY CRITERIA AT 35-40 MPH.
A FEW GUSTS MAY TOUCH 45 MPH NEAR LAKE ERIE AND AT THE EAST END OF
LAKE ONTARIO BUT COVERAGE WILL NOT BE GREAT ENOUGH TO JUSTIFY A WIND
ADVISORY.
WITH THE STEADY PRECIP PULLING OUT OF THE EAST TODAY...NOT MUCH IN
THE WAY OF FORCING OR DEEP MOISTURE TO PRODUCE ANY MEASURABLE
PRECIP. WRAP AROUND MOISTURE WITHIN THE COMMA HEAD OF THE OCCLUDING
LOW WILL PASS WELL NORTH OF THE AREA THROUGH CANADA. WE WILL
PROBABLY SQUEEZE OUT THE LITTLE REMAINING MOISTURE IN THE COLD AIR
ADVECTION/HEIGHT FALL REGIME...SO HAVE CARRIED SOME SPRINKLES AND
FLURRIES. BY LATE IN THE DAY...COLD AIR DEEPENS ENOUGH TO SUPPORT
INCREASING PROBABILITIES OF SOME LIGHT LAKE EFFECT SNOW SHOWERS EAST
OF BOTH LAKES ERIE AND ONTARIO. WILL JUST GO WITH CHANCE POPS FOR
AREAS JUST SOUTH OF BUFFALO AND WATERTOWN LATE THIS AFTERNOON TO
COVER THE POTENTIAL WITH LITTLE OR NO ACCUMULATION.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH TUESDAY/...
MAIN CONCERN FOR TONIGHT WILL REVOLVE AROUND LAKE EFFECT SNOW
POTENTIAL WITH A WESTERLY FLOW OF MARGINALLY COLD AIR WILL BE IN
PLACE WITH 850MB TEMPS AROUND -10C.
OFF LAKE ERIE...THERMODYNAMICS ARE VERY MARGINAL WITH LAKE INDUCED
EQUILIBRIUM LEVELS AROUND 5K FEET...BUT FAVORABLE LONG FETCH ON 250
FLOW EARLY THIS EVENING VEERING TO 260-270 OVERNIGHT SHOULD PROVIDE
JUST ENOUGH LAKE MODIFICATION OF THE BOUNDARY LAYER TO SUPPORT SOME
LIGHT LAKE SNOW. EXPECT A WEAK AREA OF LAKE EFFECT TO DEVELOP ACROSS
THE MORE DISTANT BUFFALO SOUTHTOWNS THIS EVENING THEN DRIFT SOUTH
INTO SKI COUNTRY OVERNIGHT. ANY ACCUMS SHOULD BE VERY LIGHT WITH
NOTHING MORE THAN AN INCH OR TWO EXPECTED...WHICH WOULD BE MOST
LIKELY ACROSS THE HIGHER TERRAIN OF THE BOSTON HILLS AND THE
CHAUTAUQUA RIDGE WHERE ADDED LIFT FROM UPSLOPING MAY HELP TO ENHANCE
THE LIGHT SNOW SHOWERS.
OFF LAKE ONTARIO...THERMODYNAMICS ARE SLIGHTLY BETTER THAN ON LAKE
ERIE WITH EQUILIBRIUM LEVELS AROUND 7K FEET. EXPECT A BROAD AREA OF
LIGHT LAKE EFFECT SNOW SHOWERS TO DEVELOP LATE THIS AFTERNOON OR
EARLY EVENING JUST SOUTH OF WATERTOWN INTO THE NORTHERN PORTION
OF THE TUG HILL PLATEAU. THE SNOW SHOWERS SHOULD CONSOLIDATE INTO A
MORE COHERENT BAND LATER THIS EVENING AS THE SHEAR IN THE BOUNDARY
LAYER DECREASES WITH WINDS BECOMING WELL ALIGNED. EXPECT THIS BAND
TO DRIFT SLOWLY SOUTH ACROSS THE TUG HILL REGION AND REACH
NORTHERN/CENTRAL OSWEGO COUNTY LATE TONIGHT AND EARLY SUNDAY
MORNING. GIVEN THE MARGINAL THERMODYNAMICS...HAVE OPTED NOT TO HOIST
AN ADVISORY JUST YET TO ALLOW DAY SHIFT TO MONITOR THE PROGRESS OF
LAKE SNOW DEVELOPMENT. EXPECT THE GREATEST ACCUMULATIONS TO BE
ACROSS THE TUG HILL PLATEAU WHERE ADDED LIFT FROM UPSLOPE WILL HELP
TO ENHANCE SNOWFALL RATES. THIS WILL NEED TO BE MONITORED CLOSELY AS
SOME OF THESE VERY MARGINAL EVENTS PRODUCE DECENT SNOWFALL AMOUNTS
ON THE TUG HILL...PRIMARILY DUE TO THE EFFICIENT TERRAIN UPSLOPING.
