Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 161947 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 247 PM EST TUE DEC 16 2014 .SYNOPSIS...
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A COLD FRONT OVER WEST VIRGINIA WILL CROSS THE AREA THIS EVENING. HIGH PRESSURE BUILDS IN TONIGHT AND REMAINS FOR THE SECOND HALF OF THE WEEK...BRINGING MAINLY DRY CONDITIONS. THE EXCEPTION WILL BE POSSIBLE RAIN AND SNOW SHOWERS WEST OF THE ALLEGHENY FRONT TONIGHT THROUGH WEDNESDAY NIGHT. LOW PRESSURE MAY BRING A WINTRY MIX TO THE AREA THIS WEEKEND.
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&& .NEAR TERM /TONIGHT/...
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MAIN AREA OF RA MOVG ONTO THE DELMARVA. IN ITS WAKE THE RMDR OF THE AFTN WL BE CLDY. ANOTHER AREA OF RW WL BE MOVG INTO THE HIGHLANDS AFTR 4 PM...REACHING THE BAY ARND 10 PM...BUT AMTS W/ THIS WL BE LGT - PERHAPS A FEW HUNDREDTHS OF AN INCH AT BEST. THERE IS A THIN BAND OF CLRG SKIES ACROSS THE SHEN VLLY...BUT BLV THAT WL CLOSE IN FAIRLY QUICKLY. SKIES XPCTD TO BE CLDY TNGT...W/ SOME CLRG PSBL LATE TNGT AS HIGH PRES BEGINS TO BUILD INTO THE AREA. UPSLOPE SHRA PSBL IN THE HIGHLANDS...LIQUID VARIETY. LOWS 35-40.
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&& .SHORT TERM /WEDNESDAY/...
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HIGH PRES BUILDS INTO THE AREA WED CREATING M SUNNY SKIES AND BRZY CONDS. COMFORTABLE TEMPS FOR MID DEC - E OF THE BLUE RDG SHOULD SEE HIGHS IN THE L50S. UPSLOPE CONDS TO CONT IN THE HIGHLANDS WHICH COULD BRING SCT SNSH. LTL TO NO ACCUM XPCTD.
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&& .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
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LOW PRESSURE AT THE SURFACE AND ALOFT WILL CONTINUE TO SLOWLY SPIN INTO THE CANADIAN MARITIMES WEDNESDAY NIGHT AND THURSDAY...WHILE HIGH PRESSURE BUILDS SOUTHEAST FROM THE UPPER MIDWEST. A FAST ZONAL UPPER LEVEL JET WILL STRETCH FROM TEXAS ACROSS THE MID SOUTH. THEREFORE NO SIGNIFICANT WEATHER MAKERS OR WEATHER CHANGES. FORECAST SOUNDINGS STILL SHOW A SHALLOW SATURATED LAYER WITHIN THE UPSLOPE FLOW OVER THE MOUNTAINS THROUGH WEDNESDAY NIGHT. USED SNOW SHOWER/FLURRIES WORDING IN THE GRIDS...BUT COULD ALSO BE DZ/FZDZ. LOWS NEAR OR BELOW FREEZING ACROSS THE AREA. A WEAK MID LEVEL SHORTWAVE WILL APPROACH FROM THE WEST LATE THURSDAY AFTERNOON AND INTO THE OVERNIGHT HOURS. THIS WILL LIKELY INCREASE MID AND HIGH LEVEL CLOUDS...WHICH MAY HELP MUTE HIGH TEMPERATURES IN THE 40S. HOWEVER SOME MIXING WILL OCCUR AND ENOUGH GRADIENT STILL IN PLACE TO HAVE SOME GUSTS ABOVE 20 KT. HOWEVER OVERALL TRANQUIL WEATHER WHICH WILL CONTINUE INTO THURSDAY NIGHT...WITH LOWS FALLING BACK DOWN TO NEAR FREEZING. THE LONG TERM PERIOD WILL START OUT WITH A FAIRLY SEASONABLE DAY ON THURSDAY. TEMPS MAY BE JUST A COUPLE OF DEGREES BELOW NORMAL THANKS TO CANADIAN HIGH PRESSURE RIDGING INTO THE MID-ATLANTIC...BUT WITH WEAK RIDGING/ZONAL FLOW ALOFT THERE SHOULD BE ENOUGH SUNSHINE TO KNOCK OFF SOME OF THE CHILL DURING THE DAY. HIGH PRESSURE WILL