February 10, 2013 Forecast Discussion

000
FXUS61 KALY 110015
AFDALY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ALBANY NY
715 PM EST SUN FEB 10 2013

.SYNOPSIS…
HIGH PRESSURE ALONG THE EASTERN SEABOARD WILL SLIDE OFFSHORE
TONIGHT. A STORM WILL CROSS THE UPPER GREAT LAKES TOMORROW…AND
MOVE TO THE MARITIMES BY TUESDAY. IT WILL DRAG A WARM FRONT ACROSS
THE REGION MONDAY…WITH A WINTRY MIX FOR A FEW HOURS BEFORE
CHANGING TO RAIN. TWO COLD FRONTS WILL FOLLOW LATE MONDAY. TUESDAY
WEAK HIGH PRESSURE WILL CREST OVER THE REGION.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/…
…WINTER WEATHER ADVISORY ISSUED FOR MIXED PRECIPITATION LATE
TONIGHT AND TOMORROW MORNING…BUT INTO THE AFTERNOON OVER
NORTHERN AREAS…

AS OF 7 PM EST…CLEAR SKIES…CALM WINDS…AND A RELATIVELY
FRESH/DEEP SNOWPACK HAS ALLOWED TEMPS TO ONCE AGAIN PLUMMET AFTER
SUNSET…WITH TEMPS ALREADY FALLING INTO THE SINGLE DIGITS TO LOWER/MID
TEENS ACROSS PORTIONS OF THE SOUTHERN ADIRONDACKS AND LAKE
GEORGE/SARATOGA REGIONS…AND GENERALLY MID TEENS TO LOWER 20S
ELSEWHERE. UNTIL CLOUDS ARRIVE AND THICKEN AFTER MIDNIGHT…TEMPS
SHOULD CONTINUE TO DROP…SO HAVE LOWERED FORECAST MINS BY AT
LEAST 5-8 DEGREES IN MOST AREAS…WHICH STILL MAY NOT BE ENOUGH.
EXPECT MINS TO FALL INTO THE SINGLE DIGITS ACROSS THE SOUTHERN
ADIRONDACKS…LAKE GEORGE SARATOGA REGION…AND SHELTERED VALLEYS
ACROSS WESTERN NEW ENGLAND…WITH TEENS ELSEWHERE. TEMPS SHOULD
THEN HOLD NEARLY STEADY AROUND MIDNIGHT…BEFORE RISING THEREAFTER
AS CLOUDS THICKEN…AND SOUTH WINDS DEVELOP.

HIGH PRESSURE IS GRADUALLY EASING EAST OF THE REGION AS THE NEXT
AREA OF UNSETTLED WEATHER APPROACHES FROM THE CENTRAL U.S. CLOUDS
WILL THICKEN…AND BETWEEN MIDNIGHT AND DAYBREAK…LIGHT SNOW OR A
MIX OF SNOW AND SLEET SHOULD DEVELOP OVER AREAS WEST OF THE HUDSON
VALLEY. BY DAYBREAK…LIGHT MIXED PRECIPITATION SHOULD BEGIN OVER
MOST OF THE FORECAST AREA…WITH JUST PATCHY COVERAGE OF
PRECIPITATION OVER WESTERN NEW ENGLAND.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH WEDNESDAY/…
PRECIPITATION SHOULD TRANSITION TO FREEZING RAIN OVER MOST AREAS
SHORTLY AFTER DAYBREAK. THE LENGTH OF TIME OF THE FREEZING RAIN
SHOULD BE SHORTEST IN THE CAPITAL DISTRICT…MID HUDSON VALLEY…
SOUTHERN BERKSHIRES AND NW CT. THERE COULD BE AN INCH OR TWO OF
SNOW IN NORTHERN AREAS BEFORE THE CHANGE TO FREEZING RAIN. THERE
ARE SOME CONSIDERABLE UNCERTAINTIES AS TO WHEN THE TEMPERATURES
WILL RISE ABOVE FREEZING…ESPECIALLY WITH THE SNOW PACK IN THE
REGION. SOME AREAS IN THE SCHOHARIE VALLEY…HELDERBERGS AND
EASTERN CATSKILLS COULD TAKE UNTIL AROUND NOON…AS UP TO A
QUARTER INCH OF ICE IS POSSIBLE BEFORE CHANGING TO A COLD RAIN. UP
TO A TENTH OF AN INCH OF ICE IS POSSIBLE IN OTHER AREAS.

