Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 151946 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 246 PM EST MON DEC 15 2014 .SYNOPSIS... HIGH PRESSURE BUILDS ACROSS THE REGION THROUGH TONIGHT. LOW PRESSURE IS CENTERED OVER THE MIDDLE OF THE COUNTRY. A COLD FRONT ASSOCIATED WITH THAT LOW WILL PASS THROUGH THE AREA TUESDAY AFTERNOON. HIGH PRESSURE IS EXPECTED TO RETURN FOR THE LATTER PART OF THE WEEK. && .NEAR TERM /TONIGHT/... QUITE A PLSNT AFTN FOR MID DEC W/ HIGHS REACHING THE M50S IN MANY LOCALES. ALONG THE CHES BAY TEMPS STRUGGLING TO REACH 50. HIGH PRES OVR THE AREA OVRNGT SO NO WX PROBS XPCTD IN THE MID ATLC. LOWS TEMPS SHOULD DROP INTO THE M30S OVR THE MAJORITY OF THE CWA...PRBLY L40S IN THE CITIES. && .SHORT TERM /TUESDAY/... FAIRLY WOUND-UP LOW PRES AREA OVR MO/IA WL BE TRACKING ENE TOWARDS LAKE ERIE TUE AFTN. A COLD FNT XTNDS S FM THE LOW INTO TX. RW AHD OF THE FNT ON THE E SIDE OF THE MS RVR. THESE RW WL BE MOVG INTO THE CWA DURG THE MRNG HRS...LASTING THRU THE AFTN. HV LKLY POPS IN THE FCST...WHICH SEEMS THE BEST WAY TO GO GIVEN THE THAT THE LN CURRENTLY SEEN ON RDR IS NOT CONTINUOUS. QPF WL BE UNDER 1/10 OF AN INCH. HIGHS TUE SHOULD RANGE FM THE MU40S IN THE W TO THE L50S IN THE CITIES. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... BY TUESDAY EVENING...THE UPPER LEVEL TROUGH AXIS WILL LIFT ACROSS THE AREA AS ANOTHER SHORTWAVE TROUGH DIGS SOUTH FROM CENTRAL CANADA AND ENVELOPS THE FIRST SYSTEM. A CLOSED LOW WILL FORM OVER THE GREAT LAKES FROM THE COMBINATION OF THESE TWO TROUGHS AND ONLY SLOW DRIFT EAST THROUGH WEDNESDAY NIGHT. THE SURFACE COLD FRONT WILL BE CROSSING THE AREA...IF NOT ALREADY THROUGH...BY 00Z WEDNESDAY. WILL SEE A SHARP CUTOFF TO THE SHOWERS EAST OF THE MOUNTAINS...AND ONLY PERHAPS A FEW SHOWERS WILL LINGER WEDNESDAY EVENING EAST OF DC. AS THE FLOW TURNS WESTERLY...COLDER/DRIER AIR WILL ONLY SLOWLY FILTER IN OVERNIGHT. LOWS GENERALLY IN THE 30S TO AROUND 40 EXCEPT THE HIGHEST ELEVATIONS. THIS MEANS ANY UPSLOPE PRECIPITATION WILL BE SLOW TO CHANGE OVER TO SNOW. NOT A TERRIBLY IMPRESSIVE SETUP WITH THE DUE WESTERLY FLOW AND A VERY SHALLOW MOISTURE LAYER THAT WILL LIMIT ICE NUCLEATION. MAY BE MORE DRIZZLE/FLURRIES WITH LOW CLOUDS. WITH ELONGATED LOW PRESSURE OVER THE EASTERN GREAT LAKES/NEW ENGLAND AND STRONG HIGH PRESSURE BUILDING INTO THE UPPER MIDWEST...WEDNESDAY WILL FEATURE GUSTY WEST WINDS. A MIX OF CLOUDS AND SUN IS EXPECTED WITH MORE CLOUDS TOWARD THE MOUNTAINS...WITH THE LOW TO THE NORTH AND A STRONG ZONAL JET OVERHEAD. SIDED WITH WARMER GUIDANCE WITH GOOD MIXING AND DOWNSLOPE FLOW. HIGH IN THE MID 40S TO MID 50S. IF ANY UPSLOPE PCPN LINGERS IN THE MOUNTAINS...IT WILL BE LIGHT AND WANING AS MOISTURE THINS THROUGH THE DAY. THE UPPER LEVEL LOW WILL BE PULLING EAST WEDNESDAY NIGHT. ONE FINAL SHORTWAVE TROUGH MAY PIVOT THROUGH THE MID ATLANTIC BUT WILL HAVE MINIMAL IMPACT ON THE SENSIBLE WEATHER. WINDS WILL DIMINISH BUT NOT BECOME COMPLETELY CALM...ALLOWING LOW TEMPERATURES TO SETTLE NEAR OR JUST BELOW 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 6Z 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. && .AVIATION /19Z MONDAY THROUGH SATURDAY/... VFR CONDS FOR THE RMDR OF THE AFTN AND TNGT. SKIES SHOULD DEGRADE TUE MRNG AS A CD FNT MOVES INTO THE AREA. MVFR CIGS PSBL ALONG W/ RW. MVFR CIGS MAY LINGER THROUGH PART OF TUESDAY EVENING/NIGHT. VFR WEDNESDAY/WEDNESDAY NIGHT. WESTERLY WINDS MAY GUST ABOVE 20KT ON WEDNESDAY. MVFR AND IFR CONDITIONS ARE POSSIBLE IN SHOWERS AND LOW CEILINGS A LOW PRESSURE PASSES NEAR THE AREA SATURDAY. && .MARINE... WINDS XPCTD TO RMN BLO SCA LVLS TNGT AND TUE. A FEW GUSTS COULD COME DOWN IN RW TUE AFTN. A LOW LEVEL INVERSION WILL LIKELY KEEP WINDS BELOW SCA CRITERIA TUESDAY NIGHT. SCA CONDITIONS ARE LIKELY ON WEDNESDAY WITH STRONG WESTERLY WINDS...AND COULD LINGER INTO WEDNESDAY NIGHT FOR PORTIONS OF THE WATERS. 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. && .TIDES/COASTAL FLOODING... WATER LEVELS RUNNING ABOUT A HALF TO 3/4 FT ABV ASTRO NORMALS. WHILE ELEVATED...NO ISSUES EXPECTED TONIGHT. THE SAME CAN`T BE SAID WITH CERTAINTY FOR TUE-TUE NIGHT AS WINDS TURN SOUTHERLY. THE RISK IS NOT SIGNIFICANT...BUT LEVELS MAY REACH THE MINOR THRESHOLDS. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...NONE. && $$ PRODUCTS...WOODY!/ADS/CEB

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