March 6, 2013 Forecast Discussion

000
FXUS61 KALY 061808
AFDALY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ALBANY NY
108 PM EST WED MAR 6 2013

.SYNOPSIS…
— Changed Discussion
A LOW PRESSURE SYSTEM WILL MOVE OFF THE MID ATLANTIC COAST TODAY
INTO THURSDAY…PASSING WELL SOUTH OF LONG ISLAND. THIS WILL BRING
SOME LIGHT SNOW OR RAIN TO SOUTHERN PORTIONS OF THE AREA LATER TODAY
AND TONIGHT. THE COMBINATION OF MOISTURE FROM THE COASTAL STORM…
AND UPPER LEVEL ENERGY APPROACHING FROM THE GREAT LAKES REGION WILL
BRING A MORE WIDESPREAD LIGHT TO MODERATE SNOWFALL TO THE AREA FOR
LATE THURSDAY AFTERNOON AND NIGHT.
End Changed Discussion —

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/…
— Changed Discussion —
AS OF 1230 PM…NOT MUCH CHANGE TO THE PREVIOUS FORECAST EXCEPT TO
RAISE TEMPS A FEW DEGREES. SPOTTY LIGHT PCPN ASSOCIATED WITHTHE
EASTERLY FLOW CONTINUES AND WILL CONTINUE TO FORECAST 20 TO 40
PERCENT POPS ACROSS THE REGION THIS AFTERNOON. MOST PLACES GETTING
AT LEAST SOME PCPN…BUT MUCH OF THIS PCPN IS NOT ENOUGH TO BE
MEASUREABLE. THE INCREASE IN TEMPS BASED ON CURRENT READINGS HAS
RESULTED IN A MAINLY RAIN PCPN TYPE FORECAST ACROSS LOW-LYING AREAS
FOR THE REST OF THE AFTERNOON.

.PREVIOUS DISCUSSION…
AS OF 950 AM EST…OVERCAST SKIES NOW PRETTY MUCH ENCOMPASSING THE
ENTIRE AREA LATE THIS MORNING…AS AN EASTERLY FLOW IS PROVIDING A
MOIST FETCH OFF THE ATLANTIC OCEAN. LOW PRESSURE WAS LOCATED OVER
THE DELMARVA…WITH HIGH PRESSURE OVER THE CANADIAN MARITIMES
INDUCING THE EASTERLY FLOW. MADE ONLY SOME MINOR ADJUSTMENTS TO
TEMPERATURES AND POPS/WEATHER BASED ON CURRENT TRENDS AND OBS.
CHANGED WORDING TO MENTION JUST LIGHT RAIN OR SNOW THROUGH TODAY
AND INTO THIS EVENING…WITH ONLY WEAK ASCENT ACROSS THE AREA.

WE EXPECT THESE ISOLATED LIGHT SHOWERS OF SNOW/SNOW GRAINS AND
FLURRIES…AND PERHAPS EVENTUALLY LIGHT RAIN/DRIZZLE…TO PERSIST
THROUGH MUCH OF THE DAY FROM THE CAPITAL REGION AND AREAS SOUTH
AND EAST…AND EVENTUALLY EXPANDING NORTHWEST INTO THE SARATOGA
REGION AND MOHAWK VALLEY BY THIS AFTERNOON. THE VERTICAL EXTENT OF
THE CLOUDS PRODUCING THESE SHOWERS IS RATHER SHALLOW…WITH
SOMEWHAT LIMITED ICE CRYSTAL GROWTH. BASED ON CLOUD TOP TEMPS OF
AROUND -10C…THIS APPEARS TO SUPPORT SNOW GRAINS…OR EVEN
DRIZZLE. AS THE DAY PROGRESSES…AND HIGH/MID LEVEL CLOUDS ABOVE
THE LOWER STATUS DECK INCREASE AND THICKEN…THE AREAL COVERAGE OF
THESE SHOWERS SHOULD INCREASE DUE TO SEEDER/FEEDER PROCESSES…AND
ALSO SHOULD PROMOTE MORE ICE CRYSTAL GROWTH IN THE CLOUDS. IN
AREAS WHERE THE BOUNDARY LAYER IS COLD ENOUGH…THIS SHOULD ALLOW
FOR MAINLY SNOW. HOWEVER…IN SOME VALLEY AREAS WHERE THE BOUNDARY
LAYER INITIALLY IS WARMER…SOME RAIN OR DRIZZLE WILL BE POSSIBLE.
THE STEADIER…AND MORE WIDESPREAD PRECIPITATION IS EXPECTED TO
DEVELOP LATER THIS AFTERNOON ACROSS THE MID HUDSON VALLEY…SE
CATSKILLS…AND ACROSS NW CT. IN THESE AREAS…A SLUSHY COATING
WILL BE POSSIBLE BY SUNSET ON COLDER SURFACES…ESP ACROSS HIGHER
ELEVATIONS.

