Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 251623 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 1123 AM EST TUE NOV 25 2014 .SYNOPSIS... HIGH PRESSURE...WHICH RETURNS TO THE OHIO VALLEY TODAY...WILL BE RIDGING EASTWARD TO THE MID ATLANTIC. LOW PRESSURE WILL DEVELOP OFF THE COAST OF THE SOUTHEASTERN UNITED STATES THIS EVENING AND TRACK NORTH UP THE ATLANTIC COAST LATE TONIGHT INTO WEDNESDAY. HIGH PRESSURE WILL BUILD IN LATE IN THE WEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... SOUTHWESTERLY 175KT UPPER LEVEL JET IS BRINGING COPIOUS HIGH LEVEL CLOUDS EAST OF THE APPALACHIANS. DRY LOW LEVEL AIRMASS HAS NOW INFILTRATED THE ENTIRE CWA NOW WITH DEW POINTS IN THE 30S. SHOWERS CONTINUE TO STREAM NORTHEAST ALONG A BAROCLINIC ZONE STRETCHING FROM THE NE GULF OF MEXICO TO EAST OF THE DELMARVA. WITH THE DRIER AIR NOW IN PLACE...IT MAY BE TOUGH FOR ANY OF THIS TO WORK BACK TOWARD POINT LOOKOUT...SO TRIMMED POPS BACK A BIT. OTHERWISE SURFACE HIGH PRESSURE TO THE SOUTHWEST WILL REMAIN IN CONTROL. RH FIELDS STILL FORECAST TO THIN...PUSH SOUTHEAST...SO SOME FILTERED SUNSHINE IS POSSIBLE THIS AFTERNOON WEST OF I-95. WEAK CAA CONTINUES EAST OF THE MOUNTAINS. FORECAST TEMPERATURES ARE ON TRACK NOW...WITH MINIMAL RECOVERY IN THE EAST AND A BIGGER REBOUND IN THE WEST WHICH SAW A COOLER START. HIGHS IN THE MID 50S TO NEAR 60 FOR MOST. && .SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY NIGHT/... BASED ON INITIAL ANALYSIS OF 12Z GFS/NAM (WHICH SHOW MINIMAL CHANGES)...HAVE GONE AHEAD AN ISSUED WINTER HEADLINES. FULL DISCUSSION TO FOLLOW THIS AFTERNOON. PREVIOUS DISCUSSION... WHILE ITS STILL NOT STELLAR...00Z GDNC HAS COME INTO BETTER AGREEMENT IN TERMS OF SYNOPTIC EVOLUTION OF UPCOMING STORM SYSTEM LT TUE NGT INTO WED EVNG. LOPRES SHUD BE DVLPG OFF THE GA/SC COAST ALONG STALLED FRNTL BNDRY TUE NGT...FORCED BY S/WV ENERGY TRACKING JUST N OF THE GLFMEX CST. THE SFC LOW WL BE POSITIONED JUST OFF CAPE HATTERAS BY WED MRNG. BNDRY LYR TEMPS AT THIS PT WL STILL BE QUITE WARM...AND DEWPTS SHUD BE AOA 32F AS WELL. THUS...COOLING WL HV TO COME FM EVAP INITIALLY...AND THEN ENHANCED BY COOLER AIR DRAINING SWD. LIFT AHD OF THE LOW SUFFICIENT TO PROMPT A SHARP/SUDDEN BGNG TO PCPN...BUT THAT SHUD BE IN THE FORM OF RA. BY SUNRISE...AS PCPN ADVANCES NWD...THE AMS MAY BE MARGINALLY COLD ENUF TO SUPPORT A RASN MIX ALONG/W OF BLURDG. DUE TO THE THERMAL NATURE OF THE PROFILE /IE...WM GRND/BLYR/ SNOW WL HV AN ELEV DEPENDENCY TO IT...FAVORING SNOW IN THE HILLS. THE SFC LOW WL TRACK FM HATTERAS TO OFF LONG ISLAND DURING THE DAY WED. THE KEY QSTN REMAINS HOW MUCH COLD AIR WL BE PRESENT. LIKE THE PRVS FCSTR...AM COUNTING ON DYNAMICS AND COOLER AIR DRAINING SWD ON WRN SIDE OF LOW. THE TRACK OF THE H8 LOW HUGGING THE COAST FAVORS AT LEAST SOME COOLING ACRS CWFA AS WELL. AM KEEPING SAME THOUGHT PROCESS GOING IN THIS FCST...MAINLY SNOW BLURDG WEST...RASN I-95 TO BLURDG...AND PRIMARILY RAIN TO THE SE. HWVR...AS THE LOW PULLS AWAY...THE COOLER AIR SHUD BE DRAGGED SWD...AND HV A CHANGEOVER TAKE PLACE. EVEN THEN...IT/LL BE TOUGH FOR ACCUMS TO