Area Forecast Discussion
Issued by NWS Sterling, VA

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519 FXUS61 KLWX 081517 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 1017 AM EST MON FEB 8 2016 .SYNOPSIS...
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LOW PRESSURE WILL MOVE OUT TO SEA TODAY. ANOTHER LOW PRESSURE SYSTEM WILL DIVE SOUTH INTO THE OHIO VALLEY TODAY BEFORE PASSING THROUGH OUR AREA TONIGHT INTO TUESDAY. HIGH PRESSURE WILL SLOWLY BUILD TOWARD OUR AREA DURING THE MIDDLE PORTION OF THE WEEK.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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REGION REMAINS SANDWICHED WITH DEEPENING LOW PRESSURE OFFSHORE AND A SECOND LOW OVER THE GREAT LAKES...DIPPING INTO THE OH RIVER VALLEY THIS AFTN. PRECIPITATION WILL MOVE INTO THE WESTERN MOUNTAINS THIS AFTERNOON WHERE A WINTER WEATHER ADVISORY REMAINS IN EFFECT. THE ADVISORY WILL LIKELY BE EXTENDED...OR MAY NEED TO BE UPGRADED TO A WARNING...WILL HAVE TO FINE TUNE THE PERIODS OF HEAVIEST SNOW. FIRST WAVE OF PRECIP WILL CONTINUE TO PUSH EAST THRU THE AFTN. ANYTHING MOVING EAST OF THE BLUE RIDGE BY NIGHTFALL WILL BE VERY LIGHT...AND EVEN SO...NOT EXPECTED SUBSTANTIAL QPF ANYWHERE TODAY. AS THE PCPN PUSHES EAST...GENERALLY EXPECTING ALL RAIN OR MAYBE A RAIN/SNOW MIX NEAR THE MASON-DIXON LINE AND IN THE HIGHER ELEVATIONS. NO CHANGE AT THIS TIME TO FORECAST HIGHS IN GENERALLY IN THE 40S AT LOWER ELEVATIONS.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY NIGHT/... TRICKY FORECAST STILL IN PLACE FOR THE PCPN TONIGHT THRU TUESDAY NIGHT WITH MANY FACTORS STILL IN PLACE. ONE THING THAT SEEMS TO HAVE BEEN CONSISTENT FOR MANY MODEL RUNS NOW IS THE HINT OF THE HEAVIEST BAND OF PCPN ALIGNING OVER NE MD/SE PA/N DE. AS SUCH...AM ISSUING A WINTER STORM WATCH BEGINNING TONIGHT AND LASTING THRU TUES NIGHT WITH THE POTENTIAL OF 7 INCHES OR MORE OF SNOW IN A 24 HOUR TIME PERIOD FOR FREDERICK COUNTY EAST AND SOUTH TO ACCOUNT FOR BALTIMORE METRO. IN ADDITION TO THE PREVIOUSLY MENTIONED SFC LOW TO THE NORTHWEST...SECONDARY LOW FORMS OVER VA TONIGHT...DEEPENING AS IT PUSHES OFFSHORE DURING THE DAY TUES. 00Z GFS DEEPENS THE LOW MORE THAN THE OTHER MODEL SOLUTIONS...AND AS SUCH...SEEING THE HIGHEST QPF AMTS IN THIS LATEST RUN. WHILE THE PLACEMENT OF THE HEAVIEST BAND IS COMING INTO BETTER AGREEMENT...THE EXACT AMT OF QPF AND THE RESULTING SNOW IS STILL UNCERTAIN...THOUGH WITH INCRSG CONFIDENCE