Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 200800 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 400 AM EDT MON APR 20 2015 .SYNOPSIS... A WARM FRONT EXTENDING FROM LOW PRESSURE IN THE GREAT LAKES WILL LIFT NORTH THIS MORNING. A COLD FRONT WILL PUSH EAST ACROSS THE REGION LATE MONDAY. AN UPPER LOW WILL THEN PERSIST ACROSS THE GREAT LAKES TO NEW ENGLAND THROUGHOUT THE WEEK. && .NEAR TERM /THROUGH TONIGHT/... EARLY THIS MORNING...PRIMARY SFC LOW IS CENTERED OVER MI...WITH ANOTHER WAVE OF LOW PRESSURE OVER CENTRAL VA. LLJ/UPPER JET STREAK INDUCED MDT/HVY RAINFALL IS PIVOTING NE...WITH DRYING NOTED IN WV IMAGERY. MOST OF THE HEAVIER RAINFALL WILL LIKELY EXIT TO THE NE BY AROUND 8 AM IF NOT SOONER. HAVE CANCELLED THE FLOOD WATCH WHERE HEAVY RAIN ENDED...AND WILL FOLLOW SUIT AS SOON AS THE REST EXITS. A FEW LIGHTER SHOWERS MAY LINGER. A WARM FRONT LOCATED OVER CENTRAL VA EARLY THIS MORNING WILL QUICKLY LIFT TO THE NORTH...LEADING TO A RELATIVE DRY BREAK INTO THE MIDDAY HOURS. HOW THE ATMOSPHERE IS ABLE TO RECOVER WILL DETERMINE SVR WX CHANCES LATER TODAY. MAY TAKE LLVL CLOUDS A BIT TO SCOUR OUT...THEN QUESTION BECOMES HOW MUCH MID/HIGH LEVEL DEBRIS CLOUD PERSISTS. MODEL CONSENSUS IS FOR HIGHS IN THE 70S...ALTHOUGH READINGS WILL SOAR IF PROLONGED SUN DEVELOPS. SHOWERS/STORMS WILL LIKELY INITIATE ALONG A PRE-FRONTAL TROUGH...AIDED BY TERRAIN...DURING THE EARLY AFTERNOON HOURS. THESE STORMS WILL PROPAGATE EASTWARD THROUGH LATE AFTERNOON/EARLY EVENING. COVERAGE IS SOMEWHAT IN QUESTION...BUT SCATTERED-NUMEROUS SEEMS PLAUSIBLE. CONSISTENT INDICATIONS OF AROUND 1000 J/KG INSTBY AND 30 KT BULK SHEAR WILL LEAD TO THE POTENTIAL FOR ORGANIZED STORMS. THERE MAY BE SOME DISCRETE CELLS INITIALLY...EVENTUALLY MORPHING INTO LINE SEGMENTS. PRIMARY THREAT WILL BE DMGG WINDS...ALTHOUGH STEEP MID LVL LAPSE RATES WILL BRING THE POTENTIAL OF LARGE HAIL TOO. WHILE HODOGRAPHS NOT OVERLY IMPRESSIVE...THERE IS SOME LLVL VEERING AND A VERY SMALL CHANCE OF A TORNADO FROM ANY STRONG DISCRETE CELLS. AT THIS TIME...NO AREA OF THE CWA IS PARTICULARLY FAVORED...ALTHOUGH PARAMETERS MAY BE SLIGHTLY BETTER EAST OF THE MOUNTAINS. STORMS WILL EXIT EASTERN PARTS OF THE AREA THIS EVENING. COLD FRONT TRAILING THE LOW WELL TO THE NORTH WILL CROSS OVERNIGHT. SHOWERS MAY LINGER LONGER IN THE UPSLOPE REGIONS. TEMPS DROP INTO THE 40S WEST...BUT SLOWER ADVECTION LIMITS LOWS TO THE 50S IN THE EAST. && .SHORT TERM /TUESDAY/... VERTICALLY STACKED LOW NORTH OF THE GREAT LAKES ON TUESDAY WITH WESTERLY FLOW LOCALLY. IT WILL BE COOLER BEHIND THE COLD FRONT...BUT BREEZY DOWNSLOPE COMPONENT WILL HELP TEMPS RISE INTO THE 60S...WITH NEAR 70 IN THE EAST. