Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 170015 AAA AFDLWX AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 815 PM EDT THU APR 16 2015 .SYNOPSIS... HIGH PRESSURE WILL CONTINUE TO MOVE OFF THE COAST THROUGH TONIGHT. A WEAK COLD FRONT WILL PASS THROUGH THE REGION FRIDAY AND HIGH PRESSURE WILL RETURN FOR SATURDAY. THE HIGH WILL MOVE OFF THE COAST SUNDAY AND A WARM FRONT WILL MOVE INTO THE AREA SUNDAY NIGHT INTO MONDAY. A COLD FRONT WILL PASS THROUGH LATE MONDAY INTO MONDAY NIGHT BEFORE HIGH PRESSURE RETURNS FOR THE MIDDLE PORTION OF NEXT WEEK. && .NEAR TERM /THROUGH FRIDAY/... INTERMEDIATE UPDATE...CONTINUED SMALL CRAFT ADVISORY INTO THE LATE NIGHT HRS. HIGHER GUSTS FROM THE PAST COUPLE OF HRS OVER THE ERN HALF OF THE CWA NEAR BEGINNING TO WANE A BIT...BUT STILL EXPECTED A FEW ISOLATED 15-20KT GUSTS OVER BOTH LAND/WATER. FROM PREV DISC... THE RETURN FLOW AROUND THE HIGH HAS COMBINED WITH THE UPPER-LEVEL DISTURBANCE TO BRING PLENTY OF CLOUDS AND EVEN SOME SHOWERS TO CENTRAL VIRGINIA INTO THE POTOMAC HIGHLANDS. THE FIRST WAVE OF PRECIP ESSENTIALLY BROKE THROUGH THE INTENSE DRY BARRIER SET UP BY THE HIGH PRESSURE AREA OFF THE COAST. DURING THE EVE HRS...A WEAK UPPER WAVE WILL CONTINUE SLIDING OVER THE UPPER MIDWEST AND INTO THE AREA - CARRYING LIGHT RAIN OVER THE POTOMAC HIGHLANDS. A FEW ISOLATED SHOWERS WILL DOT THE LANDSCAPE ELSEWHERE...ONLY TRACE AMOUNTS INTO THE OVERNIGHT HRS. SLY FLOW WILL CONTINUE TO INCREASE MOISTURE ACROSS OUR AREA...RESULTING IN PLENTY OF CLOUDS. MOST LOCATIONS MAY END UP DRY DUE TO A LACK OF FORCING. A COLD FRONT WILL MOVE INTO THE REGION FRIDAY. THE TEMPERATURE GRADIENT WILL BE WEAK ALONG THE FRONT...SO WARM CONDITIONS ARE EXPECTED EVERYWHERE. LEANED TOWARD THE WARMER GUIDANCE...WITH THE THINKING THAT SOME SUNSHINE WILL BREAK OUT AS DRIER AIR ALOFT CLEARS OUT ANY HIGH AND MID-LEVEL CLOUDS LEAVING JUST A SCT TO BKN CU DECK. MAX TEMPS WILL RANGE FROM THE 60S IN THE MOUNTAINS TO THE MID AND UPPER 70S NEAR WASHINGTON AND BALTIMORE INTO CENTRAL VIRGINIA. THE WARM AND RELATIVELY MOIST CONDITIONS WILL CAUSE SOME INSTABILITY TO DEVELOP. THIS MAY BE ENOUGH FOR A FEW SHOWERS AND POSSIBLY EVEN A THUNDERSTORM...ESPECIALLY LATER IN THE AFTERNOON EAST OF THE BOUNDARY FOR LOCATIONS NEAR AND EAST OF THE BLUE RIDGE MOUNTAINS. THE THREAT FOR SEVERE WEATHER IS LOW DUE TO LIMITED INSTABILITY...WEAK SHEAR PROFILES AND A LACK OF A SIGNIFICANT LIFTING MECHANISM SINCE FORCING ON THE FRONT WILL BE WEAK. && .SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/... THE FRONT WILL MOVE OFF TO THE EAST FRIDAY EVENING. ANY LEFTOVER SHOWERS FRIDAY EVENING NEAR AND EAST OF INTERSTATE 95 WILL DISSIPATE OVERNIGHT AS DRIER AIR MOVES IN FROM THE NORTHWEST. LEANED TOWARD THE WARMER GUIDANCE DUE TO A NORTHWEST WIND INCREASING MIXING BEHIND THE FRONT...PREVENTING RADIATIONAL COOLING. HIGH PRESSURE WILL CONTINUE TO BUILD OVERHEAD SATURDAY THROUGH SATURDAY NIGHT. DRY AND SEASONABLE CONDITIONS ARE EXPECTED. && .LONG TERM /SUNDAY THROUGH THURSDAY/... A LARGE AND SLOW-MOVING UPPER-LEVEL TROUGH WILL APPROACH THE REGION