FXUS61 KGYX 100831
AFDGYX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAY ME
331 AM EST THU DEC 10 2009
.SYNOPSIS...
LOW PRESSURE WILL CONTINUE TO MOVE EAST THROUGH THE CANADIAN
MARITIMES THROUGH FRIDAY AS HIGH PRESSURE BUILDS SOUTH OF THE
REGION. THE PRESSURE GRADIENT BETWEEN THESE TWO SYSTEMS WILL
CREATE A STRONG WESTERLY FLOW OVER THE AREA THROUGH SATURDAY. THE
RIDGE OF HIGH PRESSURE WILL MOVE OFFSHORE ON SUNDAY AS A WEAK
TROUGH OF LOW PRESSURE MOVES EAST. THE TROUGH WILL SLOWLY MOVE
EAST OF THE REGION SUNDAY NIGHT AND MONDAY. HIGH PRESSURE WILL
BUILD OVER THE AREA MONDAY NIGHT. ANOTHER TROUGH OF LOW PRESSURE
WILL APPROACH FROM THE WEST ON TUESDAY AND WILL CROSS THE AREA ON
WEDNESDAY AS LOW PRESSURE MOVES NORTHEAST ALONG THE TROUGH.
&&
.NEAR TERM /THROUGH TODAY/...
THE FORECAST PROBLEM FOR TODAY (AS IT WILL BE THROUGH FRIDAY) WILL
BE WIND GUSTS.
CURRENTLY...THE FORECAST AREA IS IN THE WAKE OF THE SYSTEM THAT
BROUGHT THE SNOW...RAIN AND WIND WEDNESDAY. THE SURFACE LOW THAT
DEVELOPED ON THE OCCLUSION WAS LOCATED OVER EASTERNMOST MAINE
EARLY THIS MORNING. IN THE WAKE OF THE FRONT AND THE LOW...THE
SURFACE DROPPED OFF QUICKLY...AND THE LOW LEVEL MOISTURE IN PLACE
FORMED LOW CLOUDS AND PATCHY DENSE FOG.
THE LOW CLOUDS AND FOG SHOULD START TO LIFT AS THE GRADIENT STARTS
TO INCREASE BEHIND THE SURFACE LOW. THE LOW WILL DEEPEN FAIRLY RAPIDLY
AS A 175 KNOT 300 MB JET APPROACHES FROM EASTERN NEW YORK STATE.
THE TIGHTENING GRADIENT WILL RESULT IN WINDS INCREASINGLY QUICKLY
AFTER SUNRISE. THE FORECAST PROBLEM THEN BECOMES GUSTS.
MODEL SOUNDINGS SUGGEST THAT 40 TO 45 KNOTS OF WIND WILL BE AVAILABLE
AT THE TOP OF THE INVERSION IN THE COLD AIR ADVECTION. THIS WOULD
TRANSLATE TO WIND GUSTS TO NEAR 40 MPH...AND THIS WAS INCLUDED IN
THE GRIDDED FORECAST. TOYED WITH THE IDEA OF A WIND ADVISORY FOR
THE HIGHER TERRAIN...BUT DECIDED TO HOLD OFF FOR NOW.
THE CLOUDS IN PLACE ACROSS THE UPSLOPE AREAS MAY HAVE A HARD TIME
BREAKING TODAY...AND AREAS THAT HAVE SUNSHINE THIS MORNING COULD
LOSE IT AS CONVECTIVE TEMPERATURES ARE MET. SHOULD SEE MINUS 25 TO
MINUS 30 AIR AT 500 MB CROSS THE REGION THIS AFTERNOON...AND THIS
SHOULD BE WHEN CUMULUS CLOUDS SHOULD COVER AS MUCH AREA AS THEY
WILL.
WHILE THE FLOW OVER THE MOUNTAINS IS BROADLY CYCLONIC...IT IS NOT
IDEAL FOR GOOD UPSLOPE SNOW. KEPT A MENTION OF SHOWERS IN NORTHERN
NEW HAMPSHIRE AND MENTIONED A LIGHT ACCUMULATION...BUT MOISTURE
COULD BE THE LIMITING FACTOR HERE. AS WINDS IN THE BOUNDARY LAYER
SHIFT TO THE WEST...IT IS POSSIBLE THAT THE CONNECTICUT RIVER VALLEY
COULD SEE SNOW SHOWERS EXTEND FROM LAKE ONTARIO. NOT EXPECTING
MUCH IN THE WAY OF ACCUMULATION...AS THE ACTIVITY WOULD HAVE TO
CROSS A FORMIDABLE MOUNTAIN RANGE. HIGHS TODAY WERE BASED ON A
BLEND OF MOS NUMBERS...AND COULD BE THE WARMER TEMPERATURES WE SEE
FOR SOME TIME.
&&
.SHORT TERM /TONIGHT THROUGH 6 PM FRIDAY/...
ANOTHER SHORT WAVE IN THE NORTHERN STREAM WILL PASS THIS EVENING.