AS FOR TODAY/S TEMPS…HAVE GENERALLY SIDED CLOSER TO…OR A SHADE
BELOW A MAV/MET MOS BLEND…WITH MAXES APPROACHING OR SLIGHTLY
EXCEEDING 40 IN VALLEY AREAS…AND REACHING THE MID/UPPER 30S
ACROSS HIGHER ELEVATIONS. SHOULD LIGHT PRECIPITATION BE MORE
WIDESPREAD THAN CURRENTLY ANTICIPATED…EVEN COOLER MAX TEMPS MAY
OCCUR.
— End Changed Discussion —

&&

.SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY NIGHT/…
TONIGHT…THE NORTHERN EDGE OF THE PRECIPITATION SHIELD ASSOCIATED
WITH THE DEVELOPING COASTAL STORM IS EXPECTED TO EXPAND
NORTH/NORTHWEST ACROSS MUCH OF THE MID HUDSON VALLEY REGION…NW
CT…AND INTO THE CENTRAL AND SOUTHERN BERKSHIRES THIS EVENING.
THERMAL PROFILES SUGGEST MOST OF THIS SHOULD BE IN THE FORM OF
SNOW…AFTER SOME RAIN MAY BE MIXED IN INITIALLY. THE NORTHERN
EDGE OF THE PRECIP SHIELD SHOULD STAY MAINLY SOUTH AND EAST OF THE
CAPITAL REGION THROUGH MIDNIGHT…ALTHOUGH SOME SPOTTY LIGHT
SNOW/SNOW SHOWERS MAY OCCUR NORTH AND WEST OF THE MORE STRATIFORM
PRECIP…AS LOW LEVEL ATLANTIC MOISTURE CONTINUES TO BUILD WEST.
AS FOR SNOWFALL AMTS THROUGH DAYBREAK…EXPECT GENERALLY 1-2 INCHES
ACROSS THE MID HUDSON VALLEY…NW CT…AND SOUTHERN
BERKSHIRES…WITH AN INCH OR LESS FURTHER N AND W…WITH ONLY A
COATING POSSIBLE FROM THE CAPITAL REGION AND AREAS N AND W.

THURSDAY…PRECIPITATION MAY BECOME QUITE SPOTTY THURSDAY
MORNING…AS THE MAIN PRECIP SHIELD ASSOCIATED WITH THE COASTAL
STORM SHIFTS S/E OF THE REGION. HOWEVER…DURING THE MID TO LATE
AFTERNOON HOURS…AS LOW-MID LEVEL MOISTURE CONTINUES TO STREAM
WESTWARD AROUND THE INTENSIFYING COASTAL STORM…UPPER LEVEL
DYNAMICS WITH THE APPROACH OF A SHORTWAVE FROM THE GREAT LAKES
REGION SHOULD ENHANCE LIFT AND RESULT IN A DEVELOPING AREA OF
LIGHT SNOW…ESP FROM INTERSTATE 90 NORTHWARD. EXPECT ADDITIONAL
SNOWFALL ACCUMS OF AROUND AN INCH IN MOST AREAS…ALTHOUGH LOCALLY
HIGHER AMTS COULD OCCUR IN PORTIONS OF THE WESTERN ADIRONDACKS AND
LAKE GEORGE AREA BY SUNSET. AS FOR TEMPS…GENERALLY SIDED CLOSER
TO THE COLDER MET MOS ASSUMING CLOUDS AND PRECIPITATION OCCUR.

THURSDAY NIGHT…THE AFOREMENTIONED UPPER LEVEL SHORTWAVE
APPROACHING FROM THE GREAT LAKES WILL CONTINUE TO WORK IN TANDEM
WITH A STRONG MID LEVEL INFLUX OF ATLANTIC MOISTURE TO PRODUCE A
PERIOD OF SNOW ACROSS MOST OF THE AREA…WITH SOME BURSTS OF
MODERATE SNOW POSSIBLE…ESP FROM THE CAPITAL REGION AND POINTS N
AND E. IT APPEARS THAT A WIDESPREAD 2-4 INCHES OF ADDITIONAL
SNOWFALL SHOULD OCCUR IN MOST AREAS FROM THE CAPITAL REGION AND
AREAS N AND E BY SUNRISE FRIDAY…WITH AN ADDITIONAL 1-2 INCHES
POSSIBLE ACROSS SOUTHERN AREAS. IT IS POSSIBLE THAT LOCALLY HIGHER
AMTS OCCUR…ESP FOR E/NE FACING HIGHER ELEVATIONS…SUCH AS
ACROSS THE NE CATSKILLS/HELDERBERGS AND SCHOHARIE VALLEY DUE TO
ADDITIONAL UPSLOPE PROCESSES. SHOULD CONFIDENCE INCREASE THAT
HIGHER AMTS MAY OCCUR…THE ISSUANCE OF WINTER WEATHER ADVISORIES
WOULD BE NEEDED. AS FOR TEMPS…GENERALLY USED A MAV/MET MOS
BLEND…WITH MID/UPPER 20S EXPECTED IN MOST AREAS…EXCEPT SLIGHTLY
COLDER ACROSS THE ADIRONDACKS.

