Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 240134 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 934 PM EDT WED APR 23 2014 .SYNOPSIS...
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HIGH PRESSURE WILL BUILD OVER THE AREA THROUGH THURSDAY. A COLD FRONT WILL PASS THROUGH THE AREA FRIDAY AND ANOTHER COLD FRONT IS EXPECTED TO MOVE THROUGH SATURDAY. HIGH PRESSURE WILL BUILD IN ON SUNDAY AS THE COLD FRONT STALLS TO OUR SOUTH. SEVERAL WAVES OF LOW PRESSURE WILL DEVELOP ALONG THE STALLED BOUNDARY...BRINGING UNSETTLED CONDITIONS TO THE AREA NEXT WEEK.
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&& .NEAR TERM /THROUGH THURSDAY NIGHT/...
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AT 01Z...1024 MB HIGH PRESSURE WAS LOCATED OVER GREAT LAKES WHILE 996 MB LOW CONTINUES IN THE GULF OF MAINE. THIS HAS KEPT UP THE PRESSURE GRADIENT OVER THE NORTHEAST PORTION OF THE CWA THROUGH THIS EVENING. WIND GUSTS BETWEEN 20 AND 30 MPH ARE STILL BEING REPORTED IN FROM DC METRO...AS FAR WEST AS MARTINSBURG...AND EXTENDING ALONG AND EAST OF THE I-95 CORRIDOR. FURTHER WEST... THERE HAS BEE A QUICK DECOUPLING OF HIGHER WINDS AS THE AIRMASS STABILIZES DUE TO LOSS OF DAYTIME HEATING. LATEST 18Z NAM PROGS 925 MB NORTHWESTERLY WINDS OF 25 TO 30 KT TO CONTINUE EAST OF THE BLUE RIDGE THROUGH 09Z...THEN GRADUALLY DIMINISH FROM WEST OT EAST TO LESS THAN 20 KT BY 18Z ON THURSDAY. EXPECTING WINDS WILL ABATE IN MANY LOCATIONS WEST OF THE I-95 CORRIDOR BETWEEN 10 PM AND MIDNIGHT...WITH WINDS STILL A BIT GUSTY EAST OF I-95 TILL MAYBE AN HOUR LATER. IN AREAS WHERE WINDS DECOUPLE EAST OF THE BLUE RIDGE...ONE CONCERN IS THAT WITH THE DRY AIR AND DEW POINTS IN THE UPPER 20S TO MID 30S...ALONG WITH CLEAR SKIES...THAT COMBINATION COULD ALLOW FOR SOME PATCHY FROST IN PLACES MAINLY AWAY FROM DC AND BALTIMORE METRO AREAS. HOWEVER...LOWERING DEW POINTS OVERNIGHT WILL HELP KEEP A BIT OF A SPREAD BETWEEN AIR AND DEW PT TEMPS. THUS NOT EXPECTING ANY WIDESPREAD FROST CONDITIONS TO DEVELOP TONIGHT... ALTHOUGH A FEW AREA COULD SEE SOME PATCHY FROST IN SOME OF THE COLDER VALLEYS MAINLY WEST OF THE BLUE RIDGE. ON THURS...PLENTY OF SUNSHINE EXPECTED WITH COOLISH TEMPS FOR THIS TIME OF YEAR. RED FLAG FIRE WEATHER IS CONCERN ACROSS MAINLY THE NORTHEAST PORTION OF THE CWA...FROM CARROLL CO MD ACROSS TO HARFORD CO AND SOUTH INTO ANNE ARUNDEL COUNTIES IS MORNING NW WINDS GUSTING TO 20/25 MPH ALONG WITH DEW POINTS IN THE 20S. THUS HAVE CONVERTED PORTION OF PREVIOUS FIRE WATCH INTO A RED FLAG WARNING. SPS FOR ENHANCED FIRE DANGER MAY ALSO BE NEEDED FURTHER WEST. SEE FIRE WX DISCUSSION BELOW FOR DETAILS. PREVIOUS FORECAST DISCUSSION FOLLOWS.