SOME QUESTIONS ABOUT WHETHER A QUARTER INCH OF FREEZING RAIN IS
POSSIBLE IN SOUTHERN VT AND THE NORTHERN BERKSHIRES…IT DEPENDS
ON WHEN THE SNOW AND SLEET CHANGES OVER. SOME TEMPERATURES IN
NORTHERN AREAS AND IN PROTECTED VALLEYS WITHIN TERRAIN MAY BARELY
GET ABOVE FREEZING IN THE AFTERNOON. BUT…BOUNDARY LAYER WINDS DO
TURN TO WEST AND BECOME RELATIVELY STRONG…SO ANY MIXING COULD
CAUSE TEMPERATURES TO JUMP QUICKLY IN THE AFTERNOON…AND THE NEXT
SET OF 00Z GUIDANCE WILL HOPEFULLY SHED SOME LIGHT ON THAT
POSSIBILITY.

BY TOMORROW NIGHT…THE COLD FRONT SHOULD TRACK THROUGH…AND
PRECIPITATION SHOULD BECOME SHOWERY. BOUNDARY LAYER TEMPERATURES
DO NOT COOL TOO MUCH…AND THE WEST WINDS INCREASE. CLOUDS WITHIN
THE SOUTHERN PERIPHERY OF THE UPPER SYSTEM…ALONG WITH LAKE
EFFECT MOISTURE SHOULD KEEP MOSTLY CLOUDY TO CLOUDY CONDITIONS OVER
THE REGION. WITH THE MIXING DUE TO THE WINDS AND THE SKY
COVER…LEANING TOWARD WARMER GUIDANCE FOR NIGHTTIME LOWS…ALONG
WITH SCATTERED RAIN SHOWERS BECOMING SNOW SHOWERS WHILE DECREASING
IN COVERAGE.

ON TUESDAY…A REINFORCING SHOT OF COOLER AIR TRACKS THROUGH THE
REGION AS THE UPPER IMPULSE EXITS. THERE COULD BE ISOLATED TO
SCATTERED RAIN AND SNOW SHOWERS ASSOCIATED WITH THE FORCING AND
PROXIMITY TO THE UPPER IMPULSE AS WELL AS LAKE EFFECT MOISTURE. IT
SHOULD BE QUITE BREEZY TUESDAY AFTERNOON WITH SOME MIXING…EVEN
WITH MORE CLOUDS THAN SUN. HIGHS TUESDAY AROUND 40 TO MID 40S IN
THE VALLEYS…AND MID TO UPPER 30S IN AREAS OF TERRAIN.

WINDS CONTINUE THROUGH TUESDAY NIGHT…AND PERIODS OF CLOUDS…
PERHAPS CONTINUING MOSTLY CLOUDY FOR MUCH OF THE NIGHT…DEPENDING
ON HOW MUCH LAKE EFFECT MOISTURE STREAMS EAST. THE DIFFERENCE IN
LAKE TEMPERATURES AND BOUNDARY LAYER TEMPERATURES IS NOT QUITE AS
IDEAL AS IT COULD BE FOR LAKE EFFECT SNOW BANDS…BUT STILL…
THERE SHOULD BE CONSIDERABLE CLOUDS REMAINING OVER THE REGION.
SO…LEANING TOWARD WARMER GUIDANCE FOR LOW TEMPERATURES TUESDAY
NIGHT. WEDNESDAY SHOULD SEE INCREASING PERIODS OF SUN WITH HIGHS
IN THE MID TO UPPER 30S…AROUND 30 TO LOWER 30S IN HIGHER
TERRAIN.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/…
WE START THIS LONG TERM PORTION WITH A PROGRESSIVE AND NEAR ZONAL
UPPER FLOW ACROSS THE NORTHERN TIER OF THE CONUS. THIS SHOULD ALLOW
THE SOUTHERN STREAM WAVE TO REMAIN SOUTH TO FURTHER REDUCE THE
IMPACT TO OUR REGION. HOWEVER…THERE IS AN ADDITIONAL SHORT WAVE
SEEN IN THE GLOBAL MODELS DIVING SOUTHWARD TOWARD THE UPPER GREAT
LAKES REGION. A THERMAL TROUGH AXIS APPEARS TO BE ASSOCIATED WITH
THIS FEATURE AS WE WILL RETAIN THE SLIGHT CHANCE POPS FOR LIGHT SNOW
WEDNESDAY NIGHT.

