Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 252126 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 526 PM EDT THU JUN 25 2015 .SYNOPSIS... A WARM FRONT WILL STALL OUT NEAR NORTHERN MARYLAND THIS EVENING. 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. && .NEAR TERM /THROUGH FRIDAY/...
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A POTENT UPPER-LEVEL DISTURBANCE IS TRACKING THROUGH THE OHIO VALLEY THIS AFTERNOON. A WARM FRONT IS MOVING NORTH TOWARD NORTHERN VIRGINIA. THE WARM FRONT WILL STALL OUT NEAR NORTHERN MARYLAND AREA LATE THIS AFTERNOON AND EVENING. A SOUTHERLY FLOW BEHIND THE BOUNDARY WILL USHER IN MUCH MORE MOISTURE...WITH DEWPOINTS RETURNING TO THE UPPER 60S AND LOWER 70S. THE INCREASED MOISTURE WILL ALLOW FOR INSTABILITY TO DEVELOP. THE UPPER-LEVEL DISTURBANCE...WHICH IS THE REMNANTS FROM AN MCS EARLIER TODAY...WILL ALSO BE MOVING THROUGH OUR AREA LATE THIS AFTERNOON AND EVENING. THIS WILL CAUSE SHOWERS AND THUNDERSTORMS TO INCREASE IN COVERAGE FROM WEST TO EAST DURING THIS TIME. THERE IS A THREAT FOR SEVERE THUNDERSTORMS...WITH DAMAGING WIND GUSTS AND LARGE HAIL BEING THE PRIMARY THREATS. CERTAINTY IS STILL A BIT LOW DUE TO QUESTIONS ABOUT EXACTLY HOW UNSTABLE THE ATMOSPHERE WILL BE. ALTHOUGH SEVERE WEATHER CANNOT BE RULED OUT ACROSS THE ENTIRE CWA...THE BEST CHANCE FOR SEVERE THUNDERSTORMS AT THIS TIME APPEARS THAT IT WILL BE ACROSS CENTRAL VIRGINIA INTO SOUTHERN MARYLAND...AND A SEVERE THUNDERSTORM WATCH IS NOW IN EFFECT FOR THIS AREA UNTIL MIDNIGHT. THIS IS WHERE CONFIDENCE IS HIGHEST FOR MORE INSTABILITY DUE TO SOUTHERLY WINDS AND GREATER SUNSHINE TODAY. ALSO...WITH THE BOUNDARY OVERHEAD THERE IS A THREAT FOR AN ISOLATED TORNADO AS WELL. THE DEEP MOISTURE WILL ALSO CAUSE PWATS TO SURGE LATE THIS AFTERNOON AND EVENING. THUNDERSTORMS WILL CONTAIN VERY HEAVY RAINFALL. LOCALIZED FLASH FLOODING IS POSSIBLE DURING THIS TIME. DID NOT ISSUE A FLASH FLOOD WATCH AT THIS TIME DUE TO THE FAST MOVEMENT OF THUNDERSTORMS DUE TO STRONGER WINDS ALOFT. COVERAGE OF CONVECTION SHOULD DISSIPATE OVERNIGHT...BUT LEFT CHANCE POPS IN SINCE THE STALLED BOUNDARY WILL REMAIN NEARBY. 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 /21Z THURSDAY THROUGH TUESDAY/...
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TERMINALS WILL BE IMPACTED THIS EVENING DUE TO SHOWERS AND THUNDERSTORMS. A FEW STRONG TO SEVERE THUNDERSTORMS ARE POSSIBLE MAINLY AROUND KCHO. COVERAGE OF CONVECTION SHOULD DIMINISH OVERNIGHT...BUT A COUPLE SHOWERS CANNOT BE RULED OUT. SHRA/TSRA EXPECTED TO MOVE IN FROM WEST TO EAST BETWEEN 21Z AND 3Z THIS AFTERNOON/EVENING. SOME THUNDERSTORMS MAY BECOME SEVERE WITH LOCALLY DAMAGING WINDS AND LARGE HAIL BEING THE PRIMARY THREATS. AN ISOLATED TORNADO CANNOT BE RULED OUT. THE BEST CHANCE FOR SEVERE STORMS WILL BE ACROSS THE SOUTHERN TERMINALS...KCHO...KIAD AND KDCA. 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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SOUTHERLY WINDS WILL INCREASE LATE THIS AFTERNOON AND EVENING BEHIND A WARM FRONT. LOW PRESSURE WILL RIDE ALONG THE BOUNDARY...PASSING OFF TO OUR EAST OVERNIGHT. A SMALL CRAFT ADVISORY IS IN EFFECT FOR THE MIDDLE PORTION OF THE BAY AND LOWER TIDAL POTOMAC RIVER. SHOWERS AND THUNDERSTORMS WILL BE CAPABLE OF PRODUCING GUSTY WINDS...LARGE HAIL AND WATERSPOUTS THIS EVENING...MAINLY IN CENTRAL AND SOUTHERN PORTIONS OF THE BAY. CONVECTION WILL DISSIPATE IN COVERAGE OVERNIGHT. 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... TIDAL ANOMALIES ARE AROUND ONE-HALF FOOT ABOVE NORMAL. THE ANOMALIES MAY INCREASE A BIT THIS EVENING...BUT WATER LEVELS SHOULD REMAIN BELOW MINOR FLOODING THRESHOLDS. ANOMALIES WILL DECREASE LATE INTO FRIDAY AS THE FLOW TURNS OFFSHORE. AS LOW PRESSURE APPROACHES SATURDAY...THE FLOW WILL PROMOTE A STRONGER PUSH UP THE BAY AND THE POTENTIAL FOR MINOR FLOODING WILL INCREASE. && .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...RCM/HTS

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