Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 230926
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
426 AM EST MON FEB 23 2015

.SYNOPSIS...
HIGH PRESSURE REMAINS OVER THE REGION THROUGH TUESDAY. A COLD
FRONT IS EXPECTED TO PASS THROUGH TUESDAY NIGHT INTO WEDNESDAY.
ANOTHER AREA OF LOW PRESSURE WILL PASS JUST SOUTH OF THE REGION
WEDNESDAY NIGHT. HIGH PRESSURE WILL RETURN FOR THE LATTER PORTION
OF THE WEEK.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
HIGH PRESSURE CENTERED OVER THE NORTHERN PLAINS WILL BUILD TO THE
SOUTH AND EAST TODAY...KEEPING THE REGION ON THE EASTERN PERIPHERY.
WHILE MOST OF THE AREA SHOULD REMAIN DRY AS THE RESULTANT OF THE
COLD...DRY AIRMASS BEING USHERED IN WITH THE HIGH...TWO AREAS COULD
POTENTIALLY SEE SNOWFLAKES THIS MORNING. 08Z OBS OVER SW PA
CURRENTLY SHOWING LIGHT SNOW...SO THINKING THAT PATCH COULD MOVE
INTO THE NW CORNER OF THE CWA THRU 12Z. A WEAK SHORTWAVE RIDING THE
SOUTHERN BIT OF THE UPPER LVL TROUGH COMBINING WITH NW FLOW COULD
GENERATE LIGHT SNOW SHOWERS ON THE WESTERN SLOPES OF THE ALLEGHENY
THEN THRU THE MORNING...THOUGH LESS THAN A TENTH OF AN INCH
EXPECTED. SECONDLY...MODELS TRYING TO PRODUCE LIGHT PCPN ASSOCIATED
WITH WEAK LOW RIDING THE FRONT TO THE SOUTH. THINKING THE PCPN MIGHT
BE OVERDONE ACROSS MOST OF THE CWA WITH LACK OF MOISTURE EXPECTED
AFTER 12Z. DID INCLUDE SLIGHT CHC POPS ACROSS THE SOUTHERN TIER OF
THE CWA THOUGH TO ACCOUNT FOR THE NORTHERN EXTENT OF ANY OVERRIDING
PCPN. THE SNOW WILL BE LIGHT ENOUGH IN NATURE TO NOT RESULT IN ANY
ACCUM. DRY WX THEN FOR THIS AFTN AS THE HIGH TAKES HOLD OF THE
REGION.

ALONG WITH THE DRIER AIR...COLD TEMPS BEING USHERED IN...AS
MANY AREAS WILL STRUGGLE TO REACH THE UPPER 20S...AND EVEN THE 20S
IN THE WESTERN/NORTHERN EXTENDS OF THE AREA. THE COLDER TEMPS HAVE
HOWEVER BEEN SLOW TO MOVE IN THIS MORNING. AS SUCH...HAVE ADJUSTED
THE WIND CHILL ADVISORY FOR WESTERN ALLEGHENY...GRANT AND MINERAL
TO START IT LATE THIS AFTN AND CONTINUING IT THROUGH TONIGHT TO
ACCOUNT FOR THE BETTER CHC OF WHEN CRITERIA WILL BE MET. AS THE
SURGE OF CAA ARRIVES...WINDS WILL INCREASE...WITH GUSTS INTO THE
20S EXPECTED THROUGH THE DAY.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/...
MAIN CONCERN TONIGHT WILL BE THE WELL BELOW NORMAL TEMPERATURES AS
THE HIGH SETTLES OVER THE MID ATLANTIC. WIND CHILL CONTINUES THROUGH
THE NIGHT. COULD SEE TEMPS DROPPING DOWN 5 TO 10 BELOW ZERO OVER
OTHER PORTIONS OF THE WESTERN SLOPES...MAINLY IN PENDLETON AND
HIGHLAND COUNTIES. AM NOT ISSUING WIND CHILL ADVISORY THOUGH DUE TO
A LACK OF WIND. COULD ALSO SEE ISOLATED AREAS ALONG THE MASON-DIXON
LINE DROP TO 5 BELOW ZERO...BUT DUE TO COVERAGE AND LACK OF
WIND...WILL NOT ISSUE ANY PRODUCTS THERE AS WELL.
ELSEWHERE...APPARENT TEMPS WILL BE IN THE SINGLE DIGITS ABV ZERO.

