FXUS61 KGYX 071518
AFDGYX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAY ME
1018 AM EST MON DEC 7 2009
.SYNOPSIS...
A WEAK BOUNDARY OVER SOUTHEASTERN QUEBEC WILL DRIFT SOUTH INTO
THE MOUNTAINS TODAY. WEAK LOW PRESSURE OVER THE NORTHERN PLAINS
WILL RACE EASTWARD ALONG THIS BOUNDARY LATER TODAY AND TONIGHT
PRODUCING A FEW SNOW SHOWERS WITH SOME LIGHT ACCUMULATION POSSIBLE
FOR MOUNTAIN SECTIONS. HIGH PRESSURE WILL BUILD OVER THE AREA TUESDAY
AND TUESDAY NIGHT. A WARM FRONT EXTENDING FROM LOW PRESSURE OVER
THE GREAT LAKES WILL APPROACH THE REGION LATE TUESDAY NIGHT AND
WEDNESDAY. THIS WILL BRING SNOW...RAIN AND GUSTY WINDS NEAR THE
COAST. AS THE FRONT PASSES WEDNESDAY EVENING...THE PRECIPITATION
WILL TAPER OFF LATER AT NIGHT. HIGH PRESSURE BUILDING IN BEHIND
THE SYSTEM THURSDAY AND FRIDAY WILL BRING BLUSTERY AND COLDER
CONDITIONS TO NORTHERN NEW ENGLAND.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
LIGHT SNOW SHOWERS ACROSS THE HIGHER TERRAIN AROUND DAYBREAK WILL
SPREAD SOUTHWARD THIS AFTERNOON AND BECOME MORE WIDESPREAD...AS
EVIDENCED BY SATELLITE AND SURFACE OBSERVATIONS ACROSS NORTHERN
NEW YORK. HAVE KEPT THE FORECAST SIMILAR TO THE PREVIOUS FORECAST
EXCEPT FOR TOUCHING UP THE SNOW SHOWER WORDING A LITTLE BIT.
TEMPERATURE AND SKY TRENDS GENERALLY UNTOUCHED.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM TUESDAY/...
1030 MILLIBAR HIGH CENTER OVER DELMARVA REGION BUILDS BY TO OUR
SOUTH TODAY AND WILL PROVIDE SOME EARLY SUNSHINE TO FAR SOUTHERN
AND EASTERN SECTIONS BEFORE CLOUDS BEGIN TO THICKEN AHEAD OF NEXT
DISTURBANCE. SHORT WAVE OVER NORTHERN PLAINS EARLY THIS MORNING
WILL RACE EAST-NORTHEAST ALONG WITH ASSOCIATED WEAK SURFACE LOW.
THIS FEATURE WILL TRACK ACROSS NORTHERN NEW ENGLAND LATE TODAY AND
EARLY TONIGHT ALONG THE WEAK BOUNDARY CURRENTLY OVER SOUTHEASTERN
QUEBEC. EXPECT SNOW SHOWER ACTIVITY TO INCREASE IN COVERAGE BY
AFTERNOON AHEAD OF THIS DISTURBANCE WITH BULK OF THE ACTIVITY
CONFINED TO THE NORTHERN HALF OF THE FORECAST AREA WHERE AN INCH
OF ACCUMULATION IS NOT OUT OF THE QUESTION. THE SYSTEM EXITS THE
COAST IN THE PREDAWN HOURS WITH ANY LINGERING FLURRIES CONFINED TO
THE HIGHER TERRAIN. A BLEND OF MET/MAV USED TO INITIALIZE MAX AND
MIN TEMPERATURES WITH SREF AS FIRST GUESS FOR POP FIELDS.
&&
.LONG TERM /TUESDAY THROUGH SUNDAY/...
THE MAIN EVENT WILL BE WEDNESDAY AND WEDNESDAY NIGHT...WITH THE
POTENTIAL FOR A HIGH IMPACT EVENT WITH REGARD TO SNOW INLAND AND
WIND CLOSER TO THE COAST. AFTER THAT...COLD AND BLUSTERY CONDITIONS
INTO THE UPCOMING WEEKEND WITH THE COLDEST AIR SO FAR THIS SEASON.