ON SUNDAY EXPECT ANY REMAINING ACTIVITY ON LAKE ERIE TO QUICKLY
DISSIPATE DURING THE MORNING AS A SURFACE RIDGE CRESTS OVER THE LAKE
WITH WARMING TEMPS ALOFT AND QUICKLY BACKING FLOW. ANY LEFTOVER
ACTIVITY MAY SPREAD A FEW FLURRIES ACROSS METRO BUFFALO INTO THE
NIAGARA PENINSULA BUT THIS SHOULD NOT BE MEASURABLE. OFF LAKE
ONTARIO BAND SHOULD STILL BE GOING EARLY ACROSS OSWEGO COUNTY AND
THE SOUTHERN TUG HILL...BUT THEN QUICKLY SHIFT NORTH AND DISSIPATE
DURING THE MIDDAY/EARLY AFTERNOON. A FEW SNOW SHOWERS MAY CROSS
WATERTOWN AND THE THOUSAND ISLANDS WITH LITTLE OR NO ACCUM.
OUR ATTENTION THEN TURNS BACK TO THE SYNOPTIC SCALE. A LOW WILL
DEVELOP SUNDAY EVENING OFF THE CAROLINAS AND TRACK OUT TO SEA WITH
INTENSE RIGHT ENTRANCE REGION JET DYNAMICS ALLOWING AN AREA OF
PRECIP TO BREAK OUT ACROSS THE MID ATLANTIC INTO SOUTHERN NEW
ENGLAND. OUR CWA WILL BE DISPLACED WELL WEST OF THIS MAIN AREA OF
FORCING...HOWEVER THE PASSAGE OF DE-AMPLIFYING MID LEVEL TROUGH AND
WEAK SURFACE TROUGH MAY BE ENOUGH TO SUPPORT A LITTLE LIGHT SNOW.
GIVEN THE WEAK FORCING AND MAIN FOCUS WELL EAST OF THE AREA...HAVE
UNDERCUT GUIDANCE POPS AND JUST KEPT LOW CHANCE.
ANOTHER AREA OF LOW PRESSURE WILL MOVE INTO THE GREAT LAKES MONDAY
NIGHT SPREADING MORE PRECIP INTO THE REGION. GFS THERMAL PROFILES
WOULD SUPPORT ALL SNOW...HOWEVER FROM A PATTERN RECOGNITION
STANDPOINT THIS DOES NOT MAKE SENSE WITH THE SURFACE LOW TRACKING
NORTH AND WEST OF THE REGION. GFS APPEARS MUCH TOO COLD IN THE LOWER
HALF OF THE COLUMN...AND SUSPECT MUCH OF THIS FIRST WAVE OF PRECIP
WILL BE AT LEAST MIXED WITH RAIN MUCH OF MONDAY NIGHT. HAVE OPTED TO
GO WITH A RA/SN MIX FOR MOST AREAS...EXCEPT ALL SNOW ACROSS THE
NORTH COUNTRY WHICH TYPICALLY HOLDS ONTO THE COLD AIR BETTER.
&&
.LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/...
AN IMPORTANT LONGWAVE PATTERN CHANGE WILL TAKE PLACE DURING THE
EARLY PART OF THE LONG TERM PERIOD...RESULTING IN A RETURN TO MUCH
COLDER TEMPERATURES BY THE MIDDLE OF NEXT WEEK...ALTHOUGH THESE WILL
BE NOTHING EXTREME FOR EARLY JANUARY. BROAD LONGWAVE TROUGHING
ACROSS THE WESTERN CONUS WILL KEEP A SOUTHWEST TO NORTHEAST STORM
TRACK ACROSS THE NATION THROUGH THE SHORT TERM PORTION OF THE
FORECAST...BEFORE THE TROUGH AMPLIFIES AND SHIFTS EAST INTO THE
EASTERN HALF OF THE CONTINENT BY MIDWEEK. THE TROUGH IS THEN
EXPECTED TO FLATTEN AS IT MOVES INTO THE ATLANTIC WITH THE FLOW
BECOMING MORE ZONAL BY THURSDAY AND EARLY FRIDAY ALONG WITH
TEMPERATURES WARMING CLOSER TO NORMAL LEVELS.