BEGIN TO RETREAT TO THE NORTH ON FRIDAY AS A STRONG SHORTWAVE MOVING ACROSS THE MIDDLE OF THE COUNTRY DEVELOPS SURFACE LOW PRESSURE NEAR THE TEXAS GULF COAST. MODELS REALLY BEGIN TO DIVERGE IN SOLUTIONS AT THIS POINT. THE PRIMARY VARIANCE INVOLVES THE STRENGTH OF THE SHORTWAVE TROUGH AS IT CONTINUES ITS MARCH ACROSS THE EASTERN CONUS. DETERMINISTICALLY...THE EURO HAS A MUCH MORE AMPLIFIED SHORTWAVE...WHILE THE GFS NEARLY ELIMINATES THE SHORTWAVE ALTOGETHER...AND THE STRENGTH OF THE SURFACE LOW REFLECTS THIS WITH THE EUROS SURFACE LOW BEING NEARLY 20 MB DEEPER AT 06Z SUNDAY OVER SOUTHEAST VIRGINIA. WITHIN THE ENSEMBLE MEMBERS OF BOTH MODELS THERE ARE RUNS THAT RESEMBLE THE DETERMINISTIC RUNS OF THE OPPOSITE MODEL...SO BOTH SOLUTIONS REMAIN POSSIBLE...WITH SOME SOLUTION IN BETWEEN BEING MOST LIKELY. DESPITE THE LARGE SPREAD AMONGST GLOBAL MODELS...THERE ARE SOME ASPECTS THAT WE CAN BE PRETTY CONFIDENT ABOUT. CLOUD COVER WILL BEGIN TO INCREASE FRIDAY NIGHT AS MOISTURE ADVECTS IN AHEAD OF THE APPROACHING LOW FRIDAY NIGHT. MOST OF THE AREA WILL LIKELY SEE SOME FORM OF PRECIP SATURDAY AND SATURDAY NIGHT AS THE LOW CENTER PASSES NEAR THE AREA. AS EXPECTED...THERE IS UNCERTAINTY IN P-TYPE AT THIS POINT...BUT HIGHER ELEVATIONS WILL HAVE A BETTER CHANCE AT SNOW THAN LOW ELEVATIONS...SO GENERALLY STUCK WITH MOSTLY SNOW ACROSS THE WESTERN PORTION OF THE CWA WITH MORE OF A MIX BAG OF WINTRY PRECIP FOR THE EASTERN PORTION. HIGH PRESSURE WILL BUILD BACK INTO THE AREA SUNDAY AND TEMPS WILL BE SLIGHTLY BELOW NORMAL WITH DRY CONDITIONS TO BEGIN NEXT WEEK.
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&& .AVIATION /19Z TUESDAY THROUGH SUNDAY/...
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LOW CLDS/VSBYS WL BE SLOW TO IMPROVE FOR THE RMDR OF THE AFTN. CD FNT WL CROSS THE RGN THIS EVE. SCT RW WL BE PSBL THIS EVE THEN IMPRVG CIGS/VSBY OVRNGT. BRZY W WINDS XPCTD WED. VFR CONDS. VFR CONDITIONS WEDNESDAY NIGHT-THURSDAY NIGHT. WNW WIND GUSTS ABOVE 20 KT POSSIBLE DURING THE DAYLIGHT HOURS OF THURSDAY. MVFR AND IFR CONDITIONS ARE POSSIBLE IN SHOWERS AND LOW CEILINGS A LOW PRESSURE PASSES NEAR THE AREA SATURDAY.
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&& .MARINE...
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NO PROBS FORESEEN ON THE WATERS TNGT. HIGH PRES WL BLD INTO THE WATERS WED. AS A RESULT WIND ARE XPCTD TO GUST 20-25 KT. SCA HAS ALREADY BEEN ISSUED FOR THIS. WINDS WILL DIMINISH WEDNESDAY EVENING WITH CONFIDENCE NOT HIGH ENOUGH AT THIS TIME TO EXTEND THE SCA. A SCA IS LIKELY DURING DIURNAL MIXING OF GUSTY WNW FLOW ON THURSDAY OVER PORTIONS IF NOT ALL OF THE WATERS. WINDS DIMINISH AGAIN THURSDAY EVENING. A SMALL CRAFT MAY BE NEEDED INTO THE DAY THURSDAY IN BREEZY NORTHWEST WINDS. A SMALL CRAFT ADVISORY WILL LIKELY BE NEEDED SATURDAY AS LOW PRESSURE PASSES NEAR THE AREA.
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&& .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY FROM 11 AM TO 6 PM EST WEDNESDAY FOR ANZ530>534-538>543. && $$ PRODUCTS...WOODY!/ADS/CEB

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