COLD AIR ADVECTION BEHIND A PASSING SHORT WAVE WILL RESULT IN AN
UPSLOPE/DOWNSLOPE CLOUD PATTERN TUESDAY MORNING. THE AIRMASS MAY
BE TOO DRY FOR MUCH IN THE WAY OF UPSLOPE SNOW IN THE FAVORED
LOCATIONS...WITH DRY CONDITIONS ELSEWHERE. THE BEST COLD AIR
ADVECTION OCCURS THROUGH EARLY AFTERNOON...SO WINDS COULD GUST TO
20 MPH DURING THAT TIME. HIGHS TUESDAY WERE BASED ON A MOS BLEND.
MODELS ARE IN FAIRLY GOOD AGREEMENT WITH THE MASS FIELDS FOR
TUESDAY NIGHT INTO WEDNESDAY NIGHT...AND THERE IS BETTER CONFIDENCE
IN THE OVERALL SYNOPTIC SETUP. THE COLUMN STARTS COLD AND DRY AND
MOISTENS IN THE INCREASING WARM AIR ADVECTION. BECAUSE OF THIS...LEFT
THE MENTION OF PRECIPITATION OUT OF THE FORECAST FOR TUESDAY NIGHT.
THE STRONG WARM AIR ADVECTION AND THICKENING CLOUD COVER WILL
RESULT IN LOWS OCCURRING BEFORE MIDNIGHT...WITH STEADY OR SLOWLY
RISING TEMPERATURES THEREAFTER.
A LONG WAVE TROUGH THAT STARTS IN THE INTERMOUNTAIN WEST CRESTS
ACROSS THE PLAINS...AND THE WAVE BREAKS ACROSS THE MIDWEST WEDNESDAY.
THE WARM AIR ADVECTION BECOMES VERY IMPRESSIVE WEDNESDAY MORNING
AHEAD OF A WARM FRONT (OR OCCLUSION) EXTENDING FROM DEEP LOW PRESSURE
OVER THE GREAT LAKES. THE FRONTOGENETIC FORCING BETWEEN 850-700 MB
PEAKS ACROSS NEW HAMPSHIRE AND SOUTHWEST MAINE LATE WEDNESDAY
MORNING AND EARLY WEDNESDAY AFTERNOON. WOULD EXPECT TO SEE A
FRONTOGENETICALLY FORCED BAND OF MODERATE TO HEAVY PRECIPITATION
TO DEVELOP ACROSS SOUTHEAST NEW HAMPSHIRE AND STRETCH ACROSS
INTERIOR SECTIONS OF WESTERN AND CENTRAL MAINE.
AS MENTIONED EARLIER...THE COLUMN STARTS COLD...AND THIS SHOULD RESULT
IN THE PRECIPITATION STARTING AS SNOW IN ALL AREAS. HOWEVER...WITH
THE SURFACE FRONT TO THE SOUTH...THE BOUNDARY LAYER WILL BECOME
THE PROBLEM FOR PRECIPITATION TYPE NEAR THE COAST. THE BANDED SNOW
MAY PRODUCE ADVISORY LEVELS SNOWS NEAR THE COAST BEFORE THE
BOUNDARY WARMS. FURTHER INLAND...THIS PROCESS MAY BE SHUNTED AS
MODELS HINT AS SOME WEAK COLD AIR DAMMING. HOWEVER...THE STRONG
WARM AIR ADVECTION WILL OVERWHELM THE COLUMN...AND BY LATE AFTERNOON
JUST ABOUT ALL AREAS THE COLUMN WILL BECOME TOO WARM TO SUPPORT
SNOWFLAKE PRODUCTION.
THE CRITICAL FORECAST QUESTION BECOMES...WILL THE BANDING
POTENTIAL PUT DOWN WARNING CRITERIA SNOW BEFORE THE COLUMN BECOMES
TOO WARM TO SUPPORT SNOWFLAKE PRODUCTION. AT THIS POINT...THIS
APPEARS AT LEAST POSSIBLE. MOST AREAS IN THE FRONTOGENETIC AREA
SEE A MAXIMIZATION OF THE SNOW GROWTH AREA BETWEEN 1400 UTC AND
2100 UTC WEDNESDAY. THIS COULD RESULT IN 1+ INCH PER HOUR SNOW FOR
A FEW HOURS BEFORE ANY MIX. THE BEST CHANCE OF THIS WILL EXTEND
FROM JUST NORTH OF CON THROUGH IZG TO NORTH OF AUG AND WVL.