LOOKING AT THE FORECAST DETAILS...A DEEP AREA OF LOW PRESSURE WILL
MOVE EASTWARD JUST TO THE NORTH OF LAKE ONTARIO TUESDAY WHILE THE
UPPER TROUGH GETS CARVED OUT ACROSS THE GREAT LAKES REGION. THIS
WILL BRING WITH IT A FAIRLY HIGH PROBABILITY OF SNOW FOR OUR REGION
WITH MUCH COLDER SWEEPING IN BEHIND IT.
SOME OF THE COLDEST AIR OF THE SEASON IS EXPECTED BY WEDNESDAY AND
WEDNESDAY NIGHT IN THE NORTHERLY FLOW ON THE BACK SIDE OF THE LOW.
LOOKS LIKE A FAIRLY GOOD SET UP FOR LAKE EFFECT SNOW SOUTH AND
SOUTHEAST OF THE LAKES BUT IT WILL LIKELY BE MULTIBANDED WITH SHORT
FETCHES ACROSS THE LAKES. WE WILL HAVE TO KEEP AN EYE OUT FOR
CONNECTIONS WITH GEORGIAN BAY AND LAKE HURON.
AS MENTIONED ABOVE THERE IS FAIRLY GOOD CONFIDENCE THAT THE UPPER
TROUGH WILL MOVE QUICKLY EAST THURSDAY WITH THE FLOW BECOMING MORE
ZONAL. WARM ADVECTION WILL BRING TEMPERATURES BACK TO MORE SEASONAL
VALUES. ANOTHER IMPULSE FROM THE CANADIAN PRAIRIES IS EXPECTED TO
DIG THE UPPER TROUGH AGAIN BY FRIDAY BUT IT WILL BE MORE OF A
GLANCING BLOW AS ANOTHER SURFACE LOW MOVES QUICKLY EAST ACROSS
SOUTHERN QUEBEC.
&&
.AVIATION /13Z SATURDAY THROUGH WEDNESDAY/...
DEEP LOW PRESSURE OVER SOUTHWESTERN QUEBEC EARLY THIS MORNING WILL
WITHDRAW NORTHEASTWARD TODAY. FAIRLY STRONG GUSTY WINDS IN THE WAKE
OF THIS LOW BE AN ISSUE FOR TAKE OFFS AND LANDINGS...ESPECIALLY FOR
SMALLER AIRCRAFT. STRATO CUMULUS CIGS WILL GENERALLY RANGE BETWEEN
25 HUNDRED AND 35 HUNDRED FEET AS THE ATMOSPHERE STAYS WELL MIXED.
AS COLD ADVECTION OCCURS TODAY THERE MAY BE SOME LIMITED LAKE EFFECT
SNOW SHOWERS...GENERALLY JUST SOUTH OF BUFFALO AND WATERTOWN. THERE
IS A BETTER CHANCE TONIGHT AS THE COLD AIR DEEPENS. THE LAKE EFFECT
AREAS TONIGHT WILL SEE IFR CONDITIONS BUT WINDS WILL WEAKEN LATE
TODAY AND TONIGHT.
LOOKING FURTHER AHEAD...WEAK LAKE SNOWS/MVFR CONDITIONS MAY PERSIST
EAST OF THE GREAT LAKES INTO SUNDAY MORNING...BEFORE DYING OUT AS A
LOW-LEVEL RIDGE PUSHES ACROSS THE AREA. ANOTHER AREA OF LOW PRESSURE
MOVING THROUGH THE GREAT LAKES MONDAY AND TUESDAY WILL THEN BRING
ANOTHER ROUND OF PRECIPITATION TO THE AREA MONDAY NIGHT AND TUESDAY
WITH ASSOCIATED CIG/VSBY RESTRICTIONS. IT MAY BE A MIX MONDAY NIGHT
BUT MAINLY SNOW TUESDAY. LAKE EFFECT SNOWS WILL BECOME LIKELY SOUTH
AND SOUTHEAST OF BOTH LAKES ERIE AND ONTARIO FROM LATE TUESDAY INTO
WEDNESDAY AS TEMPERATURES DROP SIGNIFICANTLY.
