Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 260227 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 1027 PM EDT THU JUN 25 2015 .SYNOPSIS...
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A WARM FRONT WILL STALL OUT NEAR NORTHERN MARYLAND TONIGHT. LOW PRESSURE WILL MOVE ACROSS THE AREA TONIGHT AND A COLD FRONT WILL STALL ACROSS THE AREA FRIDAY. THE BOUNDARY WILL BUILD NORTH AS A WARM FRONT FRIDAY NIGHT INTO SATURDAY BEFORE LOW PRESSURE PASSES BY TO THE NORTH SATURDAY EVENING. THE COLD FRONT WITH THE LOW WILL MOVE THROUGH THE AREA SATURDAY NIGHT AND HIGH PRESSURE WILL BUILD TOWARD THE AREA EARLY NEXT WEEK.
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&& .NEAR TERM /THROUGH FRIDAY/...
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A POTENT UPPER-LEVEL DISTURBANCE IS TRACKING THROUGH CWA THIS EVENING. A WARM FRONT IS STADDLED ACROSS NORTHERN VIRGINIA. THE WARM UNSTABLE AIR SOUTH OF THE FRONT COMBINED WITH PLENTY OF SHEAR HAS RESULTED IN A GOOD AMOUNT OF THUNDERSTORM COVERAGE...WITH MOST OF THE STRONG TO SEVERE THUNDERSTORMS CONFINED TO AREAS SOUTH OF THE FRONT. STORMS ARE NOW MOVING OUT OF THE CWA WITH THE SEVERE THUNDERSTORM WATCH CLEARED FROM MOST OF OUR CWA AS WELL. REMAINING STORMS SHOULD CLEAR THE AREA LATE THIS EVENING AS THE SHORTWAVE PUSHES EAST. THE REMAINDER OF THE NIGHT SHOULD FEATURE A FEW STRAY SHOWERS DUE TO THE STALLED FRONT BUT OTHERWISE WILL BE MUCH MORE TRANQUIL...THOUGH THE EXCESS MOISTURE MAY RESULT IN PATCHY FOG ESPECIALLY IN THE MORE SHELTERED WESTERN VALLEYS. THE BOUNDARY WILL DROP SLOWLY SOUTH AS A COLD FRONT FRIDAY...BUT THERE WILL BE LITTLE DEWPOINT OR TEMPERATURE GRADIENT ASSOCIATED WITH IT. LOW PRESSURE WILL STRENGTHEN AS IT MOVES THROUGH THE MIDWEST...BUT IT SHOULD REMAIN FAR ENOUGH AWAY NOT TO HAVE SIGNIFICANT IMPACT ON OUR WEATHER YET. A FEW SHOWERS AND THUNDERSTORMS ARE EXPECTED DUE TO THE HEATING OF THE DAY. THE BEST CHANCE FOR THUNDERSTORMS WILL BE FROM THE POTOMAC HIGHLANDS INTO CENTRAL VIRGINIA WHERE INSTABILITY WILL BE A BIT HIGHER SOUTH AND WEST OF THE BOUNDARY. MAX TEMPS WILL RANGE FROM THE UPPER 70S IN NORTHERN MARYLAND TO THE MID AND UPPER 80S ACROSS CENTRAL VIRGINIA.