COLD PERIOD CONTINUES INTO TUESDAY...THOUGH SHOULD SEE WARMER TEMPS
THAN TODAY AS SOUTHERLY FLOW SETS UP WAA AHEAD OF THE NEXT
APPROACHING COLD FRONT. NOT ANTICIPATING THE EXTENSION OF THE WIND
CHILL ADVISORY TO BE NEEDED. GENERAL CONSENSUS OF THE 00Z MODELS
KEEP PCPN TO THE WEST THROUGH 00Z WED...AND AS SUCH WILL RUN WITH A
DRY FORECAST.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
LOPRES RAMBLES ACRS SERN CNDA TUE NGT-WED...DROPPING A REINFORCING
CDFNT ACRS THE CWFA. BELIEVE THAT FROPA WL OCCUR TUE NGT...MOST LKLY
AFTR MIDNGT. CLDS WL INCR WELL AHD OF THE FNT...MAINLY IN THE EVNG
HRS. AREA NOT WELL SITUATED WRT JETMAX STRUCTURE OR VORTICIY PTTN TO
RECEIVE ADDED LIFT. THEREFORE BELIEVE FNT WL PASS THRU DRY FOR ALL
BUT THE MTNS...WHERE UPSLP ENHANCEMENT MAY BE ABLE TO SQUEEZE OUT
CHC POPS. DUE TO THIS UNCERTAINTY OF LOW PROBABILITY...HV ACCUM
GRIDS BLANK.

CAA WL TAKE RESIDENCE ON WED. DOWNSLOPING WL PROVIDE A PD OF PRTL
SUNSHINE E OF THE APLCNS...WHILE THE FLOW PTTN WL YIELD CONTD UPSLP
SHSN TO THE WRN SLOPES. H8 TEMPS CHG OVER 24 HRS TUE NGT TO WED DAY
ON THE ORDER OF 2-3 DEGC. ITS NOT A HUGE CHG...AND SUBSEQUENTLY HV
KEPT WINDS ON THE LIGHTER SIDE.

WED NGT A BIT TRICKIER AS AN AREA OF LOPRES SHOOTS EWD TO THE S OF
THE AREA...PER GFS/NAM. THE CATCH IS THAT THE EURO SEND THE LOW A
BIT FURTHER N...CLIPPING SRN CWFA W/ A SWATH OF PCPN. THERMALLY...
THIS WOULD BE COLD ENUF FOR SNOW. IF ITS WERE TO HPPN...CHO-EZF ONT
HE EDGE...SO ACCUMS WUD BE SMALL. HV ATTEMPTED TO MAINTAIN A PINCH
OF CONTINUITY...AND CONFINED A 20 POP ACRS THE FAR S. THIS WL NEED
TO BE WATCHED IN CASE LATER GFS/NAM RUNS CARRY LOW MORE LIKE CURRENT
ECMWF.

OVERALL...TEMP CHGS IN GRIDS NOT THAT SGFNT. STAYED SLGTLY WARMER
MIN-T TUE NGT DUE TO INSUALTING BLANKET OF SLY WNDS/CLDS. WHILE CAA
NOT INCREDIBLY STRONG WED...DID SHADE ABT A DEGF COOLER TO ACCNT FOR
EFFECTS OF CDFNT/CAA. BLENDED GDNC FOR WED NGT MIN-T. END RESULT WL
BE CONTINGENT UPON BOTH THE LOW AS WELL AS HOW FAR S ARCTIC AIR CAN
PLUNGE ONCE AGN.

THURSDAY THROUGH SUNDAY/...

ARCTIC HIGH PRESSURE BUILDS INTO THE AREA OVERNIGHT WEDNESDAY..WITH
COLD AND DRY WEATHER OVER THE CWA.  00Z ECMWF/GEFS HAVE SIMILAR
TRACK FOR NEXT LOW PRESSURE SYSTEM DEVELOPING IN THE GULF ON
THURSDAY...WILL NOT INCLUDE ANY POPS AT THIS TIME AS IMPACTS APPEAR
TO STAY TO OUR SOUTH THRU THURSDAY.

MODELS BEGIN TO DIVERGE SIGNIFICANTLY BEYOND THURSDAY...WITH SOME
MODELS MOVING PIECES OF ENERGY TO OUR SOUTH FRIDAY AND AGAIN ON
SATURDAY...BRINGING PRECIPITATION TO PARTS OF THE CWA. OTHERS KEEP
OUR ENTIRE AREA COMPLETELY DRY. FOR NOW WILL KEEP PREVIOUS FORECAST
OF SLIGHT CHANCE POPS GOING LATE FRIDAY NIGHT THROUGH SUNDAY.
REGARDLESS...AIR TEMPERATURES WILL BE WELL BELOW NORMAL THROUGH
AT LEAST SATURDAY EVENING.

