Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 091435 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 1035 AM EDT WED JUL 9 2014 .SYNOPSIS... A COLD FRONT OVER THE GREAT LAKES WILL APPROACH TODAY AND MOVE THROUGH THE AREA TONIGHT. THE FRONT WILL STALL OUT TO THE SOUTH THURSDAY THROUGH FRIDAY AS HIGH PRESSURE BUILDS IN FROM THE NORTH. && .NEAR TERM /THROUGH THURSDAY/... ANALYSIS THIS MORNING SHOWS A COLD FRONT OVER THE GREAT LAKES AND HIGH PRESSURE OVER THE ATLANTIC. A WEAK SURFACE TROUGH IS LOCATED EAST OF THE POTOMAC HIGHLANDS WHILE AN UPPER-LEVEL DISTURBANCE MOVES THROUGH IN THE SOUTHWEST FLOW ALOFT. THE UPPER-LEVEL DISTURBANCE HAS TRIGGERED A FEW SHOWERS NEAR AND EAST OF INTERSTATE 95. THESE SHOWERS SHOULD DISSIPATE BY THIS AFTERNOON. MID-LEVEL CLOUDS SHOULD GIVE WAY TO SOME SUNSHINE...AND WITH A SOUTHWEST FLOW IN PLACE...MORE WARM AND HUMID CONDITIONS ARE EXPECTED. MAX TEMPS WILL RANGE FROM THE 70S IN THE MOUNTAINS TO THE UPPER 80S/NEAR 90 ACROSS MOST OTHER LOCATIONS. THE WARM AND HUMID CONDITIONS WILL LEAD TO MODERATE AMOUNTS OF INSTABILITY THIS AFTERNOON. THE MODIFIED 12Z KIAD RAOB SHOWS AROUND 1000-1500 J/KG OF MLCAPE DEVELOPING. THE PRESSURE TROUGH SHOULD STRENGTHEN OVER THE AREA THIS AFTERNOON AND THIS WILL BE THE MAIN LIFTING MECHANISM FOR CONVECTION. SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED THIS AFTERNOON AND EVENING...AND WITH MODERATE CAPE AND MARGINAL SHEAR PROFILES...THERE IS A THREAT FOR LOCALLY DAMAGING WIND GUSTS OR LARGE HAIL. DO NOT EXPECT THE EVENT TO BE NEARLY AS WIDESPREAD AS TUESDAY SINCE SHEAR AND INSTABILITY WILL NOT BE AS STRONG AND THE LIFTING MECHANISM WILL NOT BE AS STRONG EITHER. THE COLD FRONT WILL SLOWLY DROP INTO THE REGION TONIGHT. CONVECTION SHOULD DISSIPATE ACROSS MOST AREAS DUE TO THE LOSS OF DAYTIME HEATING...BUT AN ISOLATED SHOWER OR THUNDERSTORM CANNOT BE RULED OUT. SWLY FLOW ALOFT WILL LEAD TO DISTURBANCES CROSSING THE REGION THURSDAY AFTERNOON. SHOWERS AND ISOLATED THUNDERSTORMS WILL BE POSSIBLE MAINLY ALONG RIDGELINES WHERE TERRAIN CIRCULATIONS WILL BE POSSIBLE. FCST MAX TEMPS ARE IN THE LOW TO MID 80S THURSDAY. && .SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY/... COLD FRONT WILL RESIDE SOUTH OF THE CWA THURSDAY NIGHT INTO FRIDAY...WITH HIGH PRESSURE TO THE NORTH. THIS SHOULD LEAD TO A RELATIVE LULL IN CONVECTION DURING THE FORECAST PERIOD BUT STILL CAN/T RULE OUT A FEW THUNDERSTORMS DURING PEAK HEATING FRIDAY AFTERNOON MAINLY ACROSS THE SOUTHERN TIER OF THE CWA CLOSER TO THE BOUNDARY AND WHERE MOISTURE AND INSTABILITY MAY BE A LITTLE BETTER. STAYED CLOSE TO MOS WITH NEAR CLIMO TEMPS. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... WHATEVER IS LEFT OF THE BOUNDARY MENTIONED IN THE SHORT TERM WILL LIKELY LIFT BACK NORTH AS A WARM FRONT OVER THE WEEKEND...PROBABLY MORESO SUNDAY. THIS WILL ALLOW DEWPOINTS/PRECIPITABLE WATER VALUES TO CREEP UPWARD. FLAT RIDGING MAY HELP TO CURB A LOT OF THUNDERSTORM ACTIVITY ON SATURDAY BUT A FEW DIURNAL STORMS CAN/T BE RULED OUT. SLIGHTLY LOWER HEIGHTS AND A SURFACE TROUGH MAY HELP FOR A LARGER COVERAGE FOR SUNDAY. THIS TREND CONTINUES ON MONDAY AS A COLD FRONT ENTERS THE CWA...GRADUALLY PUSHING THROUGH DURING THE MIDDLE OF THE WEEK. UNTIL IT MOVES THROUGH THERE WILL BE A CHANCE OF CONVECTION. && .AVIATION /14Z WEDNESDAY THROUGH SUNDAY/... SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED THIS AFTERNOON AND EVENING. LOCALLY GUSTY WINDS AND HAIL ARE POSSIBLE IN THE STRONGER STORMS...BUT SEVERE STORMS WILL NOT BE AS WIDESPREAD AS TUESDAY. A COLD FRONT WILL CROSS THE REGION TONIGHT AND WINDS WILL BECOME NORTHERLY TO START THURSDAY BEFORE TURNING TOWARD THE EAST THURSDAY AFTERNOON. ISO TSRA IS EXPECTED THURSDAY AFTERNOON. FRONTAL BOUNDARY REMAINS TO THE SOUTH FRIDAY INTO SATURDAY THEN LIFTS BACK NORTH SUNDAY. BEST CHANCE OF CONVECTION DURING THIS TIME LOOKS TO BE SUNDAY. && .MARINE... SOUTH-SOUTHWEST WINDS WILL CONTINUE OVER THE WATERS THIS AFTERNOON...BUT SPEEDS SHOULD REMAIN BELOW SCA CRITERIA. A SFC TROUGH WILL BRING SHOWERS AND THUNDERSTORMS TO THE WATERS THIS AFTERNOON AND EVENING. SOME MAY BRING GUSTY WINDS AND LOW VSBYS. A COLD FRONT WILL CROSS THE WATERS TONIGHT AND WINDS WILL BECOME NORTHERLY AND BELOW SCA CRITERIA. RELATIVELY WEAK GRADIENT SHOULD PRECLUDE SCA CONDITIONS INTO THE FIRST PART OF THE WEEKEND. WILL HAVE TO WATCH SOUTHERLY FLOW BY SUNDAY AS MARGINAL SCA CONDITIONS MAY BE POSSIBLE UP THE BAY BY EVENING. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...NONE. && $$ SYNOPSIS...BPP/HAS NEAR TERM...BJLHAS SHORT TERM...BPP LONG TERM...BPP AVIATION...BJL/BPP/HAS MARINE...BJL/BPP/HAS

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