000
FXUS61 KALY 032346
AFDALY
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ALBANY NY
646 PM EST WED DEC 3 2008
.SYNOPSIS...
A STRONG COLD FRONT WILL APPROACH FROM GREAT LAKES REGION TONIGHT
AND CROSS THE AREA THURSDAY TRIGGERING SNOW AND RAIN SHOWERS. IN
THE WAKE OF THE FRONT...A MUCH COLDER AIRMASS WILL BE USHERED IN
RESULTING IN LAKE EFFECT SNOW FOR THE WESTERN ADIRONDACKS THURSDAY
NIGHT AND FRIDAY. HIGH PRESSURE WILL BUILD BACK IN FOR
SATURDAY...HOWEVER ANOTHER STORM SYSTEM IS EXPECTED TO IMPACT THE
REGION SATURDAY NIGHT AND SUNDAY.
&&
.NEAR TERM /THROUGH THURSDAY/...
PLEASANT SEASONABLE DAY ACROSS AREA TODAY AS SURFACE RIDGE SHIFTED
SOUTHEASTWARD. HAVE COLD FRONT APPROACHING FROM THE WEST WITH
BROAD SOUTHWEST FLOW AHEAD OF BOUNDARY. FRONTAL POSITION EASILY
SEEN ON SURFACE PLOTS BY ABRUPT WIND SHIFT...PRESSURE FALLS AND
DROP IN TEMPERATURES. MODELS ARE IN FAIRLY GOOD AGREEMENT WITH
MOVEMENT OF FRONT THROUGH REGION AND TEMPERATURES FOR TONIGHT AND
THURSDAY. OVERALL NO BIG CHANGES TO GRIDS AS CURRENT FORECAST IS
ON TRACK WITH COLD FRONT MOVING ACROSS FORECAST AREA DURING THE DAY.
BEST UPPER SUPPORT WILL BE TO OUR NORTH AND WEST. LIKELY TO
CATEGORICAL POPS ACROSS FORECAST AREA EXCEPT FOR THE SOUTHERN MOST
PORTION OF FORECAST AREA WHERE CHANCE SHOULD CONTINUE TO WORK.
WILL BE COLD ENOUGH FOR PRECIPITATION TO START OUT AS SNOW THEN
MIX WITH AND CHANGE TO RAIN ACROSS MUCH OF THE FORECAST AREA
THURSDAY AFTERNOON. ONLY LIGHT ACCUMULATIONS OF SNOW ARE EXPECTED
MAINLY ACROSS THE HIGHER TERRAIN NORTH AND WEST OF THE CAPITAL
DISTRICT.
&&
.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
DURING THIS PERIOD (GFS/NAM/ECM/GEM) MODELS PRETTY MUCH IN
AGREEMENT BOTH DYNAMICALLY AND TIMING OF SYSTEMS THROUGH FCA. CDFNT
HAS EXITED THE REGION...AND CAA WELL UNDERWAY. AT FIRST FCA IN
ANTICYCLONIC FLOW...AS COLD LAYER DEEPENS WITH CAP BTWN 5K FT AND
8K FT. HWVR AS THE EVENING PROGRESSES NIZIOL INSTABILITY CLASS
INCRG TO MODERATE...CAP VANISHES...AND 500 HPA SHORT WAVE COMBINE
TO PRODUCE LAKE EFFECT BAND. THE BAND MAY INITIALLY SET UP AS FAR
SOUTH AS MHWK VALLEY...BUT SHIFT NORTH AS FAR AS THE 270 H850 HPA
VECTOR. THE DYNAMIC SUPPORT FOR LK EFFECT CONTINUES INTO
FRI...HWVR STEERING AT H850 CONTINUES TO FLUCTUATE FM 290 TO 270
THRU FRI NT BEFORE SWINGING TO 220 AS DYNAMICS BREAK DOWN SAT
MORNING. RESULT WILL BE MAINLY A SINGLE BAND...BUT ONE SHEARED
AROUND A BIT...AND THE FIRE HOSE EFFECT...WILL RESULT IN ALOT OF
-SHSN FM MHWK VALLEY ACROSS ENTIRE W ADIRONDACKS...BUT MORE
SIGNIFICANT AMOUNTS CONFINED TO THE WEST...AND THESE MAY WARRANT
AN ADVISORY AT SOME POINT FOR LATE THURSDAY NIGHT INTO FRIDAY.