&&
.MARINE...
LOW PRESSURE TRACKING EAST FROM SOUTHERN ONTARIO WILL PRODUCE A
STRONG WEST TO SOUTHWEST FLOW ACROSS THE LOWER LAKES TODAY WITH GALE
FORCE GUSTS EXPECTED INTO THE AFTERNOON. THE GRADIENT WILL BEGIN TO
RELAX LATE TODAY AS THE LOW CONTINUES TO WITHDRAW EASTWARD. GALES
WARNINGS WILL END A LITTLE EARLIER THAN THE PREVIOUS FORECAST.
QUIET WEATHER IS EXPECTED MARINE WISE THROUGH MONDAY THEN ANOTHER
DEEP LOW IS FORECAST TO TRACK JUST TO THE NORTH OF THE LOWER LAKES
TUESDAY WITH GALE FORCE WINDS POSSIBLE ONCE AGAIN.
&&
.BUF WATCHES/WARNINGS/ADVISORIES...
NY...NONE.
MARINE...GALE WARNING UNTIL 3 PM EST THIS AFTERNOON FOR LEZ020-040-041.
GALE WARNING UNTIL 4 PM EST THIS AFTERNOON FOR
LOZ042>045-062>065.
SMALL CRAFT ADVISORY UNTIL 5 PM EST THIS AFTERNOON
FOR SLZ022-024.
&&
$$
SYNOPSIS...HITCHCOCK
NEAR TERM...HITCHCOCK
SHORT TERM...HITCHCOCK
LONG TERM...JJR/SAGE
AVIATION...SAGE
MARINE...SAGE
AREA FORECAST DISCUSSION
NWS SEATTLE WA
350 PM PST SUN DEC 30 2007
.SYNOPSIS...SHOWERS WILL COME TO END TONIGHT OVER THE LOWLANDS AS
THE UPPER LEVEL TROUGH SHIFTS EAST AND AN UPPER LEVEL RIDGE OFF THE
COAST MOVES CLOSER TO THE AREA. OTHER THAN A FEW LINGERING MORNING
SHOWERS IN THE CASCADES MONDAY WILL BE DRY DAY AS THE UPPER LEVEL
RIDGE MOVES OVER WESTERN WASHINGTON. THE RIDGE WILL MOVE EAST ON
TUESDAY...ALLOWING A LOW PRESSURE SYSTEM TO APPROACH THE COAST. THUS
EXPECT A CHANCE OF RAIN ON THE COAST ON TUESDAY WITH RAIN LIKELY
EVERYWHERE ON WEDNESDAY. THE UNSETTLED WEATHER WILL CONTINUE INTO
NEXT WEEKEND.
