991
FXUS61 KGYX 182017 AAD
AFDGYX
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE GRAY ME
317 PM EST WED DEC 18 2024
SYNOPSIS
A WEAK WINTER STORM WILL MOVE THROUGH SOUTHERN NEW ENGLAND
TONIGHT AND SPREAD PRECIPITATION ACROSS MOST OF NORTHERN NEW
ENGLAND. RATHER MILD TEMPERATURES FOR THE SECOND HALF OF
DECEMBER WILL LEAD TO A MIX OR RAIN AND SNOW DEPENDING ON
SURFACE TEMPERATURES. MOSTLY RAIN IS EXPECTED ACROSS SOUTHERN
NEW HAMPSHIRE AND THE SOUTHWESTERN MAINE INTO THE LOWER KENNEBEC
RIVER VALLEY. SOME LIGHT SNOW WILL ACCUMULATE IN THE HIGHER
TERRAIN. COOLER AIR COME IN BEHIND THE SYSTEM FOR THURSDAY AND
THURSDAY NIGHT. A WEAK CLIPPER PASSES THROUGH FRIDAY NIGHT,
WITH TRULY ARCTIC AIR MOVING INTO NEW ENGLAND FOR THE WEEKEND
THROUGH EARLY NEXT WEEK.
NEAR TERM /THROUGH TONIGHT/
SHORT DURATION...MARGINAL WINTER STORM SYSTEM ANTICIPATED
TONIGHT. OVERALL TRENDS TODAY HAVE CONTINUED TOWARDS THE WARMER
AND LESS SNOWY.
THE OVERALL STORM TRACK HAS CHANGED LITTLE FROM YESTERDAY.
HOWEVER TEMPS THIS AFTERNOON WERE ABLE TO CLIMB SEVERAL DEGREES
THAN FORECAST THRU THE THIN CLOUD COVER...LEAVING US WITH A
WARMER STARTING POINT THAN PREVIOUS MODEL RUNS. OF MORE
CONSEQUENCE IS THAT THE OVERALL FORCING ALOFT HAS WEAKENED
CONSIDERABLY. DPROG/DT OF WAA AND FRONTOGENESIS SHOWS THAT
MAGNITUDE HAS CONSISTENTLY COME DOWN EACH SUCCESSIVE MODEL RUN.
WHAT THIS DOES IS REDUCE OUR PRECIP INTENSITIES OVERNIGHT. HOW
DOES THAT EFFECT THE SNOW OUTPUT? THE PRIMARY DRIVER OF GETTING
SURFACE TEMPS TO NEAR FREEZING WAS COMING THRU COOLING THAT
OCCURS DUE TO MELTING SNOWFLAKES AS THEY FALL. HEAVY SNOW ALOFT
IS MORE LIKELY TO DROP SURFACE TEMPS TO NEAR FREEZING...BUT THE
LIGHTER SNOW EXPECTED TONIGHT WILL STRUGGLE TO COOL THE SURFACE.
SO OVERALL MY THINKING IS LIGHT SNOW ACCUMULATIONS IN THE
MTNS...WITH A RAIN/SNOW MIX THRU THE FOOTHILLS. SOME LIGHT
ACCUMULATION IS POSSIBLE THERE...MAINLY ON GRASSY OR ELEVATED
SURFACES. THRU I-95 AND CLOSER TO THE COAST IT SHOULD BE ALL
RAIN. THE MIDCOAST TOWARDS THE END OF THE PRECIP MAY COOL ENOUGH
FOR A QUICK HALF TO 1 INCH...BUT OVERALL AMOUNTS ARE TOO LOW AND
IMPACTS EXPECTED TO OCCUR OVERNIGHT ENOUGH NOT TO EFFECT THE
MORNING COMMUTE. SO NO WINTER WEATHER ADVISORIES ARE
ANTICIPATED.
SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/
WINDS WILL LARGELY BE NORTHWESTERLY EARLY THU...ALLOWING
DOWNSLOPING FLOW TO CLEAR OUT CLOUDS AND PRECIP SOUTH OF THE
MTNS. NORTHWEST UPSLOPE WILL KEEP SNOW SHOWERS GOING IN THE MTNS
EARLY IN THE DAY. BY AFTERNOON FROUDE NUMBER FORECASTS ARE QUITE
HIGH...SO SNOW SHOWERS AND FLURRIES WILL LIKELY HAVE NO TROUBLE
CROSSING THE RIDGELINES AND MOVING SOUTHEAST TOWARDS I-95. I
HAVE ADDED FLURRIES TO THOSE REGIONS WHERE I EXPECT SNOW TO BE
FALLING BUT NO ACCUMULATION LIKELY. CAA NORTHWEST WINDS CONTINUE
THU NIGHT...AND THAT MIXING WILL KEEP TEMPS STEADILY FALLING VS
RADIATING. I HAVE BLENDED IN RAW 2 M TEMPS RATHER THAN MOS TO
ELIMINATE ANY RADIATIONAL COOLING TREND.
LONG TERM /FRIDAY THROUGH WEDNESDAY/
IMPACTS:
- SOME OF THE COLDEST AIR OF THE CALENDAR YEAR OF 2024 WILL
BRING SUB-ZERO WIND CHILL READINGS, ESPECIALLY ON SATURDAY
NIGHT TO THE MAJORITY OF THE REGION.
- LIGHT SNOW SHOWERS POSSIBLE ON FRIDAY
- VERY LOW CONFIDENCE FOR LIGHT SNOW ON CHRISTMAS EVE
OVERVIEW: NORTHEAST CONUS WILL BE UNDER A LONGWAVE TROUGH FRIDAY
THROUGH MONDAY NEXT WEEK BRINGING WELL BELOW NORMAL TEMPERATURES
THIS WEEKEND. 500MB HEIGHTS INCREASE TUESDAY THROUGH WEDNESDAY
NEXT WEEK WITH A RETURN TO ZONAL FLOW. OVERALL FORECAST
CONFIDENCE OF PATTERN EVOLUTION IS ABOVE NORMAL THROUGH MONDAY
BEFORE SPREAD INCREASES SIGNIFICANTLY BY CHRISTMAS.
FORECAST DETAILS: PERIOD WILL START ON FRIDAY WITH A 500MB
TROUGH MOVING INTO THE NORTHEAST WITH A LOW OVER THE GREAT LAKES
AND A DEVELOPING SURFACE LOW OFF THE MID-ATLANTIC COAST. THIS
SYSTEMS LOOK TO PHASE TOO LATE TO BRING APPRECIABLE SNOWFALL TO
OUR REGION, WITH GOOD AGREEMENT THAT THE PHASING WILL OCCUR
OVER THE CANADIAN MARITIMES IN ALL MODEL CAMPS. THERE COULD
STILL BE SOME LIGHT SNOW ON FRIDAY AND EVEN SOME OCEAN ENHANCED
SNOW SHOWER ACTIVITY. STRONG CAA ON SATURDAY AS A ARCTIC SHOT OF
AIR MOVES INTO NEW ENGLAND, THIS WILL BRING WIND CHILL VALUES
IN THE SUB-ZERO READINGS FROM SATURDAY EVENING THROUGH SUNDAY
MORNING FOR MOST AREAS, WITH A VERY COLD WEEKEND EXPECTED AT THE
SKI RESORTS. SNOW SHOWER ACTIVITY WILL PEAK IN THE MOUNTAINS ON
NW FLOW ON SATURDAY BEFORE ENDING BY SUNDAY MORNING. HIGH
PRESSURE CRESTS OVER THE AREA SUNDAY NIGHT WITH A POSSIBLE
OPTIMAL RADIATIONAL COOLING NIGHT, THE QUESTION WILL BE, HOW LOW
WILL IT GO IN REGARDS TO TEMPERATURES. SOME COLD SPOTS COULD
REACH -15F WITH CLOSE TO ZERO FOR MOST AREAS. TEMPERATURES WILL
BEGIN TO MODERATE ON MONDAY AS FLOW BECOMES MORE ZONAL.