IN MOST OF THE AREA IT WILL BE DRY WITH STRONG CAA...AND VARYING
CLOUDINESS THU NT INTO FRI. FRIDAY NIGHT LARGE SFC HIGH BUILDS FM
OHIO VALLEY INTO FCA..AND MUCH OF NIGHT WILL BE CLEAR...WITH 15
HOURS OF NIGHT AND CLEAR SKIES WILL TAKE TEMPS SEVERAL DEGREES BLOW
BLENDED GUID. SAT SFC HIGH WILL SLIDE OFFSHORE...WHILE AT 500HPA
SEVERAL SHORT WAVES DEEPEN THE TROF...AND BRING A CLIPPER SFC LOW
INTO THE GRTLKS. DURING THIS PERIOD MAIN IMPACTS OVER FCA WILL BE
INCRG CLOUDS...WHILE COLD AIRMASS REMAINS ACROSS FCA.
&&
.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
CLIPPER SYSTEM WILL BEGIN TO IMPACT THE REGION DURING THE SATURDAY
NIGHT TIME PERIOD. THIS STORM WILL BE QUITE WEAK AND MOISTURE
STARVED AS IT/LL BE COMING OUT OF THE NORTHERN STREAM. IT DOES
APPEAR...HOWEVER...THAT THIS SYSTEM WILL UNDERGO A RAPID
CYCLOGENESIS ONCE IT REACHES THE COAST OF MAINE...AS THE 500 HPA
LOW WILL GO NEGATIVE AND CUT OFF...ALLOWING FOR SOME ATLANTIC
MOISTURE TO GET INVOLVED. HOWEVER...IT APPEARS THAT THIS WILL BE TOO
LATE TO HAVE ANY IMPACT ON OUR CWA...AS ANY ADDITIONAL MOISTURE WILL
ONLY AFFECT PARTS OF EASTERN NEW ENGLAND. WITH 850 HPA TEMPS
SUFFICIENTLY COLD /ABOUT -8 TO -12 DEGREES C/ THIS WILL BE ENTIRELY
A SNOW EVENT FOR THE ENTIRE CWA. THE MAJORITY OF THE MREF
MEMBERS...ALONG WITH THE OPERATIONAL 12Z GFS/ECMWF ALL AGREE THAT
THIS WILL BE A RATHER LIGHT QPF EVENT...WITH MAYBE 1-2 INCHES OF
SNOW CWA WIDE...MAINLY LATE SATURDAY NIGHT INTO SUNDAY EARLY AFTN.
LAKE EFFECT WILL ONCE AGAIN GET GOING IN THE WAKE OF SYSTEM AS CAA
USHERS IN EVEN COLDER AIR BEHIND THE CLIPPER. WITH THE ANTICIPATED
NW FLOW /ABOUT 300-320 DEGREES/ WILL HAVE TO WATCH TO SEE IF THE
LAKE EFFECT WILL GET INTO WESTERN PARTS OF THE MOHAWK VALLEY.
ALTHOUGH IT LOOKS TO BE A QUICK HITTER...COULD HAVE SOME GOOD
SNOWS...AS SFC-700 HPA TEMP DIFFERENTIAL LOOKS IMPRESSIVE AT CLOSE
TO 30 DEGREES C WHICH WOULD ALLOW THE NIZIOL STABILITY CLASS TO
BRIEFLY GET INTO THE EXTREME CATEGORY.
STRONG HIGH PRESSURE /ABOUT 1030 HPA/ TAKES OVER FOR MONDAY...WHICH
SHOULD QUICKLY LOWER THE INVERSION HEIGHTS AND SQUELCH THE LAKE
EFFECT. NEXT FEATURE TO WATCH WILL BE A SOUTHERN STREAM STORM FOR
THE TUES/WED TIME PERIOD. THE LAST FEW RUNS OF THE GFS HAVE
CONSISTENTLY BEEN SHOWING A HIGH QPF MILLER A TYPE OF STORM TO COME
UP THE EASTERN SEABOARD. THE LATEST 12Z OPERATIONAL RUN OF THE GFS
IS THE MOST EXTREME OF THE 12Z MREF SUITE...SHOWING A STRONG SUB 990
HPA LOW RIDING UP THE EASTERN SEABOARD. THIS SCENARIO WOULD BRING A
RAIN TO SNOW EVENT FOR THE REGION. IT/S IMPORTANT TO NOTE THAT MANY
OF THE MREF ENSEMBLE MEMBERS SHOULD A FASTER...WEAKER AND MORE
INLAND TRACK...WHICH ALLOWS FOR MAINLY RAIN ACROSS THE REGION. AT
THE SAME TIME...THE LATEST 12Z OPERATIONAL RUN OF THE ECMWF SHOWS NO
PHASING...AND A WEAK SOUTHERN STREAM STORM WHICH GOES WIDE RIGHT AND
HAS NO EFFECT ON THE REGION. STILL...MANY MREF MEMBERS ARE SHOWING A
HIGH QPF EVENT...AS ATLANTIC AND GULF MOISTURE WOULD GET INVOLVED.
