Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 260023 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 823 PM EDT SAT APR 25 2015 .SYNOPSIS... LOW PRESSURE WILL MOVE SOUTHEAST ACROSS THE CAROLINAS TONIGHT AND OFF THE COAST SUNDAY MORNING. THE LOW REMAINS OFFSHORE AS HIGH PRESSURE GRADUALLY BUILDS IN FROM THE WEST FOR THE FIRST HALF OF THE WEEK. ANOTHER LOW MAY IMPACT THE REGION FOR THE LATTER HALF OF THE WEEK. && .NEAR TERM /THROUGH SUNDAY/... AS OF 00Z...RAIN EXTENDS FROM THE LOWER GREAT LAKES TO THE DELMARVA COAST ALONG AN AREA OF CONVERGENCE ALOFT. A SURFACE LOW IS LOCATED ACROSS THE TN VALLEY. ALONG THE LEADING EDGE OF THE RAIN MOVING NORTHWARD...DEWPTS DRASTICALLY DROP OFF INTO THE UPPER 20S/30S. AS THE RAINDROPS MOVE INTO THE DRY ENVIRONMENT...THEY COOL IN THE LOWER 1-2K FEET AND RE-FREEZE RESULTING IN SLEET BEING OBSERVED NEAR THE LEADING EDGE. AS RAIN MOVES NORTHWARD DEWPTS WILL RISE INTO THE 30S/40S TONIGHT. NO SLEET ACCUMULATION IS EXPECTED. AS THE LOW MOVES EASTWARD THE BAND OF RAIN CURRENTLY OVER THE MID-ATLANTIC WILL ALSO MOVE EASTWARD. THIS AREA OF RAIN IS EXPECTED TO TAPER OFF AFTER 6Z TONIGHT MOVING EAST OF I-95 BY 10Z SUNDAY. TEMPERATURES WILL NOT FALL MUCH OVERNIGHT AND BASICALLY TRENDED MIN TEMPS TO ADJUSTED MET GUIDANCE. FORECAST RAINFALL AMOUNTS GENERALLY LINE UP PRETTY WELL WITH WPC QPF AMOUNTS AND WILL BE GENERALLY HEAVIER ACROSS THE SW PORTION WITH AMOUNTS AROUND ONE HALF INCH...DC METRO AROUND ONE- QUARTER OF AN INCH...BALTIMORE BETWEEN 1-2 TENTHS. HI RES CAM MODELS SHOW GOOD AGREEMENT WITH 12Z NAM/GFS/SREF ON TIMING OF PRECIP ACROSS AREA. LATEST HRRR GUIDANCE SUGGEST THE PRECIP COULD EVEN BE MORE SCATTERED IN COVERAGE THIS EVENING. FOR SUNDAY...THERE COULD BE LINGERING LIGHT PRECIP ACROSS THE SRN TIER OF THE CWA JUST AFTER 12Z...BUT CLOUDS AND PRECIP WILL PUSH SOUTH AS HIGH PRESSURE BUILDS INTO THE REGION FROM THE GREAT LAKES. HIGH TEMPS STILL COOL FOR THIS TIME OF YEAR...AND USED A BLEND OF MOS/ADJ MAV. && .SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/... REGION REMAINS POSITIONED UNDER UPPER LVL LOW CENTERED OVER THE CANADIAN MARITIMES WHILE SFC LOW SETTLES WELL OFFSHORE TO START THE WORK WEEK. GENERALLY EXPECTING DRY CONDITIONS SUN NIGHT WITH A BREAK IN THE SHORTWAVE ENERGY...THOUGH A SFC TROF COULD GENERATE ISO SHOWERS SECOND HALF OF THE NIGHT. TEMPS DROPPING INTO THE 30S FOR LOWS SUN NIGHT COULD RESULT IN ANY PCPN NEAR DAYBREAK BEING A RAIN/SNOW OR EVEN ALL SNOW...WITH LITTLE TO NO ACCUM. THE REGION WILL BE SANDWICHED BETWEEN HIGH PRESSURE OVER THE GREAT LAKES AND THE LOW OFFSHORE MONDAY...RESULTING IN ELEVATED WINDS...WITH GUSTS 25-30 MPH. POPS INCREASE AFTR 12Z MON AS NEXT SHORTWAVE/VORT MAX ROUNDS THE LOW...WITH THE BETTER CHC WESTERN AND EASTERN FRINGES OF THE