FXUS61 KBOX 262136
AFDBOX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
436 PM EST SAT DEC 26 2009
.SYNOPSIS...
LOW PRESSURE NEAR CHESAPEAKE BAY WILL MOVE NORTH ACROSS NEW ENGLAND
LATE TONIGHT AND EARLY SUNDAY. ANOTHER WEAK LOW PRESSURE WILL LIKELY
AFFECT OUR REGION LATE SUNDAY NIGHT AND MONDAY. VERY COLD AND
BLUSTERY CONDITIONS WILL FOLLOW IN THE WAKE OF THIS LOW MONDAY NIGHT
INTO WEDNESDAY. A COASTAL STORM MAY BRING MORE WINTRY PRECIPITATION
TO SOUTHERN NEW ENGLAND SOMETIME BETWEEN NEW YEARS EVE AND NEXT
SATURDAY.
&&
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
LATEST WATER VAPOR LOOP INDICATES MOISTURE TRANSPORTING NE FROM THE
EASTERN PACIFIC AND GULF OF MEXICO REGIONS. AT THE SURFACE...LOW
PRESSURE WAS CENTERED NEAR CENTREVILLE MARYLAND AT 2030Z...IN
PROXIMITY TO THE CHESAPEAKE BAY. RADAR INDICATED A BATCH OF LIGHT
RAIN SHOWERS LOCATED FROM EASTERN LONG ISLAND EXTENDING NORTHWEST
INTO THE BERKSHIRES. THIS IS ASSOCIATED WITH AN APPROACHING SSE LOW
LEVEL JET EMANATING FROM THE MID ATLANTIC COAST...ALLOWING FOR
INCREASING LOW LEVEL CONVERGENCE AND LIFT.
TEMPERATURES ACROSS THE FAR INTERIOR REMAINED JUST BELOW FREEZING
LATE THIS AFTERNOON. THE NAM12 HAS DONE A GOOD JOB MAINTAINING THE
SFC HIGH PRESSURE COLD AIR DAMMING SIGNATURE WITH AGEOSTROPHIC H950
FLOW REMAINING FROM THE NORTH NORTHEAST. TEMPERATURES BETWEEN 1000
AND 2000 FT REMAIN THE COLDEST WITHIN VERTICAL TEMPERATURE PROFILES.
WILL CONTINUE TO NOTE BOUNDARY LAYER TEMPERATURES SLOWLY RISING THIS
EVENING ACROSS THE INTERIOR...AS THE SE LOW LEVEL JET INCREASES.
HAVE NOTED LIGHT SNOW AND SOME FREEZING DRIZZLE AS PREDOMINANT
PTYPES. MOST AREAS WILL CHANGE OVER TO RAIN AS BOUNDARY LAYER
TEMPERATURES CONTINUE TO INCREASE...BUT MAY CONTINUE TO SEE
POCKETS OF FREEZING RAIN LINGER TONIGHT IN SOUTHERN NEW HAMPSHIRE
AND FAR NORTHWEST FRANKLIN COUNTY. HAVE CONTINUED A WINTER WEATHER
ADVISORY ACROSS THESE AREAS THIS EVENING. PLEASE REFER TO THE LATEST
WSWBOX FOR DETAILS.
GOOD LOW LEVEL INFLOW AND ISENTROPIC LIFT AHEAD OF A COLD FRONT AND
TRIPLE POINT LOW TONIGHT. HAVE CATEGORICAL POPS ALL AREAS BY OR
SHORTLY AFTER MIDNIGHT.
CHANCE FOR ISOLD THUNDER TOWARDS DAYBREAK SOUTH COAST. NAM/GFS
INDICATE SHOWALTER INDICES DROPPING TO AROUND MINUS 1 BY 12Z.
OTHERWISE CONVECTIVE PARAMETERS ARE MARGINAL. DECIDED NOT TO INCLUDE
THE MENTION AT THIS TIME.
OTHERWISE TEMPERATURES WILL REMAIN STEADY OR SLOWLY RISE TONIGHT.
PRECIPITABLE WATER VALUES BRIEFLY CLIMB TO NEAR 1G/KG BY DAYBREAK.
RAIN WILL BE LOCALLY HEAVY FOR A TIME LATE. PLEASE SEE HYDROLOGY
SECTION FOR DETAILS.
