HAMweather.com Area Forecast Discussion for County Warning Area ALY

Thu, 16 Feb 2012 05:17:59 GMT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ALBANY NY
1000 PM EST WED FEB 15 2012

.SYNOPSIS...
HIGH PRESSURE WILL BRIEFLY BUILD IN OVER NEW YORK AND NEW ENGLAND
TONIGHT. LOW PRESSURE WILL APPROACH FROM THE LOWER GREAT LAKES
REGION TOMORROW...AND MOVE NORTH OF THE REGION INTO CANADA
TOMORROW NIGHT...BRINGING A LIGHT MIXTURE OF RAIN AND SNOW. AN
UPPER LEVEL DISTURBANCE WILL CONTINUE THE THREAT OF SNOW SHOWERS
MAINLY NORTH AND WEST OF THE CAPITAL REGION ON FRIDAY WITH
TEMPERATURES STILL RUNNING ABOVE NORMAL FOR MID FEBRUARY.

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
AS OF 950 PM EST...MOSTLY CLOUDY SKIES REMAINED ACROSS THE
NORTHEAST THIRD OF THE FA WITH MAINLY CLEAR SKIES ACROSS THE
SOUTHWEST TWO THIRDS WITH TEMPS GENERALLY IN THE UPPER 20S TO
AROUND 40. AS HIGH PRESSURE CONTINUES TO BUILD IN FROM PA AND THE
ERN GREAT LAKES REGION...SKIES ARE EXPECTED TO GRADUALLY BECOME
PARTLY CLOUDY OR MOSTLY CLEAR THROUGH THE PERIOD AROUND MIDNIGHT
AS WEAK COLD AIR ADVECTION OCCURS WITH H850 TEMPS FALLING TO -3C
TO -6C AROUND MIDNIGHT. THIS WILL TRANSITION TO A WARM ADVECTION
REGIME OVERNIGHT AHEAD OF LOW PRESSURE MOVING INTO THE
MIDWEST/UPPER MS RIVER VALLEY. SOME MID AND HIGH CLOUDS WILL BEGIN
TO STREAM IN FROM THE SOUTH AND WEST TOWARDS SUNRISE AHEAD OF THE
NEXT COMPLEX STORM SYSTEM. LOWS WILL GENERALLY BE IN THE LOWER TO
MID 20S WITH SOME UPPER TEENS OVER THE SRN DACKS. THIS WAS CLOSE
TO A BLEND OF THE MET/MAV MOS GUIDANCE.

.SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY/...
TOMORROW...THE DAY BEGINS DRY...AND MID AND HIGH CLOUDS CONTINUE
TO THICKEN AND LOWER. THE ISENTROPIC LIFT INCREASES FROM SOUTHWEST
TO NORTHEAST ON THE 295K SFC LATE IN THE AFTERNOON. THE H850 LLJ
INCREASES TO 35-40 KTS. THE PCPN MOVES IN FROM WEST TO EAST DURING
THE DAY AHEAD OF AN OCCLUDING FRONTAL BOUNDARY OVER THE UPPER MID
ATLANTIC REGION...AS THE PRIMARY LOW PRESSURE SYSTEM MOVES THROUGH
THE CNTRL-ERN GREAT LAKES REGION INTO SRN ONTARIO AND SW QUEBEC BY
THE EARLY EVENING. A SECONDARY LOW FORMS NEAR THE MID ATLANTIC
COAST/DELMARVA REGION AFTER 00Z. THE MAIN IMPACT FOR THE REGION
WILL BE THE STRONG QG LIFT FROM THE THERMAL AND VORTICITY
ADVECTION. WE INCREASED POPS TO CATEGORICAL AND LIKELY VALUES
PRIOR TO 7 PM FROM WEST TO EAST. THE PCPN BASED ON CRITICAL
THICKNESSES/BUFFER MODEL SOUNDINGS WILL START OUT AS RAIN AND
TRANSITION TO SNOW...ESPECIALLY OVER THE HIGHER TERRAIN AS THE
COLUMN COOLS. THE MODEL SOUNDINGS FROM THE NAM/GFS HAVE AN
ISOTHERMAL APPEARANCE TO THEM WITH THE COOLING COLUMN. THE VALLEYS
WILL BE THE LAST TO SEE A TRANSITION TO SNOWFALL. TEMPS WILL BE
MILD AHEAD OF THE THRUST OF PCPN WITH HIGHS IN THE LOWER TO MID
40S IN THE VALLEYS...AND MID TO U30S OVER THE MTNS. ANY
ACCUMULATIONS IN THE VALLEYS PRIOR TO 7 PM WILL LIKELY BE CONFIDE
TO THE GRASSY SURFACES...BUT THE HIGHER TERRAIN NORTH AND WEST OF
ALBANY MAY RECEIVE UP A COATING TO AN INCH OF SLUSHY SNOWFALL.
 
