Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 241512 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 1012 AM EST TUE FEB 24 2015 .SYNOPSIS... HIGH PRESSURE PUSHES OFFSHORE TODAY. A COLD FRONT WILL PASS THROUGH THE MID ATLANTIC STATES TONIGHT INTO WEDNESDAY. LOW PRESSURE WILL TRACK ACROSS GEORGIA WEDNESDAY NIGHT. HIGH PRESSURE WILL RETURN FOR THE LATTER PORTION OF THE WEEK. && .NEAR TERM /TODAY/...
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COLD HIGH PRES HAS MIGRATED IN THE PAST 2 DAYS FM N DAKOTA TO VA. THE AIRMASS WAS AS COLD AS -24 ON SUN IN ND. THIS MRNG IT WAS -17 IN BAYARD WV...-4 AT IAD. SFC LOW OVER THE SE US WILL PUSH OFFSHORE TODAY AND TRACK NE OFFSHORE OF THE AREA WHILE THE SOUTHERN STREAM ALIGNS ACROSS THE MID ATLANTIC MIDDAY...WITH MULTIPLE SHORTWAVES EMBEDDED IN THE FLOW. WHILE THE PCPN IS EXPECTED TO REMAIN SOUTH AND OUT OF THE AREA...CANNOT RULE OUT LIGHT SNOW THIS AFTN OVER THE SOUTHERN TIER OF COUNTIES OF THE CWA. A VERY DRY AIRMASS IS IN PLACE THOUGH...AND WITH SUCH LIGHT PCPN NOT ANTICIPATING ANY ACCUM. DESPITE SOUTHERLY FLOW...TEMPS REMAIN WELL BELOW NORMAL WITH 850MB TEMPS AROUND -10 CELSIUS.
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&& .SHORT TERM /TONIGHT THROUGH WEDNESDAY/... ANY PCPN THREAT FROM THE SYSTEM DURING THE DAY WILL DIMINISH QUICKLY THIS EVENING AS THE LOW TRACKS TO THE EAST. ATTENTION WILL THEN TURN TO AN APPROACHING COLD FRONT AS ITS PARENT MOVES THROUGH SOUTHERN CANADA. GENERAL CONSENSUS AMONG THE 00Z MODEL SUITE BRINGS THE FRONT THROUGH LATE TONIGHT THROUGH THE DAY WED...THOUGH ALMOST STALLING/WEAKENING FOR A BIT DURING THE DAY BEFORE CLEARING THE AREA. THINKING THE PASSAGE WILL BE MAINLY DRY AS THERE REMAINS MINIMAL MOISTURE IN PLACE...ALONG WITH MINIMAL DYNAMICS/FORCING ALOFT AS THE SOUTHERN AND NORTHERN STREAMS REMAIN WELL OUT OF THE AREA. THE BEST CHC FOR ANY PLACE TO SEE POPS WOULD BE THE WESTERN SLOPES OF THE ALLEGHENY DUE TO UPSLOPING AS A WESTERLY FLOW SETS UP DURING THE DAY. EVEN THIS MIGHT BE OVERDONE THOUGH DUE TO THE FACT THERE WILL BE MINIMAL MOISTURE TRANSPORT TO EVEN RESULT IN THE SNOW SHOWERS. HAVE CAPPED WITH JUST A COUPLE TENTHS OF AN INCH DURING THE PERIOD. MIN TEMPS TONIGHT WILL BE A GOOD DEAL WARMER WITH CLOUD COVER AND WEAK WAA. HIGHS ON WED COULD EVEN PUSH INTO THE UPPER 30S ACROSS MUCH OF THE AREA. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... A SECOND AREA OF LOPRES IN AS MANY DAYS WL TRACK EWD IN THE SRN STREAM WED NGT INTO THU MRNG. LIKE GDNC SUITE 24 HRS AGO...THERES STILL QUITE A SPREAD AS TO HOW FAR NWD TO TAKE THE NRN EDGE OF PCPN. THE NAM REPRESENTS THE NRNMOST TRACK...WHILE GFS LEADS THE SRN CAMP. HV CONCERNS THAT BOTH GROUPS OFF THE MARK. FCST REPRESENTS AN ENSEMBLE BLEND TO ACCOUNT FOR THESE UNCERTAINTIES. THE END RESULT WL BE CHC POPS FM LT WED EVNG INTO THU MRNG...BUT NO WHERE ARE POPS HIER THAN CHC. HV KEPT THE NRN TIER OF CNTYS DRY...AND A LINE FM SHD- DCA-NAK ROUGHLY DELINIATES EDGE OF PCPN SHIELD IN THE DATABASE. PTYPES WUD BE BE SNW DUE TO COLD FCST TEMPS /WHICH ALSO ARE BLENDED/ DURING THIS TIME. IN THE WAKE OF THIS LOW...NRN STREAM ENERGY WL TAKE OVER FOR THU AFTN AND THU NGT. THERE ARE TWO FACTORS TO CONSIDER... 