December 8, 2014 Forecast Discussion

000
FXUS61 KALY 090009
AFDALY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ALBANY NY
709 PM EST MON DEC 8 2014

.SYNOPSIS…
AS A DEVELOPING COASTAL STORM APPROACHES OUR AREA….A
LONG DURATION PERIOD OF RAIN AND SNOW…AND POSSIBLY SLEET AND
FREEZING RAIN…WILL IMPACT THE REGION BETWEEN LATE TONIGHT TUESDAY
AND THURSDAY AS THE COASTAL STORM SITS AND SPINS CLOSE TO OUR
REGION. THE HEAVIEST PRECIPITATION ASSOCIATED WITH THIS STORM IS
EXPECTED TUESDAY AND TUESDAY EVENING.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/…
AS OF 700 PM EST…MAINLY QUIET WEATHER MOST OF THE NIGHT…WITH
WIDESPREAD PCPN NOT EXPECTED TO MOVE INTO SOUTHERN PARTS OF THE
REGION UNTIL SHORTLY BEFORE SUNRISE TUESDAY. THE ONE PROBLEM MAY
BE FREEZING DRIZZLE ACROSS THE SOUTHERN ZONES AS LOW LEVEL
ATLANTIC MOISTURE SPREADS WESTWARD AND NORTHWARD IN THE EASTERLY
FLOW. HAVE ISSUED A WINTER WEATHER ADVISORY FOR THE MID HUDSON
VALLEY AND LITCHFIELD COUNTY STARTING AT MIDNIGHT TO COVER
THIS…AND KEPT THE ADVISORY IN EFFECT UNTIL 16Z TUESDAY TO COVER
ANY MIXED PCPN (ESPECIALLY FREEZING RAIN) THAT MAY OCCUR TUESDAY
MORNING.

FOR THE REST OF THE REGION WINTER STORM WARNING AND WATCHES WILL
START AT 400 AM…AND WILL BE DISCUSSED IN THE SHORT TERM SECTION.

LOWS TONIGHT WILL OCCUR EARLY TONIGHT AND BE IN THE UPPER TEENS
AND 20S…THEN SLOWLY RISE 3 TO 4 DEGREES BY SUNRISE TUESDAY.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY NIGHT/…
VERY COMPLEX WINTER STORM WILL HAVE A LARGE IMPACT ON THE REGION
THROUGH THE ENTIRE SHORT TERM PERIOD…ESPECIALLY TUESDAY AND
EARLY TUESDAY NIGHT.

HAVE UPGRADED THE WESTERN AND SOUTHERN ADIRONDACKS…THE MOHAWK
AND SCHOHARIE VALLEYS AND THE EASTERN CATSKILLS TO WINTER STORM
WARNINGS THROUGH 12Z WEDNESDAY…WITH SNOWFALL AMOUNTS OF 7 TO 14
INCHES…ALONG WITH SOME MIXED PCPN POSSIBLE. THE LOWEST TERRAIN
AREAS IN THESE REGIONS MAY NOT EXCEED 7 INCHES OF SNOW DUE TO THE
MIXING OF PCPN WITH SLEET…FREEZING RAIN AND RAIN…BUT ON
AVERAGE MOST AREAS WILL GET HEAVY SNOW.

DUE TO THE EXTREMELY TIGHT GRADIENT IN TEMPERATURES ACROSS THE
REGION…AND THE MINOR TEMPERATURE VARIATIONS THAT OCCUR BETWEEN
EACH MODEL…AND EVEN BETWEEN DIFFERENT RUNS OF THE SAME MODEL…
HAVE DECIDED THAT THERE IS STILL TOO MUCH UNCERTAINTY TO MAKE A
DECISION BETWEEN A WARNING OR AN ADVISORY FOR A LARGE PART OF THE
FORECAST AREA THAT INCLUDES THE SARATOGA REGION…CAPITAL DISTRICT…
THE UPPER PART OF THE MID HUDSON VALLEY…THE TACONICS…SOUTHERN
VERMONT AND BERKSHIRE COUNTY. THIS WAS COORDINATED WITH
SURROUNDING OFFICES TO THE EAST WHO ALSO KEPT ADJOINING PARTS OF
THEIR FORECAST AREAS IN THE WINTER STORM WATCH.