WHILE THE SHORT WAVE MAY RESULT IN ADDITIONAL UPSLOPE CLOUDS AND
SNOW SHOWERS IN THE MOUNTAINS...WIND MAY BE THE MORE IMPORTANT
PROBLEM.
MODEL SOUNDINGS SUGGEST THE DEPTH OF THE MIXED LAYER WILL RISE TO
NEAR 6000 FEET. THIS WOULD ALLOW ACCESS TO 50 TO 55 KNOTS OF WIND
AT THE TOP OF THE INVERSION. NORMALLY...THIS WOULD NOT BE AS MUCH
OF A PROBLEM AT NIGHT...WHEN TURBULENT MIXING IS MITIGATED BY THE
LATE OF HEATING FROM SUNSHINE. HOWEVER...GIVEN HOW COLD THE COLUMN
WILL BE...MENTIONED WIND GUSTS TO 40 MPH FOR TONIGHT. IF MODELS
ARE INSISTENT ON THE DEPTH OF THE MIXED LAYER...A WIND ADVISORY
COULD BECOME NECESSARY FOR TONIGHT...ESPECIALLY FOR THE TERRAIN.
OTHERWISE...WOULD EXPECT MORE A TRADITIONAL UPSLOPE/DOWNSLOPE
CLOUD COVER FOR TONIGHT...AS WINDS SHIFT BEHIND THE SHORT WAVE
THIS EVENING. KEPT THE MENTION OF SNOW SHOWERS LIMITED TO THE
MOUNTAINS...AND A BLEND OF MOS NUMBERS WERE USED FOR LOW.
WINDS MAY BE MORE OF A PROBLEM ON FRIDAY. WHILE WINDS AT THE TOP
OF THE INVERSION REMAIN NEAR 50 TO 55 KNOTS...DAYTIME HEATING
SHOULD STEEPEN LAPSE RATES AND ALLOW MORE MOMENTUM TO THE SURFACE.
WOULD EXPECT WIND GUSTS TO 45 TO PERHAPS 50 MPH WILL BE POSSIBLE
IN THE TURBULENT MIXING FRIDAY. TOO FAR OUR FOR AN ADVISORY FOR
FRIDAY...BUT THE POTENTIAL WILL BE MENTIONED IN THE HAZARDOUS
WEATHER OUTLOOK.
ONCE AGAIN...EXPECT MORE OF A TRADITIONAL UPSLOPE/DOWNSLOPE
CLOUD COVER FOR FRIDAY. CONDITIONS MAY BECOME A BIT MORE FAVORABLE
FOR UPSLOPE SNOW SHOWERS FOR THE FAVORED LOCATIONS...THOUGH
MOISTURE MAY BE THE LIMITING FACTOR. HIGHS FRIDAY WERE BASED ON A
MOS BLEND.
&&
.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
GUSTY WESTERLY FLOW WILL CONTINUE THROUGH SATURDAY AS SURFACE
RIDGE GRADUALLY MOVES EAST AND OFF THE COAST. TROUGH OF LOW
PRESSURE MOVES EAST FOR SUNDAY BUT MODELS CONTINUE TO INDICATE
THAT NORTHERN AND SOUTHERN SYSTEMS ALONG TROUGH WILL NOT PHASE.
THERE COULD BE SOME LIGHT SNOW ASSOCIATED WITH THIS
SYSTEM...HOWEVER ANY ACCUMULATIONS SHOULD BE MINIMAL.
A WEAK RIDGE OF HIGH PRESSURE BUILDS IN BEHIND TROUGH MONDAY. GFS
INDICATES THAT LOW PRESSURE MOVING EAST THROUGH SOUTHERN CANADA
TUESDAY WILL DRAG AN ARCTIC FRONT ACROSS AREA TUESDAY NIGHT WITH
SIGNIFICANT DEVELOPMENT ALONG FRONT. ECMWF MODEL DIFFERS
CONSIDERABLY ON SOUTHWARD PROGRESSION OF COLD AIR AND DEVELOPMENT
ALONG FRONT...SO UNCERTAINTY IN FORECAST INCREASES EARLY NEXT
WEEK.
&&
.AVIATION /07Z THURSDAY THROUGH MONDAY/...
IN THE NEAR TERM /TODAY/....STILL A FAIR AMOUNT OF IFR AND LIFR
CONDITIONS AS LOW LEVEL MOISTURE REMAINS TRAPPED UNDER THE
INVERSION BEHIND THE OCCLUDED FRONT. A WEAK SURFACE GRADIENT
ALLOWED FOG TO FORM AS WELL...BUT THIS SEEMS TO BE LIFTING AS THE
WESTERLY GRADIENT IS STARTING TO REACT TO DEEPENING LOW PRESSURE
TO THE NORTHEAST.
WITH COLD AIR ADVECTION AND FAIRLY STEEP LAPSE RATES...WOULD
EXPECT AREAS THAT BREAK THIS MORNING TO FILL BACK IN WITH CLOUDS.
