February 22, 2013 Forecast Discussion

000
FXUS61 KALY 221749
AFDALY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ALBANY NY
1249 PM EST FRI FEB 22 2013

.SYNOPSIS…
HIGH PRESSURE WILL BRING FAIR AND DRY WEATHER WITH SEASONABLE
TEMPERATURES TODAY. THE HIGH WILL MOVE EAST OF MAINE TONIGHT…AS
A WARM FRONT APPROACHES ASSOCIATED WITH LOW PRESSURE OVER THE
GREAT LAKES REGION. ANOTHER LOW PRESSURE SYSTEM DEVELOPING NEAR
THE DELMARVA REGION TO OPEN THE WEEKEND…WILL TRACK NORTHEAST
JUST SOUTH OF LONG ISLAND AND SOUTHERN NEW ENGLAND BY SUNDAY…AND
COULD BRING SOME ACCUMULATING SNOW FROM THE CAPITAL REGION AND
BERKSHIRES NORTH…AND A WINTRY MIXTURE TO THE SOUTH.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/…
AS OF 1215 PM EST…UPDATE THIS AFTERNOON TO INCREASE CLOUD COVER
DUE TO ALREADY THICK HIGH LEVEL CIRRUS. AS A RESULT…LOWERED MAX
TEMPS A FEW DEGREES AS WELL. DRY CONDITIONS WILL CONTINUE…WITH
SEASONABLE TEMPERATURES AND LIGHTER WINDS COMPARED TO THE PAST FEW
DAYS.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY/…
TONIGHT…THE SFC HIGH SHIFTS DOWNSTREAM OVER MAINE AND THE NEW
BRUNSWICK WITH THE WARM FRONT CREEPING CLOSE TO PA AND NY. SOME
WEAK ISENTROPIC LIFT WILL OCCUR ON THE 295K SFC. THIS WILL BRING
SOME LIGHT SNOW FROM SOUTHWEST TO NORTHEAST ACROSS ERN NY AND WRN
NEW ENGLAND. IT WILL TAKE A LITTLE TIME FOR THE COLUMN TO
SATURATE…AND WE GENERALLY INCREASED POPS AFTER MIDNIGHT FROM
SLIGHT CHC TO CHC VALUES OVER THE FCST AREA. THE THICKENING AND
LOWERING CLOUDS WILL NOT ALLOW TEMPS TO DROP OFF TOO MUCH. WE
LEANED CLOSER TO WARMER METMOS VALUES WITH LOWS IN THE MID AND
U20S IN THE VALLEYS…AND TEENS TO L20S OVER THE MTNS. THE WARM
ADVECTION PCPN IS WEAK…SO ANY ACCUMS WITH THE LIGHT SNOW PRIOR
TO DAYBREAK WILL BE COATING TO HALF AN INCH RANGE.

SATURDAY…FORECAST BECOMES TRICKY AND CHALLENGING ON THE WEEKEND
WITH THE MODEL GUIDANCE CONTINUING TO SHOW PLENTY OF DISSONANCE.
THE BIGGEST DISCREPANCY IS THE 00Z NAM AND ASSOCIATED 21Z/03Z SREFS
WHICH CONTINUE TO GENERATE A POTENT COASTAL LOW LATE SATURDAY PM
NEAR THE DELMARVA COAST…AND THE TRACK IS FAVORABLE SOUTH OF LONG
ISLAND SAT NIGHT WITH TOTAL LIQUID EQUIVALENTS OF 1-2+ INCHES BY
SUNDAY PM. THIS SCENARIO…THOUGH PLAUSIBLE…SEEMS OFF COMPARED
TO THE GFS…CANADIAN GUIDANCE…AND THE LATEST ECMWF. FOR SOME
REASON…THE OPERATIONAL NAM SEEMS TO BE SUFFERING FROM SOME
CONVECTIVE FEEDBACK ISSUES…AS CONVECTION IS EXPECTED OVER THE
SOUTHEAST TODAY. NOT MUCH CONFIDENCE WAS PUT INTO THE SREF AND 00Z NAM.

