Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 231345 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 945 AM EDT THU JUL 23 2015 .SYNOPSIS... HIGH PRESSURE OVER THE OHIO VALLEY AND GREAT LAKES WILL DOMINATE OVER THE NEXT SEVERAL DAYS. THE HIGH WILL SHIFT EASTWARDS OVER THE WEEKEND...ALLOWING A COLD FRONT TO MOVE IN FROM THE NORTHWEST LATER SUNDAY AND MONDAY. THE FRONT WILL DISSIPATE OVER THE REGION TUESDAY BEFORE ANOTHER COLD FRONT APPROACHES FROM THE NORTHWEST LATE NEXT WEEK. && .NEAR TERM /THROUGH TONIGHT/... CLOSED UPPER LOW IS SPINNING OVER QUEBEC THIS MORNING...WITH A JET STREAK ROUNDING ITS BASE THROUGH THE MID-ATLANTIC. A SHORTWAVE TROUGH IS MOVING ACROSS THE MID MS VALLEY. AT THE SFC...A STATIONARY FRONT IS DRAPED ACROSS THE SE STATES...WITH WEAK/BROAD HIGH PRESSURE CENTERED OVER THE OHIO VALLEY. THE TROUGH WILL BE PASSING TO OUR SOUTH THIS AFTERNOON AND EVENING...AND COMBINE WITH A WEAK WAVE OF SFC LOW PRESSURE TO PRODUCE PRECIP AS NEARBY AS SOUTHERN VA. MODEL CONSENSUS KEEPS PRECIP TO OUR SOUTH...AS IT WILL BE BUTTING INTO A DRY ATMOSPHERE. MADE MINOR TEMP ADJUSTMENTS BASED ON LTST LAMP GDNC....OTRW PREV FCST IN GOOD SHAPE. SUNNY SKIES THIS MRNG...BUT XPCT SOME DIURNAL CU DVLPMNT TAFTN. CLDS WL BE MUCH THICKER FM CHO-EZF-NHK AS THESE AREAS WL BE CLOSER TO THE VORT. MAIN SYNOPTIC FEATURES STAY IN PLACE TONIGHT. CLOUDS SHOULD DECREASE AS TROUGH AND JET ENERGY DEPART. LOWS WILL FALL TO NEAR THE DEW POINTS...WITH 50S WEST OF I-81 CORRIDOR AND 60S EAST. && .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... THE MID-ATLANTIC WILL REMAIN BETWEEN WEATHER SYSTEMS ON FRIDAY...WITH THE BROAD SFC HIGH REMAINING IN CONTROL. MID/UPPER LEVEL PATTERN INCHES EASTWARD...WHICH WILL ALLOW TEMPERATURES TO BE A COUPLE DEGREES WARMER...BUT SHOULD STAY SUB-90F WITH POSSIBLE EXCEPTION OF URBAN CENTERS. DEW POINTS MAY TICK UP A FEW DEGREES TOO...BUT REMAIN ON THE COMFORTABLE END OF THE SPECTRUM. HIGH PRESSURE WILL SHIFT EAST FROM THE OHIO VALLEY TO THE WESTERN ATLANTIC DURING THE COURSE OF FRIDAY NIGHT AND SATURDAY. THIS WILL ALLOW WINDS TO SHIFT TO A SOUTHERLY DIRECTION...SO THAT WHILE FRIDAY NIGHT SHOULD STILL BE RELATIVELY COMFORTABLE...A MODEST INCREASE IN BOTH WARMTH AND HUMIDITY WILL OCCUR SATURDAY AND SATURDAY NIGHT. GFS AND NAM SUGGEST A SMALL RISK OF TERRAIN-BASED CONVECTION OVER THE MOUNTAINS IN WESTERN VIRGINIA AND EASTERN WEST VIRGINIA SATURDAY AFTERNOON...BUT HAVE NOT BITTEN ON THIS THREAT JUST YET. A WEAK PASSING SHORTWAVE MAY ENHANCE THIS POSSIBILITY. EVEN IF IT HAPPENS...IT SHOULD BE FAIRLY ISOLATED AND REMAIN WEST OF THE METRO...MEANING THE VAST MAJORITY OF THE REGION WILL ENJOY ONE MORE DAY OF DRY...IF SLIGHTLY WARMER AND MORE HUMID...WEATHER. SATURDAY NIGHT SHOULD TURN OUT DRY EVEN IF THERE IS ANY AFTERNOON CONVECTION...THOUGH LOWS WILL TURN OUT WARMER THAN PRIOR NIGHTS. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... WEAKENING COLD FRONT WILL APPROACH FROM THE NORTHWEST ON SUNDAY...WITH AN INCREASE IN SOUTH TO SOUTHWEST FLOW AHEAD OF IT. THIS WILL RESULT IN A CONTINUED INCREASE IN WARMTH AND HUMIDITY... AND SUNDAY WILL BEGIN TO FEEL UNCOMFORTABLE FOR SOME. AS THE FRONT MOVES CLOSER...THE RISK OF THUNDERSTORMS WILL BEGIN TO INCREASE SUNDAY AFTERNOON AND LINGER THROUGH MONDAY AS THE FRONT MOVES INTO THE CWA. BY TUESDAY IT STALLS AND FALLS APART ON MOST GUIDANCE BUT THE LINGERING BOUNDARY MAY STILL HELP TO TRIGGER SPOTTY CONVECTION. GUIDANCE STARTS TO GET OUT OF SYNC AFTER THIS POINT BUT THE NEXT FRONT WILL LIKELY APPROACH LATER THURSDAY INTO FRIDAY. WITH THE FIRST FRONT WASHING OUT...TEMPERATURES WILL STAY PRETTY WARM...BUT A RETURN OF THE SIGNIFICANT HEAT FROM EARLIER THIS WEEK IS NOT EXPECTED AS THE RIDGE ALOFT WILL REMAIN TO THE SOUTHWEST AND THE FLOW ALOFT WILL MOSTLY REMAIN FROM THE NORTHWEST IN OUR REGION...SHIFTING A BIT MORE WESTERLY LATER NEXT WEEK. && .AVIATION /14Z THURSDAY THROUGH MONDAY/... VFR CONDITIONS EXPECTED THROUGH TODAY WITH HIGH PRESSURE IN CONTROL. NW FLOW GENERALLY LESS THAN 10 KT...ALTHOUGH KCHO MAY SWING AROUND TO THE E OR SE. WINDS CALM OVERNIGHT. PERHAPS A LITTLE HIGHER CHANCE OF MVFR VSBY IN BR NEAR KCHO AREA EARLY FRIDAY MORNING. VFR CONTINUES INTO FRIDAY WITH NW OR N WINDS LESS THAN 10 KT. VFR CIGS AND VIS EXPECTED AT ALL TERMINALS FRIDAY NIGHT THROUGH SATURDAY NIGHT...ASIDE FROM VERY SLIGHT RISK OF MVFR OR IFR CIGS/VIS FROM PATCHY EARLY MORNING FOG PRIMARILY AT INLAND TERMINALS. RISK OF THUNDERSTORMS WITH MVFR/IFR CIGS/VIS FROM HEAVY RAINS WILL INCREASE SUNDAY AND MONDAY. WINDS WILL BE FROM THE WEST TO NORTH FRIDAY NIGHT BEFORE BECOMING SOUTH TO SOUTHWEST SATURDAY AND SUNDAY. SPEEDS SHOULD REMAIN GENERALLY BELOW 10 KNOTS THROUGH SATURDAY WITH SOME INCREASE TO 10-20 KNOTS POSSIBLE SUNDAY AFTERNOON. WINDS WILL RELAX AGAIN SOMEWHAT ON MONDAY. && .MARINE... BROAD HIGH PRESSURE CENTERED TO THE NW OF THE AREA WILL CONTROL THE WEATHER THROUGH FRIDAY. PREVAILING FLOW WILL BE NW OR N THROUGH THIS PERIOD...ALTHOUGH LOCAL VARIABILITY COULD DEVELOP. SPEEDS GENERALLY 10 KT OR LESS. NO ISSUES CURRENTLY EXPECTED FRIDAY NIGHT THROUGH SATURDAY NIGHT WITH HIGH PRESSURE SHIFTING EAST. THE RISK OF SCA WINDS AND SCATTERED THUNDERSTORMS WILL INCREASE SUNDAY AND MONDAY AS A COLD FRONT APPROACHES. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...NONE. && $$ SYNOPSIS...RCM NEAR TERM...ADS/HTS SHORT TERM...ADS/RCM LONG TERM...RCM AVIATION...ADS/RCM MARINE...ADS/RCM

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