HIGHER DEW POINT AIR ADVECTING OVER THE COLD SNOWPACK WILL ALLOW FOR
FOG PATCHES TO DEVELOP...AND THE FOG COULD BE LOCALLY DENSE. HAVE
THIS MENTIONED IN THE GRIDS.
&&
.SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/...
SUNDAY...NAM IS A FEW HOURS SLOWER THAN THE GFS...BUT OVERALL MINOR
DIFFERENCES WITH RESPECT TO THE TIMING OF THE COLD FRONT. HAVE RAIN
DEPARTING THE EAST COAST BETWEEN 15Z AND 18Z. OTHERWISE EXPECT
PARTIAL CLEARING DURING THE AFTERNOON FROM SOUTHWEST TO NORTHEAST.
BOUNDARY LAYER TEMPS ARE FAIRLY MILD TO BEGIN THE DAY...WITH COOLER
AIR DELAYED UNTIL NIGHTFALL. HIGHS SHOULD REACH 50 TO 55 DEGREES IN
CONNECTICUT...INTERIOR RHODE ISLAND AND INTERIOR SOUTHEAST
MASSACHUSETTS.
SUNDAY NIGHT...COOL AND DRY WEST TO SOUTHWEST FLOW EXPECTED...BUT
CLOUDS WILL BE INCREASING OVERNIGHT AHEAD OF THE NEXT SHORT WAVE
DISTURBANCE. HAVE CHANCE POPS FOR SNOW SHOWERS ACROSS THE WEST
TOWARDS DAYBREAK MONDAY.
&&
.LONG TERM /MONDAY THROUGH SATURDAY/...
MEDIUM RANGE MODELS SHOWING DECENT CONSISTENCY THROUGH THE EARLY
PORTION OF THE LONG TERM...BUT HAVING MAJOR TIMING AND CONTINUITY
ISSUES BEYOND WEDNESDAY ESPECIALLY WITH THE ECMWF. THIS COULD HAVE
MAJOR IMPLICATIONS WITH THE POSSIBILITY OF STORMY WEATHER SOMETIME
FROM NEW YEARS EVE INTO NEXT SATURDAY.
MONDAY...STRONG SHORTWAVE STILL PROGGED TO MOVE ACROSS THE REGION.
EXPECT LIGHT SNOW TO DEVELOP AS A WEAK SURFACE WAVE MAY EVEN FORM AND
CROSS THE REGION LATE MONDAY...AS SOME MODEL RUNS HAVE SHOWN THIS.
SHOULD SEE AN INCH OR TWO OF SNOW FROM THIS SYSTEM...BUT COULD HAVE A
FEW LOCALLY HIGHER AMOUNTS IF THE ATLANTIC IS TAPPED A BIT. HAVE
CARRIED LIKELY POPS FOR MOST AREAS BY MIDDAY MONDAY...BUT SHOULD PUSH
OFFSHORE RATHER QUICKLY WITH A 50 KT H85 JET APPROACHING.
TEMPERATURES ALONG COASTAL MA AND COASTAL RI SHOULD BE WARM ENOUGH TO
ALLOW A MIX WITH OR CHANGE TO RAIN.
MONDAY NIGHT...ANOTHER MID LEVEL SHORTWAVE MOVES ACROSS THE REGION...
WITH ITS ASSOCIATED ARCTIC SURFACE FRONT. VERY STRONG LAPSE RATES
AS MODELS CONTINUE TO DROP H85 TEMPS DOWN TO -23C TO -26C INTO
NORTHERN NEW ENGLAND BY 12Z TUESDAY...BUT APPEARS THAT MOST OF THE
MOISTURE WILL BE CARRIED OFF WITH THE EARLIER SYSTEM. HOWEVER...WITH
SUCH A STRONG UPPER LEVEL SYSTEM...WOULD NOT BE SURPRISED TO SEE SOME
SNOW SQUALLS WITH THE FRONTAL PASSAGE. W-NW WINDS WILL START TO ROAR
AS THE COLD AIR RUSHES IN.