OUR FCST IS GOING TO REFLECT A BLEND OF THE ECMWF/GFS PROFILES IN
THE GRIDDED FORECAST FOR SAT-SUN. THIS SCENARIO IS ALSO SUPPORTED
BY THE LATEST HPC GUIDANCE TOO. THERE LATEST QPF IS USED IN THE
FORECAST THROUGH THE WEEKEND.

THE TRACK…EVOLUTION…PTYPE ISSUES AND QPF REMAIN CHALLENGING
TO NOT SUPPORT A WINTER STORM WATCH FOR ANY PORTION OF THE FCST
AREA. ACTUALLY…THE MAJORITY OF THE FCST AREA…CURRENT SNOWFALL
PROJECTIONS REFLECTS POTENTIAL ADVISORIES LATE SATURDAY INTO
SUNDAY. THE AREAS WE ARE WATCHING FOR THE HIGHEST SNOWFALL
TALLIES…WHICH MAY BE OVER A 24-HR PERIOD WOULD BE SRN VT AND THE
BERKSHIRES.

THE WARM ADVECTION PCPN CONTINUES SATURDAY MORNING WITH ADDITIONAL
LIGHT SNOW AMOUNTS WITH THE WARM FRONT LIKELY HUNG UP JUST
SOUTH…OR OVER PORTIONS OF THE FCST AREA. THE UPSTREAM UPPER LOW
AND ITS REFLECTION OF THE SFC LOW REMAIN HUNG UP OVER THE GREAT
LAKES REGION. MEANWHILE…A SHORT-WAVE ROUNDS THE BASE OF THE
UPPER TROUGH NEAR THE UPPER MID ATLANTIC REGION FOR A COASTAL LOW
TO FORM NEAR THE VA/NC COAST BY THE AFTERNOON. A NEW AREA OF
ISENTROPIC LIFT WILL LIKELY BLOSSOM FROM PA/NJ INTO SRN NY LATE IN
THE DAY. THE BOUNDARY LAYER TEMPS ARE EXPECTED TO WARM ENOUGH FOR THE
PCPN TO MIX WITH RAIN…ESPECIALLY BELOW 1000 FEET. THIS WILL
LIKELY BE SHORT-LIVED…AS THE COASTAL WAVE WILL DRAW IN COLDER
AIR TOWARDS NIGHTFALL. ACCUMULATIONS SATURDAY WILL RANGE FROM THE
HALF INCH TO TWO INCH RANGE OVER THE REGION BEFORE THE CHANGEOVER
TO RAIN. HIGHS WILL GENERALLY BE IN THE M30S TO L40S.

SATURDAY NIGHT INTO SUNDAY…OUR CONFIDENCE IS FAIRLY HIGH FOR A
QUICK TRANSITION TO SNOW BASED ON THE CRITICAL PARTIAL THICKNESSES
FROM THE GFS/ECMWF AND MODEL SOUNDINGS FROM THE CAPITAL REGION
NORTH. THE COLD AIR MAY UNDER CUT THE SUBFREEZING AIR ALOFT FOR A
BRIEF PERIOD OF SLEET AND FREEZING RAIN OVER THE SRN BERKS…NW
CT…SRN TACONICS…MID HUDSON VALLEY…AND ERN CATSKILLS. WE ARE
NOT SUPER CONFIDENT HERE. THE LATEST HPC WINTER WX GUIDANCE WOULD
HAVE TRACES TO A COUPLE TENTHS OF AN INCH OF ICE IN THE SOUTHERN
ZONES. THIS LOOKS A BIT HIGH. WE TRIED TO KEEP A CHC OF FREEZING
RAIN IN SAT NIGHT FOR LOCATIONS SOUTH OF THE CAPITAL
REGION…THOUGH A WINDOW OF LIKELY POPS WAS ADDED WITH COATING TO
PERHAPS A TENTH OF AN INCH FOR NW CT…AND THE SRN TACONICS.
ELSEWHERE…THE BEST QG LIFT DUE TO DIFFERENTIAL THERMAL ADVECTION
FROM THE COASTAL WAVE MAY PRODUCE A PERIOD OF LIGHT TO MODERATE
SNOWFALL…ESPECIALLY FROM THE CAPITAL REGION NORTH AND WEST
INITIALLY…BEFORE SPREADING INTO THE SRN ZONES. THE DYNAMICAL
COOLING WILL HAVE TO OCCUR QUICKLY FOR THE TRANSITION TO SNOW TO
OCCUR SOONER IN THE VALLEY LOCATIONS. THE BEST H850-700 FGEN STAYS
SOUTH AND EAST OF THE BULK OF THE FCST AREA. OVERALL…SAT NIGHT
SNOW ACCUMS HINGING HEAVILY ON THE GFS/ECMWF WILL BE IN THE 2-5
INCH RANGE…WITH SOME 3-7 INCH AMOUNTS POSSIBLY ACROSS SRN VT.
LOWS WILL RANGE FROM THE M20S TO NEAR 30F…WITH UPPER TEENS AND
L20S OVER THE SRN DACK REGION.