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... AN ELONGATED TROUGH OF LOW PRESSURE WILL SET UP ACROSS THE NORTHERN POTOMAC HIGHLANDS TUESDAY NIGHT...ALLOWING FOR A SLIGHT CHANCE OF RAIN SHOWERS ALONG THE RIDGES. LOWS WILL BE MAINLY IN THE 40S. THROUGH THE DAY WEDNESDAY INTO WEDNESDAY NIGHT...ADDITIONAL UPPER LEVEL SUPPORT WILL PIVOT ACROSS THE LOWER GREAT LAKES TO AID IN PUSHING A COLD FRONT THROUGH THE AREA. A CHANCE OF SHOWERS AND PERHAPS A THUNDERSTORM OR TWO COULD DEVELOP IN ANY ONE PORTION OF THE REGION. HIGHS WEDNESDAY WILL BE MAINLY IN THE MIDDLE 60S WHILE LOWS WEDNESDAY NIGHT WILL DROP DOWN TO THE MIDDLE 40S...WITH EXCEPTION TO THE UPPER 30S IN THE POTOMAC HIGHLANDS. HIGH PRESSURE WILL BUILD IN FROM THE WEST THURSDAY THROUGH FRIDAY. DRY CONDITIONS AND COOLER THAN AVERAGE TEMPERATURES WILL EVOLVE. TEMPERATURES WILL BE 7 TO 10 DEGREES BELOW AVERAGE. THERE COULD BE A FEW LINGERING RAIN OR PERHAPS A SNOW SHOWER ACROSS THE HIGHER RIDGES OF THE POTOMAC HIGHLANDS THURSDAY INTO THURSDAY NIGHT DUE TO A SLIGHT UPSLOPE WIND COMPONENT. BY FRIDAY NIGHT AND CONTINUING THROUGH SATURDAY...MOISTURE WILL INCREASE FROM WEST TO EAST AND THE CHANCE FOR RAIN SHOWERS WILL OVERSPREAD THE REGION ONCE AGAIN. A LOW PRESSURE SYSTEM IS EXPECTED TO PASS ALONG THE SOUTHERN FRINGE OF OUR CWA SATURDAY INTO SATURDAY NIGHT. A FEW RAIN SHOWERS COULD STILL LINGER INTO SUNDAY BUT FOR THE MOST PART HIGH PRESSURE WILL TRY TO TAKE CONTROL BRIEFLY. TEMPERATURES WILL REMAIN BELOW NORMAL FRIDAY THROUGH THE WEEKEND. THE NEXT COLD FRONT COULD SWING ACROSS THE REGION FROM THE NORTHWEST...BRINGING A SLIGHT CHANCE OF RAIN SHOWERS MONDAY. && .AVIATION /08Z MONDAY THROUGH FRIDAY/... MDT/LOCALLY HEAVY RAIN WILL EXIT FROM S TO N EARLY THIS MORNING. VSBYS WILL IMPROVE BUT QUESTIONABLE HOW QUICKLY MVFR/IFR CIGS WILL SCOUR OUT...LIKELY BY MID/LATE MORNING. VFR LIKELY DURING MIDDAY HOURS. THUNDERSTORMS DEVELOP LATE AFTERNOON/EVENING AND COULD CONTAIN STRONG WIND GUSTS/HAIL. COVERAGE/ORGANIZATION NOT EXPECTED TO BE DEFINED ENOUGH TO PLACE SPECIFICS IN TAFS AT THIS TIME. WINDS SHIFT TO S THIS MORNING WITH WARM FRONT...THEN W WITH COLD FRONT TONIGHT. GUSTS TO AROUND 20 KT THIS AFTERNOON AND TUE AFTERNOON. VFR CONDITIONS TUESDAY