FOR NOW HAVE GENERALLY FORECAST 3 TO 10 INCHES IN THE WATCH
AREA…WITH MOST AREAS GENERALLY FORECAST TO GET 7 INCHES OR LESS…
EXCEPT FOR THE HIGHER TERRAIN OF SOUTHERN VERMONT.

MOST OF THE PCPN WILL OCCUR ON TUESDAY…WITH A LARGE DRY SLOT
SURGING NORTHWARD AND CUTTING OFF THE STEADIEST AND HEAVIEST PCPN
EARLY TUESDAY NIGHT.

WITH THE UPPER LOW EVENTUALLY PARKING ITSELF OVER EASTERN NY…
OCCASIONAL LIGHT SNOW WILL LIKELY CONTINUE WEDNESDAY AND THURSDAY
AS WELL. THERE COULD STILL BE SOME MIXED PCPN WEDNESDAY…BUT ALL
SNOW IS EXPECTED WEDNESDAY NIGHT.

HIGHS TUESDAY WILL BE 30 TO 40. LOWS TUESDAY NIGHT IN THE MID 20S
TO LOWER 30S. HIGHS WEDNESDAY GENERALLY IN THE 30S. LOWS WEDNESDAY
NIGHT 20 TO 30.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/…
WE WILL STILL BE DEALING WITH A CUT-OFF UPPER LEVEL LOW WHICH WILL
BE CENTERED RIGHT OVER THE REGION ON THURSDAY…BUT THE SYSTEM WILL
HAVE LOST ITS BAROCLINICITY BY THEN RESULTING IN MAINLY SCATTERED TO
LIKELY SNOW SHOWERS. BEST CHANCE FOR ANY LIGHT MEASURABLE SNOWFALL
WILL BE OVER THE HIGHER TERRAIN WEST AND EAST OF THE HUDSON RIVER
VALLEY. THE CUT-OFF LOW WILL ONLY SLOWLY MEANDER TO THE
EAST-NORTHEAST THURSDAY NIGHT INTO FRIDAY…WITH THE CORE MOVING
INTO NEW ENGLAND. OUR AREA WILL CONTINUE TO BE UNDER THE INFLUENCE
OF THE CYCLONIC FLOW ASSOCIATED WITH THIS SYSTEM…ALTHOUGH DRIER
AIR WILL GRADUALLY WORK IN FROM THE WEST…ESPECIALLY ON FRIDAY AS
WE WILL BE ON THE WESTERN PERIPHERY OF THE CIRCULATION. SO WILL
CONTINUE TO MENTION CHANCE POPS FOR SNOW SHOWERS THURSDAY
NIGHT…DECREASING TO SLIGHT CHANCE IN THE VALLEYS FOR FRIDAY. THERE
WILL CONTINUE TO BE A SOMEWHAT BETTER CHANCE FOR A PASSING SNOW
SHOWER OVER THE HIGHER TERRAIN ON FRIDAY WITH THE NORTHWEST CYCLONIC
FLOW PERSISTING.

IT LOOKS LIKE DRIER WEATHER WILL FINALLY PREVAIL FOR THE
WEEKEND…ALTHOUGH THE DEGREE OF CLOUD COVER WILL DEPEND ON HOW
QUICKLY THE CUT-OFF LOW MOVES OUT TO SEA. THE ECMWF IS RATHER SLOW
WITH THE DEPARTURE OF THE CUT-OFF LINGERING CYCLONIC FLOW UNTIL
SUNDAY…WHILE THE GFS HAS AN UPPER LEVEL RIDGE BUILDING IN BY LATE
SATURDAY. AGAIN…THIS WILL HAVE IMPLICATIONS ON CLOUD COVER BUT WE
ARE EXPECTING PRECIP-FREE CONDITIONS THROUGH THE UPCOMING WEEKEND.
DESPITE RISING UPPER LEVEL HEIGHTS/TEMPS…SURFACE TEMPS ARE ONLY
EXPECTED TO BE SLIGHTLY ABOVE NORMAL DUE TO EXPECTED SHALLOW MIXING
THIS TIME OF YEAR.

