Area Forecast Discussion
Issued by NWS Sterling, VA

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KLWX 270823 AAA AFDLWX AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 423 AM EDT SAT JUN 27 2015 .SYNOPSIS...A STATIONARY FRONT OVER THE SOUTHERN MID ATLC STATES WILL LIFT NORTH AS A WARM FRONT THROUGH THIS EVENING. A COLD FRONT WILL PASS THROUGH THE AREA LATE TONIGHT. HIGH PRESSURE WILL BE IN PLACE FOR MONDAY WITH WEAK COLD FRONT TUESDAY NIGHT. && .NEAR TERM /THROUGH TONIGHT/...UPPER LEVEL TROUGH OVER THE MID SECTION OF THE COUNTRY IS EXPECTED TO DEEPEN NEXT 36 HRS AS IT TAKES ON MORE OF A NEUTRAL TO NEGATIVE TILT AS IT LIFTS INTO THE ERN GRT LKS AND ONTARIO. ACCOMPANYING SFC CYCLONE OVR SW OH WILL LIFT ENE TO NCNTRL PA BY 12Z SUN. A SECONDARY WEAKER SFC LOW MAY TRY TO DEVELOP ALONG TRIPLE POINT OVER NRN VA THIS EVENING. RAIN...POSSIBLY HEAVY AT TIMES WITH EMBEDDED T-STORMS WILL CONTINUE TO SPREAD NORTHEAST THIS MORNING IN ZONE OF WARM AIR ADVECTION WITH RAINFALL RATES OF HALF TO AN INCH PER HOUR. AFTER 18Z...IT APPEARS SOME AREAS WILL BE ABLE TO GET INTO THE WARM SECTOR WITH AN INCREASING RISK OF SEVERE T-STORMS INCLUDING TORNADOES. GUIDANCE SHOWS DIFFERENT SOLUTIONS WITH RESPECT TO WARM FRONTAL POSITION WITH GFS SHOWING AREAS ALONG AND EAST OF I-95 TO THE PA AND DE BORDER BREAKING OUT INTO THE WARM SECTOR WHILE THE ECMWF IS MORE CONSERVATIVE ONLY INDICATING AREAS FROM DC EAST TO ANNAPOLIS AND POINTS SOUTH GETTING INTO THE WARM SECTOR. A FEW HP SUPERCELLS APPEAR LIKELY GIVEN 0-6KM SHEAR VALUES OF 30 M/S AND 0-3 KM SRH OF 350 M^2/S^2 WITH AN ATTENDANT RISK OF A COUPLE OF TORNADOES AND VERY HEAVY RAINFALL AND FLASH FLOODING. WITH RESPECT TO FLOODING POTENTIAL...GUIDANCE STILL SHOWS AREAS NORTH AND EAST OF THE POTOMAC RIVER DOWN TO ALEXANDRIA RECEIVING THE HEAVIEST RAINFALL IN THE ORDER OF 1 TO 3 INCHES. CDFNT WILL CLEAR THE CHES BAY JUST AFTER 06Z SUN ENDING THE SVR AND FLOODING THREAT. && .SHORT TERM /SUNDAY/...WRAP AROUND MOISTURE AROUND DEEP SFC CYCLONE OVER THE NORTHEAST AND CYCLONIC FLOW WILL MAINTAIN BKN SKIES WITH THE RISK OF A FEW SHOWERS MAINLY NORTHERN AND FAR WESTERN AREAS. BREEZY AND MUCH COOLER THAN NORMAL WITH TEMPS STRUGGLING TO HIT 80F. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...ANY WRAP-AROUND/ UPSLOPE RAIN SHOWERS IN THE POTOMAC HIGHLANDS WILL END SUNDAY EVENING AS THE STRONG LOW PRESSURE SYSTEM PULLS AWAY FROM NEW ENGLAND. A MUCH COOLER AND DRIER AIRMASS WILL BE FOUND IN ITS WAKE...WHICH WILL ALLOW TEMPERATURES TO DROP INTO THE 50S EXCEPT IN THE URBAN AREAS AND COASTAL PLAIN. MONDAY WILL BE A DRY DAY AS SHORTWAVE RIDGING QUICKLY SLIDES ACROSS THE AREA. TEMPERATURES WILL REMAIN