THURSDAY…THE AFOREMENTIONED SHORT WAVE ACROSS THE GREAT LAKES
REGION BEGINS TO AMPLIFY AS ADDITIONAL ENERGY DIVES INTO THIS
UPSTREAM TROUGH. IN TURN…THE DOWNSTREAM RIDGE WILL AMPLIFY WHICH
SHOULD RESULT IN A TRANQUIL PRECIP-FREE DAY. THE H850 TEMPS CLIMB
TOWARD -4C ALONG WITH A STRENGTHENING SOUTHWEST FLOW TO RESULT IN
TEMPS CLIMBING ABOVE FREEZING FOR MANY LOCATIONS.

THURSDAY NIGHT INTO FRIDAY…
LATEST TRENDS IN OPERATIONAL GLOBAL MODELS AND ENSEMBLES SUGGEST THE
UPSTREAM TROUGH WILL CONTINUE TO AMPLIFY AS RIDGE ACROSS THE WEST
COAST BUILDS. THIS IS WHERE THE INDIVIDUAL MODELS DIVERGE SOMEWHAT
WITH TRACK AND INTENSITY OF THE SURFACE FEATURES AND UPPER LEVEL
FEATURES. AN ASSOCIATED FRONTAL BOUNDARY IS EXPECTED TO APPROACH OR
JUST SLIDE EAST OF THE REGION DURING FRIDAY. THIS IS WHERE WE WILL
PLACE POPS FOR THE ENTIRE REGION WITH THE HIGHER VALUES NORTH AND
WEST OF ALBANY IN CLOSER PROXIMITY TO THE CYCLONIC FLOW. SINCE
BOUNDARY LAYER TEMPS WILL BE ABOVE FREEZING…THE CHANCE FOR RAIN
AND/OR SNOW SHOWERS WILL EXIST.

FRIDAY INTO SATURDAY…
LATEST ECMWF AND GFS ENSEMBLES ALL SIGNAL THE POTENTIAL FOR ANOTHER
COASTAL STORM THAT COULD IMPACT THE REGION DURING THIS TIME FRAME.
THIS POTENTIAL COAST SYSTEM IS EXPECTED TO DEVELOP IN THE VICINITY
OF THE DELMARVA REGION LATE IN THE DAY FRIDAY AND BEGIN ITS TRACK
NORTHEAST FRIDAY NIGHT INTO SATURDAY. A COUPLE OF THE ENSEMBLE
MEMBERS SUGGEST A RATHER DEEP LOW NEAR BOSTON BY 12Z SATURDAY.
THERE IS A HIGH STANDARD DEVIATION SEEN IN THE BOTH THE SURFACE AND
UPPER LEVEL FEATURES WHICH PLACES THIS FORECAST IN RATHER LOW
CONFIDENCE. THE ECMWF SIGNALS THAT THIS LOW TO TRACK ACROSS EASTERN
NEW ENGLAND WITH A DEFORMATION AXIS ACROSS UPSTATE NEW YORK FRIDAY
NIGHT INTO SATURDAY. WE WILL GO WITH A LOW POPS AT THIS TIME AND
WATCH TRENDS VERY CLOSELY.

TEMPERATURES THROUGH THE PERIOD WILL AVERAGE NEAR NORMAL WITH
PRECIPITATION NEAR TO PERHAPS ABOVE NORMAL /DEPENDING ON THE TRACK
OF THAT SYSTEM LATER IN THE WEEK/

&&

.AVIATION /00Z MONDAY THROUGH FRIDAY/…
VFR CONDITIONS SHOULD CONTINUE THROUGH THE OVERNIGHT HOURS…WITH
HIGH AND MID LEVEL CLOUDS ARRIVING AFTER MIDNIGHT…AND THICKENING
SHORTLY THEREAFTER.

WITHIN A FEW HOURS OF DAYBREAK…LIGHT PRECIPITATION SHOULD
OVERSPREAD THE TAF SITES. AT KPOU…THE PRECIP SHOULD START AS A
FREEZING RAIN/SLEET MIX. AT KALB/KPSF…THE PRECIP SHOULD BEGIN AS A
BRIEF MIX OF SNOW/SLEET…BEFORE TRANSITIONING TO A FREEZING
RAIN/SLEET MIX. AT KGFL…A PERIOD OF LIGHT SNOW AND SLEET SHOULD
BEGIN AROUND DAYBREAK.

