Area Forecast Discussion
Issued by NWS Sterling, VA

Current Version | Previous Version | Text Only | Print | Product List | Glossary On
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 271406 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 1006 AM EDT SUN JUL 27 2014 .SYNOPSIS... LOW PRESSURE OVER MINNESOTA IS EXPECTED TO TRACK ACROSS PENNSYLVANIA TONIGHT. AN ASSOCIATED COLD FRONT WILL MOVE THROUGH THE REGION MONDAY. HIGH PRESSURE WILL BUILD IN BEHIND THE FRONT BRINGING COOLER AND DRIER CONDITIONS DURING MIDWEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... SEVERE WEATHER EXPECTED TODAY AND TONIGHT FOR THE MID-ATLANTIC REGION. AS OF 14Z...AN UPPER LEVEL DISBURBANCE HAS REACHED THE APPALIACIANS IN THE WESTERLY FLOW ALOFT. SHOWERS ARE EXITING THE NRN PIEDMONT AND SRN MD THIS MORNING IN RESPONSE TO A DISTURBANCE THAT CAME THROUGH THIS MORNING. SUBSIDENCE BEHIND THE FIRST DISTURBANCE HAS LED TO CLEARING ACROSS NRN MD AND THE POTOMAC HIGHLANDS. ALTHOUGH MID TO HIGH LEVEL CLOUDS ARE BEGINING TO STREAM INTO FROM THE NEXT DISTURBANCE...PATCHES OF CLEARING WILL CONTINUE FROM WEST TO EAST AHEAD OF THE NEXT DISTURBANCE LEADING TO DESTABILIZATION ACROSS THE AREA. A LULL OF ACTIVITY IS EXPECTED THIS MORNING AS THE ATM BECOMES MORE UNSTABLE. PER THE 12Z IAD RAOB...CAPE VALUES ARE EXPECTED TO BE AROUND 2K-2.5K J/KG BY THIS AFTERNOON AND EVENING. 0-6KM SHEAR OF 42KTS AND 0-1KM OF 17 KTS ARE OBSERVED IN THE SOUNDING RAOB. THIS SHEAR PROFILE IS FAVORABLE FOR ORGANIZED CONVECTION TODAY AND WILL LIKELY INCREASE THIS AFTERNOON AND EVENING. THUNDERSTORMS ACROSS IN/OH/KY WILL MOVE EASTWARD WITH TIME. THESE SHOWERS WILL HAVE A OVERALL SE-E TRACK AND REACH THE CENTRAL FOOTHILLS BY MIDDAY. MID TO HIGH LEVEL CLOUDS WILL LIMIT INSTABILITY SOME AND THEREFORE CONVECTION SHOULD BE ISO-SCT AS IT REACHES THE REGION. ELSEWHERE...THUNDERSTORMS ARE EXPECTED TO INTIATE THIS AFTERNOON ACROSS THE OHIO VALLEY FROM LAKE ERIE THROUGH THE OHIO VALLEY AHEAD OF THE MAIN SHORTWAVE TROUGH AND COLD FRONT. THESE STORMS WILL TRACK EASTWARD AND BE STRONG. ANY HEATING BOUNDARY OR OUTFLOW FROM DECAYING THUNDERSTORMS WILL ALSO LIKELY CAUSE THUNDERSTORM INTIATION ACROSS THE REGION THIS AFTERNOON. COVERAGE IS EXPECTED TO BE SCATTERED THIS AFTERNOON BUT CONDITIONS ARE FAVORABLE FOR SEVERE THUNDERSTORMS. PREVIOUS DISCUSSION... THIS IS GOING TO BE THE TIME WHEN SEVERE WEATHER IS MOST LIKELY...WHICH WOULD BE LATER THIS AFTERNOON INTO EARLY THIS EVENING WEST OF THE BLUE RIDGE MOUNTAINS AND THIS EVENING EAST OF THE BLUE RIDGE MOUNTAINS. HOWEVER...KEEP IN MIND THAT SEVERE STORMS OUT AHEAD OF THIS LINE MAY DEVELOP ACROSS ALL AREAS THIS AFTERNOON. THE COMBINATION OF THE INSTABILITY...SHEAR PROFILES AND LIFTING MECHANISMS SUCH AS OUTFLOW BOUNDARIES...A SURFACE TROUGH AND THE APPROACHING COLD FRONT WILL ENHANCE THE THREAT FOR SEVERE THUNDERSTORMS. IN FACT SUPERCELLS WITH SIGNIFICANT SEVERE WEATHER IS POSSIBLE THIS AFTERNOON AND EVENING IF THE INGREDIENTS ALL COME TOGETHER. DAMAGING WINDS...LARGE HAIL AND ISOLATED TORNADOES WILL BE THE PRIMARY THREATS ALONG WITH VERY HEAVY RAINFALL. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM MONDAY/... THE POTENT SHORTWAVE WILL MOVE INTO UPSTATE NEW YORK LATER TONIGHT WHILE THE POTENT COLD FRONT LIKELY JUMPS TO THE PRESSURE TROUGH OFF TO OUR EAST BY MONDAY MORNING. THE DRY SLOT ALONG WITH COLD ADVECTION SHOULD SUPPRESS CONVECTION LATE TONIGHT. MIN TEMPS WILL RANGE FROM THE 50S IN THE ALLEGHENY HIGHLANDS TO THE LOWER AND MIDDLE 70S IN WASHINGTON AND BALTIMORE. && .LONG TERM /MONDAY THROUGH SATURDAY/... THE NEXT 24 HRS LOOK TO BE VERY ACTIVE WX WISE...WITH A DOWNWARD TREND IN ACTIVITY EXPECTED THEREAFTER. CD FNT LOOKS TO BE MOVING OFFSHORE MIDDAY MON...BRINGING AN END TO THE CNVCTV CHCS AND USHERING IN THE COOLER AIR THAT WL END WHAT IS TYPICALLY THE HOTTEST TIME IN THE HOTTEST MONTH OF THE YR (CLIMATOLOGICALLY TEMPS BEGIN TO DROP IN EARLY AUG). BRZY CONDS AREA XPCTD MON AFTN. AFTR THAT SVRL DAYS OF M CLR SKIES W/ COMFORTABLE TEMPS ARE XPCTD. DWPTS IN THE 50S...HARD NOT TO ENJOY THAT IN JUL. HIGH TEMPS TUE-THU SHOULD BE IN THE LM80S (COOLER IN THE MTNS) W/ LOWS IN THE MU50S. (WARMER IN THE CITIES). NO REALLY HOT WX ON TAP FOR THE MID ATLC RGN. AS HAS BEEN DISCUSSED B4 THE PRIMARY REASON FOR THIS IS THE UPR LVL WRN RDG/ERN TROF. DRY AND HOT IN THE W - NW ICC WEB SITE SHOWS MULTIPLE WILDFIRES ONGOING IN OR/WA - W/ 2 IN WA BEING ESPECIALLY LARGE. THIS PATTERN LOOKS TO RMN IN PLACE UNTIL AT LEAST NEXT WKND. && .AVIATION /13Z SUNDAY THROUGH THURSDAY/... ROUNDS OF SHOWERS AND THUNDERSTORMS ARE EXPECTED THROUGH THIS EVENING. THUNDERSTORMS MAY BECOME SEVERE...ESPECIALLY LATER THIS AFTERNOON AND EVENING. DAMAGING WINDS...LARGE HAIL AND ISOLATED TORNADOES ARE POSSIBLE. CIGS/VSBYS WILL BE REDUCED TO MVFR/IFR LEVELS BRIEFLY DURING TIMES OF CONVECTION. CONVECTION SHOULD DISSIPATE OVERNIGHT AS A COLD FRONT MOVES OFF TO OUR EAST. CD FNT WL CROSS THE AREA MON MRNG. LINGERING SHOWERS/ANY LOWER CIGS SHOULD IMPROVE BY AFTN THEN GUSTY NWRLY WINDS. THESE SHOULD DIMINISH BY EVE. VFR CONDS MON NGT THRU THU. && .MARINE... A SOUTHERLY FLOW WILL CONTINUE THROUGH TONIGHT. A SMALL CRAFT ADVISORY IS IN EFFECT FOR THE WATERS THIS AFTERNOON AND EVENING. IT WILL BE MARGINAL DUE TO RELATIVELY COOLER WATERS...BUT A STRENGHENING PRESSURE GRADIENT AND WIND FIELD SHOULD CAUSE GUSTS AROUND 20 KNOTS. A SMALL CRAFT ADVISORY REMAINS IN EFFECT FOR LATE TONIGHT ALONG THE MARYLAND CHESAPEAKE BAY FROM SANDY POINT TO SMITH POINT AND THE LOWER TIDAL POTOMAC RIVER FROM COBB ISLAND TO SMITH POINT. ROUNDS OF SHOWERS AND THUNDERSTORMS ARE EXPECTED THROUGH TONIGHT. SEVERE THUNDERSTORMS ARE A CONCERN...ESPECIALLY LATER THIS AFTERNOON THROUGH THIS EVENING. DAMAGING WINDS...LARGE HAIL AND ISOLATED WATERSPOUTS ARE POSSIBLE. PLEASE PAY ATTENTION TO THE LATEST FORECASTS REGARDING WATCHES AND WARNINGS FOR SEVERE WEATHER. SCA IN EFFECT FOR ALL OF THE WATERS DURG THE DAY MON AS A CD FNT MOVES OFFSHORE AND WNW WINDS STRENGTHEN. NO PROBS FORESEEN MON NGT-MIDWK. && .TIDES/COASTAL FLOODING... A SOUTHERLY FLOW HAS CAUSED TIDAL ANOMALIES BETWEEN ONE HALF AND ONE FOOT ABOVE NORMAL EARLY THIS MORNING. WILL HAVE TO KEEP AN EYE ALONG THE UPPER TIDAL POTOMAC SHORE NEAR WASHINGTON DC. AT THIS TIME...THE FLOW APPEARS THAT IT IS LIGHT ENOUGH FOR WATER LEVELS TO REMAIN JUST BELOW MINOR FLOODING THRESHOLDS NEAR HIGH TIDE THIS MORNING. THE HIGH TIDE THIS AFTERNOON WILL BE THE LOWER OF THE TWO...SO NO TIDAL FLOODING IS EXPECTED. THE FLOW WILL BEGIN TO TURN OFFSHORE LATE TONIGHT SO ANOMALIES SHOULD COME DOWN A BIT. THEREFORE...TIDAL FLOODING IS NOT EXPECTED. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY FROM 3 PM THIS AFTERNOON TO MIDNIGHT EDT TONIGHT FOR ANZ530-531-535-536-538-539-542. SMALL CRAFT ADVISORY FROM 10 AM TO 7 PM EDT MONDAY FOR ANZ530- 531-535-536-538-539-542. SMALL CRAFT ADVISORY FROM 3 PM THIS AFTERNOON TO 7 PM EDT MONDAY FOR ANZ532>534-537-540-541-543. && $$ UPDATE...HAS PREVIOUS DISCUSSIONS...BJL/WOODY!

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