BY SUNDAY…THE FCST AREA WILL LIKELY REMAIN IN AN UPPER
DEFORMATION ZONE FOR PERSISTENT LIGHT TO POSSIBLY MODERATE SNOWFALL
WITH THE COASTAL LOW PASSING EAST OF CAPE COD. HOWEVER…THE UPPER
LEVEL LOW OVER SRN ONTARIO AND ONTARIO WILL KEEP THE SNOWS
GOING…ESPECIALLY OF THE WESTERLY UPSLOPE VARIETY FOR THE WRN
DACKS…SRN GREENS…NRN TACONICS…AND BERKS. ADDITIONAL LIGHT
ACCUMS ARE POSSIBLE. THE COLD ADVECTION KICKS IN DURING THE
AFTERNOON…BUT WITH THE PCPN LIGHTENING INTENSITY IT COULD
TRANSITION BACK TO RAINFALL. MAX TEMPS WILL BE IN THE M30S TO NEAR
40F IN THE VALLEY LOCALES…AND U20S TO M30S OVER THE HILLS AND
MTNS.

OVERALL…TOTAL QPF FROM THE GFS/ECMWF RANGES FROM A QUARTER OF AN
INCH TO THREE QUARTERS OF AN INCH. THE CAN GGEM WAS A BIT HIGHER
WITH A HALF AN INCH TO AN INCH. THE GEFS PLUME FOR ALY AT 00Z
YIELDS AN /EYEBALLED/ MEAN OF ABOUT 4 TENTHS WITH A TIGHT CLUSTER OF
ABOUT 3 TENTHS OF AN INCH. SNOWFALL ACCUMS FOR SAT INTO SUNDAY /3
PERIODS/ CURRENTLY ARE IN THE 2 TO 6 INCH RANGE FROM THE HUDSON
RIVER VALLEY WEST…S-CNTRL TACONICS…AND SRN LITCHFIELD
COUNTY…AND 6-10 INCHES FOR THE NRN TACONICS…LITCHFIELD
HILLS…BERKSHIRES AND…AND SRN VT.

THESE TOTALS COULD CHANGE DRASTICALLY WITH A SHIFT IN THE STORM
TRACK…AND DIFFERING THERMAL PROFILES.