MUCH TOO EARLY FOR ANY TYPE OF WATCH...AND THIS INFORMATION WILL
BE INCLUDED IN THE HAZARDOUS WEATHER OUTLOOK.
THE WIND FIELD BECOMES VERY IMPRESSIVE DURING THE LATE MORNING AND
AFTERNOON. THE GRADIENT ITSELF COULD SUPPORT WIND ADVISORY GUSTS
JUST AHEAD OF THE WARM FRONT OR OCCLUSION. 0000 UTC NAM SOUNDINGS
SUGGEST 50 TO 60 KNOT WINDS MAY BE AVAILABLE NEAR THE TOP OF THE
LOW WARM AIR ADVECTION INDUCED INVERSION. FOR NOW...INCLUDED
STRONG WIND GUSTS IN THE GRIDDED FORECASTS...BUT AGAIN MUCH TOO
EARLY FOR ANY TYPE OF HEADLINES.
THE AFTERNOON TIDE WEDNESDAY WOULD BE A TIDE THAT WOULD NEED TO
BE WATCHED. WHILE THE ASTRONOMICAL TIDE IS RELATIVELY LOW (9.5 FT
AT PORTLAND)...A STORM SURGE PRODUCED BY STRONG WINDS AND PRESSURE
FALLS...COMBINED WITH BUILDING SEAS...COULD RESULT IN SPLASHOVER.
THE HEAVIEST PRECIPITATION SHOULD END WITH THE PASSAGE OF THE OCCLUSION
WEDNESDAY EVENING FROM SOUTHWEST TO NORTHEAST. AFTER THIS...THE
MAIN SYNOPTIC LIFT MOVES THROUGH BEFORE 0600 UTC THURSDAY. MAINTAINED
A MENTION OF PRECIPITATION FOR ALL AREAS...WITH SOUTHERN ZONES
HAVING THE LOWEST CHANCE OF RAIN. WEST WINDS COULD BECOME GUSTY AS
THE MIXED LAYER INCREASES BEHIND THE FRONT AND 40 KNOTS WOULD BE
AVAILABLE AT THE TOP OF THE INVERSION.
NOT MUCH CHANGE IN TEMPERATURE IS EXPECTED RIGHT BEHIND THE FRONT...
BUT MOST AREAS WILL NOT BE ABLE TO PRODUCE SNOWFLAKES. THIS MEANS
THERE COULD BE A PERIOD OF FREEZING RAIN AWAY FROM THE COAST.
CYCLONIC FLOW WILL RESULT IN CLOUDS WITH UPSLOPE SNOW SHOWERS
LATER WEDNESDAY NIGHT AND THURSDAY. AFTER THIS...BLUSTERY AND
COLDER FOR THE WEEKEND.
&&
.AVIATION /15Z MONDAY THROUGH FRIDAY/...
SHORT TERM /THROUGH 11Z TUESDAY/...VFR. AREAS OF MVFR CEILINGS AND
VSBYS EXPECTED MAINLY IN THE HIGHER TERRAIN WITH SNOW SHOWERS THROUGH
EARLY TUESDAY MORNING.
LONG TERM /TUESDAY THROUGH FRIDAY/...VFR CONDITIONS ARE EXPECTED
TUESDAY AND TUESDAY EVENING AS HIGH PRESSURE BUILDS OVER NORTHERN
NEW ENGLAND. AS A WARM FRONT APPROACHES FROM CENTRAL NEW ENGLAND
LATE TUESDAY NIGHT...CONDITIONS WILL DETERIORATE FROM SOUTHWEST TO
NORTHEAST BETWEEN 0600 UTC AND 1200 UTC WEDNESDAY. BY 1500 UTC
WEDNESDAY...ALL TERMINALS SHOULD BE LIFR WITH PRECIPITATION AND
LOW CEILINGS. LOW LEVEL WIND SHEAR IS POSSIBLE WEDNESDAY...WITH
WINDS GUSTING NEAR 35 KNOTS AT KPWM AND KPSM INTO WEDNESDAY
EVENING.
