008
FXUS61 KALY 200525
AFDALY
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ALBANY NY
1225 AM EST FRI DEC 20 2024
SYNOPSIS
AN UPPER LEVEL DISTURBANCE WILL BRING PERIODS OF SNOW
FOR TODAY INTO TOMORROW WITH MOST AREAS SEEING A LIGHT ACCUMULATION.
IT WILL TURN BREEZY LATER TOMORROW ALONG WITH CLEARING SKIES AND
MUCH COLDER TEMPERATURES FOR THE REST OF THE WEEKEND. ANOTHER CHANCE
OF LIGHT SNOW IS EXPECTED FOR MONDAY NIGHT INTO CHRISTMAS EVE.
NEAR TERM /UNTIL 6 AM THIS MORNING/
AS OF 1225 AM EST...SURFACE HIGH PRESSURE IS PASSING WELL NORTH
OF THE REGION ACROSS QUEBEC. A LIGHT NORTHERLY FLOW OVER THE
AREA HAS ALLOWED FOR TEMPERATURES TO COOL OFF ACROSS THE ENTIRE
AREA, WITH TEMPERATURES DOWN INTO THE 20S AND ALREADY TEENS IN
THE ADIRONDACKS. LOWS LOOK TO FALL INTO THE MID TEENS TO MID 20S
BY DAYBREAK.
IR SATELLITE IMAGERY SHOWS MID LEVEL CLOUDS HAVE ALREADY MOVED
INTO THE REGION FROM THE WEST, THANKS TO THE NEXT SYSTEM
APPROACHING FROM THE MIDWEST. THIS SYSTEM IS STILL WELL OFF TO
THE WEST, WITH SURFACE LOW PRESSURE LOCATED JUST SOUTH OF
CHICAGO. BASED ON THE LATEST CAMS, DRY WEATHER IS EXPECTED
THROUGH THE REST OF THE OVERNIGHT HOURS, WITH ANY LIGHT SNOW
AHEAD OF THIS FEATURE ONLY REACHING AS FAR EAST AS WESTERN NEW
YORK AND SOUTHERN TIER TOWARDS SUNRISE FRIDAY. OTHERWISE, IT
WILL REMAIN OVERCAST ACROSS THE REGION THROUGH THE REST OF THE
NIGHT WITH LIGHT NORTHERLY WINDS.
SHORT TERM /6 AM THIS MORNING THROUGH SATURDAY NIGHT/
KEY MESSAGE:
- SLIPPERY TRAVEL INCLUDING THE FRIDAY P.M COMMUTE FROM A TOTAL
OF 1 TO 3 INCHES OF LIGHT/FLUFFY SNOW EXPECTED FROM LIGHT
SNOW TOMORROW INTO SATURDAY MORNING. WHILE SNOW WILL MAINLY BE
LIGHT, SNOW LIKELY TURNS STEADY FOR A PERIOD SATURDAY MORNING
BEFORE ENDING. PROBABILITIES FOR GREATER THAN 2 INCHES OF
SNOW RANGE 30 TO 50% MAINLY FOR AREAS WEST OF THE HUDSON
RIVER.
DISCUSSION:
WE START OFF OUR FRIDAY DRY YET CLOUDY BUT A WEAKENING CLIPPER
DISTURBANCE AND UPPER LEVEL TROUGH FROM THE MIDWEST/OHIO VALLEY
WILL TRACK EASTWARD INTO THE MID-ATLANTIC. WHILE THE STRONGEST
CYCLONIC VORTICITY ADVECTION WILL BE DISPLACED MAINLY TO OUR
SOUTH AND EAST, SUFFICIENT WEAK WARM AIR ADVECTION WILL DEVELOP
ACROSS EASTERN NY AND WESTERN NEW ENGLAND TO SUPPORT LIGHT SNOW
DEVELOPING AND SPREADING EASTWARD ACROSS THE AREA BY MID TO LATE
MORNING FOR AREAS MAINLY WEST OF THE CAPITAL DISTRICT BEFORE
ENOUGH MOISTURE/FORCING ADVANCES EASTWARD INTO THE CAPITAL
DISTRICT, MID-HUDSON VALLEY AND WESTERN NEW ENGLAND BY EARLY TO
MID AFTERNOON. TEMPERATURES ONLY RISE INTO THE UPPER 20S TO LOW
30S SO TEMPERATURES WILL SUPPORT AN ALL SNOW EVENT. WHILE SNOW
WILL REMAIN MAINLY LIGHT THROUGH THE AFTERNOON, UPSLOPE
ENHANCEMENTS IN THE EASTERN AND NORTHERN CATSKILLS INCLUDING THE
HELDERBERGS WILL LEAD TO STEADIER SNOWFALL RATES. MEANWHILE, A
MORE POTENT COASTAL DISTURBANCE WILL BE DEVELOPING OFF THE EAST
COAST WITH THE STRONGEST MOISTURE PLUME REMAINING OFF SHORE.