GET GOING NEAR THE COAST SINCE GRND WARM AND SFC TEMPS MID-UPR 30S. THE LOW WL HV ACCESS TO RICH ATLC MSTR TRANSPORT...AND PCPN SHUD BE MDT TO OCNLLY HVY DURING THE DAY. SNW RATIOS SHUD BE ON THE LOW SIDE THO DUE TO THE WARM BNDRY LYR AND DEWPTS BARELY SUBFRZG. THUS...AM COUNTING ON A HVY/WET SNOW. HV RAISED SNW TTLS TO ACCT FOR THE QPF...BUT MINIMIZED THE INCREASE DUE TO RATIOS. CHGS IN FINAL SNW TTL MAP SHIFTED UPWD BUT SUBTLY. BACK EDGE OF PCPN SHIELD SHUD BE CROSSING AREA LT WED AFTN...JUST AS SHARPLY AS ONSET. AM NOT DEPICTING THAT IN GRIDS DUE TO UNCERTANTIES GIVEN ITS LT 3RD PD TIMING. SIMILARLY...HV LEFT CHC POPS INTO WED EVNG TO ACCT FOR UNCERTAINTIES AND PSBL NRN STREAM ENERGY TRIGGERING ADDTL SHSN. BY WED EVNG...TEMPS SHUD BE COLD ENUF FOR ANY PCPN TO BE SNOW ANYWHERE. USED A BLEND OF TEMPS FOR MIN-T TNGT...THEN SIDED COOLER WED MAXT DUE TO BEST GUESS STORM TRACK SFC-H8 AND ONGOING PCPN PREVENTING MUCH DIURNAL WARMING. THE WED THEME CARRIES INTO MIN-T WED NGT. && .LONG TERM /THURSDAY THROUGH MONDAY/... A SHORTWAVE TROUGH THAT IS CURRENTLY ACROSS BRITISH COLUMBIA/ALBERTA THIS MORNING WILL DIVE INTO THE OHIO VALLEY WED NIGHT WHILE THE COASTAL STORM MOVES TOWARD NOVA SCOTIA. SFC LOW PRESSURE IN RESPONSE TO THE SHORTWAVE TROUGH IS PROGGED TO WEAKEN AS IT TRACKS ACROSS THE CONUS IN THE NEXT FEW DAYS. THE TRACK WILL TAKE THE SFC LOW ACROSS THE SOUTHERN MID-ATLANTIC AND INTO SW VA/NC BY THURSDAY AFTERNOON. SNOW SHOWERS ARE EXPECTED ACROSS THE WESTERN SLOPES BUT LIMITED MOISTURE WITH THIS SFC LOW WILL LEAD TO LIGHT ACCUMULATION. LIGHT SNOW SHOWERS MAY ALSO MOVE INTO THE SOUTHERN MID-ATLANTIC LATE WEDNESDAY NIGHT/THURS MORNING. LITTLE MOISTURE AND RISING PRESSURE TENDENCIES SHOULD ONLY ALLOW FOR SCT SHOWERS. TEMPERATURES WILL CLIMB INTO THE UPPER 30S AND LOW 40S BY THURS AFTERNOON. SNOW SHOWERS ARE EXPECTED TO STAY CONFINED TO THE SOUTHERN MID-ATLANTIC...SOUTH OF I-66 AND WASHINGTON DC. ANY SNOW SHOWERS MAY CHANGE TO RAIN SHOWERS BEFORE EXITING TO THE SOUTH AND EAST. 00Z GFS IS THE WETTEST SOLUTION AND LIGHT ACCUMULATION WOULD BE POSSIBLE. AT THIS TIME...MENTIONING LITTLE TO NO ACCUMULATION DUE TO THE CONTINENTAL AIRMASS AND LACK OF MOISTURE. WESTERLY WINDS BEHIND THE SFC LOW WILL LEAD TO UPSLOPE SNOW SHOWERS ON THE WESTERN SLOPES THURSDAY AND THURSDAY NIGHT. LITTLE TO NO ACCUMULATION IS EXPECTED AT THIS TIME. SNOWPACK FROM SNOWFALL ON WEDNESDAY WILL LIKELY MELT SOME DURING THE DAY AND REFREEZE OVERNIGHT THROUGH THE END OF THE WEEK. HIGH PRESSURE WILL MOVE INTO THE REGION FRIDAY AND ANY UPSLOPE SNOW SHOWERS WILL DISSIPATE BY FRIDAY AFTERNOON. COLDER AIR WILL FILTER INTO THE REGION FRIDAY AND FCST MAX TEMPS WILL RANGE FROM THE 20S IN THE MTNS TO THE UPPER 30S NEAR I-95. HIGH PRESSURE MOVES OFF THE COAST BY SATURDAY AND THE UPPER LEVEL PATTERN BECOMES MORE ZONAL. A COLD FRONT WILL SLOWLY MOVE THROUGH THE GREAT LAKES REGION THIS WEEKEND. RETURN FLOW AROUND THE HIGH WILL ALLOW TEMPS TO RISE INTO THE 50S/60S SUNDAY AND MONDAY. WARMER TEMPS WILL LEAD TO MORE MELTING OF SNOWPACK FROM THE SNOWFALL FROM WEDNESDAY. SHOWERS MAY MOVE