NOW OF SEEING AT LEAST 7 INCHES. TIMING LOOKS TO HAVE THE HEAVIER SNOW MOVE IN SECOND HALF OF TONIGHT...LASTING INTO THE MORNING...WITH LIGHTER SNOW FOR A PERIOD OR EVEN A BREAK IN THE PCPN...THEN ANOTHER BURST PSBL TUES AFTN. THE OTHER ISSUE AT HAND IS THE THERMAL PROFILES AND THE RESULTING P-TYPE. INITIAL AGREEMENT WITH MOST AREAS EAST OF THE BLUE RIDGE SEEING A RAIN/SNOW MIX FIRST PART OF TONIGHT. AS THE PCPN INCREASES IN INTENSITY...GENERALLY AFTR 03/04Z...SHOULD SEE A CHANGEOVER TO SNOW FOR AREAS MAINLY NORTH AND WEST OF A DC TO CHARLOTTESVILLE LINE. PORTIONS OF SOUTHERN MD WILL STAY ALL RAIN...AT LEAST FOR TONIGHT. 00Z MODEL SUITE SHOWING COOLER WET BULB TEMPS...WITH NORTHERN HALF OF THE CWA FULLY BELOW FREEZING...AND DC METRO WITH PERIODS OF AT OR JUST BELOW FREEZING. ANOTHER THING WORKING AGAINST SNOW TOTALS IS THAT AT FIRST NO SNOW MIGHT ACCUMULATE WITH THE WARMER TEMPS. SO A DELAY IN SNOW ACCUMULATION IS PSBL...WHICH MAY AFFECT TOTALS. PCPN BEGINS TO TAPER OFF ACROSS CENTRAL VA TOMORROW NIGHT...LINGERING ALONG THE I-95 CORRIDOR AND THE UPSLOPE REGIONS POTENTIALLY ALL THE WAY THRU WED WITH THE REGION REMAINING ON THE WESTERN SIDE OF THE LOW AND CONTINUOUSLY BEING IMPACTED BY SHORTWAVES PROGRESSING ACROSS THE MID-ATLANTIC. WHILE CRITERIA LVL SNOW WONT BE PSBL OVER THE EASTERN AREAS...ADVISORY LVL SNOW MIGHT BE PSBL ON THE ALLEGHENY FRONT. NOT TO BE FORGOTTEN...THE POTENTIAL FOR COLD TEMPS CONTINUES FOR WED NIGHT...WITH WIND CHILLS BELOW ZERO BCMG MORE LIKELY FOR THE WESTERN PORTIONS OF THE CWA. WILL CONTINUE TO HIGHLIGHT IN THE HWO WITH THE POTENTIAL NEED OF A WIND CHILL ADVISORY. && .LONG TERM /THURSDAY THROUGH SUNDAY/... THE H5 TROF AXIS WL REMAIN THRU THE WKND...MEANING THE COLD PTTN WL REMAIN IN PLACE. IF ANYTHING...WE/LL BE GETTING INCRSGLY COLDER. INIT ROUND OF CAA ENDS THU. GUSTY NW WINDS WL RELAX AT THAT POINT. THEN ANOTHER NRN STREAM S/WV AND SFC REFLECTION TRACKS S OF AREA LT FRI...WHICH DRAGS DOWN EVEN COLDER AIR FOR SAT-SUN. FOR THE MOST PART...TEMPS WL REMAIN SUBFREEZING THRU THE XTNDD. MIN-T WL BE IN THE TEENS...OR LOWER. SAT NGT WUD BE THE COLDEST NIGHT...WITH PSBL SUBZERO READINGS IN THE MTNS. WIND CHILLS WL BE A CONCERN. THE LOW ITSELF CUD PROVIDE SCT SHSN JUST ABT ANYWHERE FRI/FRI NGT. IN ADDITION THERE WL BE CONTD UPSLOPE POTL THU BEFORE FLOW BECOMES DISRUPTED. THE PTTN WUD SUPPORT ADDTL UPSLOPE IN THE WAKE OF THE LOW. && .AVIATION /15Z MONDAY THROUGH FRIDAY/...