TUESDAY-WEDNESDAY...HIGH PRES BUILDS ACROSS THE CENTRAL U.S...BUT
WE WILL REMAIN IN STRONG W-NW FLOW WITH ARCTIC AIR. DAYTIME HIGHS
TUESDAY WILL STRUGGLE TO BREAK 30F...AND MAY REMAIN BELOW 20 ACROSS
THE HIGHER TERRAIN. WIND CHILL READINGS WILL FALL BELOW ZERO AT
TIMES... ESPECIALLY TUESDAY ACROSS THE HIGHER TERRAIN OF CENTRAL AND
WESTERN MASSACHUSETTS AND SOUTHERN NEW HAMPSHIRE. LOOKS LIKE MOST
AREAS WILL SEE WIND CHILLS BELOW ZERO TUESDAY NIGHT...AND AROUND -10F
ACROSS THE HIGHER TERRAIN INTO S NH. WINDS EXPECTED TO DIMINISH
WEDNESDAY AS THE CENTER OF A HIGH PRESSURE APPROACHES...AND WILL
ALLOW TEMPERATURES TO SLOWLY MODERATE.
THURSDAY-SATURDAY...BIG QUESTIONS AT THIS TIME-FRAME...WITH THE
POSSIBILITY OF A SOUTHERN STREAM STORM TURNING THE CORNER AND MOVING
NORTH ALONG THE EASTERN SEABOARD. MODELS HAVING MAJOR TIMING AND
CONTINUITY ISSUES...SO CONTINUE TO HAVE LOW CONFIDENCE WITH THIS
PORTION OF THE FORECAST. CERTAIN INGREDIENTS COULD BE IN PLACE FOR A
SNOW STORM...WITH MOST MODELS DEPICTING A HIGH PRESSURE ACROSS QUEBEC
TO KEEP THE COLD AIR IN PLACE. STILL TOO MANY THINGS HAVE TO FALL
INTO PLACE JUST RIGHT TO PREDICT SUCH A STORM AT THIS TIME. OPTED TO
GO WITH A CHANCE OF SNOW OR RAIN FOR NOW...AND WILL LET FUTURE SHIFTS
FINE TUNE THE DETAILS AS TIME PROGRESSES.
&&
.AVIATION /22Z SATURDAY THROUGH THURSDAY/...
THIS AFTERNOON...HIGH CONFIDENCE OF MVFR CIGS WITH LOCALIZED IFR
/VLIFR HIGHER TERRAIN SUCH AS ORH/ AND SCATTERED LIGHT RAIN AS LOW OFF
VIRGINIA COAST TRACKS NE. LIGHT PRECIP TYPE OF -FZDZ/-SN IN S NH AND
FAR NC MA EXPECTED TO CHANGE OVER TO -RA/-DZ DURING MID TO LATE
AFTERNOON.
TONIGHT...HIGH CONFIDENCE FOR IFR TO LIFR CIGS AND VSBYS IN RAIN.
VLIFR AT ORH. EAST TO SOUTHEAST WINDS WILL INCREASE OVER THE CAPE AND
ISLANDS...AND POSSIBLY SOUTHEAST MASS...WITH 25 TO 30 KNOT GUSTS
POSSIBLE. WINDS WILL BE EVEN STRONGER AROUND 2000 FEET...WHERE LOW
LEVEL JET SOUTHEAST WINDS OF 55 TO 60 KNOTS ARE FORECAST. AREA OF
THESE STRONGER WINDS SHOULD PRIMARILY EXTEND FROM BOS-PVD TO CAPE
AND ISLANDS...SO INTRODUCED LOW LEVEL WIND SHEAR AT THOSE TERMINALS
GENERALLY 06-12Z TIME-FRAME.
SUNDAY...MEDIUM CONFIDENCE OF MVFR/IFR CIGS LINGERING THOUGH MUCH OF THE
DAY...THOUGH MOST RAIN LEAVES THE AREA BY MIDDAY. CIGS SHOULD IMPROVE
TO VFR BDL/BAF DURING THE AFTERNOON. EASTERLY WINDS START OFF THE
DAY...SURFACE LOW TRACKS OVER THE AREA AROUND MIDDAY WITH SURFACE WINDS
BECOMING WEST IN THE AFTERNOON.
OUTLOOK...SUNDAY NIGHT THROUGH THURSDAY...
