FXUS61 KLWX 100420
AFDLWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
1120 PM EST WED DEC 9 2009
.SYNOPSIS...
A COLD FRONT WILL CONTINUE TO MOVE OUT INTO THE ATLANTIC
OVERNIGHT. HIGH PRESSURE WILL BUILD IN BEHIND THE FRONT THROUGH
FRIDAY...BRINGING DRY AND COLD CONDITIONS. LOW PRESSURE WILL
PASS SOUTH OF THE AREA SUNDAY...WITH ANOTHER STORM SYSTEM AFFECTING
THE AREA ON TUESDAY.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
THE COLD FRONT WILL CONTINUE TO MOVE OFF TO OUR EAST OVERNIGHT.
A STRONG PRESSURE GRADIENT BETWEEN HIGH PRESSURE OVER THE PLAINS
AND LOW PRESSURE OVER SOUTHERN CANADA WILL CAUSE BREEZY CONDITIONS
TONIGHT. WILL CAP WIND GUSTS JUST BELOW ADVISORY CRITERIA OVER THE
HIGHEST ELEVATIONS OVERNIGHT. PREVIOUS DISCUSSION FOLLOWS.
A WESTERLY FLOW WILL USHER IN COLDER CONDITIONS OVERNIGHT. MIN
TEMPS WILL RANGE FROM THE TEENS IN PORTIONS OF THE POTOMAC
HIGHLANDS TO THE MIDDLE 30S IN WASHINGTON AND BALTIMORE.
UPSLOPE SNOW SHOWERS ARE POSSIBLE BEHIND THE FRONT OVERNIGHT...BUT
WIND TRAJECTORY WILL REMAIN MORE WESTERLY THAN NORTHWESTERLY. WITH
THE MORE WESTERLY TRAJECTORY...NOT EXPECTING SIGNIFICANT
ACCUMULATING SNOWFALL ALONG THE WESTERN SLOPES...POSSIBLY AROUND AN
INCH TO JUST UNDER AN INCH AND A HALF.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/...
HIGH PRESSURE BUILDS EAST DURING THE DAY TOMORROW...WITH SUNNY SKIES
AND COOLER MAX TEMPS. WINDS ALOFT WILL CONTINUE TO BRING WIND GUSTS
BETWEEN 25 AND 30 KT TO THE AREA.
&&
.LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/...
STRONG CAA CONTINUES THU NGT THRU SAT...AS 1030MB SFC RIDGE SLIDES
SEWD INTO SERN CONUS. WITH CLOSED LOW OFF CANADIAN MARITIMES...PRES
GRADIENT WILL BE TIGHT...WITH GUSTY NW WINDS XPCD THRU THE PERIOD.
AFTN MAXIMA STRUGGLE TO REACH FREEZING...WITH LOWS IN THE TEENS MANY
AREAS WEST OF INTERSTATE 95. THU NGT XPCT THAT WIND CHILL ADVISORY
WILL BE NECESSARY OVER THE POTOMAC HIGHLANDS...AS NW WINDS OF 20 TO
30 MPH AND TEMPS FALLING INTO THE SINGLE DIGITS WILL PRODUCE WIND
CHILL INDICES BELOW ZERO.
WEAK SHRTWV PASSES N OF THE AREA SAT NGT/SUN...PROMPTING
CYCLOGENESIS OFF CAROLINA COAST. MODELS TRENDING LESS ROBUST WITH
MOISTURE AND DEPTH OF COLD AIR OVR MID ATLANTIC IN RECENT RUNS...SO
WILL KEEP PRECIP CHANCES AOB 40 PERCENT FOR NOW. ANOTHER STORM
SYSTEM LOOKS TO AFFECT THE AREA TUESDAY.
&&
.AVIATION /04Z THURSDAY THROUGH MONDAY/...
WINDS HAVE SHIFTED TO THE WEST/SOUTHWEST BEHIND THE FRONT
OVERNIGHT. WIND GUSTS UP TO 30 KNOTS ARE POSSIBLE ALONG WITH VFR
CONDITIONS.
VFR CONDS XPCD THU NGT THRU SAT. NEXT CHANCE OF SUB-VFR CIG/VSBY SAT
NGT INTO SUNDAY AS LOW PRESSURE AFFECTS THE AREA.
&&
.MARINE...
HAVE RAISED A GALE WARNING FOR THE ENTIRE MARINE AREA FOR THE
OVERNIGHT HOURS. GRADIENT WINDS HAVE INCREASED AROUND A STRONG LOW
PRESSURE SYSTEM LOCATED OVER THE GREAT LAKES. WIND GUSTS AROUND 35
KT WILL BE LIKELY OVERNIGHT...WITH SOME HIGHER GUSTS WITHIN SHOWERS.
S/SW WINDS ARE EXPECTED. WEST WINDS WILL BE THE RULE ON
THURSDAY...WITH SMALL CRAFT CONDITIONS CONTINUING.
TIGHT PRESSURE GRADIENT AND CAA WILL KEEP STRONG WINDS OVER THE
WATERS THU NIGHT...SMALL CRAFT ADVISORY CONTINUES. SIMILAR
CONDITIONS XPCD FRI...BEFORE HIPRES MOVES OVER THE WATERS FRI NGT
AND SAT...BRINGING LIGHTER WINDS
&&
.TIDES/COASTAL FLOODING...
TIDES REMAIN ONE TO TWO FEET ABOVE NORMAL THIS EVENING...BUT
WATER LEVELS REMAIN BELOW THRESHOLDS FOR MINOR COASTAL FLOODING. A
WESTERLY FLOW WILL CAUSE TIDAL ANOMALIES TO DECREASE OVERNIGHT.
THEREFORE...THE COASTAL FLOOD ADVISORY HAS BEEN ALLOWED TO EXPIRE.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 6 AM THURSDAY TO 7 AM EST FRIDAY FOR
ANZ530>543.
GALE WARNING UNTIL 6 AM EST THURSDAY FOR ANZ530>543.
&&
$$
UPDATE...LASORSA
PREVIUOS DISCUSSION...RDH/LISTEMAA/SBK