FRIDAY…THE AFOREMENTIONED UPPER LEVEL SHORTWAVE SHOULD CONTINUE
TRANSLATING TO OUR S AND W…WITH DECREASING UPPER LEVEL DYNAMICS
AND MOISTURE TRANSPORT INTO THE REGION. SO…ALTHOUGH SNOW WILL
LIKELY BE ONGOING IN MANY AREAS FRI MORNING…EXPECT IT TO TAPER
OFF BY AFTERNOON FROM N TO S. SOME ADDITIONAL ACCUMS WILL BE
POSSIBLE FRI MORNING BEFORE THE SNOW TAPERS OFF…ESP FROM THE
CAPITAL REGION AND AREAS TO THE SOUTH AND WEST. SOME CLEARING MAY
OCCUR BY LATE FRI AFTERNOON ACROSS NORTHERN AREAS. EXPECT MAX
TEMPS TO REACH 35-40 IN MOST VALLEY AREAS…AND LOWER/MID 30S
ACROSS HIGHER ELEVATIONS.

FRI NT…EXPECT SKIES TO BECOME MOSTLY CLEAR. TEMPS SHOULD FALL
INTO THE 20S IN MOST AREAS…WITH SOME TEENS POSSIBLE ACROSS THE
SOUTHERN ADIRONDACKS.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/…
WE BEGIN THIS WEEKEND WITH A LARGE AREA OF SURFACE HIGH PRESSURE
THAT WILL STRETCH ALONG THE ENTIRE EASTERN SEABOARD. UNDER A GOOD
DEAL OF MARCH SUNSHINE…AND H850 TEMPS CLIMBING INTO THE LOWER
POSITIVE SINGLE DIGITS…WE SHOULD SEE TEMPS CLIMB WELL INTO THE 40S
AND PERHAPS TOUCHING 50F IN VALLEY LOCATIONS AND LOW-MID 40S
ELSEWHERE. THIS HIGH IS EXPECTED TO SLIDE OFFSHORE HEADING INTO
SUNDAY AS NEXT UPSTREAM SYSTEM DEVELOPS. QUESTION WILL BE IF WE
WILL SEE AN INCREASE CHANCE FOR SHOWERS ON SUNDAY AS THE ECMWF
REMAINS RATHER AGGRESSIVE WITH THE FRONTAL APPROACH AS OPPOSED TO
THE GFS/GGEM. FOR NOW…WE WILL PLACE LOW CHANCE POPS NORTH AND
WEST OF THE CAPITAL REGION FOR LATE IN THE DAY SUNDAY. AS A
REMINDER…WE DO SWITCH OUR CLOCKS FORWARD THIS WEEKEND /SUNDAY AT 2
AM TO BE EXACT/ TO EDT.

LOOKING AHEAD IN EARLY NEXT WEEK…THAT UPSTREAM SYSTEM WILL
APPROACH THE EASTERN SEABOARD. GLOBAL MODELS ALL OFFER A UNIQUE
PERSPECTIVE WITH TRENDS FAVORING THE MAIN STORM TRACK TO REMAIN WEST
OF THE LOCAL REGION. MOST OF THE REGION WILL EXPERIENCE A PERIOD OF
WET WEATHER BUT SOME OF THE BOUNDARY LAYER TEMPS MAY EXPERIENCE A
WINTRY MIXTURE…MAINLY INTO THE TERRAIN.

THE STORMS ASSOCIATED COLD FRONT IS FORECAST TO MOVE THROUGH TUESDAY
WITH A BRISK WEST-NORTHWEST FLOW AND A RETURN TO COLDER TEMPERATURES
AS THOSE H850 TEMPS PLUNGE BACK BELOW 0C.