SUNDAY NIGHT...VFR TO START...THEN MAY LOWER TO MVFR CIGS AFTER
MIDNIGHT ACROSS CT VALLEY INTO SW NH. CHANCE OF MVFR VSBYS IN LOCAL
-SN.
MONDAY...MVFR CONDITIONS POSSIBLE IN LIGHT SNOW...ESPECIALLY ALONG
AND SOUTH OF THE MASS PIKE.
MONDAY NIGHT...LOCAL MVFR CIGS/VSBY POSSIBLE ACROSS E MA EARLY...
OTHERWISE VFR WITH GUSTY NW WINDS.
TUESDAY...VFR. NW WIND GUSTS UP TO 30-35 KT POSSIBLE ALONG THE COAST
AND ACROSS THE HIGHER TERRAIN.
WEDNESDAY...VFR WITH DIMINISHING WINDS.
THURSDAY...VFR.
&&
.MARINE...
TONIGHT...GALE WARNINGS CONTINUE ACROSS MOST OF THE COASTAL WATERS.
BEST PRESSURE FALLS OCCUR BETWEEN 06Z AND 12Z TONIGHT. A LOW LEVEL
SE JET 60-65 KT APPROACHES LATE. WILL SEE SCATTERED ESE WIND GUSTS
30 TO 35 KT. SMALL CRAFT ADVISORIES REMAIN POSTED ACROSS BOSTON
HARBOR AND NARRAGANSETT BAY.
SUNDAY...MARGINAL MORNING GALES ACROSS THE EASTERN WATERS. OTHERWISE
A LEFTOVER SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS DURING THE
AFTERNOON FOR E AND S SWELL.
SUNDAY NIGHT...A SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS EXPECTED TO
CONTINUE FOR LEFTOVER E AND S SWELL. WINDS EXPECTED TO SHIFT TO SW
BUT REMAIN BELOW SCA CRITERIA AT NIGHT.
OUTLOOK...MONDAY THROUGH THURSDAY...
MONDAY...WINDS MAY BRIEFLY DIMINISH BELOW SMALL CRAFT PRIOR TO THE
PASSAGE OF AN ARCTIC FRONT. W-NW WINDS MAY GUST TO 30 KT LATE IN THE
DAY.
MONDAY NIGHT THROUGH TUESDAY NIGHT...W-NW GALES LIKELY. STRONGEST
WINDS WILL PROBABLY OCCUR LATE MONDAY NIGHT AND TUESDAY.
WEDNESDAY...WINDS CONTINUE TO DIMINISH...BUT SEAS LIKELY TO TAKE A
BIT LONGER ACROSS THE OUTER COASTAL WATERS.
THURSDAY...RELATIVELY TRANQUIL CONDITIONS FOR THIS TIME OF YEAR WITH
A HIGH PRESSURE ACROSS THE COASTAL WATERS.
&&
.HYDROLOGY...
QPF AMOUNTS ARE EXPECTED TO RANGE FROM 0.25 TO 0.75 INCH...WITH THE
HIGHEST AMOUNTS EXPECTED ALONG THE SOUTH COAST. SOME BRIEF URBAN AND
POOR DRAINAGE FLOODING MAY OCCUR...PARTICULARLY ALONG THE SOUTH COAST
DUE TO THE COMBINATION OF BRIEFLY HEAVY RAINFALL NEAR DAYBREAK AND
MELTING SNOW.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
MA...WINTER WEATHER ADVISORY UNTIL 7 PM EST THIS EVENING FOR
MAZ002>004-008-026.
NH...WINTER WEATHER ADVISORY UNTIL 10 PM EST THIS EVENING FOR
NHZ011-012-015.
RI...NONE.
MARINE...GALE WARNING UNTIL NOON EST SUNDAY FOR ANZ231-232-250-251-254-
255.
GALE WARNING UNTIL 6 AM EST SUNDAY FOR ANZ233>235-237-256.
SMALL CRAFT ADVISORY UNTIL 6 AM EST SUNDAY FOR ANZ230-236.
&&
$$
SYNOPSIS...BELK/STRAUSS
NEAR TERM...STRAUSS
SHORT TERM...STRAUSS
LONG TERM...BELK
AVIATION...BELK/NMB
MARINE...BELK/STRAUSS
HYDROLOGY...STRAUSS