&&
.SHORT TERM...SATELLITE IMAGERY SHOWS BACK END OF A COOL UPPER LEVEL
TROUGH STILL OVER WESTERN WASHINGTON THIS AFTERNOON. ACARS SOUNDINGS
AND THE SANDPOINT PROFILER SHOW WINDS IN THE 850-700 LAYER ARE
BEGINNING TO DECREASE BUT SNOW CONTINUING IN THE MOUNTAINS. PASS
REPORTS CONTINUE TO REPORT SNOW HEAVY AT TIMES WITH LOCAL VISIBILITY
RESTRICTIONS. ESTIMATED NEW SNOW TOTALS FROM LAST NIGHT THROUGH THIS
AFTERNOON FROM THE NORTHWEST AVALANCHE CENTER RANGE FROM 10-20
INCHES. THESE TOTALS ARE FROM THE AUTOMATED INSTRUMENTS AND WITH THE
STRONG WINDS BLOWING THE SNOW AROUND THIS TOTALS ARE LIKELY TO BE ON
THE LOW SIDE OF THE ACTUAL AMOUNTS. IR SATELLITE IMAGERY SHOWS MORE
CU OFFSHORE MOVING IN TONIGHT SO EVEN THOUGH THE WIND ALOFT ARE
BEGINNING TO DECREASE WILL KEEP THE WINTER STORM WARNING IN PLACE
FOR THE CASCADES UNTIL THE EARLY MORNING HOURS ON MONDAY. UPPER
LEVEL RIDGE OFFSHORE NEAR 140W MOVING EASTWARD OVERNIGHT AND WILL BE
OVER WESTERN WASHINGTON BY 00Z TUE. IN ADDITIONS SURFACE GRADIENTS
GOING OFFSHORE ON MONDAY. THE COMBINATION OF THESE TWO FEATURES WILL
RESULT IN A DRY DAY FOR THE LOWLANDS AND ALSO A DRY DAY FOR THE
MOUNTAINS AFTER A FEW LINGERING SHOWERS IN THE MORNING. RIDGE SHIFTS
EAST ON TUESDAY ALLOWING FIRST A WARM FRONT TO BRUSH THE NORTHERN
PORTION OF THE AREA LATE IN THE DAY THEN THE TRAILING COLD FRONT
LATE TUESDAY INTO WEDNESDAY. STRONG SOUTHWESTERLY FLOW ALOFT
ASSOCIATED WITH THIS FRONT AND WITH THE UPPER LEVEL TROUGH BEHIND
THE FRONT DIGGING SOUTH THE FRONT WILL STALL OVER WESTERN WASHINGTON
CREATING SOME SIGNIFICANT RAINFALL AMOUNTS FOR THE SOUTH SLOPES OF
THE OLYMPICS.
.LONG TERM...EXTENDED MODELS IN GENERAL AGREEMENT ABOUT THE PATTERN
DEVELOPING OVER THE EXTENDED PERIOD WITH AN UPPER LEVEL TROUGH
SETTING UP OFFSHORE AND SYSTEMS SPINNING OUT OF THE BASE OF THE
TROUGH MOVING THROUGH WESTERN WASHINGTON. SURFACE GRADIENTS NEVER
REALLY GO ONSHORE WITH ANY OF THESE FEATURES WHICH MAKE THE
PRECIPITATION TYPE DIFFICULT ON OCCASION. FOR NOW GIVEN THE PATTERN
IT IS WAY TO EARLY TO PICK OUT ANY DETAILS AND WILL STICK WITH THE
BROADBRUSH CLIMO LIKELY POPS FOR THE EXTENDED. FELTON
&&
.AVIATION...APPEARS WINDS WILL CONTINUE TO DIMINISH THIS EVENING AS
PRESSURE GRADIENTS CONTINUE TO WEAKEN. GUSTY WESTERLY WINDS TO 30 KT
REMAIN POSSIBLE TROUGH THE EVENING AS A LARGE AREA OF SHOWERS
CONTINUES TO MOVE INLAND FROM THE OFFSHORE WATERS.
MVFR CIGS 020-028 FT CENTRAL AND SOUTH PUGET SOUND AREA THIS
PM...OTHERWISE GENERALLY VFR CIGS. EXPECT SCATTERED MVFR CONDITIONS
WITH GUSTY WINDS 20-25 KTS TO CONTINUE THIS EVENING NEAR HEAVIER
SHOWERS.
AT KSEA...BKN023-030 BKN070. ISOLATED SHOWERS. WIND AT S-SW 12-15KT
G22-25KT ESPECIALLY NEAR HEAVIER SHOWERS UNTIL 02-03Z. AFTER 03Z
SCT020 BKN045-050 BKN120. WIND S 7-10KT. PRANGE
&&
.MARINE...ONSHORE GRADIENTS CONTINUE TO WEAKEN THIS AFTERNOON LONG
WITH THE GALE FORCE WINDS ALONG THE COAST AND IN THE STRAIT. APPEARS
WINDS WILL CONTINUE TO DIMINISH DROPPING BELOW GALE FORCE CRITERIA
BY LATE EVENING. GUSTY WEST WINDS 30-40 KT REMAIN POSSIBLE TROUGH
THE EVENING AS A LARGE AREA OF SHOWERS IS STILL MOVING INLAND FROM
THE OFFSHORE WATERS. A SMALL CRAFT ADVISORY WILL REMAIN INTO THE
EVENING HOURS FOR THE NORTHERN INLAND WATERS.
