Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 260128 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 928 PM EDT FRI JUL 25 2014 .SYNOPSIS... HIGH PRESSURE WILL CONTINUE TO PUSH OFFSHORE TONIGHT. A WEAK TROUGH WILL SET UP OVER THE AREA SATURDAY. AN UNSEASONABLY STRONG COLD FRONT WILL APPROACH THE AREA SUNDAY BEFORE MOVING THROUGH MONDAY. CANADIAN HIGH PRESSURE WILL RETURN FOR TUESDAY AND WEDNESDAY. && .NEAR TERM /THROUGH SATURDAY/... AS OF 01Z...1018 MB SFC HIGH CENTERED OVER SERN VA/NERN NC BORDER. SELY FLOW FROM THIS IS ACROSS THE LWX CWA...ALLOWING DEWPOINTS TO RETURN TO THE MID TO UPR 50S...LOW TO MID 60S FOR CNTRL VA. MIN TEMPS GENERALLY LOW 60S NW...MID 60S SOUTH...AND UPR 60S TO 70F FOR URBAN NEAR SHORE LOCALES. HIGH PRESSURE WILL BE WELL OFF THE EAST COAST SATURDAY MORNING AND SLY FLOW WILL CONTINUE TO DRAW IN HIGHER DEWPTS AS WELL AS WARMER TEMPS. FCST MAX TEMPS WILL REACH THE MID TO UPPER 80S SATURDAY AFTERNOON. WESTERLY FLOW ALOFT WILL LEAD TO UPSTREAM DISTURBANCES REACHING THE MID-ATLANTIC AND A LEE TROUGH TO FORM. A SHORTWAVE TROUGH CURRENTLY RESPONSIBLE FOR SHOWERS AND THUNDERSTORMS ACROSS IA-IL WILL REACH THE AREA SATURDAY AFTERNOON. IT IS EXPECTED TO WEAKEN BUT WITH THE SLY FLOW ADVECTING WARM AND MOIST CONDITIONS INTO THE REGION A FEW SHOWERS WILL BE POSSIBLE IN THE HIGHLANDS AND AHEAD OF THE LEE TROUGH. SCATTERED SHOWERS WITH ISOLATED THUNDERSTORMS ARE POSSIBLE ACROSS THE I-95 CORRIDOR SAT LATE MORNING THROUGH THE AFTERNOON. ACTIVITY WILL WANE TOWARDS SUNSET. A STRONG SHORTWAVE TROUGH WILL DROP INTO THE NRN PLAINS SATURDAY WHILE CONVECTION WILL BE ONGOING AHEAD OF A COLD FRONT ACROSS THE MIDWEST SATURDAY AFTERNOON AND EVENING. SOME SHOWERS AND THUNDERSTORMS ARE EXPECTED TO BECOME SEVERE AND THIS ACTIVITY WILL PROPAGATE EASTWARD AND POTENTIALLY IMPACT THE POTOMAC HIGHLANDS LATE SATURDAY NIGHT/EARLY SUNDAY MORNING. THERE ARE UNCERTAINTIES PERTAINING TO THE TRACK OF A POTENTIAL MCS SUNDAY MORNING WHICH WILL THEN IMPACT THE AMT OF CLOUD COVER AND THEREFORE INSTABILITY THE MID- ATLANTIC GAINS ON SUNDAY. && .SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY/... A WARM FRONT WILL MOVE ACROSS THE REGION SATURDAY NIGHT/SUN MORNING AND MOISTURE WILL CONTINUE TO ADVECT INTO THE MID-ATLANTIC SUNDAY. LOW PRESSURE WILL BE ACROSS THE GREAT LAKES AND A COLD FRONT WILL BE STRETCHED FROM PA TO OHIO TO MO. AS THE STRONG SHORTWAVE TROUGH NEARS SHEAR WILL INCREASE AND SHOWERS AND THUNDERSTORMS ARE LIKELY. DEPENDING ON THE AMT OF INSTABILITY THE REGION GETS WITH THE DEPARTING MCS FROM THE OHIO VALLEY... SEVERE STORMS MAY BE POSSIBLE WITH THE THREATS OF DMG WINDS LARGE HAIL ISOLATED TORNADOES AND HEAVY RAIN. SREF ENSEMBLE MEMBERS SHOW A RANGE OF CAPE SOLUTIONS FOR SUNDAY WITH 500 TO 3000 J/KG POSSIBLE. ONE THING THAT IS CERTAIN IS THAT SHEAR PROFILES INCREASE SUNDAY AND HODOGRAPHS BECOME LINEAR WITH 40-50 KTS AT 10-15K FEET. A STRONG LINE OF THUNDERSTORMS WILL BE POSSIBLE SUN AFTERNOON AND EVENING. OUTFLOW BOUNDARIES AND THE CLOSE PROXIMITY TO THE SFC LOW ACROSS OH/PA/NY WILL LEAD TO THE THREAT OF SVR THUNDERSTORMS CAPABLE OF PRODUCING TORNADOES. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... SHEAR PROFILES INCREASE MARKEDLY SUNDAY EVENING...INCLUDING IN THE LOWEST FEW KILOMETERS. THIS WILL ENHANCE/ORGANIZE CONVECTION ON THE NOSE OF A 50+ KNOT 500 MB JET. HIGH PWATS AND MODERATE CAPE SUGGEST A MYRIAD OF HAZARDS FROM SEVERE WEATHER TO HEAVY RAIN PERSISTING WELL INTO SUNDAY EVENING AS A STRONG SHORTWAVE TROUGH DIVES TOWARDS THE REGION FROM THE GREAT LAKES. MODELS DIFFER IN HOW QUICKLY THE UPPER TROUGH AND SURFACE COLD FRONT CROSS THE AREA...BUT IF THE FRONT DOES NOT CLEAR THE COAST BY MONDAY AFTERNOON THEN A SEVERE WEATHER THREAT COULD ARISE AGAIN. BEST CHANCE FOR THIS WOULD BE EAST OF THE BLUE RIDGE MOUNTAINS. FOLLOWING AN ACTIVE START TO THE WEEK...A LARGE AREA OF HIGH PRESSURE WILL BUILD TOWARD THE REGION FROM CANADA RESULTING IN DRY WEATHER AND BELOW NORMAL TEMPERATURES AND HUMIDITY FOR MOST OF THE WEEK. && .AVIATION /01Z SATURDAY THROUGH WEDNESDAY/... VFR CONDITIONS PREVAIL OUTSIDE OF VALLEY FOG LOCATIONS TONIGHT AS MOISTURE INCREASES WITH THE HIGH NOW OFF THE COAST. SLY WINDS AROUND 10-15 KTS WILL OCCUR THROUGH THE AFTERNOON. A FEW ISO SHOWERS WILL BE POSSIBLE NEAR DCA-BWI-MTN SATURDAY AFTERNOON. SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE SUNDAY AND MVFR/IFR CONDITIONS WILL BE POSSIBLE. A FEW THUNDERSTORMS MAY PRODUCE GUSTY WINDS...LARGE HAIL AND ISOLATED TORNADOES. MVFR OR LWR CIGS/VSBYS IN SHWRS/TSTMS SUN NIGHT-MON...IMPROVING TO VFR MON NIGHT. SW WIND AROUND 10 KTS BECOMING NW 15-20 KTS AND GUSTY MON EVENING W/ COLD FROPA. && .MARINE... SLY FLOW 10 TO 15 KT...WITH SOME POSSIBLE SCA GUSTS LATE TONIGHT...MIDNIGHT SHIFT WILL HAVE TO MONITOR THIS. SLY FLOW WILL INCREASE SATURDAY AFTERNOON AS CHANNELING OCCURS. A SCA IS IN EFFECT FROM THE MD CHESAPEAKE BAY SOUTH OF POOLES ISLAND AND LOWER TIDAL POTOMAC RIVER SUN AFTERNOON THROUGH THE EVENING. ISOLATED SHOWERS ARE POSSIBLE SAT AFTERNOON. A COLD FRONT APPROACHES SUNDAY AND SHOWERS AND THUNDERSTORMS ARE LIKELY. SOME STORMS MAY PRODUCE GUSTY WINDS LARGE HAIL AND WATERSPOUTS CREATING LOW VSBYS. SHOWERS/STRONG STORMS LIKELY SUN NIGHT-MON...SUBSIDING MON EVENING. SCA WINDS/SEAS PROBABLE MON EVENING INTO TUES WITH GUSTY NW FLOW BEHIND COLD FRONT. && .CLIMATE... A RECORD EVENT REPORT (RER) WAS SENT FOR THE 57F THAT BWI REACHED THIS MORNING. THAT IS A NEW MIN TEMP RECORD FOR BALTIMORE. IT BROKE THE OLD RECORD OF 59F. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY FROM 1 PM SATURDAY TO 2 AM EDT SUNDAY FOR ANZ531>534-537-539>543. && $$ SYNOPSIS...BAJ/HAS NEAR TERM...BAJ/HAS SHORT TERM...HAS/DFH LONG TERM...DFH AVIATION...BAJ/HAS/DFH MARINE...BAJ/HAS/DFH CLIMATE...BAJ

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