FORECAST CONFIDENCE IS VERY LOW FOR SENSIBLE WEATHER NEXT WEEK
WITH A WEAK WAVE COMING ACROSS THE UPPER PLAINS THAT THE MODELS
AREN'T SURE TO DO WITH. DIFFICULT TO LATCH ONTO ANYTHING AT THIS
POINT, SO STUCK CLOSE WITH THE NBM, BUT A PERIOD OF SNOW CAN'T
COMPLETELY BE RULES AT BEFORE CHRISTMAS FOR COASTAL AREAS.
AVIATION /20Z WEDNESDAY THROUGH MONDAY/
SHORT TERM...VFR CONDITIONS PREVAIL CURRENTLY BUT WIDESPREAD IFR
OR LOWER CONDITIONS ARE LIKELY TONIGHT. PRECIP WILL OVERSPREAD
THE AREA THIS EVENING AND CIGS WILL LOWER TO MAINLY IFR. RA IS
LIKELY AT MOST TAF SITES...BUT HIE AND LEB AND TO A LESSER
EXTENT CON MAY BE ABLE TO STAY ALL OR MOSTLY SN. WIND SHIFT AND
AN END TO STEADY PRECIP ARRIVES AROUND DAYBREAK THU. VFR RETURNS
SOUTH OF THE MTNS...BUT MVFR CIGS REMAIN POSSIBLE AT HIE WHERE
UPSLOPING CONTINUES THRU THU. WIDESPREAD VFR THU NIGHT.
LONG TERM...MVFR CIGS AND VISIBILITY COULD POSSIBLE RETURN ON
FRIDAY DUE TO SOME LIGHT SHOWER ACTIVITY, BUT OVERALL AVIATION
IMPACTS WILL BE LIMITED. WILL HAVE TO WATCH PORTSMOUTH DUE TO
THE POTENTIAL OF SOME LOCAL OCEAN ENHANCEMENT SNOW FRIDAY
AFTERNOON BUT A LOW PROBABILITY OUTCOME AT THIS TIME. COLD AND
WINDY FOR THE REMAINDER OF THE WEEKEND, WITH SNOW SHOWERS
IMPACTING WHITEFIELD ON SATURDAY.
MARINE
SHORT TERM...LIGHT AND VARIABLE WINDS THIS EVENING WILL SHIFT TO
NORTHWESTERLY BEHIND DEPARTING SURFACE LOW EARLY THU. WIND GUSTS
AROUND 25 KT ARE LIKELY OUTSIDE THE BAYS AND POSSIBLE IN THE
BAYS THRU THU AFTERNOON. SCA REMAINS IN EFFECT FOR ALL WATERS.
LONG TERM...A DEVELOPING SURFACE LOW FRIDAY WILL STAY WELL
OFFSHORE BEFORE DEEPENING OVER THE CANADIAN MARITIMES THIS
WEEKEND. THIS WILL BRING SCA CONDITIONS TO THE WATERS ONCE AGAIN
AS A COLD FRONT AND ARCTIC SHOT OF AIR PUSH THROUGH THE AREA.
THIS WILL BE THE COLDEST AIRMASS OF THE SEASON THUS FAR.
GYX WATCHES/WARNINGS/ADVISORIES
ME...NONE.
NH...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 5 AM TO 7 PM EST THURSDAY FOR
ANZ150>154.
NEAR TERM...LEGRO
SHORT TERM...LEGRO
LONG TERM...DUMONT
AVIATION...DUMONT/LEGRO
MARINE...DUMONT/LEGRO
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