A RIDGE OF HIGH PRESSURE IS EXPECTED TO BUILD EAST OF THE CASCADES
THE FIRST PART OF NEXT WEEK. AS THE NEXT WEATHER SYSTEM APPROACHES
FROM THE WEST. THIS WILL BRING A PERIOD OF RATHER STRONG SELY FLOW
TO THE AREA. COMPUTER GUIDANCE REMAINS RATHER INCONSISTENT FOR THE
PACIFIC STORM SYSTEMS FROM MIDWEEK ON. MARINERS SHOULD KEEP A CLOSE
EYE ON LATEST FORECAST FOR THE NEXT SEVERAL DAYS. PRANGE
&&
.AVALANCHE...MORNING DISCUSSION FOLLOWS. INCREASINGLY STRONG WINDS
AND HEAVY SNOWFALL OVERNIGHT CONTINUE EARLY SUNDAY. THE RESULTS OF
THIS WEATHER HAVE BURIED RECENT WEAK LAYERS AND PRODUCED MUCH MORE
COHESIVE SURFACE SNOW...ALL OF WHICH TOP OFF VERY LARGE AMOUNTS OF
RECENT UNCONSOLIDATED SNOW THAT MAY STILL POSE SUFFOCATION
POTENTIAL. FINALLY SOME OLD DEEPLY BURIED CRUSTS WITH WEAK FACETED
LAYERS LURKING NEARBY. MAJOR OROGRAPHIC SNOWFALL REMAINDER OF DAY
SHOULD DEVELOP PROGRESSIVELY LARGER AND MORE SENSITIVE WIND SLABS
OVER WEAKNESSES NOTED ABOVE..ESPECIALLY ON SOUTHEAST THROUGH
NORTHEAST EXPOSURES. SOME SLIDES MAY INVOLVE ALL OF THE RECENT SNOW
TO THE EARLY DECEMBER CRUST. ALTHOUGH DEEPER RELEASES MAY BE MORE
PREVALENT EAST SLOPE LOCATIONS THE LOADING MAY TRIGGER SOME ISOLATED
DEEPER RELEASES WEST SLOPES AS WELL. BOTTOM LINE...TO HELP CLOSE OUT
2007 SAFELY...TRAVEL IN AVALANCHE TERRAIN NOT RECOMMENDED SUNDAY AND
CONSIDERABLE CAUTION STILL URGED FOR MONDAY...DETAILS AT NWAC.US.
MOORE
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
.WINTER STORM WARNING OLYMPICS UNTIL 7 PM TONIGHT.
.WINTER STORM WARNING CASCADES UNTIL 6 PM THIS EVENING.
.HIGH SURF WARNING COAST UNTIL MIDNIGHT TONIGHT.
.GALE WARNING COASTAL WATERS AND STRAIT OF JUAN DE FUCA THROUGH LATE
THIS EVENING.
.SMALL CRAFT ADVISORY NORTHERN INLAND WATERS AND FOR ROUGH BAR
CONDITIONS.
$$
WEATHER.GOV/SEATTLE
AREA FORECAST DISCUSSION
NWS SEATTLE WA
940 AM PST SUN DEC 30 2007
.SYNOPSIS...SHOWERY WEATHER WILL PREVAIL ACROSS THE AREA TODAY UNDER
A COOL...MOIST..AND UNSTABLE AIR MASS. IMPROVING WEATHER WILL OCCUR
TONIGHT AS HIGH PRESSURE BUILDS OVER THE REGION. DRY WEATHER WILL
PREVAIL ON MONDAY UNDER HIGH PRESSURE ALOFT. ALAS...THIS DRY SPELL
WILL BE SHORT LIVED. THE UPPER HIGH WILL MOVE EAST OF THE AREA ON
TUESDAY...ALLOWING A LOW PRESSURE SYSTEM TO APPROACH THE COAST. THUS
EXPECT A CHANCE OF RAIN ON THE COAST ON TUESDAY WITH A BETTER CHANCE
EVERYWHERE ON WEDNESDAY.