AFTER THE WARM FRONT OR OCCLUSION PASSES WEDNESDAY EVENING...THE
PRECIPITATION WILL START TO TAPER OFF...BUT LOW CEILINGS ARE EXPECTED
THROUGH 1200 UTC THURSDAY. BEHIND THE FRONT...SOUTHWEST WINDS MAY
GUST TO 25 KNOTS WEDNESDAY NIGHT AT KPWM...KPSM AND KAUG.
AS LOW PRESSURE MOVES INTO THE MARITIMES AND HIGH PRESSURE BUILDS
EAST FROM THE OHIO VALLEY...VFR CONDITIONS SHOULD RETURN TO ALL
TERMINALS THURSDAY. THE EXCEPTION COULD BE KLEB...WHERE THE UPSLOPE
FLOW COULD KEEP MVFR CONDITIONS IN PLACE MUCH OF THE DAY. WEST
WINDS WILL GUST TO 25 TO 30 KNOTS THURSDAY AT ALL TERMINALS...AND
THE GUSTINESS MAY PERSIST INTO FRIDAY.
&&
.MARINE...
SHORT TERM /THRU TONIGHT/...WINDS AND SEAS EXPECTED TO REMAIN
BELOW SMALL CRAFT THRESHOLD.
LONG TERM /TUESDAY THROUGH FRIDAY/...WINDS SHOULD REMAIN BELOW SMALL
CRAFT LEVELS IN THE COLD AIR ADVECTION TUESDAY MORNING...AND DROP
BELOW 10 KNOTS BY EVENING. AS THE GRADIENT INCREASES AHEAD OF A
WARM FRONT EXTENDING FROM LOW PRESSURE OVER THE GREAT LAKES. THE
GRADIENT CERTAINLY SUPPORTS SMALL CRAFT WINDS ACROSS ALL WATERS
LATE TUESDAY NIGHT...AND MAY APPROACH GALE FORCE ACROSS SOUTHERN
WATERS.
AS THE LOW SPINS ACROSS THE GREAT LAKES...THE GRADIENT TIGHTENS
QUICKLY AHEAD OF THE WARM FRONT OR OCCLUSION ACROSS CENTRAL NEW
ENGLAND WEDNESDAY MORNING. THE TIGHTEST GRADIENT SHOULD OCCUR
BETWEEN 1800 UTC WEDNESDAY AND 0000 THURSDAY...JUST AHEAD OF THE
OCCLUSION. THE 0000 UTC NAM MODEL SOUNDING SUGGESTS NEAR STORM
POTENTIAL NEAR 0000 UTC THURSDAY...BUT THE GFS IS NOT QUITE AS
BULLISH. FOR NOW...SINCE THE MIXED LAYER SHOULD BE VERY LOW IN THE
WARM AIR ADVECTION...WILL NOT GO QUITE AS HIGH AS STORM. HOWEVER...
THIS MAY BE AN EVENTUALITY SHOULD THE GFS COME AROUND TO THE NAM
TYPE SOLUTION.
AS THE OCCLUSION PASSES...THERE WILL BE A LULL IN THE WINDS AS THE
GRADIENT BECOMES BAGGY...BUT THE DEPTH OF THE MIXED LAYER
INCREASES DRAMATICALLY BEHIND THE FRONT...AND GALE FORCE WINDS
LOOK LIKELY FOR LATER WEDNESDAY NIGHT INTO THURSDAY. AS THE LOW
TRACKS INTO THE MARITIMES AND HIGH PRESSURE APPROACHES FROM THE
OHIO VALLEY...GALE FORCE WINDS COULD CONTINUE INTO FRIDAY.
&&
.GYX WATCHES/WARNINGS/ADVISORIES...
ME...NONE.
NH...NONE.
MARINE...NONE.
&&
$$
NEAR TERM...STJEAN