THANKS FOR THE COLLAB WITH BTV AND BOX FOR A POTENTIAL WATCH. IT
WAS DECIDED TO BE PRUDENT TO WAIT…AS OUR CONFIDENCE WAS NOT GREAT
ENOUGH FOR THE POTENTIAL OF 7" OR MORE IN 12 HOURS…9" OR MORE IN
24 HOURS THIS FAR OUT.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/…
SUNDAY NIGHT-MONDAY…LINGERING SNOW SHOWERS WILL REMAIN POSSIBLE
ACROSS THE REGION…ESP ACROSS PORTIONS OF THE LAKE GEORGE/SARATOGA
REGION AND UPPER HUDSON RIVER VALLEY INTO SOUTHERN VT THROUGH
MIDNIGHT. WILL KEEP CHC POPS IN THESE AREAS…AND SLIGHT CHC POPS
FURTHER SOUTH…THROUGH MIDNIGHT…THEN CONFINE SLIGHT CHC POPS TO
NORTHERN AREAS AFTER MIDNIGHT AS SOME UPSLOPE/OROGRAPHIC SNOW
SHOWERS MAY PERSIST. WILL KEEP MONDAY DRY…ALTHOUGH SOME CLOUDS MAY
PERSIST IN THE MORNING…WITH ADDITIONAL HIGH/MID LEVEL CLOUDS
APPROACHING FROM THE SOUTHWEST LATE IN THE DAY. FOR TEMPS…EXPECT
SUN NT/MON AM MINS TO FALL INTO THE 20S IN MOST AREAS…EXCEPT FOR
SOME TEENS ACROSS HIGHER ELEVATIONS ACROSS THE S/W ADIRONDACKS. MAX
TEMPS MONDAY SHOULD REACH THE LOWER 40S WITHIN THE HUDSON RIVER
VALLEY…WITH GENERALLY MID TO UPPER 30S ELSEWHERE.

MONDAY NIGHT-WED…MODELS INDICATE NEXT SYSTEM TO APPROACH FROM THE
SOUTHWEST DURING THIS TIME PERIOD…ALTHOUGH DIFFER ON TIMING…AND
PATH OF SFC LOW. MOST DETERMINISTIC MODELS…AS WELL AS ENSEMBLES
SUGGEST THAT ONE SFC LOW TRACKS INTO THE GREAT LAKES REGION…WHILE
A SECONDARY LOW DEVELOPS ACROSS THE GULF COAST REGION AND THEN
TRACKS N TO NE. THE TRACK OF THE SECONDARY LOW WILL BE CRITICAL TO
OUR REGION…AS A PATH FURTHER WEST COULD RESULT IN WARMER AIR
INFILTRATING FROM THE SOUTHEAST…ALLOWING FOR THE POSSIBILITY OF A
WINTRY MIX OR PLAIN RAIN…RATHER THAN MORE IN THE WAY OF SNOW WITH
A TRACK SLIGHTLY FURTHER EAST. THERE ARE ALSO TIMING ISSUES…AS THE
00Z/22 ECMWF REMAINS SLOWEST AMONGST DETERMINISTIC MODELS…HOLDING
OFF MOST OF THE PRECIP UNTIL LATE TUE OR TUE NT…WHILE MOST OTHER
MODELS AND GEFS SUGGEST PRECIP DEVELOPS TUE MORNING…IF NOT LATE
MONDAY NIGHT. AT THIS TIME…HAVE TRIED TO ENCOMPASS THESE GENERAL
IDEAS BY BRINGING SLIGHT CHC TO LOW CHC POPS INTO THE REGION PRIOR
TO DAYBREAK TUE…THEN HIGH CHC POPS FOR TUE AFTERNOON AND
NIGHT…WITH CHC POPS CONTINUING INTO WED. AS FOR P-TYPE…HAVE
GENERALLY UTILIZED FORECAST SFC TEMPS…ALLOWING FOR PRECIP TO BEGIN
MAINLY AS SNOW…THEN MIXING WITH OR CHANGING TO RAIN LATE TUE INTO
A PORTION OF TUE NT IN VALLEY LOCATIONS. HOWEVER…CAN NOT RULE OUT
SLEET AND/OR FREEZING RAIN FOR PORTIONS OF THE REGION AS WELL. FOR
TEMPS…EXPECT MAINLY 30S FOR MAXES TUE-WED…WITH OVERNIGHT MINS
MAINLY IN THE 20S TO LOWER 30S.