INTO THE MTNS SUNDAY AND MONDAY AS THE COLD FRONT NEARS THE REGION. && .AVIATION /16Z TUESDAY THROUGH SATURDAY/... VFR CONDITIONS WILL CONTINUE THROUGH THIS AFTERNOON AND EVENING. NORTHWEST WINDS AROUND 10 KT OR LESS WILL BECOME LIGHT AND VARIABLE THIS EVENING. PCPN WL APPROACH FM THE S TNGT...BUT IT SHUD COME AFTR MIDNGT AND INIT BE IN THE FORM OF RA /PERHAPS RASN MRB/. CONDS XPCTD TO BE DROPPING RAPIDLY TO IFR WED MRNG AS LOPRES TRACKS UP THE COAST. SUBIFR XPCTD MOST OF THE DAY. DCA-BWI SHUD HV PRIMARILY RA CHGG TO SNW ELY-MID AFTN. MRB MAINLY SNW. CHO/IAD IN THE TRANSITION ZONE IN BTWN. UNCERTAINTIES STILL LINGER AS TO POSITIONING OF RA/SN LINE AND THE MVMT OF THAT LINE. LGT SN IS POSSIBLE WED NIGHT INTO THURSDAY AT CHO AND MAY LEAD TO REDUCED VSBYS. HIGH PRESSURE MOVES INTO THE REGION BY FRIDAY AND VFR CONDITIONS ARE EXPECTED THROUGH THE WEEKEND. && .MARINE... WNDS HV DIMINISHED TO SUB-SCA ELY THIS MRNG...AND SHUD REMAIN THAT WAY THRU THE DAY. DO XPCT SLY FLOW TO VEER WLY DURING THE MRNG. WINDS WL CONT TO VEER NLY THIS EVNG AS LOPRES DVLPS OFF THE SERN CONUS COAST AND APPROACH LOCAL WATERS. SPDS WL INITIALLY BE LGT... BUT WL BE INCRSG AS THE PRES GRADIENT INCREASES. SCA ALREADY IN PLACE FOR THE MID BAY/LWR PTMC AFTR 1AM. HV EXTNDD ADVY INTO WED AND INCLD NRN BAY AS THE LOW PASSES NEARBY. DEPENDING ON STRENGTH AND TRACK OF LOW...GLW NOT OUT OF THE QSTN...AS WELL AS THE PSBLTY OF A HEADLINE OF SOME KIND UP THE PTMC TO DCA. LIKEWISE...SCA CONDS SHUD LINGER INTO WED EVNG...BUT THE MAGNITUDE OF WHICH WL BE CONTINGENT UPON STORM EVOLUTION. NW WINDS ARE EXPECTED THURSDAY AS A DISTURBANCE CROSSES SOUTH OF THE WATERS AND WINDS WILL LIKELY INCREASE LEADING TO SCA CONDITIONS THURSDAY NIGHT AND INTO FRIDAY. HIGH PRESSURE MOVES SOUTH OF THE WATERS FRI NIGHT-SATURDAY. NRLY WINDS WILL BE NEAR SCA CONDITIONS DURING THIS TIME. && .TIDES/COASTAL FLOODING... WATER LVLS REMAIN SLGTLY ELEVATED...BUT SHOULD REMAIN WITHIN A FEW INCHES OF ASTRO NORMS THRU TNGT. LOPRES TRACKING UP THE COAST MAY CAUSE AN INCREASE WED...BUT QUICK SPEED OF SYSTEM AND NLY WINDS SUGGEST THAT MINOR FLOODING NOT LKLY AT THIS TIME. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...WINTER STORM WARNING FROM 3 AM TO 6 PM EST WEDNESDAY FOR MDZ003-501-502. WINTER STORM WARNING FROM 6 AM TO 6 PM EST WEDNESDAY FOR MDZ004>006. WINTER WEATHER ADVISORY FROM 8 AM TO 6 PM EST WEDNESDAY FOR MDZ007-009>011. VA...WINTER STORM WARNING FROM 3 AM TO 6 PM EST WEDNESDAY FOR VAZ025>031-036>040-503-504. WINTER STORM WARNING FROM 6 AM TO 6 PM EST WEDNESDAY FOR VAZ042-501. WINTER WEATHER ADVISORY FROM 8 AM TO 6 PM EST WEDNESDAY FOR VAZ050>053-502. WV...WINTER STORM WARNING FROM 3 AM TO 6 PM EST WEDNESDAY FOR WVZ050>053-055-501>506. MARINE...SMALL CRAFT ADVISORY FROM 1 AM TO 6 PM EST WEDNESDAY FOR ANZ532>534-537-540>543. SMALL CRAFT ADVISORY FROM 6 AM TO 6 PM EST WEDNESDAY FOR ANZ530-531-538-539. && $$ SYNOPSIS...HTS NEAR TERM...ADS SHORT TERM...ADS/HTS LONG TERM...HAS AVIATION...ADS/HAS/HTS MARINE...HAS/HTS TIDES/COASTAL FLOODING...HTS

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