THUS, OVERALL MOISTURE AND FORCING AMOUNTS FOR EASTERN NY AND
WESTERN NEW ENGLAND REMAIN LIGHT THROUGH SUNSET. ENSEMBLE AND
PROBABILISTIC GUIDANCE IS IN GOOD AGREEMENT WITH TOTAL QPF
AMOUNTS REMAINING AROUND OR UNDER 0.05" FOR MOST AREAS THROUGH
00 UTC FRIDAY. THUS, TOTAL SNOWFALL AMOUNTS GENERALLY EXPECTED
TO RANGE FROM 0.5 TO 1.5 INCHES (HIGHEST AMOUNTS IN THE
NORTHERN/EASTERN CATSKILLS) WITH SLRS NEAR 12 - 14:1 GIVING US A
LIGHT/FLUFFY SNOW. DESPITE THE LOW SNOWFALL AMOUNTS, SOME
SLIPPERY TRAVEL CONDITIONS EXPECTED FOR THE FRIDAY EVENING
COMMUTE.
WARM AIR ADVECTION WEAKENS FRIDAY NIGHT AS THE PARENT SHORTWAVE
TROUGH ESCAPES OFFSHORE. THUS, SNOWFALL RATES WILL LIKELY TURN
EVEN WEAKER FRIDAY NIGHT AND SHOULD EVEN COME TO AN END AT
TIMES, ESPECIALLY AFTER MIDNIGHT. TEMPERATURES OVERNIGHT STAY
CHILLY IN THE 20S WITH EVEN TEENS IN THE SOUTHERN/WESTERN
ADIRONDACKS AND SOUTHERN VT SO ANY UNTREATED SURFACES WILL
REMAIN SLIPPERY.
HEADING INTO THE PRE-DAWN HOURS TONIGHT INTO EARLY SATURDAY
MORNING (09 - 15 UTC), SNOWFALL RATES PICK BACK UP AGAIN AS A
POTENT ARCTIC FRONT AND UPPER LEVEL TROUGH APPROACH FROM THE
WEST. IN FACT, HIGH RESOLUTION GUIDANCE SHOWS POTENTIAL FOR A
MESOSCALE SNOW BAND TO DEVELOP OVER THE CAPITAL DISTRICT IN
RESPONSE TO SOME MOHAWK HUDSON CONVERGENCE (MHC). FORECAST
SOUNDINGS SHOW STRONG LIFT INTERSECTING THE SNOW GROWTH ZONE
DURING THIS WINDOW SUPPORTING HIGHER SLR NEARING 15:1 AND A
QUICK 1 TO 2 INCHES OF LIGHT/FLUFFY SNOW. AS WINDS BECOME MORE
NORTHWESTERLY LATE SATURDAY MORNING BEHIND THE ARCTIC FRONT, THE
MHC SIGNAL WEAKENS AND THE SNOW BAND DIMINISHES. ALL SNOW ENDS
BY MIDDAY SATURDAY. NORTHWEST WINDS TURN BREEZY BEHIND THE
FRONT, BECOMING SUSTAINED 10 - 15KTS WITH GUSTS UP TO 25KTS.
WITH A FRESH 1-3 INCHES OF LIGHT/FLUFFY SNOW ON THE GROUND AND
BREEZY WINDS, SOME SNOW MAY BLOW AROUND. OTHERWISE, IT WILL FEEL
QUITE CHILLY BETWEEN THE WINDS AND TEMPERATURES STRUGGLING TO
RISE OUT OF THE 20S. IT WILL FEEL MORE LIKE SINGLE DIGITS AND
TEENS.
LONG TERM /SUNDAY THROUGH THURSDAY/
KEY MESSAGES:
- HIGH CONFIDENCE IN UNUSUALLY COLD TEMPERATURES SUNDAY AND SUNDAY
NIGHT.
- THERE IS A 40 TO 60 PERCENT PROBABILITY FOR A WIDESPREAD LIGHT
SNOW ACROSS THE REGION ON CHRISTMAS EVE.
DISCUSSION:
AN UPPER-LEVEL TROUGH AXIS BEGINS TO DEPART TO THE EAST AS A ~1036
HPA HIGH PRESSURE SYSTEM BUILDS IN FROM THE WEST. THE CORE OF THE
COLD AIR ALOFT MOVES IN SATURDAY NIGHT INTO SUNDAY WITH 850 HPA
TEMPERATURES BETWEEN -16C AND -20C (ABOUT -2 STDEV). ANY LINGERING
LAKE-EFFECT AND UPSLOPE SNOW SHOWERS WILL TAPER OFF SATURDAY EVENING
ALONG WITH PARTIAL CLEARING. DESPITE A LINGERING BREEZE,
TEMPERATURES SATURDAY NIGHT WILL FALL BACK TO THE SINGLE DIGITS IN
MOST AREAS WITH SOME HIGHER ELEVATIONS AREAS BELOW ZERO. MOST AREAS
LOOK TO FALL SHORT OF COLD ADVISORY CRITERIA OF -10 TO -20 F.