FROM THE UPPER MIDWEST DURING THE SECOND HALF OF THE WEEKEND. RAIN CHANCES WILL INCREASE FROM SOUTHWEST TO NORTHEAST AHEAD OF A WARM FRONT DURING THE DAY SUNDAY. AN INCREASING LOW- LEVEL JET WILL USHER PLENTIFUL MOISTURE INTO THE REGION...IN TANDEM WITH UPPER-LEVEL DIVERGENCE FROM THE RIGHT ENTRANCE REGION OF AN 250 MB JET. THIS SHOULD SET THE STAGE FOR A WIDESPREAD SOAKING RAIN SUNDAY NIGHT...SOME OF WHICH MAY BE HEAVY. NOT ENOUGH CONFIDENCE AT THIS TIME TO INCLUDE ANY FLOODING MENTION IN THE HWO BUT AT LEAST SPOTTY NUISANCE FLOODING COULD BE POSSIBLE DURING THIS TIME. PARTS OF THE AREA MAY WARM SECTOR MONDAY...BUT THAT DEPENDS ON HOW FAR NORTH THE WARM FRONT CAN GET GIVEN RAIN-COOLED AIR AND CLOUD DEBRIS. AT LEAST ISOLATED ELEVATED THUNDER IS POSSIBLE LATE SUNDAY NIGHT INTO MONDAY EVENING THOUGH. RAIN CHANCES SLOWLY DIMINISH AS A COLD FRONT/TROUGH AXIS PIVOT THROUGH THE AREA LATER MONDAY NIGHT. HIGH PRESSURE BRIEFLY RETURNS LATE TUESDAY INTO WEDNESDAY...BEFORE ANOTHER SYSTEM APPROACHES FROM THE WEST BY LATE NEXT WEEK. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/... VFR CONDITIONS ARE EXPECTED THROUGH THIS EVENING. A FEW SHOWERS MAY IMPACT KCHO DURING THIS TIME. HIGH AND MID-LEVEL CLOUDS WILL INCREASE ELSEWHERE. SOUTH TO SOUTHEAST WINDS WILL GUST AROUND 15 TO 20 KNOTS THIS AFTERNOON BEFORE DIMINISHING TOWARD SUNSET. A FEW SHOWERS ARE POSSIBLE LATE TONIGHT INTO FRIDAY MORNING...ESPECIALLY ACROSS THE NORTHERN TERMINALS. CIGS/VSBYS MAY APPROACH MVFR LEVELS AT THIS TIME. THE BEST CHANCE FOR MVFR LEVELS WILL BE AT KCHO DUE TO DEEPER MOISTURE. A COLD FRONT WILL PASS THROUGH THE TERMINALS LATER FRIDAY INTO FRIDAY EVENING. A FEW SHOWERS AND PERHAPS A THUNDERSTORM ARE POSSIBLE. VFR CONDITIONS ARE EXPECTED BEHIND THE FRONT FRIDAY NIGHT. VFR W/ NLY FLOW 10 KT SAT-SAT NIGHT. FLOW BECOMES ELY 10- 15 KT SUN-SUN NIGHT W/ LWR CIGS/RA LEADING TO SUB-VFR. FLOW BECOMES SLY INTO MON AND INCREASES 10-20 KT. SUB-VFR CONDS MAY BECOME MORE SCTD DURING THIS TIME. && .MARINE... MARGINAL SMALL CRAFT ADVISORY GUSTS CONTINUE OVER THE WATER LATE THIS EVE. SCA THRU MIDNIGHT. SLY WINDS CONTINUE TONIGHT...BUT THE GRADIENT WILL BE WEAK ENOUGH FOR SUB SCA CONDITIONS. A COLD FRONT WILL PASS THROUGH THE WATERS LATE FRIDAY INTO FRIDAY EVENING. SOUTH TO SOUTHWEST WINDS AHEAD OF THE FRONT WILL SHIFT TO THE NORTHWEST BEHIND THE FRONT. WINDS SHOULD REMAIN BELOW SCA CRITERIA. THERE MAY BE A FEW SHOWERS AND EVEN A COUPLE THUNDERSTORMS AHEAD OF THE FRONT FRIDAY AFTERNOON. SHOULD THUNDERSTORMS DEVELOP...THEY WILL BE CAPABLE OF PRODUCING LOCALLY GUSTY WINDS. MARGINAL SCA GUSTS POSSIBLE SAT-SAT NIGHT IN NLY CHANNELING...THEN ELY FLOW AS HIGH PRESSURE ESTABLISHES ITSELF TO THE NORTH AND A WARM FRONT DEVELOPS TO THE SOUTH...INCREASING THE GRADIENT. SCA LIKELY SUN-MON...W/ OUTSIDE CHANCE OF GALE BUT NOT ENOUGH CONFIDENCE FOR HWO MENTION JUST YET GIVEN HIGHEST LLJ OVERNIGHT. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL MIDNIGHT EDT TONIGHT FOR ANZ530>543. && $$ UPDATE...GMS PREV DISCUSSION...BJL/DFH

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