Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 020252 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 1052 PM EDT WED OCT 1 2014 .SYNOPSIS... HIGH PRESSURE WILL BUILD OVERHEAD THROUGH THURSDAY. A STRONG COLD FRONT WILL APPROACH THE AREA FRIDAY BEFORE PASSING THROUGH FRIDAY NIGHT INTO EARLY SATURDAY. HIGH PRESSURE WILL RETURN FOR THE WEEKEND...BRINGING DRIER AND NOTICEABLY COOLER CONDITIONS. THE HIGH WILL MOVE OFFSHORE EARLY NEXT WEEK. && .NEAR TERM /THROUGH THURSDAY/... UPR LOPRES CONTS TO LIFT NEWD THIS EVNG. BROAD/DIFFUSE HIPRES AFFECTING CWFA ATTM. A RATHER SUBSTANTIAL PATCH OF LOW CLD STRETCHES FM THE ERN WVA PNHNDL SEWD ACRS VA. BASES/CIGS GNLY 3000-4000 FT. THERE/S NOT MUCH FLOW TO SPEAK OF AT THIS POINT. DONT REALLY FORSEE THIS AREA MIXING OUT OVNGT...HWVR SUSPECT IT WONT BE REINFORCED EITHER. INSTEAD...ITLL BE TRAPPED UNDER SUBSIDENCE INVRSN /EVIDENT IN LWX 00Z RAOB/...PERHAPS LWRG THRU THE NGT. AS LONG AS THESE CLDS ARE AROUND...THE FOG THREAT-- AT LEAST DENSE FOG-- WL BE DELAYED. THATS NOT THE CASE ACRS MD... WHERE SKIES ARE MOCLR AND FOG HAS ALREADY BEGUN DVLPG. WL BE REVAMPING CLDS/WX GRIDS TO ACCOUNT FOR GOING TRENDS. WITH RIDGING IN PLACE THURSDAY...A MIX OF SUN AND CLOUDS ARE EXPECTED ONCE CLDS MIX OUT. FURTHER WEST...TERRAIN CIRCULATIONS MAY CAUSE A CU FIELD TO DEVELOP ACROSS THE VA HIGHLANDS. && .SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/... MAIN STORY OF THE PERIOD WILL BE A STRONG COLD FRONT SWINGING THROUGH THE AREA. A LARGE TROUGH WILL DIG INTO THE UPPER MIDWEST DURING THE DAY FRIDAY...ASSUMING A NEGATIVE TILT AS IT PIVOTS ACROSS THE GREAT LAKES/OHIO VALLEY FRIDAY NIGHT. 500 MB LOW CUTS OFF IN THE PROCESS AND MOVES ROUGHLY FROM CHICAGO EAST TO PITTSBURGH OVERNIGHT. STRONG AND DEEP LIFT AHEAD OF THIS TROUGH ALONG A SURFACE COLD FRONT WILL DRIVE A BAND OF SHOWERS MOVING ACROSS THE AREA FROM WEST TO EAST FRIDAY AFTERNOON AND FRIDAY NIGHT. THE LATEST GUIDANCE HAS SLOWED THE TIMING OF THE FRONT SOMEWHAT SO MOST OF THE RAIN LOOKS TO BE OVERNIGHT FRIDAY NIGHT...ESPECIALLY EAST OF THE BLUE RIDGE. THE OVERNIGHT TIMING OF THE FRONTAL PASSAGE WOULD MEAN LOWER INSTABILITY LEVELS AND THUS A LOWER CHANCE OF THUNDERSTORMS OVERALL. HOWEVER THE AFOREMENTIONED LIFT AND STRONG HEIGHT FALLS/COOLING ALOFT MAY STILL RESULT IN A LINE OF HEAVIER SHOWERS WITH ISOLATED LIGHTNING STRIKES DESPITE LOW CAPE. NAM/GFS/ECMWF NOW IN BETTER AGREEMENT WITH THE STRENGTH OF THE SOUTHERLY LOW-LEVEL JET AS WELL PRECEDING THE COLD FRONT...BUT AGAIN THE OVERNIGHT TIMING WOULD TEND TO WORK AGAINST MIXING THE MAJORITY OF THIS WIND TO THE SURFACE. ANY HEAVIER BANDS OF SHOWERS COULD MIX SOME OF THIS WIND DOWN BUT OVERALL THE SEVERE THREAT APPEARS TOO LOW TO WARRANT A MENTION IN THE HWO FOR NOW. WILL CONTINUE TO MONITOR. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... THE FRONT PULLS EAST OF THE AREA SATURDAY MORNING LEAVING IN ITS WAKE A MUCH COOLER AND DRIER AIRMASS OVER THE WEEKEND. AS THE TROUGH AXIS PIVOTS OVER THE AREA...FAVORABLE TRAJECTORIES FOR UPSLOPE WILL BE LIKELY WITH SHOWERS POSSIBLE OVER THE WESTERN SLOPES. SOME SNOWFLAKES MAY BE MIXED IN AS WELL GIVEN 850 MB TEMPS CRASHING TO BETWEEN 0 AND -2 C SATURDAY NIGHT. SPOTTY FREEZING TEMPERATURES WILL BE POSSIBLE ALONG THE RIDGES AS WELL OVERNIGHT SATURDAY NIGHT. THE AIRMASS WILL QUICKLY MODERATE AS HIGH PRESSURE MOVES EAST RESULTING IN A LOW-LEVEL SOUTHWESTERLY FLOW BY EARLY NEXT WEEK. THE NEXT STORM SYSTEM AND CHANCE OF RAIN WILL MOVE ACROSS THE AREA FROM WEST TO EAST MONDAY NIGHT THROUGH