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&& .SHORT TERM /FRIDAY THROUGH SATURDAY/... A WEAK COLD FRONT SHOULD BE MOVING ACROSS THE APPALACHIANS MTNS FRIDAY MORNING AS A SFC LOW MOVES ACROSS THE GREAT LAKES. RETURN FLOW WILL BE USHERING IN WARM AND MOIST CONDITIONS AHEAD OF THE FRONT AND PWAT VALUES ARE EXPECTED TO RISE AROUND 1.3 INCHES BY FRI AFTERNOON. MID LEVEL FORCING ALONG THE SFC FROPA WILL BE MOVING ACROSS THE MID ATLANTIC FRIDAY AFTERNOON. SHOWERS ARE EXPECTED TO SPREAD ACROSS THE REGION AHEAD AND ALONG THE FROPA. SFC HEATING IN CENTRAL VA WILL LIKELY LEAD TO HEAVIER SHOWERS AND EVEN A ISO THUNDERSTORM. A BRIEF PERIOD OF DRYING WILL MOVE INTO THE REGION BEHIND THE FROPA SATURDAY NIGHT. A SECOND COLD FRONT WILL ROTATE AROUND THE GREAT LAKES LOW AND MOVE ACROSS THE MID ATLANTIC SATURDAY. DEPENDING ON THE SPEED OF THE FROPA TEMPS WILL RANGE FROM THE 50S TO THE MID 70S ACROSS THE REGION. AT THIS TIME KEPT TEMPS EAST OF THE BLUE RIDGE AND VALLEY LOCATIONS IN THE MID TO UPPER 70S. IF THE FROPA MOVES FASTER TEMPS WILL BE LOWER. LITTLE QPF IF ANY IS EXPECTED WITH THE FROPA. LEANED TOWARDS THE GFS AND PUT CHANCE OF SHOWERS FOR THE POTOMAC HIGHLANDS AND NW SUBURBS OF DC AND BALTIMORE SATURDAY DUE TO A SHORTWAVE TROUGH CROSSING THE REGION. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... THE PRESSURE GRADIENT OVER THE AREA WILL SLOWLY WEAKEN AND LEAD TO GRADUALLY SUBSIDING NORTHWEST WINDS SATURDAY NIGHT INTO SUNDAY. BREEZY AND DRY CONDITIONS ARE EXPECTED WITH TEMPERATURES NEAR NORMAL. HIGH PRESSURE WILL ANCHOR ITSELF OVER NEW ENGLAND BY SUNDAY NIGHT AS A LARGE AND SLOW-MOVING LOW PRESSURE SYSTEM TAKES SHAPE OVER THE GREAT PLAINS. CLOUDS WILL SPILL OVER THE RIDGE IN PLACE OVER THE AREA...STARTING AS THIN HIGH CIRRUS DURING THE DAY SUNDAY BUT LOWERING AND THICKENING SUNDAY NIGHT THROUGH MONDAY. CHANCES FOR RAIN GRADUALLY INCREASE FROM SOUTHWEST TO NORTHEAST MONDAY INTO MONDAY NIGHT AS THE ATMOSPHERE CONTINUES TO MOISTEN. LOW PRESSURE SLOWLY MOVES NORTHEASTWARD INTO THE OHIO VALLEY TUESDAY INTO WEDNESDAY. THERE IS A LARGE SPREAD IN THE GUIDANCE REGARDING THE EXACT TIMING AND EXTENT OF RAINFALL...AS WELL AS THE TRACK OF LOW PRESSURE AND THE NORTHWARD PROGRESSION OF A DEVELOPING WARM FRONT OVER THE CAROLINAS. THIS IS DUE TO A VERY COMPLEX PATTERN...WITH A STRONG CUTOFF LOW OVER THE CANADIAN MARITIMES INTERACTING WITH THE LOW PRESSURE MOVING OUT OF THE CENTRAL UNITED STATES...AND A RIDGE OF HIGH PRESSURE PINCHED IN BETWEEN OVER NEW ENGLAND. THEREFORE...THERE IS A HIGH LEVEL OF UNCERTAINTY IN DETAILS SUCH AS THE CHANCES FOR THUNDERSTORMS...WINDS AND RAINFALL AMOUNTS. DEPENDING ON THE EVOLUTION OF LOW PRESSURE...UNSETTLED WEATHER COULD LINGER INTO THE MIDDLE OF NEXT WEEK. && .AVIATION /01Z THURSDAY THROUGH MONDAY/...