1/ A RETURN OF MDT-STRONG CAA AND 2/ DISJOINTED VORT ENERGY. EITHER OF THESE CUD PRODUCE FLURRIES...AND IN TERMS OF PVA POTENTIALLY SHSN. ALSO IN THIS REGIME THE UPSLP SHSN POTENTIAL WL INCREASE. ONCE AGAIN UTILIZED CHC POPS TO HANDLE THE THREAT. THIS TIME THE TARGET AREA WAS APPROX BLURDG WWD...ALTHO LOW END POPS SNEAK INTO THE FOOTHILLS AT TIMES. WAS GENEROUS IN DEPICTING TEMPS PERHAPS REACHING FREEZING FOR MAXT THU. ITLL BE A FRIGID THU NGT. HWVR...DO NOT HV WINDS ALL THAT STRONG...AN OFFSHOOT OF BLENDED GDNC. A LARGE AREA OF CNDN HIPRES SETTLES OVER THE CONUS FOR THE END OF THE WEEK INTO THE BGNG OF THE WKND. AT A MINIMUM THIS SHUD SURPRESS IMPULSES FM CREATING STORMY WX. HV A SLGT TEMP RECOVERY FOR MAXT. ON THE OTHER HAND...SUBSIDENCE LEADS TO DCPLG...WHICH MEANS THAT MIN-T WL BE JUST AS COLD IF NOT COLDER. THE RDG BREAKS DOWN BY SUNDAY. THIS ALSO IS THE TIME FRAME WHEN GDNC SOLNS DIVERGE...WHICH IS NOT ATYPICAL WRT GDNC TRYING TO FIGURE OUT HOW THE PTTN CHG WL TRANSPIRE. SINCE IT WUD BE A WARMER PD...USED RA OR SNW FOR PTYPE. TEMPS MAY ACTUALLY REACH CLIMO BY DAY 7. && .AVIATION /15Z TUESDAY THROUGH SATURDAY/...
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VFR XPCTD AT THE MAJOR TAF SITES. COULD SEE A PERIOD OF MVFR CIGS AT KCHO WITH A VERY LOW CHC OF SEEING LIGHT SNOW. SLY FLOW 7-10 KTS WILL SHIFT THIS EVENING...BCMG W BETWEEN 04-08Z. BRIEF PERIOD OF LIGHT/VRB AS THE WINDS SHIFT...THEN INCRSNG BACK TO 7-10 KTS WITH THE W FLOW THEN DURING THE DAY. OUTLOOK... WED NGT-THU NGT...VARIOUS PIECES OF ENERGY WL BE GLIDING THROUGH...EACH POTENTIALLY PRODUCING PCPN. CONFIDENCE IN SPECIFICS QUITE LOW. PREVAILING THOUGHT VFR...BUT LCL MVFR-IFR PSBL DEPENDING ON OUTCOME. FRI-SAT...VFR.
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&& .MARINE... SUB-SCA CONDITIONS IN PLACE THROUGH WEDNESDAY. SOUTHERLY FLOW GENERALLY 10 KTS OR LESS TODAY WILL BECOME WESTERLY ON WED...BUT STILL REMAINING 15 KTS OR LESS. ANOTHER ROUND OF LOPRES WL BE PASSING S OF THE WATERS WED NGT INTO THU MRNG. DEPENDING UPON THE EXACT TRACK /WHICH IS STILL TBD/ AND STRENGTH OF THE LOW...SCA MAY BE PSBL. ODDS INCREAS ON THU IN THE WAKE OF THE LOW...WHEN NRN STREAM ENERGY ENTERS. HV SCA THREAT AT THAT TIME. && .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...NONE.
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&& $$ UPDATE...WOODY! PRVS...AS/HTS

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