CWA. THE STRONG SHORTWAVE WILL EXTEND ACROSS THE MID ATLANTIC FOR MOST OF THE DAY...PRODUCING SCT SHOWERS. PCPN TAPERS OFF MON EVENING AS UPPER LVL LOW PIVOTS OFFSHORE. AS THE HIGH BUILDS IN...EXPECTING TO SEE WARMING TEMPS...WITH TEMPS NEARING NORMAL BY MON NIGHT. && .LONG TERM /TUESDAY THROUGH SATURDAY/... DESPITE THE COOL START AND CONTINUED CAA BEHIND THE COLD FRONT...TEMPS WILL REBOUND A FEW DEGREES TUE AS DECREASING CLOUDS ALLOW THE LATE APRIL SUN TO DO ITS WORK. THIS SLOW WARMING TREND CONTINUES INTO WED...WITH TEMPS BACK TO NEAR NORMAL...AS A WEAK AREA OF HIGH PRESSURE BUILDS IN. MODEL DIVERGENCE INCREASES SUBSTANTIALLY BY LATE WED INTO THU WITH REGARDS TO DEVELOPING LOW OVER GOM. LATEST MODEL GUIDANCE APPEARS TO SHUNT MAIN IMPACTS TO OUR SOUTH...WITH LITTLE QPF OVER CWA. 12Z GFS FAR DIFFERENT FROM 00Z ECMWF...AS GFS HAS NO COASTAL LOW OFF THE CAROLINA COAST AND ECMWF DOES. HAVE LOWERED POPS SOME FOR THU...ALTHOUGH FOR CONSISTENCY AND TO AVOID JUMPING ON ONE MODEL CYCLE STILL KEPT CHC POPS...ALTHOUGH THAT MIGHT BE TOO HIGH. HIGH PRESSURE RETURNS BY FRIDAY...BRINGING NEAR NORMAL TEMPS. && .AVIATION /00Z SUNDAY THROUGH THURSDAY/... -RA EXPECTED AT THE TERMINALS THIS EVENING BEFORE TAPERING OFF AFTER 6Z TONIGHT. CIGS WILL CONTINUE TO LOWER TONIGHT. A BRIEF PERIOD OF IFR CONDITIONS ARE POSSIBLE 3-6Z BEFORE DRIER AIR MOVES INTO THE TERMINALS BUT AT THIS TIME CARRYING MVFR CIGS. CHO WILL LIKELY SEE THE MOST MOISTURE ALOFT AND THEREFORE IFR CIGS ARE EXPECTED TONIGHT. LIGHT S-SW WINDS WILL BECOME N TONIGHT AND INTO SUNDAY MORNING. WINDS SHOULD STAY LIGHT...LESS THAN 6KTS. VFR CONDITIONS SUN-SUN NIGHT. SUB-VFR CONDITIONS PSBL MON WITH ANY RAIN SHOWER. GUSTY NW WINDS WITH GUSTS 20-25 KTS PSBL AS WELL DURING THE DAY MON...DIMINISHING AFTR SUNSET. MVFR CIGS MAY LINGER THRU MON NIGHT. NOT EXPECTING AVIATION CONCERNS TUE/WED WITH VFR CONDITIONS. && .MARINE... RAIN WILL CONTINUE TO OVERSPREAD THE WATERS THIS EVENING. WINDS REMAIN LESS THAN 10 KTS THROUGH SUN MORNING...INCREASING SUN AFTN. GUSTS COULD BRIEFLY TOUCH 18-20 KTS SUN AFTN WITH NORTHERLY CHANNELING. SUB-SCA CONDITIONS INITIALLY SUN EVENING...WITH INCRSG WINDS OVERNIGHT. SCA CONDITIONS WITH GUSTS UP TO 20 KTS AS EARLY AS THE SECOND HALF OF SUN NIGHT...BCMG MORE LIKELY AFTR DAYBREAK MON. GUSTS UP TO 30 KTS PSBL ON THE CHESAPEAKE BAY DURING THE DAY. SCA GUSTS CONTINUE THRU MON NIGHT. SCA IS POSSIBLE TUE UNTIL THE PRESSURE GRADIENT WEAKENS WITH DEPARTING LOW. PRESSURE GRADIENT RELAXES ENOUGH FOR A RETURN TO LIGHT WINDS BY WED. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...NONE. && $$ SYNOPSIS...SEARS NEAR TERM...HAS/SMZ SHORT TERM...SEARS/SMZ LONG TERM...MSE AVIATION...SEARS/HAS/MSE/SMZ MARINE...SEARS/HAS/MSE/SMZ

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