&&

.AVIATION /10Z MONDAY THROUGH FRIDAY/...
GENERALLY VFR CONDITIONS THROUGH THE TAF PERIOD.

OVC SKIES THIS MORNING...WITH ALL SITES VFR EXCEPT KCHO...WHICH WILL
SEE MVFR CIGS THRU AT LEAST 09Z. COULD SEE LINGERING LOWER CIGS THRU
THE MORNING...BUT CONFIDENCE NOT HIGH ENOUGH FOR PREVAILING AND WILL
MENTION ONLY AS TEMPO FOR NOW. CIGS ON THE INCREASE AND SCATTERING
SKIES BY THIS AFTN.

FOG BCMG LESS LIKELY THIS MORNING AT THE TERMINALS...WITH ONLY KCHO
STILL POSSIBLY SEEING A BRIEF PERIOD OF VIS 4-5SM. KCHO COULD ALSO
SEE VERY LIGHT SNOW BRIEFLY THIS MORNING...WITH NO ACCUM EXPECTED.
NOT ENOUGH CONFIDENCE TO INCLUDE IN TAF.

NW WIND 8-10 KTS WILL INCREASE THIS MORNING...WITH GUSTS MIXING IN
BETWEEN 10-13Z. GUST START TIME +/- 1 HR FROM TAF. GUSTS BETWEEN
20-25 KTS GENERALLY EXPECTED THRU THE AFTN...ENDING 22-00Z THIS
EVENING. LIGHT/VRB WINDS TONIGHT. SLY FLOW 10 KTS OR LESS ON TUESDAY.

OUTLOOK
TUE NGT...MVFR CIGS PSBL INVOF CDFNT.
WED...MAINLY VFR.
WED NGT...WL DEPEND UPON TRACK OF LOPRES PASSING S OF TERMINALS. IF
IT STAYS FAR ENUF S...THEN VFR. OTRW...MAY BE MVFR-IFR IN SNW.
THU-FRI...LOW CONFIDENCE IN FLGT RESTRICTIONS.

&&

.MARINE...
SCA REMAINS IN EFFECT FOR ALL THE WATERS THIS MORNING THROUGH THE
FIRST HALF OF THE COMING NIGHT WITH GUSTS 20-30 KTS EXPECTED. 00Z
GUIDANCE KEEPS WINDS BELOW GALE CONDITIONS. THE SCA COULD END AS
EARLY AS 00Z FOR THE TIDAL POTOMAC. SUB-SCA CONDITIONS THEN EXPECTED
THE REMAINDER OF THE NIGHT THROUGH TUES WITH SOUTHERLY FLOW SETTING
UP TUESDAY AHEAD OF THE NEXT COLD FRONT.

CDFNT WL CROSS MARINE AREA LT TUE NGT. IN THE CAA THA ENSUES WED...
ENUF MIXING FOR LOW END SCA PSBL. HV SOME GUSTS FCST THAT WUD BARELY
TRIGGER SCA/S.

CONFIDENCE THEREAFTER WANES. LOPRES WL PASS S OF WATERS WED NGT-THU
MRNG...PERHAPS CLOSE ENUF TO IMPACT WATERS. THRU THE END OF THE WEEK
THE QSTN WL BE HOW STRONG/QUICKLY ARCTIC HIPRES WL BUILD...AND WHAT
TYPE OF P-GRAD WL RESIDE BTWN IT AND THE STORM TRACK TO THE S. THAT
IS WHAT WL DICTATE WHEN/WHERE SCA WL BE REQD. WONT CHG CURRENT
THINKING THAT WED NGT-THU A PD OF OPPORTUNITY.

&&

.EQUIPMENT...
NWR MANASSAS OUT OF SERVICE ATTM DUE TO COMMS ISSUES. TELCO HAS
BEEN NOTIFIED. TIME WHICH IT WILL RETURN TO SERVICE STILL UNKNOWN.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...WIND CHILL ADVISORY FROM 4 PM THIS AFTERNOON TO 9 AM EST
     TUESDAY FOR MDZ501.
VA...NONE.
WV...WIND CHILL ADVISORY FROM 4 PM THIS AFTERNOON TO 9 AM EST
     TUESDAY FOR WVZ501-503.
MARINE...SMALL CRAFT ADVISORY UNTIL 1 AM EST TUESDAY FOR ANZ530>543.

&&

$$
SYNOPSIS...SEARS/HTS
NEAR TERM...SEARS
SHORT TERM...SEARS
LONG TERM...HTS
AVIATION...SEARS/HTS
MARINE...SEARS/HTS
EQUIPMENT...






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