FOR THE MOST PART...VFR CEILINGS ARE EXPECTED AT THE TERMINALS...
THOUGH THERE IS A LOW PROBABILITY THAT KLEB COULD SEE MVFR
CONDITIONS IN UPSLOPE CLOUDS.
THE BIGGEST FORECAST PROBLEM WILL BE THE WIND. AS THE SURFACE LOW
OVER EASTERNMOST MAINE EARLY THIS MORNING DEEPENS...THE GRADIENT
WILL INCREASE...AND WILL SUPPORT SUSTAINED WINDS NEAR 20 KNOTS. THE
COLD AIR ADVECTION WILL ALLOW ACCESS TO 35 TO 40 KNOTS OF WIND AT
THE TOP OF THE INVERSION...SO GUSTS TO 30 KNOTS ARE POSSIBLE LATER
THIS MORNING AND THIS AFTERNOON.
IN THE SHORT TERM /TONIGHT AND FRIDAY/...MOISTURE TRAPPED UNDER
THE INVERSION SHOULD RESULT IN VFR CEILINGS FOR KAUG...KCON AND
KLEB. THERE IS A LOW PROBABILITY THAT KLEB COULD SEE MVFR CEILINGS
TONIGHT WITH UPSLOPE AND POSSIBLE SNOW SHOWERS FROM THE LAKE
EFFECT WELL TO THE WEST.
VFR CONDITIONS ARE EXPECTED FRIDAY...AS CUMULUS FILLS IN DURING
THE LATE MORNING AND AFTERNOON. WINDS WILL BE THE BIGGEST
PROBLEM...AS MODEL SOUNDINGS SUGGEST 45 KNOTS COULD BE AVAILABLE
AT THE TOP OF THE INVERSION. THIS COULD CAUSE 40 KNOT WIND
GUSTS...ESPECIALLY AT KCON AND KPSM.
LONG TERM...
MAINLY VFR CONDITIONS EXPECTED THROUGH THE PERIOD. GUSTY WESTERLY
WINDS WILL PERSIST THROUGH SATURDAY.
&&
.MARINE...
IN THE NEAR TERM /TODAY/...AS THE SECONDARY LOW TIDES ALONG THE OLD
OCCLUDED FRONT ACROSS EASTERNMOST MAINE...THE SURFACE GRADIENT HAS
WEAKENED CONSIDERABLY. IN FACT...WINDS OVER THE BAYS HAVE DROPPED
TO JUST ABOVE SMALL CRAFT LEVELS EARLY THIS MORNING.
THIS SHOULD BE SHORT LIVED AS THE SURFACE LOW DEEPENS AS IT HEADS
FOR THE MARITIMES. THE GRADIENT WILL REACT ACCORDINGLY...AND IT
SHOULD BE ABLE TO SUPPORT MINIMAL GALES OVER THE OCEAN WATERS...AND
JUST BELOW THIS IN THE BAYS. HOWEVER...MIXING IN THE COLD AIR
ADVECTION BEHIND THE LOW SHOULD ALLOW ACCESS TO 45 KNOTS WINDS AT
THE TOP OF THE INVERSION. THIS SHOULD BRING THE OCEAN WATERS
SOLIDLY BACK INTO GALE...AND RESULT IN GALE FORCE GUSTS OVER THE
BAYS.
SEAS MAY TAKE SOME TIME TO COME DOWN AS THE EAST TO SOUTHEAST
SWELL TAKES MUCH OF THE DAY TO FINALLY SORT ITSELF OUT. SEAS WILL
REMAIN ABOVE 5 FEET IN ALL WATERS FOR THE BALANCE OF THE DAY.
IN THE SHORT TERM /TONIGHT AND SATURDAY/...ANOTHER SHORT WAVE WILL
BRING COLDER AIR INTO THE MID LEVELS...AND THIS SHOULD STEEPEN
LOW LEVEL LAPSE RATES. MODEL SOUNDINGS SUGGEST THAT 50 KNOT WILL
BE AVAILABLE AT THE TOP OF THE DEEPENING INVERSION. CAPPED WINDS
AT 45 KNOTS FOR TONIGHT...AND THERE COULD BE A FEW STORM FORCE
GUSTS LATE TONIGHT AND FRIDAY.
LONG TERM...GUSTY WESTERLY WINDS WILL PERSIST THROUGH SATURDAY AS
RIDGE SLOWLY MOVES OFF THE COAST. A WEAK TROUGH WILL CROSS THE
REGION SUNDAY WITH SOME LIGHT PRECIPITATION POSSIBLE. WEAK HIGH
PRESSURE WILL BUILD ACROSS THE WATERS MONDAY.
&&
.GYX WATCHES/WARNINGS/ADVISORIES...
ME...NONE.
NH...NONE.
MARINE...GALE WARNING UNTIL 7 PM EST FRIDAY FOR ANZ150>154.
&&
$$
LONG TERM...JENSENIUS
