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rea Forecast Discussion
Issued by NWS Sterling, VA
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000
FXUS61 KLWX 180901
AFDLWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
401 AM EST WED NOV 18 2009
.SYNOPSIS...
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HIGH PRESSURE WILL DRIFT ACROSS THE NORTHEAST STATES TODAY AND
TONIGHT. A COLD FRONT WILL BRING RAIN TO THE AREA THURSDAY AND
THURSDAY NIGHT. HIGH PRESSURE BUILDS IN FRIDAY AND SATURDAY...WITH
A LOW PRESSURE AFFECTING THE AREA SUNDAY INTO MONDAY.-- End Changed Discussion --
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
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VERTICALLY STACKED LOW PRESSURE WAS SPINNING ACROSS THE MID
MISSISSIPPI VALLEY EARLY THIS MORNING...WHILE SURFACE HIGH PRESSURE
WAS LOCATED ACROSS NEW ENGLAND.
NORTHEAST FLOW HAS BECOME WELL ESTABLISHED IN THE LOWER LEVELS
ACROSS THE MID ATLANTIC...AND WAS ALLOWING MOISTURE TO BEGIN TO
INCREASE. EVIDENCE IN MOISTURE INCREASE WAS A BANK OF STRATOCU
DEVELOPING ACROSS THE CWA.
STRATOCU...AND EVENTUALLY STRATUS...WILL CONTINUE TO DEVELOP/ADVECT
WESTWARD THROUGH THE DAY TODAY RESULTING IN A GENERALLY CLOUDY SKY
ESPECIALLY IN THE AFTERNOON.
MOST OF THE CWA WILL BE DRY...HOWEVER OROGRAPHIC EFFECTS MAY ALLOW A
LITTLE LIGHT RAIN OR DRIZZLE TO DEVELOP NEAR THE
HIGHLANDS/SHENANDOAH VALLEY AREA FAVORING THE UPSLOPE SIDE. THIS
WILL ESPECIALLY BE THE CASE AS THE MOISTURE DEPTH INCREASES TOWARD
AFTERNOON.
FOR THIS REASON HIGH TEMPERATURES WILL BE LOWEST ACROSS THE
HIGHLANDS/SHENANDOAH VALLEY AREA...BUT THE LOWER SET OF GUIDANCE WAS
FAVORED ACROSS ENTIRE CWA GIVEN CLOUD COVER.-- End Changed Discussion --
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM THURSDAY/...
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NORTHEAST/EAST FLOW IN THE LOWER LEVELS CONTINUES TONIGHT. EXPECT
CHANCES FOR RAIN AND DRIZZLE TO EXPAND EASTWARD THROUGH THE CWA
OVERNIGHT AND TO NOT SOLELY BE CONFINED TO THE HIGHLANDS/SHENANDOAH
VALLEY. POP DISTRIBUTION CLOSELY RESEMBLES 21Z/03Z SREFS GUIDANCE
BUT GIVEN THE SYNOPTIC SET UP HAVE ALLOWED FOR BOTH RAIN AND DRIZZLE
AS WEATHER TYPE. AIR TEMPERATURES WILL LOWER A FEW DEGREES CLOSER TO
THE DEWPOINTS OVERNIGHT.-- End Changed Discussion --
&&
.LONG TERM /THURSDAY THROUGH TUESDAY/...
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WITH HIPRES MOVING OFF NEW ENGLAND COAST...LOW LEVELS WINDS BECOME
SELY THU...PUMPING MOISTURE INTO THE CWA. DRIZZLE PSBL IN
MRNG...WITH PRECIP BCMG MORE CNVCTV IN AFTN. INTRODUCED ISOLATED
TSTMS...AS SOME MID-LEVEL DRYING MAY ALLOW LAPSE RATES TO STEEPEN
ENOUGH FOR THUNDER. SFC WARM FRONT SHOULDNT STAY S/E OF CWA...KEEP
INSTABILITY ELEVATED. AS STACKED LOW CONTINUES MOVING N THRU GREAT
LAKES...CDFNT RACES AHEAD AND BECOMES OCCLUDED OVER THE AREA LATE IN
THE DAY...PROVIDING BEST CHANCE FOR DECENT QPF/THO GNRLY UNDER 0.5
INCH.
FRONT EXITS THU NGT...WITH NE/SW PRECIP GRADIENT OVR CWA. CLEARING
SKIES AND DOWNSLOPING SHUD OFFSET CAA FRI...KEEPING TEMPS ABOVE
CLIMATOLOGICAL NORMS.