AFTER SUCH A COLD WEEKEND...WOULD HAVE TO WATCH TO SEE IF ANY OF
THIS WOULD START AS SNOW OR FREEZING RAIN...AS WELL AS ANY
HYDROLOGIC IMPACTS ON A HIGH RAIN EVENT ON A FROZEN GROUND. MANY
QUESTIONS STILL TO BE ANSWERED REGARDING THIS SYSTEM...SO WILL HAVE
TO WATCH MODEL TRENDS THROUGH THE WEEKEND. AT THIS POINT...MAINLY
PLAYING THE FORECAST AS CHC SN/RN BASED ON ELEVATION/DIURNAL TEMPS.
&&
.AVIATION /00Z THURSDAY THROUGH MONDAY/...
VFR CONDITIONS WILL PREVAIL THROUGH THE OVERNIGHT PERIOD AS MID/HIGH
CLOUDS BEGIN TO STREAM INTO THE REGION OUT OF AHEAD OF THE NEXT
FRONTAL SYSTEM. ALTHOUGH THE BEST UPPER LEVEL DYNAMICS LIFT INTO
CANADA...STRONG THERMAL GRADIENT ALONG COLD FRONTAL BOUNDARY SHOULD
ALLOW FOR A LINE OF SHOWERS TO DEVELOP ALONG AND JUST AHEAD FAST
MOVING COLD FRONTAL BOUNDARY. THESE SHOWERS MAY DROP VSBYS/CIGS DOWN
TO MVFR FOR A BRIEF PERIOD FROM THE MID MORNING INTO THE AFTN HOURS
THURSDAY. SFC/BOUNDARY LAYER TEMPERATURES SHOULD BE JUST WARM ENOUGH
TO KEEP PRECIP IN THE FORM OF THE RAIN...AND BY THE TIME COLDER AIR
WORKS IN THE REGION AT THE SFC...PRECIP SHOULD HAVE ENDED. WITH THE
DRYING WITHIN THE CAA IN THE WAKE OF THE FRONTAL BOUNDARY...VSBYS
AND CIGS SHOULD RETURN TO VFR LEVELS. WINDS WILL BE SOUTHERLY AHEAD
OF THE BOUNDARY...BUT WILL SHIFT TO A MORE WESTERLY DIRECTION BEHIND
THE FRONT ON THURSDAY AFTN.
OUTLOOK...
FRI...VFR/MVFR...WDLY SCT/SCT -SHSN IN THE NORTH.
SAT...VFR...NO SIG WX.
SAT NT-SUN...MVFR/IFR...CHC -SN.
MON...VFR...NO SIG WX.
&&
.HYDROLOGY...
NO HYDRO PROBLEMS ARE EXPECTED OVER THE NEXT SEVERAL DAYS. IT WILL
TURN COLDER LATER THIS WEEK AND ANY PRECIPITATION SHOULD THEN COME
AS SNOW WHICH WILL NOT HAVE ANY IMMEDIATE EFFECT ON THE RIVERS.
STARTING THURSDAY NIGHT TEMPERATURES OVER THE REGION WILL AVERAGE
WELL BELOW FREEZING INTO EARLY NEXT WEEK WITH HIGHS FROM THE MID 20S
TO THE MID 30S AND LOWS MAINLY BETWEEN 10 AND 20 DEGREES. THIS WILL
BE FAVORABLE FOR ICE TO FORM AND THICKEN ON RIVERS AND LAKES.
FOR DETAILS ON THE RIVERS...PLEASE VISIT THE ADVANCED HYDROLOGIC
PREDICTION SERVICE /AHPS/ GRAPHS ON OUR WEBSITE.
&&
.ALY WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
NY...NONE.
MA...NONE.
VT...NONE.
&&
$$
SYNOPSIS...IAA
NEAR TERM...IAA
SHORT TERM...SNYDER
LONG TERM...FRUGIS
AVIATION...FRUGIS
HYDROLOGY...SNYDER