FAIR BUT COLD WEATHER IS EXPECTED ON SUNDAY AND SUNDAY NIGHT WITH
HIGH PRESSURE OVERHEAD. HIGHS WILL ONLY TOP OUT IN THE TEENS TO
LOWER 20S IN MOST AREAS WITH SOME HIGHER ELEVATION AREAS ONLY IN THE
SINGLE DIGITS. IDEAL RADIATIONAL COOLING CONDITIONS ARE EXPECTED
SUNDAY NIGHT WITH A MAINLY CLEAR SKY AND LIGHT WINDS WITH LOWS IN
THE LOW SINGLE DIGITS TO BELOW ZERO. PORTIONS OF THE ADIRONDACKS MAY
FALL BELOW -10F. A LIGHT SOUTHERLY RETURN FLOW WILL AID IN
TEMPERATURES REBOUNDING BACK INTO THE 20S ON MONDAY WITH CONTINUED
FAIR WEATHER.
CONFIDENCE CONTINUES TO INCREASE ON A LOW PRESSURE SYSTEM TO CROSS
THE REGION MONDAY NIGHT THROUGH TUESDAY, CHRISTMAS EVE. THERMAL
PROFILES ARE COLD ENOUGH FOR A PERIOD OF SNOW FOR ALL AREAS. THERE
REMAINS SOME SPREAD IN THE AMOUNT OF QPF WITH THIS SYSTEM AND,
THEREFORE, SNOWFALL AMOUNTS, BUT TRENDS WILL BE MONITORED AS THIS
MAY IMPACT HOLIDAY TRAVEL. THIS SYSTEM MAY DEPART IN TIME FOR DRIER
WEATHER TO RETURN BY CHRISTMAS DAY WITH TEMPERATURES RETURNING TO
NEAR NORMAL VALUES.
AVIATION /06Z FRIDAY THROUGH TUESDAY/
THROUGH 06Z SATURDAY...FLYING CONDITIONS ARE CURRENTLY VFR AT ALL
TERMINALS AND SHOULD STAY VFR THROUGH THE REMAINDER OF TONIGHT. LOW
PROBABILITY FOR SOME PATCHY CLOUDS BETWEEN 2000-3000 FT LATE TONIGHT
AT PSF, BUT CONFIDENCE IS NOT HIGH ENOUGH TO INCLUDE MVFR CIGS.
CLOUD BASES LOWER THROUGH THE MORNING TOMORROW, BECOMING OVERCAST
BETWEEN 3000-4000 FT BY EARLY TO MID-MORNING. LIGHT SNOW IS EXPECTED
TO BEGIN TOMORROW AFTERNOON. STILL MAY NEED TO ADJUST TIMING
SLIGHTLY, BUT BETWEEN 17-19Z AT ALB/GFL/POU AND 18-20Z AT PSF STILL
SEEMS LIKE THE MOST LIKELY START TIME OF SNOW. SNOW WILL LEAD TO IFR
VSBYS, POSSIBLY DOWN TO 1SM TOMORROW AFTERNOON AND EARLY EVENING.
EXPECTING CIGS TO DROP BELOW FUEL-ALTERNATE CRITERIA AS WELL
TOMORROW SHORTLY AFTER SNOW BEGINS, WITH POCKETS OF IFR CIGS
POSSIBLE AS WELL TOMORROW AFTERNOON AND EVENING. SNOW MAY TAPER OFF
TOMORROW EVENING AND EARLY TOMORROW NIGHT FOR A PERIOD, BUT SHOULD
REDEVELOP AROUND 06Z. EVEN IF SNOW DOES TAPER OFF FOR A PERIOD, CIGS
SHOULD REMAIN BELOW 2000 FT. WINDS WILL BE FROM THE NORTHEAST AT 4-8
KT THROUGH MOST OF THE TAF PERIOD, BECOMING MORE NORTHERLY AT 4-8 KT
TOMORROW AFTER 00-03Z.
OUTLOOK...
FRIDAY NIGHT: MODERATE OPERATIONAL IMPACT. CHANCE OF SHSN.
SATURDAY: MODERATE OPERATIONAL IMPACT. BREEZY. CHANCE OF SHSN.
SATURDAY NIGHT: NO OPERATIONAL IMPACT. NO SIG WX.
SUNDAY: NO OPERATIONAL IMPACT. NO SIG WX.
SUNDAY NIGHT: NO OPERATIONAL IMPACT. NO SIG WX.
MONDAY: NO OPERATIONAL IMPACT. NO SIG WX.
MONDAY NIGHT: MODERATE OPERATIONAL IMPACT. CHANCE OF SN.
TUESDAY: MODERATE OPERATIONAL IMPACT. CHANCE OF SN.
ALY WATCHES/WARNINGS/ADVISORIES
CT...NONE.
NY...NONE.
MA...NONE.
VT...NONE.
SYNOPSIS...FRUGIS
NEAR TERM...FRUGIS
SHORT TERM...SPECIALE
LONG TERM...RATHBUN
AVIATION...MAIN
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