TOMORROW NIGHT...PCPN SHOULD END QUICKLY FROM SOUTHWEST TO
NORTHEAST ACROSS THE REGION WITH THE OCCLUDED FRONT MOVING
THROUGH. WE CONTINUE TO HAVE GENERALLY TWO TO THREE TENTHS OF
LIQUID EQUIVALENT IN THE FORECAST FOR THIS LIGHT PCPN SYSTEM.
SNOWFALL OF 2 TO 4 INCHES IS EXPECTED OVER PORTIONS OF THE SRN
DACKS...AND THE SRN GREENS MTNS. 1 TO 3 INCHES MAY OCCUR OVER
PORTIONS OF THE BERKSHIRES...THE ERN CATSKILLS...LAKE GEORGE
REGION...AND THE EXTREME WRN MOHAWK VALLEY. EXPECT A COATING TO
MAYBE AN INCH IN THE TACONICS...LITCHFIELD HILLS...CENTRAL AND ERN
MOHAWK VALLEY...CAPITAL DISTRICT...AND THE MID HUDSON VALLEY. IT
SHOULD BE EMPHASIZED THAT THE VALLEY LOCATIONS MAY ACCUMULATE BEST
ON THE GRASSY SURFACES WITH LOWS IN THE LOWER 30S FROM THE CAPITAL
DISTRICT SOUTH AND EAST...AND THE MID TO U20S ON THE NORTH AND
WEST.

FRIDAY...UPPER LEVEL LOW CONTINUES TO CHURN OVER SRN-CNTRL QUEBEC.
A VORT MAX IN THE W/NW FLOW ALOFT MAY FOCUS SOME LAKE
ENHANCED/OROGRAPHICALLY ENHANCED SNOW SHOWERS AND FLURRIES OVER
THE WRN DACKS...AND SRN GREENS. THE MOHAWK VALLEY WILL LIKELY HAVE
A MIX OF RAIN AND SNOW AS THE BOUNDARY LAYER WARMS. ADDITIONAL
SNOW ACCUMULATIONS FOR THE WRN DACKS MAY BE AN INCH OR SO. MOST
OTHER LOCATIONS WILL BE DRY...AS HIGH PRESSURE WILL BE NUDGING IN
FROM THE OHIO VALLEY. COLD ADVECTION IS WEAK IN THE WAKE OF THE
SYSTEM WITH TEMPS STILL RUNNING 5-10 DEGREES ABOVE NORMAL.

FRI NIGHT-SATURDAY...HIGH PRESSURE BRIEFLY BUILDS IN FROM THE
SOUTH...AS A LAKE ENHANCED/WESTERLY UPSLOPE PCPN ENDS DURING THE
EVENING. THE NAM/GFS/ECMWF/CAN GGEM DIFFER ON THE TIMING OF THE
NEXT NRN STREAM SHORT-WAVE FOR SAT. CONFIDENCE IS LOW HERE...WHERE
WE JUST PLACED A SLIGHT CHC OF SNOW SHOWERS WEST OF THE HUDSON
RIVER VALLEY. THE QUESTION WILL BE WHETHER THIS SHORT-WAVE ENERGY
PHASES WITH A WAVE EJECTING OUT OF THE LOWER MS RIVER
VALLEY/SOUTHEAST FOR THE 2ND HALF OF THE WEEKEND. THE
ECMWF/CANADIAN KEEPS THE SYSTEMS UNPHASED. THE OPERATIONAL GFS AND
SOME GEFS MEMBERS BEAR WATCHING FOR A POSSIBLE COASTAL LOW.

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
HIGHLIGHT OF THE PERIOD IS AT THE START.  LOW PRESSURE DEVELOPS AND 
TRACKS RAPIDLY OVER THE DEEP SOUTH.  WHILE GFS TRACKS THIS LOW MUCH 
FURTHER NORTH...TO OFF THE DELMARVA COAST AROUND DAYBREAK SUNDAY... 
THE EURO KEEPS IT WELL SOUTH.  HOWEVER...THE EURO ALSO HAS A BUILT- 
IN MID LEVEL TROF DOWN THROUGH THE MID-ATLANTIC REGION AT THAT TIME 
THAT COMES WITH SOME LIGHT PRECIP WHILE KEEPING THE MAIN AREA OF 
PRECIP WELL TO THE SOUTH FROM ALABAMA TO VIRGINIA.  IN EITHER 
CASE...WE WOULD BE LOOKING AT PRECIP.  HPC HAS TRENDED TOWARD THIS 
ECMWF SOLUTION...WHICH OTHER MODELS APPEAR TO SUPPORT.