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VFR CONDITIONS INITIALLY TODAY. MVFR CIGS WILL LIKELY HOLD OFF UNTIL EVENING. AS THE PCPN MOVES IN LATE TODAY/THIS EVENING... EXPECTING CONDITIONS TO DROP QUICKLY TO IFR OR LOWER...ESP TONIGHT WITH THE HEAVIER PCPN. OTHER THAN KCHO...SITES SHOULD START AS LIGHT RAIN...TRANSITIONING TO RAIN/SNOW MIX...EVENTUALLY BCMG ALL SNOW BY TUES MORNING. KCHO LOOKS TO REMAIN ALL RAIN...THOUGH CANNOT RULE OUT A BRIEF RAIN/SNOW MIX TONIGHT. WINDS GENERALLY LESS THAN 12 KTS THRU THE TAF PERIOD. SUB-VFR CONDITIONS WILL CONTINUE TUES WITH THE PCPN. MARGINAL TEMPS DURING THE DAYLIGHT HOURS MAY LEAD TO MIXED RAIN AND SNOW IN THE DC AREA...WITH BETTER CHANCES FOR SNOW TO THE NORTH AND WEST. CONDITIONS EVENTUALLY IMPROVING TO VFR BY WED MORNING. GUSTY NW WINDS WL BE THE PRIMARY AVN CONCERN THU...W/ SOME G25KT LKLY. ANOTHER DISTURBANCE MAY BRING MORE SHSN FRI. WAY TOO SOON TO TELL IF THIS WL MATERIALIZE...BUT IT CUD BRING MVFR/IFR RESTRICTIONS IF IT DID.
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&& .MARINE... EXPECTING GENERALLY SUB-SCA CONDITIONS TODAY THRU A GOOD PORTION OF TUES. OCNL GUSTS TO 20 KTS PSBL THIS EVENING...BUT NOT WIDESPREAD ENOUGH ATTM TO ISSUE A SCA. AS THE LOW PUSHES OFFSHORE AND DEEPENS BY TUES NIGHT...EXPECT SCA CONDITIONS ON AT LEAST THE CHESAPEAKE BAY... SPREADING TO ALL WATERS ON WED. SCA CONDS CONT INTO THU...THEN RELAX AS BRIEF HIPRES CRESTS OVER THE RGN AHD OF ANOTHER DISTURBANCE FRI. && .TIDES/COASTAL FLOODING...
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WATER LVLS ARE ACTUALLY FAIRLY CLOSE TO NORMAL ACROSS THE NRN CHSPK BAY...BUT DEPARTURES ARE STARTING TO BE REALIZED ACROSS THE MID BAY. PLUS...WERE STILL CARRYING CLOSE TO A FOOT ABV ASTRO NORMALS ACROSS THE UPR TIDAL POTOMAC. AS SEVERAL ROUNDS OF LOW PRESSURE PASS OVER/EAST OF THE MOUTH OF THE BAY...ADDITIONAL WATER WILL BE DRAWN IN TO THE ESTUARY. THAT MAY LEAD TO COMPLICATIONS AS EARLY AS THE PM TIDE CYCLE TODAY...CARRYING THROUGH TUESDAY. MINOR INUNDATION WOULD BE MORE LIKELY FOR BOTH CYCLES ON TUESDAY.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...WINTER WEATHER ADVISORY UNTIL 1 AM EST TUESDAY FOR MDZ501-502. WINTER STORM WATCH FROM LATE TONIGHT THROUGH LATE TUESDAY NIGHT FOR MDZ004>006-011-014-503-505>508. VA...WINTER WEATHER ADVISORY UNTIL 1 AM EST TUESDAY FOR VAZ503-504. WV...WINTER WEATHER ADVISORY UNTIL 1 AM EST TUESDAY FOR WVZ501>506. MARINE...NONE.
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&& $$ SYNOPSIS...HTS NEAR TERM...SEARS/ADS SHORT TERM...SEARS LONG TERM...HTS AVIATION...SEARS/ADS/HTS MARINE...SEARS/HTS TIDES/COASTAL FLOODING...HTS

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