TRANQUIL WEATHER LOOKS TO CONTINUE INTO MONDAY…WITH HIGH PRESSURE
AT THE SURFACE AND ALOFT FIRMLY ENTRENCHED OVER THE REGION WITH GOOD
AGREEMENT BETWEEN THE ECMWF/GFS.

&&

.AVIATION /00Z TUESDAY THROUGH SATURDAY/…
A SIGNIFICANT DEVELOPING COASTAL STORM WITH MULTIPLE PRECIPITATION
TYPES WILL IMPACT THE AREA FROM EARLY TUESDAY MORNING INTO
WEDNESDAY MORNING.

SOLID STRATUS CLOUD DECK WITH CIGS IN MVFR RANGE IN PLACE ACROSS
THE TERMINALS THIS EVENING DUE TO AN INCREASINGLY MOIST E-SE LOW
LEVEL FLOW. A FEW SNOW FLURRIES WILL BE POSSIBLE THIS EVENING BUT
WILL NOT AFFECT THE VISIBILITY SO WILL JUST MENTION VCSH.

PRECIP ASSOCIATED WITH COASTAL STORM WILL DEVELOP FROM SOUTH TO
NORTH ACROSS THE AREA STARTING SHORTLY BEFORE SUNRISE AT KPOU…TO
MID MORNING AT KGFL. CONDITIONS WILL RAPIDLY DETERIORATE TO
IFR/LIFR SHORTLY AFTER PRECIP COMMENCES.

A WINTRY MIX OF SNOW…SLEET AND FREEZING RAIN IS ANTICIPATED TO
START AT KPOU…CHANGING TO RAIN SHORTLY AFTER SUNRISE. SNOW WILL
DEVELOP AT KALB/KPSF/KGFL AROUND 12Z-14Z…THEN QUICKLY CHANGE TO
A MIX OF SNOW…SLEET AND FREEZING RAIN AND EVENTUAL RAIN BY NOON
AT KALB/KPSF. MODERATE TO HEAVY RAIN WILL THE FALL THROUGH THE
AFTERNOON…POSSIBLY MIXED WITH SLEET. A WINTRY MIX IS EXPECTED TO
PREVAIL WELL INTO THE AFTERNOON AT KGFL.

THE PRECIP TYPE FORECASTS AND TIMING ARE LOW CONFIDENCE AT
THIS TIME…AS TEMPERATURE PROFILES IN THE ATMOSPHERE ARE
UNCERTAIN. LOW LEVEL COLD AIR MAY SCOUR OUT QUICKER THAN
ANTICIPATED OR LINGER LONGER INTO THE AFTERNOON…WHICH WOULD
IMPACT WHEN PRECIP TYPE TRANSITIONS OCCUR.

WINDS WILL INITIALLY BE N-NE AROUND 5-10 KTS…INCREASING TO 10-15
KTS WITH GUST NEAR OR EXCEEDING 20 KTS TUESDAY AFTERNOON.

OUTLOOK…

TUESDAY NIGHT: HIGH OPERATIONAL IMPACT. DEFINITE RA…SN…SLEET.
WEDNESDAY: HIGH OPERATIONAL IMPACT. LIKELY RA…SN.
WEDNESDAY NIGHT: HIGH OPERATIONAL IMPACT. LIKELY SN.
THURSDAY: MODERATE OPERATIONAL IMPACT. CHANCE OF SHSN.
THURSDAY NIGHT: MODERATE OPERATIONAL IMPACT. CHANCE OF SHSN.
FRIDAY: LOW OPERATIONAL IMPACT. SLIGHT CHANCE OF SHSN.
FRIDAY NIGHT TO SATURDAY: NO OPERATIONAL IMPACT. NO SIG WX.