WITH THE GFS BEING THE OUTLIER...HAVE DECIDED TO GO WITH THE LOWER 
END OF CHC POPS FOR SATURDAY NIGHT AND SUNDAY.  ONLY CONCERN WOULD 
BE WITH THE CONSISTENT RUN-TO-RUN CONSISTENCY OF THE GFS DURING THIS 
TIME FRAME /00Z AND 12Z/.  THE NEXT 00Z RUN WILL HAVE TO BE EXAMINED 
TO DETERMINE IF THE GFS WILL REMAIN THE STUBBORN OUTLIER.  THUS... 
CURRENT THINKING IS THAT THERE WILL PROBABLY BE LIGHT SNOW 
SHOWERS...WHICH MAY BOTH BEGIN AND END AS A MIX IN THE VALLEYS.   
1000-500 THICKNESSES ON THE EURO BEING NO HIGHER THAT 535 DAM ALSO 
POINT TO MORE SNOW THAN NOT.  ALL THAT SAID...THIS IS A FAST-MOVING 
SYSTEM...EXCEPT ACCORDING TO THE GFS...AND TOTAL AMOUNTS WILL 
PROBABLY BE LESS THAN AN INCH.

THIS RELATIVELY MINOR EVENT WILL BE FOLLOWED BY BRIEF TRANQUILITY 
AND PLENTIFUL SUNSHINE AS HIGH PRESSURE BUILDS IN FROM THE WEST.  
THE NEXT CHC FOR PRECIP COMES ALONG TUESDAY NIGHT AND WEDNESDAY AS 
LOW PRESSURE CLOSES IN RAPIDLY FROM THE MIDWEST.  THE TIMING IS 
UNCERTAIN...WITH THE EURO REALLY HOLDING OFF UNTIL WEDNESDAY...WHEN 
IT IS EXPECTED TO BE MOSTLY RAIN.  THE GFS IS EVEN MORE SLUGGISH 
THAN THIS...HOLDING OFF UNTIL WEDNESDAY NIGHT.

.AVIATION /03Z THURSDAY THROUGH MONDAY/...
VFR CONDITIONS WILL PREVAIL THROUGH THURSDAY MORNING AS BUILDING 
HIGH PRESSURE RESULTS IN PARTIAL CLEARING OF LOW CLOUDS THIS 
EVENING.  HIGH AND MID CLOUDS WILL BE ON THE INCREASE LATE TONIGHT 
OUT AHEAD OF THE NEXT SYSTEM...WHICH WILL SPREAD RAIN ACROSS THE 
REGION THURSDAY AFTERNOON.  EXPECTING CONDITIONS TO BE REDUCED TO 
ONLY MVFR...MAINLY FOR VSBY.  SURFACE WINDS WILL BE LIGHT... 
GENERALLY LESS THAN 5 KNOTS...WITH NO SHEAR CONCERNS.

OUTLOOK...
THU NGT...MVFR/IFR.  -RA/-SN LIKELY.
FRI-SAT...VFR...NO WX.
SAT NGT-SUN...VFR/MVFR.  CHC -SHSN POSS MIX WITH -SHRA.
MON...VFR...NO WX.

.HYDROLOGY...
NO HYDRO PROBLEMS ARE EXPECTED OVER THE NEXT SEVERAL DAYS. SOME
GAGES WILL CONTINUE TO HAVE ICE EFFECTS NORTH OF THE MOHAWK RIVER
VALLEY IN THE ALBANY HYDRO SERVICE AREA.

A LOW PRESSURE SYSTEM AND ITS OCCLUDED FRONT WILL BRING RAIN AND/OR
SNOW TO THE REGION THURSDAY AFTERNOON INTO THURSDAY NIGHT...WITH
GENERALLY LIGHT AMOUNTS OF PRECIPITATION OF A THIRD OF AN INCH OR
LESS.

SOME LAKE ENHANCED OR UPSLOPE SNOWFALL IS POSSIBLE FOR THE WESTERN
ADIRONDACKS FRIDAY INTO SATURDAY WITH LIGHT ACCUMULATIONS EXPECTED.

TEMPERATURES FOR THE WEEKEND STILL LOOK TO AVERAGE ABOVE NORMAL
FOR MID FEBRUARY.

FOR DETAILS ON SPECIFIC AREA RIVERS AND LAKES...INCLUDING
OBSERVED AND FORECAST RIVER STAGES AND LAKE ELEVATIONS...PLEASE
VISIT THE ADVANCED HYDROLOGIC PREDICTION SERVICE /AHPS/ GRAPHS ON
OUR WEBSITE.

.ALY WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
NY...NONE.
MA...NONE.
VT...NONE.