NIGHT. MVFR OR IFR CONDITIONS WEDNESDAY INTO WEDNESDAY NIGHT WITH A CHANCE OF SHOWERS OR A THUNDERSTORM. VFR CONDITIONS THURSDAY THROUGH FRIDAY. WINDS SOUTHWEST AROUND 5 KNOTS TUESDAY NIGHT BECOMING WEST TO NORTHWEST 10 TO 15 KNOTS WEDNESDAY. LIGHT AND VARIABLE WEDNESDAY NIGHT THEN WEST TO NORTHWEST 5 TO 10 KNOTS THURSDAY AND FRIDAY. && .MARINE... SOME GALE GUSTS POSSIBLE THROUGH DAWN WITH LLJ. WINDS THEN SHIFT SOUTH WITH WARM FRONT FOR TODAY...REMAINING AT SCA LEVELS. STORMS POSSIBLE LATE AFTERNOON/EVENING WITH STRONG WINDS AND HAIL. COLD FRONT CROSSES TONIGHT WITH WIND SHIFT TO WEST. PERHAPS A WEAKENING OF WINDS NEAR DAWN TUESDAY...BUT THEN INCREASE AGAIN TO SCA LEVELS DURING THE DAY. NO MARINE HAZARDS TUESDAY NIGHT. SMALL CRAFT ADVISORIES POSSIBLE WEDNESDAY WITH WIND GUSTS TO 20 KNOTS AT TIMES. NO MARINE HAZARDS WEDNESDAY NIGHT THROUGH THURSDAY NIGHT. SMALL CRAFT ADVISORIES POSSIBLE AGAIN FRIDAY WITH GUSTS 20 TO 25 KNOTS. && .TIDES/COASTAL FLOODING... ESE WINDS HAVE CAUSED WATER LEVELS TO RISE. MINOR COASTAL FLOODING IS POSSIBLE AT ANNAPOLIS AND BALTIMORE FOR HIGH TIDES MONDAY MORNING. WILL MONITOR RISES AT OTHER SITES. FLOW BECOMES SWLY LATER TODAY AHEAD OF A COLD FRONT SO THE COASTAL FLOOD THREAT IS NOT EXPECTED TO CONTINUE PAST HIGH TIDE THIS MORNING. && .EQUIPMENT... AUDIO DEGRADATION AT THE NOAA WEATHER RADIO CHARLOTTESVILLE TRANSMITTER IS EXPECTED TO CONTINUE THROUGH THIS WEEKEND. TECHNICIANS ARE SCHEDULED TO PERFORM MAINTENANCE AT THE TRANSMITTER SITE MONDAY. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...FLOOD WATCH UNTIL 10 AM EDT THIS MORNING FOR DCZ001. MD...FLOOD WATCH UNTIL 10 AM EDT THIS MORNING FOR MDZ004>006-011- 013-014-503>508. COASTAL FLOOD ADVISORY UNTIL 10 AM EDT THIS MORNING FOR MDZ011- 014. VA...FLOOD WATCH UNTIL 10 AM EDT THIS MORNING FOR VAZ052>054-505- 506. WV...FLOOD WATCH UNTIL 10 AM EDT THIS MORNING FOR WVZ053. MARINE...SMALL CRAFT ADVISORY FROM 7 AM THIS MORNING TO 6 PM EDT TUESDAY FOR ANZ530>534-537>543. GALE WARNING UNTIL 7 AM EDT THIS MORNING FOR ANZ530>543. FLOOD WATCH UNTIL 10 AM EDT THIS MORNING FOR ANZ535. SMALL CRAFT ADVISORY FROM 7 AM THIS MORNING TO 1 AM EDT TUESDAY FOR ANZ535-536. SMALL CRAFT ADVISORY FROM 10 AM TO 6 PM EDT TUESDAY FOR ANZ535- 536. && $$ SYNOPSIS...ADS NEAR TERM...ADS SHORT TERM...ADS LONG TERM...KLW AVIATION...ADS/KLW MARINE...ADS/KLW TIDES/COASTAL FLOODING...ADS EQUIPMENT...LWX

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