UPR SYSTEM LIFTS NWD OUT OF DEEP SOUTH SUN/MON...WEAKENING AND BEING
ABSORBED AS NORTHERN JET LOOKS TO BECOME MORE DOMINANT. WITH LOPRES
TO WEST AND FORMATION OF COASTAL LOW OFF NC COAST...CHC POPS SUN
INTO MON IN WHAT SHUD BE AT LEAST MODEST OVERRUNNING SITUATION. BY
LATE TUE ANOTHER SYSTEM MAY BE APPROACHING FROM THE W.-- End Changed Discussion --
&&
.AVIATION /09Z WEDNESDAY THROUGH SUNDAY/...
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MVFR CIGS EXPECTED TO DEVELOP ACROSS AREA TERMINALS THIS MORNING IN
A MOIST NORTHEAST FLOW...PERHAPS EVEN DROPPING INTO IFR AT KCHO.
TREND WILL BE FOR LOWERING CIGS WITH TIME AS MOISTURE DEPTH
INCREASES. EXPECT IFR CIGS TO SPREAD TO THE HUBS DURING THE EVENING
HOURS. ONCE IFR CIGS DEVELOP...THEY ARE LIKELY TO MAINTAIN
THEMSELVES INTO THURSDAY. IN ADDITION...WHEN RAIN/DRIZZLE IS
FALLING...IFR VSBYS MAY BE PRESENT AS WELL.
SUB-VFR VSBY/CIGS LIKELY THU...AS LIGHT RAIN AND DRIZZLE PASS OVER
THE AIRPORTS EARLY IN THE DAY...NUMEROUS SHWRS AFTN AND OVNGT. CDFNT
SHIFTS WINDS TO NW EARLY FRI MRNG. HIPRES MOVES IN FRI...WITH VFR
CONDS THRU SAT.-- End Changed Discussion --
&&
.MARINE...
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NORTHEAST/EAST FLOW WILL FLIRT WITH SMALL CRAFT ADVISORY GUSTS
ACROSS THE BAY/LOWER TIDAL POTOMAC TODAY. AT 3 AM...PATAPSCO BUOY
AND TPLM2 WERE G18 WITH HART/MILLER AND TOLLY POINT G17. FURTHER
SOUTH TANGIER ISLAND WAS G18. LWX WRF-ARW SUGGESTS POSSIBLE 18-20 KT
GUSTS TODAY ACROSS THE MID BAY AREA. WILL LIKELY EXTEND EXISTING
SMALL CRAFT ADVISORY THROUGH THIS AFTERNOON ACROSS THIS AREA.
SELY FLOW LOOKS ATTM TO RMN JUST BELOW SCA THU/THU NGT PRESSURE
GRADIENT TIGHTENS WITH LOPRES APPROACHING FROM WEST. SHOWERS AND
ISOLATED THUNDERSTORMS OVER THE WATERS BEFORE FRONT PASSES THRU
EARLY FRIDAY. NW WINDS BEHIND THE FRONT WILL BE 10 TO 15 KTS...AGAIN
JUST BELOW ADVISORY SPEEDS...WITH SIMILAR CONDS XPCD THRU WKND.-- End Changed Discussion --
&&
.TIDES/COASTAL FLOODING...
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TIDAL ANOMALIES ARE BACK ON THE RISE UNDER A NORTHEAST/EAST FLOW.
HIGH TIDE CYCLE THIS MORNING WILL BE OK...BUT NEXT ONE SLATED TO
OCCUR LATE AFTERNOON/EVENING MAY BE ABLE TO FLIRT WITH MINOR TIDAL
FLOODING THRESHOLDS ESPECIALLY IF THE TIDAL ANOMALIES INCREASE
ANOTHER 1/4 TO 1/2 FOOT WHICH MAY BE POSSIBLE GIVEN MAINTAINED LOW
LEVEL FLOW. EVENT WOULD OCCUR IN THE 12 TO 18 HOUR TIME FRAME FROM
NOW...AND CONFIDENCE IN MEETING MINOR THRESHOLDS IS NOT HIGH.
THEREFORE...WILL HOLD OFF ON ANY COASTAL FLOOD ADVISORY ATTM.-- End Changed Discussion --
&&
.EQUIPMENT...
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LWX WSR-88D IS INOPERABLE ATTM. EL TECHS WILL TROUBLESHOOT FIRST
THING THIS MORNING IN AN ATTEMPT TO RESTORE 88D TO OPERABLE STATUS.-- End Changed Discussion --
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 10 PM EST THIS EVENING FOR ANZ534-
537-543.
SMALL CRAFT ADVISORY UNTIL 6 PM EST THIS EVENING FOR
ANZ531>533.-- End Changed Discussion --
&&
$$
SYNOPSIS...PELOQUIN/SBK
NEAR TERM...PELOQUIN
SHORT TERM...PELOQUIN
LONG TERM...SBK
AVIATION...PELOQUIN/SBK
MARINE...PELOQUIN/SBK
TIDES/COASTAL FLOODING...PELOQUIN
EQUIPMENT...PELOQUIN
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12 to 24 inches forecast now - SAT AM
Cold!
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