SLIGHTLY BELOW NORMAL. NEXT SHORTWAVE TROUGH WILL BE MOVING INTO THE GREAT LAKES MONDAY NIGHT...LEADING TO AT THE VERY LEAST INCREASING CLOUDS. SOME DIFFERENCES ON HOW MUCH PRECIP MAKES IT INTO OUR AREA...BUT HAVE CONFINED POPS WEST OF I-81 OVERNIGHT. WITH THE TROUGH AXIS APPROACHING TUESDAY...EXPECT AT LEAST SCATTERED CONVECTION ACROSS THE AREA. SFC LOW LIFTS NORTH INTO QUEBEC ON WED...WITH THE TRAILING COLD FRONT BECOMING PARALLEL TO THE UPPER FLOW AND STALLING OVER THE MID-ATLANTIC. THIS LEADS TO AN UNSETTLED PATTERN IN WHICH THE DETAILS ARE A BIT MURKY. THE 00Z GFS PUSHES THE FRONT SOUTH BY FRIDAY...WHILE THE ECMWF KEEPS IT NEARBY AND CONTINUES CHANCES FOR CONVECTION. TEMPERATURES ARE EXPECTED TO REMAIN WITHIN SEVERAL DEGREES OF NORMAL THROUGH THE UPCOMING WEEK. && .AVIATION /09Z SATURDAY THROUGH WEDNESDAY/...IFR CIGS TODAY AT MOST TERMINALS IN MDT TO HVY RAINS. T- STORMS POSSIBLE TOO WITH A RISK OF DAMAGING WINDS ESPECIALLY AT KDCA AND KBWI. CIGS IMPROVE TO VFR AFTER 09Z SUN. VFR CONDITIONS EXPECTED SUNDAY NIGHT THROUGH MONDAY NIGHT. SLOW MOVING COLD FRONT APPROACHES TUESDAY AND THEN MAKES LITTLE PROGRESS. THUNDERSTORMS WITH SUB-VFR CONDITIONS WILL BE POSSIBLE TUESDAY...WITH WEDNESDAY/S THUNDERSTORM FORECAST A LITTLE LESS CERTAIN. ALSO SOUTHERLY WINDS MAY GUST ABOVE 20 KT ON TUESDAY. && .MARINE...GUSTY SERLY FLOW TODAY WITH SCA CONDITIONS. WINDS SHIFT TO WSW TONIGHT AND REMAIN GUSTY THROUGH SUN. SCA HAS BEEN EXTENDED THROUGH SUN BUT HIGHER GUSTS CAN BE EXPECTED NEAR T-STORMS. GUSTY WESTERLY WINDS WILL CONTINUE INTO SUNDAY EVENING AND THE SCA WILL LIKELY NEED TO BE EXTENDED. WINDS WILL DIMINISH ON MONDAY AS HIGH PRESSURE QUICKLY PASSES BY. SOUTHERLY FLOW WILL BECOME ESTABLISHED MONDAY NIGHT...AND CHANNELING OVER THE BAY IS POSSIBLE. SCA IS MORE LIKELY ACROSS ALL WATERS ON TUESDAY AHEAD OF A COLD FRONT. SCATTERED THUNDERSTORMS MAY ALSO DEVELOP. WINDS WILL DIMINISH TUESDAY NIGHT INTO WEDNESDAY AS THE LOW PRESSURE CENTER MOVES INTO CANADA. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...FLASH FLOOD WATCH THROUGH LATE TONIGHT FOR DCZ001. MD...FLASH FLOOD WATCH THROUGH LATE TONIGHT FOR MDZ003>006-011-013- 014-016-501>508. VA...FLASH FLOOD WATCH THROUGH LATE TONIGHT FOR VAZ025>031-036>040- 050>056-501>508. WV...FLASH FLOOD WATCH THROUGH LATE TONIGHT FOR WVZ050>053-055- 501>506. MARINE...FLASH FLOOD WATCH THROUGH LATE TONIGHT FOR ANZ535-538. SMALL CRAFT ADVISORY UNTIL 9 PM EDT SUNDAY FOR ANZ531>534- 536>543. SMALL CRAFT ADVISORY UNTIL 9 PM EDT SUNDAY FOR ANZ530-535. && $$ SYNOPSIS...LFR NEAR TERM...LFR SHORT TERM...LFR LONG TERM...ADS AVIATION...ADS/LFR MARINE...ADS/LFR

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.