&&
.SHORT TERM...SATELLITE IMAGERY SHOWS COOL UPPER LEVEL TROUGH OVER
WESTERN WASHINGTON. AMS UNSTABLE WITH PLENTY OF CU OVER THE CWA AND
OFFSHORE. ACARS SOUNDINGS INTO SEATTLE-TACOMA AIRPORT REPORTING WEST
NORTHWESTERLY FLOW ALOFT 25-40 KNOTS BETWEEN 850 AND 700 MB. WITH
THIS FLOW ALOFT THE SEATTLE METRO AREA IS IN THE OLYMPIC MOUNTAIN
RAIN SHADOW AND THIS FEATURE SHOWS UP WELL ON THE WSR-88D. WSR-88D
ALSO SHOWS CONVERGENCE ZONE FORMING OVER NORTHERN SNOHOMISH COUNTY.
WITH THE TEMPERATURES JUST ABOVE FREEZING WILL KEEP AN EYE ON THIS
FEATURE AS AN INCREASE IN PRECIPITATION INTENSITY COULD CHANCE THE
PRECIPITATION TYPE TO SNOW. SNOW CONTINUING UP IN THE MOUNTAINS WITH
MOUNTAIN OBSERVATION SITES REPORTING THREE TO SIX INCHES OF NEW SNOW
IN THE LAST SIX HOURS. THESE NUMBERS COULD BE A LITTLE LOWER THAN
THE ACTUAL TOTALS WITH THE STRONG WINDS BLOWING THE SNOW AROUND.
SNOQUALMIE PASS IS ABOUT TWO FEET AWAY FROM THEIR ALL TIME DECEMBER
SNOW RECORD...192 INCHES SET IN 1968...SNOW TOTAL AS OF 8 AM THIS
MORNING 167 INCHES. WITH THE STRONG WESTERLY FLOW ALOFT CONTINUING
THROUGH TODAY SNOW...HEAVY AT TIMES WILL CONTINUE IN THE
MOUNTAINS...BUT IT LOOKS LIKE AT THIS POINT SNOQUALMIE PASS WILL END
UP SHORT OF THEIR RECORD. NOTHING NEW IN THE 12Z MODEL RUNS THIS
MORNING WITH THE STRONG FLOW ALOFT DIMINISHING AFTER 03Z TONIGHT
WITH THE SNOW RATES DECREASING AT THAT TIME. SOME SNOW SHOWER
ACTIVITY CONTINUING IN THE MOUNTAINS THROUGH MONDAY MORNING WITH THE
LOWLAND AREAS DRYING OUT AS AN UPPER LEVEL RIDGE BUILDS INTO WESTERN
WASHINGTON. UPPER LEVEL RIDGE SHIFTS EAST ON TUESDAY WITH THE NEXT
WEATHER SYSTEM REACHING WESTERN WASHINGTON ON WEDNESDAY. CURRENT
FORECAST HAS THE TRENDS COVERED. NO UPDATE THIS MORNING. FELTON
.LONG TERM...PREVIOUS DISCUSSION FOLLOWS.
THE WEATHER PATTERN ACROSS THE PAC NW WILL ONCE AGAIN BECOME
QUITE ACTIVE. THE DAILY DETAILS ARE STILL VERY UNCERTAIN AT THIS
TIME BUT WE WILL NEED TO WATCH FOR EITHER A POTENTIAL HIGH WIND
EVENT OR LOWLAND SNOW EVENT AT SOME POINT IN TIME.
&&
.AVIATION...ONSHORE GRADIENTS REMAIN QUITE STRONG THIS MORNING WITH
GALES ALONG THE COAST AND IN THE STRAIT AND STRONG INFLOW THROUGH
THE CHEHALIS GAP. THE COMBINATION OF THE FLOW...INSTABILITY...AND
TERRAIN IS GIVING A RAIN SHADOW TO THE SEATTLE AREA AND CONFINING
SHOWERS OF RAIN AND MIXED RAIN AND SNOW TO THE
COAST...STRAIT...MOUNTAINS...AND CONVERGENCE ZONE...WITH A FEW
SCATTERED SHOWERS NICKING OFF OVER THE SOUTH SOUND.
MVFR CIGS 011-025 FT CENTRAL AND SOUTH PUGET SOUND AREA THIS
AM...OTHERWISE GENERALLY VFR CIGS. EXPECT SCATTERED MVFR CONDITIONS
WITH GUSTY WINDS 20-25 KTS THROUGHOUT TODAY NEAR HEAVIER SHOWERS.