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&& .SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/... LOW PRESSURE WILL TRACK INTO THE OHIO VALLEY FRIDAY NIGHT AND IT WILL STRENGTHEN AS IT DOES SO...THANKS TO A POTENT UPPER-LEVEL TROUGH THAT WILL BE DEVELOPING OVERHEAD. THE STALLED BOUNDARY WILL REMAIN OVER OUR REGION DURING THIS TIME...AND WITH THE INCREASED WIND FIELD THIS WILL ALLOW FOR SOUTHERLY WINDS ALOFT TO OVERRUN RELATIVELY COOLER AIR NEAR THE SURFACE. ISENTROPIC LIFT AND A STRENGTHENING LOW-LEVEL JET WITH SUBTROPICAL MOISTURE WILL LEAD TO MORE SHOWERS AND THUNDERSTORMS. LOCALLY HEAVY RAIN IS POSSIBLE...ESPECIALLY ACROSS THE POTOMAC HIGHLANDS AND SHENANDOAH VALLEY WHERE FORCING WILL BE STRONGER CLOSER TO THE APPROACHING LOW. LOW PRESSURE WILL INTENSIFY AS IS DRIFTS NORTHEAST FROM OHIO SATURDAY MORNING...REACHING LAKE ONTARIO SATURDAY NIGHT. HEAVY RAIN IS EXPECTED TO BREAK OUT LATE SATURDAY NIGHT AS A WARM FRONT LIFTS NORTH ACROSS THE AREA. THE CWA WILL BE IN THE WARM SECTOR OF THE LOW SATURDAY WITH LIFTED INDEX OF MINUS 5-10 AND PWATS WILL BE AROUND TWO INCHES. PLENTY OF DYNAMICS FROM THE LOW TO THE NW. THEREFORE A SEVERE...TORNADO...AND FLASH FLOOD THREAT EXISTS FOR THE DAY INTO THE EVENING. MAX TEMPS DEPEND ON TEMPERATURE ADVECTION VS CLOUDS AND RAIN. CURRENTLY THINKING LOW TO MID 70S NWRN HALF OF THE CWA AND UPR 70S LOW 80S SERN HALF. COLD FRONT CROSSES THE AREA LATE SATURDAY NIGHT WITH NWLY FLOW CUTTING OFF PRECIP. MIN TEMPS LOW TO MID 60S INLAND...AROUND 70 URBAN/NEAR SHORE. && .LONG TERM /SUNDAY THROUGH THURSDAY/... AFTER A WET SAT...RAIN BEGINS TO CLEAR THE AREA BY SUN MORNING...AS THE COLD FRONT PUSHES THROUGH THE AREA. COULD BE A FEW SHOWERS LEFT ON THE BACK SIDE IN THE HIGHER TERRAIN OF OUR FAR WEST...THOUGH EXPECT THOSE TO BE RATHER LIGHT. OTHER THAN THAT...IF WE ARE ABLE TO CLEAR SOON ENOUGH...SUN COULD BE A VERY NICE DAY WITH TEMPS IN U60S WEST AND M/U 70S ALONG 95 CORRIDOR...DEWPOINTS ALSO IN M/U 50S. MON LOOKS QUIET...WITH TEMPS REMAINING AOB NORMAL AND NO CHANCE OF PRECIP. NEXT CHANCE FOR UNSETTLED WEATHER TUE WITH WARM FRONT NEAR AREA. WHILE MODELS BEGIN TO DIVERGE BEYOND TUE...REMAINDER OF PERIOD APPEARS RELATIVELY QUITE...COMPARED TO RECENT DAYS...WITH TEMPS NEAR NORMAL AND LITTLE CLEAR SIGNAL FOR PRECIP. && .AVIATION /02Z FRIDAY THROUGH TUESDAY/...