AFTER THE PRECIP BEGINS…IT SHOULD EVENTUALLY CHANGE TO PLAIN
RAIN AT KPOU FIRST BY 13Z-14Z…THEN KALB AND KPSF BETWEEN 14Z-
16Z…AND LAST AT KGFL BY AROUND 17Z. THE STEADY LIGHT TO MODERATE
RAIN SHOULD THEN TAPER OFF TO PATCHY DRIZZLE DURING THE AFTERNOON.

CIGS AND VSBYS SHOULD BECOME MVFR TO IFR BY MID TO LATE
MORNING…WITH MAINLY IFR CONDITIONS EXPECTED FOR THE AFTERNOON.
AREAS OF GROUND FOG WILL BE POSSIBLE AS MILDER…MOIST AIR POURS
OVER THE COLD GROUND AND DEEP SNOWPACK ACROSS THE REGION. THIS
COULD POTENTIALLY RESULT IN LIFR/VLIFR VSBYS AT TIMES.

LIGHT/VARIABLE WINDS WILL TREND INTO THE SOUTH TO SOUTHEAST BY
DAYBREAK AT 5-10 KT…PERHAPS A BIT HIGHER AT KALB. EXPECT MAINLY
SOUTHEAST TO SOUTH WINDS THROUGH MONDAY MORNING AT 5-10
KT…TRENDING MORE INTO THE SOUTHWEST AT MOST SITES IN THE
AFTERNOON.

THERE IS A CHANCE FOR LOW LEVEL WIND SHEAR MONDAY MORNING…AS SFC
WINDS REMAIN FROM THE SOUTHEAST TO SOUTH AT GENERALLY LESS THAN 12
KT…WHILE WINDS AROUND 1500-2000 FT AGL INCREASE FROM THE SOUTH
TO SOUTHWEST AT 30-35 KT. AT THIS TIME…HAVE KEPT MENTION OF THIS
OUT OF TAFS…BUT THIS MAY NEED TO BE INCLUDED WITH SUBSEQUENT TAF
ISSUANCES.

OUTLOOK…

MON NIGHT…VFR/MVFR. CHC -SHSN.
TUE-TUE NIGHT…VFR/MVFR. SLIGHT CHC -SHRA/-SHSN.
WED-FRI…VFR. NO SIG WX.

&&

.HYDROLOGY…
TOMORROW…DAYTIME TEMPERATURES WILL BEGIN THE DAY BELOW
FREEZING…IN A WINTRY MIX…BUT RISE TO THE MID 30S TO MID 40S
DURING THE AFTERNOON. ICE GROWTH SHOULD SLOW AFTER TODAY. QPF OF
AROUND 0.35 INCHES IS LIKELY TOMORROW…PART OF WHICH WILL FALL AS
FREEZING RAIN AND SLEET. IT SHOULD HAVE NO IMMEDIATE SHORT TERM
HYDROLOGIC IMPACTS AND NO HYDRO ISSUES ARE ANTICIPATED THROUGH THE
NEXT FEW DAYS.

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…WINTER WEATHER ADVISORY FROM 4 AM TO NOON EST MONDAY FOR
CTZ001-013.
NY…WINTER WEATHER ADVISORY FROM 4 AM TO NOON EST MONDAY FOR
NYZ038>040-047>054-058>061-063>066.
WINTER WEATHER ADVISORY FROM 4 AM TO 6 PM EST MONDAY FOR
NYZ032-033-041>043-082>084.
MA…WINTER WEATHER ADVISORY FROM 4 AM TO NOON EST MONDAY FOR
MAZ025.
WINTER WEATHER ADVISORY FROM 4 AM TO 6 PM EST MONDAY FOR
MAZ001.
VT…WINTER WEATHER ADVISORY FROM 4 AM TO 6 PM EST MONDAY FOR
VTZ013>015.

&&

$$
SYNOPSIS…NAS
NEAR TERM…KL/NAS
SHORT TERM…NAS
LONG TERM…BGM
AVIATION…KL
HYDROLOGY…NAS

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