&&

.HYDROLOGY…
FLOOD WATCH FOR DUTCHESS AND EASTERN ULSTER COUNTIES ALONG WITH
LITCHFIELD COUNTY WHERE 1 TO 2 INCHES OF QPF ARE IN THE FORECAST
WITH MAINLY RAIN.

A COASTAL STORM WILL BRING WIDESPREAD PRECIPITATION TO THE REGION
BEGINNING EARLY IN THE DAY ON TUESDAY AND CONTINUING INTO TUESDAY
NIGHT. FOR NORTHWESTERN AND HIGH TERRAIN AREAS…THIS
PRECIPITATION WILL FALL PRIMARY AS SNOW OR A WINTRY MIX.
MEANWHILE…ACROSS SOUTHERN AND VALLEY AREAS…PRECIP WILL BEGIN
AS A PERIOD OF SNOW AND TRANSITION TO A WINTRY MIX AND THEN RAIN.
TOTAL LIQUID EQUIVALENT VALUES WILL BE 0.75 OVER THE WESTERN
ADIRONDACKS TO ABOUT 2 INCHES OVER WESTERN NEW ENGLAND. WITH MUCH
OF THIS FALLING AS RAINFALL OVER LITCHFIELD COUNTY…THERE WILL BE
A LOT OF RUNOFF…ESPECIALLY DURING TUESDAY AFTERNOON INTO TUESDAY
EVENING WHICH PRECIP WILL BE HEAVIEST. THIS RAINFALL MAY LEAD TO
MINOR FLOODING OF POOR DRAINAGE AND LOW LYING AREAS…ESPECIALLY
IN AREAS WHERE THE GROUND IS FROZEN. RISES ON RIVERS AND STREAMS
ARE LIKELY…AND MINOR FLOODING CANNOT BE RULED OUT ON THE
HOUSATONIC RIVER AND IT/S TRIBUTARIES IN NW CT. AS A RESULT…A
FLOOD WATCH IS IN EFFECT FOR LITCHFIELD COUNTY.

ELSEWHERE…MINOR FLOODING OF LOW LYING AREAS CANNOT BE RULED OUT
EITHER…SUCH AS IN THE MID HUDSON VALLEY AND TACONICS…BUT
CONFIDENCE WAS NOT HIGH ENOUGH TO INCLUDE THESE AREAS IN THE FLOOD
WATCH AT THIS TIME. PART OF THIS UNCERTAINTY IS DUE TO QUESTIONS
REMAINING OF HOW LONG PRECIP WILL BE WINTRY VS PLAIN RAINFALL. WHEN
THE EXACT DURATION OF PRECIP TYPES BECOME MORE CLEAR…IT IS
POSSIBLE THAT THE FLOOD WATCH MAY NEED TO BE EXPANDED.

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…FLOOD WATCH FROM 6 AM EST TUESDAY THROUGH LATE TUESDAY NIGHT
FOR CTZ001-013.
WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO 11 AM EST
TUESDAY FOR CTZ001-013.
NY…WINTER STORM WARNING FROM 4 AM TUESDAY TO 7 AM EST WEDNESDAY
FOR NYZ032-033-038>040-042-043-047-048-051-058-063-082.
WINTER STORM WATCH FROM 4 AM EST TUESDAY THROUGH WEDNESDAY
MORNING FOR NYZ041-049-050-052>054-059>061-083-084.
FLOOD WATCH FROM 6 AM EST TUESDAY THROUGH LATE TUESDAY NIGHT
FOR NYZ064>066.
WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO 11 AM EST
TUESDAY FOR NYZ064>066.
MA…WINTER STORM WATCH FROM 4 AM EST TUESDAY THROUGH WEDNESDAY
MORNING FOR MAZ001-025.
VT…WINTER STORM WATCH FROM 4 AM EST TUESDAY THROUGH WEDNESDAY
MORNING FOR VTZ013>015.

&&

$$
SYNOPSIS…GJM
NEAR TERM…GJM/JPV
SHORT TERM…GJM
LONG TERM…JPV
AVIATION…JPV
HYDROLOGY…IAA

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