AT KSEA...BKN015-025 BKN050. ISOLATED SHOWERS. WIND AT 22018G28KT
ESPECIALLY NEAR HEAVIER SHOWERS WILL GRADUALLY FALL OFF DURING THE
AFTERNOON...AFTER 00Z WILL FALL TO 19010KT. WIND AT 040 W 40-50KT
THROUGH 00Z. PRANGE/ALBRECHT
&&
.MARINE...WHOLE GALES COAST AND STRAIT AND STRONG SCA CONDITIONS
ELSEWHERE WILL CONTINUE THROUGH LATE THIS AFTERNOON OR EARLY THIS
EVENING AS A COLD TROUGH AND ASSOCIATED STRONG JET STREAM PUSHES E
AND HIGH PRES BUILDS OFFSHORE. COMBINED SEAS 20 FT EARLY THIS
MORNING WILL RISE TO 25 FT DURING THE AFTERNOON AND EVENING
HOURS...THEN SLOWLY FALL LATE TONIGHT THROUGH MON. GUSTY WINDS 30-40
KTS ALSO POSSIBLE NEAR HEAVIER SHOWER ACTIVITY THROUGHOUT THE DAY.
THOUGH MARGINAL...WILL MAINTAIN THE HIGH SURF WARNING ON THE COAST
THROUGH THIS EVENING.
HIGH PRES BUILDS E OF THE CASCADES MON AND TUE AS A FRONT APPROACHES
FROM THE W. THIS WILL BRING A PERIOD OF RATHER STRONG SELY FLOW TO
THE AREA. COMPUTER GUIDANCE IS RATHER INCONSISTENT IN THE HANDLING
OF PACIFIC STORM SYSTEMS FROM MIDWEEK ON...BUT FAST MOVING AND DEEP
LOWS MOVING TOWARD THE PACIFIC NW FROM THE W AND CENTRAL PACIFIC
COULD MAKE THINGS INTERESTING. MARINERS SHOULD KEEP A CLOSE EYE ON
LATEST FORECAST FOR THE NEXT SEVERAL DAYS. PRANGE/ALBRECHT
&&
.AVALANCHE...INCREASINGLY STRONG WINDS AND HEAVY SNOWFALL OVERNIGHT
CONTINUE EARLY SUNDAY. THE RESULTS OF THIS WEATHER HAVE BURIED
RECENT WEAK LAYERS AND PRODUCED MUCH MORE COHESIVE SURFACE
SNOW...ALL OF WHICH TOP OFF VERY LARGE AMOUNTS OF RECENT
UNCONSOLIDATED SNOW THAT MAY STILL POSE SUFFOCATION POTENTIAL.
FINALLY SOME OLD DEEPLY BURIED CRUSTS WITH WEAK FACETED LAYERS
LURKING NEARBY. MAJOR OROGRAPHIC SNOWFALL REMAINDER OF DAY SHOULD
DEVELOP PROGRESSIVELY LARGER AND MORE SENSITIVE WIND SLABS OVER
WEAKNESSES NOTED ABOVE..ESPECIALLY ON SOUTHEAST THROUGH NORTHEAST
EXPOSURES. SOME SLIDES MAY INVOLVE ALL OF THE RECENT SNOW TO THE
EARLY DECEMBER CRUST. ALTHOUGH DEEPER RELEASES MAY BE MORE PREVALENT
EAST SLOPE LOCATIONS THE LOADING MAY TRIGGER SOME ISOLATED DEEPER
RELEASES WEST SLOPES AS WELL. BOTTOM LINE...TO HELP CLOSE OUT 2007
SAFELY...TRAVEL IN AVALANCHE TERRAIN NOT RECOMMENDED SUNDAY AND
CONSIDERABLE CAUTION STILL URGED FOR MONDAY...DETAILS AT NWAC.US.
MOORE
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
1. WINTER STORM WARNING OLYMPICS UNTIL NOON TODAY.
2. WINTER STORM WARNING CASCADES UNTIL 6 PM THIS EVENING.
3. HIGH SURF WARNING COAST UNTIL MIDNIGHT TONIGHT.
4. GALE WARNING COASTAL WATERS AND STRAIT OF JUAN DE FUCA.
5. SMALL CRAFT ADVISORY REMAINING WATERS INCLUDING FOR ROUGH BAR
CONDITIONS.
$$
WEATHER.GOV/SEATTLE
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