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STORMS HAVE CLEARED THE TERMINALS FOR THE MOST PART OR WILL DO SO SHORTLY...WITH OVERALL VFR CONDITIONS RETURNING. HOWEVER...PATCHY FOG IS POSSIBLE LATE TONIGHT INTO EARLY FRIDAY MORNING. VFR CONDITIONS ARE EXPECTED FOR MOST OF FRIDAY. A FEW SHOWERS AND THUNDERSTORMS ARE POSSIBLE FRIDAY AFTERNOON...ESPECIALLY ACROSS KCHO. SHOWERS AND THUNDERSTORMS WILL INCREASE IN COVERAGE FRIDAY NIGHT AS LOW PRESSURE APPROACHES FROM THE WEST. AN EASTERLY FLOW AHEAD OF THIS WILL ALSO CAUSE LOW CLOUDS. IFR CONDITIONS ARE POSSIBLE. REDUCED AVIATION CONDS ALL DAY SATURDAY THROUGH THE EVENING AS A WARM FRONT LIFTS THROUGH THE AREA EARLY SATURDAY MORNING AND A HUMID AND UNSTABLE AIRMASS IS IN PLACE UNTIL A COLD FRONT LATE SATURDAY NIGHT. HEAVY THUNDERSTORMS WITH A SEVERE...TORNADO...AND FLOOD THREAT. STORMS END SATURDAY NIGHT AS A COLD FRONT CROSSES THE AREA FROM THE NW. NWLY FLOW COULD BE GUSTY (20 TO 25 KT) IN THE WAKE OF THE LOW. VFR CONDS EXPECTED SUN/MON. SUB-VFR POSSIBLE TUE IN ANY TSTM ACTIVITY.
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&& .MARINE...
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A SMALL CRAFT ADVISORY IS IN EFFECT FOR THE MIDDLE PORTION OF THE BAY AND LOWER TIDAL POTOMAC RIVER AS SOUTHERLY WINDS CONTINUE IN ADVANCE OF AN APPROACHING LOW PRESSURE. CONVECTION WILL DISSIPATE IN COVERAGE OVERNIGHT AND WINDS SHOULD SUBSIDE AS THE LOW PASSES EAST. AN EASTERLY FLOW WILL DEVELOP FRIDAY AND THE FLOW WILL STRENGTHEN FRIDAY NIGHT. A SMALL CRAFT ADVISORY IS IN EFFECT FOR THE MARYLAND CHESAPEAKE BAY AND LOWER TIDAL POTOMAC RIVER FRIDAY NIGHT. A FEW SHOWERS AND THUNDERSTORMS ARE POSSIBLE...ESPECIALLY FRIDAY NIGHT. SELY FLOW INCREASES SATURDAY NIGHT WARRANTING AN SCA FOR MOST WATERS AFTER MIDNIGHT. SCA EXPECTED SATURDAY INTO SUNDAY NIGHT AS LOW PRESSURE PERSISTS OVER THE ERN GREAT LAKES. HEAVY THUNDERSTORMS EXPECTED SATURDAY WITH DAMAGING WINDS/WATER SPOUTS POSSIBLE THROUGH THE EVENING HOURS. NORTHWEST FLOW OVERSPREADS THE WATERS LATE SATURDAY NIGHT AS A COLD FRONT CROSSES. SCA CONDS APPEAR LIKELY THROUGH SUN. ATM WINDS APPEAR NEAR SCA CRITERIA TUE WITH ADDITIONAL MARINE CONCERNS IN ANY TSTM ACTIVITY.
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&& .TIDES/COASTAL FLOODING...
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TIDAL ANOMALIES ARE AROUND ONE-HALF FOOT ABOVE NORMAL...BUT WATER LEVELS SHOULD REMAIN BELOW MINOR FLOODING THRESHOLDS THROUGH TONIGHT. ANOMALIES WILL DECREASE LATE INTO FRIDAY AS THE FLOW TURNS OFFSHORE. AS A STRONGER LOW PRESSURE APPROACHES SATURDAY...THE FLOW WILL PROMOTE A STRONGER PUSH UP THE BAY AND THE POTENTIAL FOR MINOR FLOODING WILL INCREASE.
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&& .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY FROM MIDNIGHT FRIDAY NIGHT TO 6 AM EDT SATURDAY FOR ANZ531>534-536>543. SMALL CRAFT ADVISORY UNTIL 2 AM EDT FRIDAY FOR ANZ532>534-537- 540>543. && $$ SYNOPSIS...BJL NEAR TERM...BJL/RCM SHORT TERM...BJL LONG TERM...MSE AVIATION...BAJ/BJL/MSE/RCM MARINE...BAJ/BJL/MSE/RCM TIDES/COASTAL FLOODING...HTS/RCM

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