Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 010147 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 947 PM EDT SUN MAY 31 2015 .SYNOPSIS... LOW PRESSURE WILL TRACK EAST INTO INTO SOUTHERN PENNSYLVANIA TONIGHT. A COLD FRONT EXTENDING SOUTH FROM THIS LOW WILL SLOWLY CROSS THE AREA LATE MONDAY INTO TUESDAY. THE BOUNDARY WILL STALL OUT JUST TO THE SOUTH FOR THE MIDDLE PORTION OF THE WEEK BEFORE WEAKENING LATE THIS WEEK. && .NEAR TERM /THROUGH MONDAY/... SFC LOW PRESSURE LOCATED OVER WESTERN PA THIS EVENING BENEATH A COMPACT SHORTWAVE TROUGH. STRONG BLOCKING RIDGE OF HIGH PRESSURE REMAINS OFFSHORE. THE LOW WILL TRACK ALONG A STALLED FRONT ACROSS PA OVERNIGHT. AS THE LOW HAS MOVED CLOSER THIS EVENING...AN AREA OF SOMEWHAT MORE ORGANIZED STORMS DEVELOPED AHEAD OF IT DUE TO THE ADDED LIFT FROM THE PASSING SHORTWAVE. THE LIKELY AREAS TO BE AFFECTED REMAIN ACROSS THE NORTHWESTERN THIRD OF THE CWA. NOT OUT OF THE QUESTION THESE STORMS COULD BE STRONG TO LOCALLY SEVERE...AND WE HAVE BEEN SEEING OCCASIONAL SEVERE REPORTS (PRIMARILY WIND) SO FAR. WHILE THERE SHOULD BE A DIMINISHING TREND TO STORMS OVERNIGHT...THE SFC LOW WILL BE LINGERING NEAR THE AREA AND MAY ALLOW FOR THE CONTINUED GENERATIONS OF SHOWERS AND A FEW STORMS. AREAS WHICH SEE OR HAVE SEEN HEAVIER RAINFALL COULD DEVELOP SOME FOG...BUT CLOUD COVER WILL BE A LIMITING FACTOR. THIS AND THE HIGHER DEWPOINTS WILL HOLD LOWS INTO THE 60S TO LOWER 70S. MONDAY WILL ONCE AGAIN BE AN ACTIVE CONVECTIVE DAY ACROSS THE REGION AS THE REMNANTS OF THE SFC LOW MEANDER AROUND THE AREA. HAVE KEPT THE CATEGORICAL POPS BUT USED OCCASIONAL WORDING SINCE STORMS WILL LIKELY BE OFF-AND-ON. SHEAR MAY BE SLIGHTLY HIGHER BUT STILL NOT SUPPORTIVE OF WIDESPREAD SEVERE. HOW MUCH INSTBY IS REALIZED WILL DEPEND ON CLOUD COVER...WHICH COULD BE FAIRLY EXTENSIVE. HOWEVER WITH BETTER FORCING...STORMS COULD ORGANIZE INTO BANDS. ANOTHER THREAT WILL BE HEAVY RAIN AND LOCALIZED FLOODING...AS MULTIPLE ROUNDS OF STORMS COULD OCCUR IN THE HIGH PWAT ENVIRONMENT. MAX T WILL DEPEND ON CLOUD COVER TOO BUT 80S WILL ONCE AGAIN BE POSSIBLE...ESPECIALLY THE SE CWA. && .SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/... WITH A BOUNDARY AND POTENTIAL DISTURBANCES LINGER INTO MONDAY NIGHT...DIFFICULT TO SAY HOW QUICKLY IT WILL DRY OFF IF AT ALL. HAVE A GRADUALLY DECREASING CHANCE OF RAIN. SOME COOLER AND DRIER AIR MAY BEGIN TO ADVECT INTO THE NW CWA OVERNIGHT...BUT SOUTH OF THE BOUNDARY IT WILL STILL BE WARM AND MUGGY. A COLD FRONT WILL SLOWLY TRACK TO OUR SOUTH TUESDAY BEFORE STALLING OUT OVER CENTRAL VIRGINIA TUESDAY NIGHT. UPPER-LEVEL LOW PRESSURE WILL REMAIN OVER THE TENNESSEE VALLEY AND GULF COAST STATES DURING THIS TIME. TUESDAY WILL TURN OUT NOTICEABLY COOLER DUE TO A NORTHERLY FLOW BEHIND THE FRONT AND ALSO PLENTY OF HIGH AND MID-LEVEL CLOUDS OVERHEAD THANKS TO A SOUTHWEST FLOW ALOFT AHEAD OF THE UPPER-LEVEL LOW. MAX TEMPS ARE EXPECTED TO REMAIN IN THE 70S FOR MOST AREAS. A FEW SHOWERS AND THUNDERSTORMS ARE POSSIBLE WITH THE BOUNDARY NEARBY. THE BEST CHANCE FOR CONVECTION WILL BE ACROSS CENTRAL VIRGINIA AND SOUTHERN MARYLAND...CLOSER TO THE COLD FRONT. THE BOUNDARY WILL STALL OUT JUST TO THE SOUTH TUESDAY NIGHT...BUT A SOUTHERLY FLOW ALOFT SHOULD ALLOW FOR OVERRUNNING ON THE COOL SIDE OF THE BOUNDARY. THEREFORE...PLENTY OF CLOUDS ARE EXPECTED ALONG WITH POSSIBLE SHOWERS. THE BEST CHANCE FOR SHOWERS WILL BE ACROSS CENTRAL VIRGINIA...BUT IF THE TREND IN GUIDANCE CONTINUES WITH STRENGTHENING THE OVERRUNNING THEN MOST AREAS WILL LIKELY SEE PRECIPITATION. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... BRIEF COOLER PERIOD IS EXPECTED DURING THE MIDDLE PART OF THE WEEK IN NORTHEASTERLY FLOW AS HIGH PRESSURE BUILDS OVER NEW ENGLAND. STALLED BOUNDARY TO THE SOUTH SHOULD BE CLOSE ENOUGH TO OFFER BOUTS OF SCATTERED SHOWERS AND THUNDERSTORMS EACH AFTERNOON AND EVENING...WITH CHANCES INCREASING LATE IN THE WEEK AS WARMER AND MORE HUMID AIR RETURNS. AN AREA OF LOW PRESSURE IS INDICATED IN THE ENSEMBLES AND WILL BE MOVING SLOWLY UP THE COAST EARLY NEXT WEEKEND BRINGING A CONTINUED CHANCE OF SHOWERS. && .AVIATION /02Z MONDAY THROUGH FRIDAY/... STORMS WILL CONTINUE AHEAD OF OHIO VALLEY LOW PRESSURE THROUGH THE REMAINDER OF THIS EVENING INTO THE OVERNIGHT. MRB REMAINS THE MOST HEAVILY AFFECTED TAF SITE BUT ONE OR TWO MORE STORMS MAY MAKE IT FURTHER SOUTH AND EAST TOWARDS IAD AND THE REST. AMENDMENTS LIKELY AS IMPACTS BECOME EVIDENT...WHICH COULD INCLUDE BRIEF IFR AND GUSTY WINDS. THUNDER WILL GRADUALLY WANE OVER THE NEXT FEW HOURS WITH DIMINISHING INSTABILITY AND THE PASSING OF THE SHORTWAVE ALOFT. SHOWERS WILL BECOME MORE WIDELY SCATTERED LATE TONIGHT. STILL HAVE SOME PATCHY FOG FOR MRB AND CHO WHERE LIGHT WINDS OVERNIGHT AND ADDED MOIST MAY AGAIN ALLOW SOME TO FORM. WINDS WILL REMAIN GENERALLY SOUTHERLY AROUND 10 KT. SHOWERS AND STORMS MAY BE MORE WIDESPREAD MONDAY WITH THE LOW OVER THE AREA...BUT ANY AVIATION IMPACTS WILL LIKELY BE SPORADIC THROUGHOUT THE DAY. LOCAL IFR CONDITIONS POSSIBLE IN HEAVY RAIN...WITH GUSTY WINDS ALSO POSSIBLE. WINDS BECOME MORE VRB WITH BOUNDARY OVER THE AREA INTO MONDAY NIGHT. A COLD FRONT WILL DROP TO THE SOUTH OF THE TERMINALS TUESDAY...BUT OVERRUNNING BEHIND THE COLD FRONT MAY LEAD TO SUBVFR CIGS FROM LOW CLOUDS ALONG WITH THE CHANCE FOR SHOWERS. A COUPLE THUNDERSTORMS CANNOT BE RULED OUT...WITH THE BEST CHANCE BEING ACROSS KCHO TUESDAY AFTERNOON AND EVENING CLOSER TO THE BOUNDARY. NELY TO ELY FLOW 10-15 KT W/ SUB-VFR PSBL IN LWR CIGS/- SHRA WED-THU AS A FRONT REMAINS STALLED TO THE SOUTH. && .MARINE... MIXING HAS ALLOWED SOUTHERLY CHANNELING TO COMMENCE AGAIN OVER THE BAY. THUNDERSTORMS OVERNIGHT WILL BE ISOLATED AT BEST...BUT A SMW IS POSSIBLE FOR GUSTY WINDS IF ONE MOVES CLOSE TO THE WATERS. THE SCA REMAINS IN EFFECT FOR THE LOWER PART OF THE BAY AND LOWER POTOMAC THROUGH THE NIGHT AND INTO MONDAY AS A LLJ WILL BE OVER THE AREA...AND CHANNELING WAS SUSTAINED LAST NIGHT. TOOK THIS UNTIL 6 PM MONDAY WHEN PRECIP IS EXPECTED TO BECOME MORE WIDESPREAD AND LIMIT MIXING. HOWEVER STORMS WILL BE POSSIBLE THROUGHOUT MONDAY WITH A STRONG WIND THREAT. A COLD FRONT WILL DROP TO THE SOUTH OF THE WATERS TUESDAY AND IT WILL STALL OUT JUST TO THE SOUTH TUESDAY NIGHT. A SMALL CRAFT ADVISORY MAY BE NEEDED FOR PORTIONS OF THE WATERS TUESDAY NIGHT. EASTERLY OR NORTHEASTERLY FLOW AS A RESULT OF A GRADIENT BETWEEN A STALLED FRONT TO THE SOUTH AND HIGH PRESSURE TO THE NORTH WILL LIKELY LEAD TO SCA GUSTS ON AT LEAST PORTIONS OF THE WATERS THROUGH WEDNESDAY. THE GRADIENT SHOULD RELAX LEADING TO DIMINISHING WINDS BY LATE IN THE WEEK. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 2 AM EDT MONDAY FOR ANZ530-531-538- 539. SMALL CRAFT ADVISORY UNTIL 6 PM EDT MONDAY FOR ANZ532>534-537- 540>543. && $$ SYNOPSIS...BJL NEAR TERM...ADS/RCM SHORT TERM...BJL/ADS LONG TERM...DFH AVIATION...BJL/ADS/DFH/RCM MARINE...BJL/ADS/DFH/RCM

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