TUESDAY. && .AVIATION /03Z THURSDAY THROUGH MONDAY/... CIGS HV DROPPED TO MVFR AT MRB. ELSW...VFR PREVAILS FOR NOW. XPCT FLGT RESTRICTIONS TO DVLP OVNGT DUE BOTH TO LWRG CIGS AS WELL AS FOG DVLPMNT. TAFS AS OF 00Z PLACING MORE EMPHASIS ON VSBYS...W/ IFR AT CLIMO FAVORED CHO/MRB AND MVFR AT IAD. HWVR...LTST TRENDS SUGGESTING LOW CIGS MAY BECOME MORE OF A PLAYER. WL MONITOR FOR PSBL ADJUSTMENTS. EITHER WAY...WE/LL HV IFR CONDS /OR PERHAPS LWR/ IN PLACE FOR START OF MRNG PUSH WEST OF THE HUBS...AND PERHAPS ENCROACHING ON IAD/DCA/BWI AS WELL. CONDITIONS WILL IMPROVE TOWARDS THURSDAY MIDDAY AND VFR CONDITIONS EXPECTED THROUGH THURS AFTERNOON. LOW CIGS/VSBYS TO IFR OR LWR PSBL FRI-SAT AM IN MOIST SOUTHERLY FLOW 10-20 KTS AND GUSTY AHEAD OF STRONG FRONT. LLWS PSBL FRI NIGHT. MODELS COMING INTO BETTER TIMING/STRENGTH AGREEMENT LENDING TO MODERATELY HIGH CONFIDENCE DURING THIS TIME. VFR RETURNS SAT PM AND PERSISTS THROUGH THE WEEKEND...WINDS TURNING WEST 10-20 KTS BEHIND FRONT. && .MARINE... LGT WNDS ON THE WATERS TNGT...W/ SPDS BLO 10 KT. WHILE THERE WONT BE A STRONG DIRECTIONAL PUSH...A NELY COMPONENT TO THE DRIFT WUD BE PREFERRED. NE-E FLOW WILL CONTINUE ON THE WATERS THURSDAY. WINDS 10-15 KTS ARE EXPECTED. THE TIGHTER GRADIENT AND THEREFORE STRONGER GUSTS ARE ACROSS THE OCEAN WATERS. A ISOLATED GUST OF 18-20KTS IS POSSIBLE ACROSS TANGIER SOUND INTO THURSDAY AFTERNOON. SCA CONDITIONS VERY LIKELY IN SOUTHERLY CHANNELING AHEAD OF STRONG COLD FRONT FRIDAY. A BAND OF HEAVY SHOWERS WHICH MAY ENHANCE GUSTY WINDS WILL APPROACH THE WATERS FROM THE WEST FRIDAY NIGHT. THE FRONT CLEARS THE WATERS SATURDAY WITH GUSTY NORTHWEST FLOW TO SCA LEVELS POSSIBLE THROUGH THE REMAINDER OF THE WEEKEND. && .TIDES/COASTAL FLOODING...
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TIDAL ANOMALIES CONTINUE AROUND A FOOT TO 1.25 FT. WE/VE MET THE MINOR TIDAL INUNDATION THRESHOLD AT PPTM2 AND SLIM2...AND ANNAPOLIS IS ON PACE TO DO THE SAME. CSTL FLOOD ADVYS IN PLACE FOR ALL THREE COUNTIES. BASED ON CURRENT DEPARTURES...AS WELL AS THE SCOPE OF THE TIDE... SUSPECT THAT BALTIMORE...SW DC...AND ALEXANDRIA WILL ALSO REACH MINOR /ADVISORY/ CRITERIA...THOUGH DO NOT EXPECT A LONG RESIDENT FLOOD. HV ADDED TO THE ADVISORY FOR THESE AREAS MIDNIGHT-5AM. DO NOT SEE BIG CHANGES IN THE WEATHER REGIME THU-FRI. WINDS WILL MAINLY BE LIGHT /OR LIGHTER/ WITH AN ONSHORE COMPONENT. WHILE DEPARTURES MAY NOT CONTINUE QUITE AS SHARP AS THEY ARE NOW... DO THINK THAT THEY WILL REMAIN ELEVATED UNTIL A COLD FRONT CROSSES LT FRI NGT. BASED ON THE TIDAL DEPARTURES WE HAVE...SEEING WHATS AT THE BAY BRIDGE TUNNEL THIS EVENING...USING CBOFS GUIDANCE /ACCOUNTING FOR THE BIAS/...AND RECOGNIZING THAT THE NIGHTTIME TIDE IS THE HIGHER OF THE TWO...WE/LL BE EXTENDING THE COASTAL FLOOD ADVISORY FOR THE WESTERN SHORE OF THE BAY FROM ST MARYS TO ANNE ARUNDEL FOR ANOTHER 25 HOURS. AM MORE CONFIDENT ON THE NIGHTTIME TIDE...BUT THE DAY CYCLE STANDS A DECENT CHANCE TOO.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...COASTAL FLOOD ADVISORY UNTIL 5 AM EDT THURSDAY FOR DCZ001. MD...COASTAL FLOOD ADVISORY UNTIL 4 AM EDT FRIDAY FOR MDZ014-017- 018. COASTAL FLOOD ADVISORY UNTIL 5 AM EDT THURSDAY FOR MDZ011. VA...COASTAL FLOOD ADVISORY UNTIL 5 AM EDT THURSDAY FOR VAZ054. WV...NONE. MARINE...NONE.
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&& $$ SYNOPSIS...HAS NEAR TERM...HTS/HAS SHORT TERM...DFH LONG TERM...DFH AVIATION...HTS/HAS/DFH MARINE...HTS/HAS/DFH TIDES/COASTAL FLOODING...HTS

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