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NW WINDS CONTINUE GUSTING INTO 20-25KT RANGE AT 01Z. EXPECT SUFFICIENT AIRMASS DECOUPLING TO TAKE NEAR SFC WIND GUSTS OUT OF THE EQUATION BY 02Z. WILL HAVE TO MONITOR FOR THIS. CLEAR SKIES OVERNIGHT. ON THUR...VFR WITH N/NW WINDS 10KT WITH GUST TO 25 KT THROUGH EARLY AFTERNOON. SHOWERS ARE EXPECTED FRIDAY AS A WEAK COLD FRONT MOVES ACROSS THE MID ATLANTIC. VCTS IS POSSIBLE FOR CENTRAL VA FRIDAY AFTERNOON AND EARLY EVENING. SLY WINDS WILL BECOME W-NW BEHIND THE FROPA FRIDAY NIGHT INTO SATURDAY. ANOTHER COLD FRONT WILL CROSS THE REGION SATURDAY. GUSTS UP TO 30KTS ARE POSSIBLE SATURDAY AFTERNOON. MODERATE CONFIDENCE IN VFR CONDITIONS WITH NORTHWEST WINDS 10 TO 15 KNOTS SUNDAY INTO SUNDAY NIGHT.
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&& .MARINE...
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CANCELLED GALE AT 6 PM...AND SCA CONTINUES ACROSS ALL MARINE AREA TONIGHT. ON THUR...AS HIGH PRES BUILDS IN...WINDS WILL GRADUALLY DIMINISH MAINLY FROM SOUTH TO NORTH...TO BELOW SCA LEVELS DURING THE AFTERNOON. MAY BE ABLE TO BE CANCELLED A FEW HRS EARLY ON THU DEPENDING ON HOW QUICKLY THE AXIS OF THE HIGH BUILDS OVER THE WATERS. SLY WINDS WILL INCREASE FRIDAY AHEAD OF A WEAK COLD FRONT. SCA MAY BE NEEDED AS GUSTS INCREASE IN THE LOWER BAY AND LOWER TIDAL POTOMAC. WINDS WILL BECOME WRLY BEFORE ANOTHER FROPA CROSS THE WATERS SATURDAY AFTERNOON. GUSTY NW WINDS ARE LIKELY SATURDAY AFTERNOON AND A GALE WARNING IS EVEN POSSIBLE. SMALL CRAFT ADVISORY GUSTS MAY LINGER THROUGH SATURDAY NIGHT AND INTO SUNDAY FOR PORTIONS OF THE WATERS. WINDS BECOME LIGHTER LATE SUNDAY INTO SUNDAY NIGHT AS HIGH PRESSURE PASSES NEAR THE REGION.
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&& .FIRE WEATHER...
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RED FLAG WARNING FOR THE GREATER BALTIMORE AREA THURSDAY. HIGH PRESSURE WILL CONTINUE TO BUILD SOUTHEAST ACROSS THE AREA THROUGH THURSDAY AFTERNOON. SKIES ARE EXPECTED TO BE MOSTLY SUNNY. THE COMBINATION OF GUSTY NORTHWEST WINDS INTO THE AFTERNOON AND CONTINUED DRY CONDITIONS WILL LEAD TO A PARTICULARLY ENHANCED FIRE WEATHER THREAT FOR THE GREATER BALTIMORE AREA. A SPECIAL WEATHER STATEMENT FOR AN ENHANCED FIRE WEATHER THREAT IS LIKELY ELSEWHERE SUCH AS WESTERN AND SOUTHERN MARYLAND...EASTERN WEST VIRGINIA... AND NORTHERN PORTIONS OF VIRGINIA. WINDS WILL EASE SOONER FOR THESE AREAS...SO A RED FLAG WARNING WAS NOT WARRANTED AS OF THIS TIME FOR THESE AREAS.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...RED FLAG WARNING FROM 10 AM TO 6 PM EDT THURSDAY FOR MDZ005>007-010-011-014. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EDT THURSDAY FOR ANZ530>543.
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&& $$ SYNOPSIS...SMZ NEAR TERM...SMZ SHORT TERM...HAS LONG TERM...DFH AVIATION...SMZ MARINE...SMZ FIRE WEATHER...BAJ

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