&&

.AVIATION /18Z WEDNESDAY THROUGH SUNDAY/…
— Changed Discussion —
A PERSISTENT MOIST EASTERLY FLOW RESULTING FROM A COASTAL LOW
PRESSURE SYSTEM NEAR THE DELMARVA AND HIGH PRESSURE OVER THE
CANADIAN MARITIMES WILL BE OVER THE REGION THROUGH MUCH OF THE REST
OF THE WORK WEEK. FLYING CONDITIONS WILL BE TRICKY TO FORECAST TODAY
THROUGH THURSDAY…AS THERE WILL BE SOME PERIODS OF PRECIPITATION
FROM THE FRINGES OF THE COASTAL LOW AS WELL AS SOME UPSLOPE FLOW.
CONDITIONS ARE EXPECTED TO BE MAINLY VFR OR MVFR FOR THE FIRST 6
HOURS OF THE TAF PERIOD WITH SCT -SHRA…ALTHOUGH SOME BRIEF
REDUCTION TO IFR IS POSSIBLE AT KPSF WHERE IT IS COLD ENOUGH FOR
SOME -SHSN TO OCCUR AS WELL AS THIS SITE BEING AT A HIGHER
ELEVATION. THE BEST CHANCE OF PRECIP WILL BE AT KPOU/KPSF.

TONIGHT AFTER 00Z THURSDAY…THERE WILL BE CONTINUED PERIODS OF
MAINLY -SN ALTHOUGH SOME -RA COULD MIX IN ESPECIALLY FOR KPOU.
AGAIN…BEST CHANCE FOR STEADIER PRECIP WILL BE AT KPOU/KPSF BUT
EVEN SOME SCT -SHSN POSSIBLE FOR KALB/KGFL. CONDITIONS EXPECTED TO
BE GENERALLY MVFR…WITH SOME POSSIBLE OCCASIONAL IFR DEVELOPING AT
KPOU/KPSF. DESPITE SIMILAR REGIME…THERE SHOULD BE SOME SLIGHT
IMPROVEMENT AFTER SUNRISE WITH SLIGHTLY HIGHER CIGS/VSBYS AND MVFR
OR EVEN SOME VFR CONDITIONS POSSIBLE.

WINDS WILL BE NORTHEASTERLY BECOMING NORTHERLY TONIGHT…WITH SPEEDS
NOT VARYING MUCH THROUGH THE 24 HOUR TAF PERIOD DUE TO THE
RELATIVELY STAGNANT PRESSURE PATTERN IN PLACE OVER THE REGION. WIND
SPEEDS WILL CONTINUE TO BE AROUND 10-12 KT WITH GUSTS OF 20-25 KT.

OUTLOOK…
THU AFTN…MVFR/IFR. -SN LIKELY KPOU/KPSF/KALB AND CHC -SN AT KGFL.
BREEZY.
THU NT…MAINLY IFR. -SN/SN LIKELY.
FRI MRNG…MVFR/IFR. -SN LIKELY AT KPOU/KPSF AND CHC -SN AT
KGFL/KALB.
FRI AFTN-SUN…VFR. NO SIG WX.
— End Changed Discussion —

&&

.HYDROLOGY…
NO HYDRO PROBLEMS ARE EXPECTED THE NEXT FEW DAYS. A STORM SYSTEM
EXPECTED TO MOVE OFF THE MID ATLANTIC COAST TODAY AND PASS SOUTH
OF LONG ISLAND TONIGHT. MOISTURE FROM THIS LOW…AND THE APPROACH
OF A STRONG UPPER LEVEL DISTURBANCE WILL PRODUCE PRECIPITATION
ACROSS THE REGION LATE THURSDAY INTO EARLY FRIDAY. AT THIS
TIME…STORM TOTAL QPF AMOUNTS THROUGH FRIDAY MORNING ARE EXPECTED
TO RANGE FROM ABOUT A QUARTER TO AROUND A HALF AN INCH…WITH THE
GREATEST AMTS EXPECTED NEAR…AND TO THE NORTH AND EAST OF THE
CAPITAL DISTRICT. THIS SHOULD BE MAINLY SNOW.

LOOKING OUT FURTHER IN TIME…HIGH PRESSURE IS EXPECTED TO BUILD
INTO THE REGION FOR THE WEEKEND. TEMPERATURES ARE EXPECTED TO
MODERATE TO ABOVE NORMAL…WITH TEMPERATURES FALLING BELOW
FREEZING AT NIGHT…SO WILL HAVE DIURNAL SNOWMELT.

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…GJM/KL
NEAR TERM…GJM/KL/JPV
SHORT TERM…KL
LONG TERM…BGM
AVIATION…JPV
HYDROLOGY…IAA/KL

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