WED NT-THU…A BROAD MID/UPPER LEVEL TROUGH SHOULD REMAIN ACROSS THE
EASTERN CONUS DURING THIS TIME PERIOD…ALLOWING FOR GENERALLY
UNSETTLED CONDITIONS WITH MOSTLY CLOUDY SKIES…AND AT LEAST SOME
SHOWERS OF SNOW…PERHAPS MIXED WITH RAIN IN VALLEY REGIONS DURING
THE DAYTIME HOURS. EXPECT MAX TEMPS TO REACH THE 30S IN MOST
AREAS…WITH OVERNIGHT MINS GENERALLY IN THE 20S.

&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/…
HIGH PRESSURE OVER THE REGION WILL CONTINUE TO SHIFT EASTWARD AT
SURFACE AND ALOFT. A LOW PRESSURE SYSTEM OVER THE MID WEST WILL
WEAKEN AS IT MOVES GRADUALLY NORTHEASTWARD OVER THE GREAT LAKES
REGION TONIGHT INTO SATURDAY. IN THE MEANTIME…A SECONDARY LOW
WILL DEVELOP ALONG THE SOUTHEAST COAST.

HIGH CIRRUS CLOUDS OVERSPREAD THE AREA THIS MORNING DESPITE THE
RIDGING. CLOUDS WILL THICKEN AND LOWER AS TIME PROGRESSES WITH MVFR
CONDITIONS DEVELOPING AFTER MIDNIGHT. IFR CONDITIONS ARE EXPECTED TO
DEVELOP AT KPOU SATURDAY MORNING AS PRECIPITATION BEGINS TO MOVE IN.
INITIALLY SNOW IS EXPECTED AT KPOU WITH MIXED PRECIPITATION POSSIBLE
AFTER 18Z.

WINDS WILL BE LIGHT AT LESS THAN 6 KNOTS.

OUTLOOK…
SAT NIGHT…MVFR/IFR IN SNOW.
SUN…MVFR/IFR. SNOW TAPERING OFF AT KALB/KGFL/KPOU WITH A CHC OF
RAIN/SNOW IN THE AFTN. KPSF…SNOW MAINLY IN THE AM.
MON…VFR. NO SIG WX.
TUE…LOWERING TO MVFR…POSSIBLY IFR. CHC SNOW/RAIN.

&&

.HYDROLOGY…
NO HYDROLOGY PROBLEMS ARE EXPECTED THE NEXT 5 DAYS.

DRY CONDITIONS ARE EXPECTED TODAY. A WARM FRONT WILL BRING SOME
LIGHT SNOWFALL TONIGHT INTO SATURDAY MORNING.

A DEVELOPING COASTAL STORM MAY BRING ACCUMULATING SNOW TO MUCH OF
THE REGION ON THE WEEKEND…ALTHOUGH SOME LIGHT RAIN MAY MIX WITH
MANY LOCATIONS SATURDAY BEFORE TRANSITIONING TO SNOW FROM THE
CAPITAL REGION NORTH BY THE EARLY EVENING…AND A WINTRY MIX TO
ALL SNOW TO THE SOUTH OVERNIGHT. THERE IS STILL UNCERTAINTY IN
HOW MUCH PRECIPITATION OCCURS AND THE PRECIPITATION TYPE DEPENDING
ON THE EXACT TRACK OF THE STORM. FOR NOW…TOTAL QPF OF LOOKS TO
RANGE FROM A THIRD OF AN INCH TO THREE QUARTERS OF AN INCH BY LATE
IN THE DAY ON SUNDAY.

DRY WEATHER IS EXPECTED ON MONDAY BEFORE ANOTHER SYSTEM ARRIVES
FOR TUESDAY WITH POTENTIALLY MORE SNOW AND RAIN.

THE PREDOMINANT PTYPE WILL CONTINUE TO BE SNOW FOR THE 5-DAY
STRETCH WITH ONLY A BRIEF PERIOD OF RAIN EXPECTED ON THE WEEKEND.

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.

&&

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

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