Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 201449
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
949 AM EST THU NOV 20 2014

.SYNOPSIS...
HIGH PRESSURE MOVES OFFSHORE EARLY TODAY...FOLLOWED BY A COLD
FRONT PASSING THROUGH THE CWA THIS AFTERNOON. BROAD HIGH PRESSURE
PUSHES EAST TONIGHT THROUGH SATURDAY. A DEEPENING LOW PRESSURE
SYSTEM WILL LIFT A WARM FRONT SUNDAY INTO MONDAY WITH THE
ASSOCIATED COLD FRONT APPROACHING AND STALLING THROUGH MID WEEK
BEFORE FINALLY PUSHING EAST.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
A COLD FRONT WILL CONTINUE TO MOVE EASTWARD ACROSS THE POTOMAC
HIGHLANDS AND SHENANDOAH VALLEY THIS MORNING. WESTERLY WINDS
BEHIND THE FRONT HAVE LED TO MTN WAVES ACROSS THIS REGION. MIXING
AS ALLOWED 25-35 KTS TO MIX DOWN BEHIND THE FRONT. AHEAD OF THE
FRONT...CONVERGENCE IN THE MID LEVELS ALOFT HAS LED TO MID-HIGH
LEVELS TO FORM ACROSS THE I-95 CORRIDOR. CLOUDS WILL MOVE EASTWARD
BY THIS AFTERNOON. WESTERLY FLOW AGAINST THE WESTERN SLOPES WILL
LEAD TO LIGHT SNOWFALL FOR THE ALLEGHENY FRONT. A STRONG JET WILL
MOVE OVERHEAD THIS AFTERNOON WHICH SHOULD LEAD TO THE DEVELOPMENT
OF CIRRUS.

THE FRONT WILL MOVE EASTWARD TODAY AND SHOULD BE THROUGH THE I-95
CORRIDOR BY LATE AFTERNOON. TEMPS AHEAD OF THE FRONT WILL RISE
INTO THE LOW TO MID 40S BY THIS AFTERNOON. WESTERLY WINDS WILL MOVE INTO
THE REGION BEHIND THE FRONT AND ANOTHER SURGE OF COLD AIR WILL
MOVE INTO THE REST OF THE MID-ATLANTIC TONIGHT.

PREVIOUS ...

AN INTERESTING FEATURE TODAY WILL BE THE DEVELOPMENT OF A STRONG
UPPER LEVEL JET THIS AFTERNOON INTO THE EVENING...WHICH SHOULD
CAUSE DEVELOPMENT OF CIRRUS AFTER NOON.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/...
OUR AREA WILL BE IN THE LOWER RIGHT QUAD OF A 140KT JET
TONIGHT...SO THIS SHOULD PRODUCE DECENT CIRRUS CLOUDS TONIGHT.
ANOTHER COLDER THAN NORMAL NIGHT WITH LOWS RANGING FROM THE UPPER
TEENS POTOMAC HIGHLANDS TO UPPER 20S METRO AREAS. EXPECTING THE
WIND TO STAY UP AND PROVIDE MIXING SO TEMPS NOT BOTTOM OUT TO NEAR
THE MID-TO-LOWER TEEEN DEWPOINTS. USED ADJMET FOR MIN TEMPS TONIGHT.

FRIDAY HIGH PRESSURE BUILDS OVERHEAD WITH NO REMARKABLE WEATHER.
WENT WITH ADJMAV FOR FRI HIGH TEMPS.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
BROAD HIGH PRESSURE BUILDS EAST FRIDAY NIGHT...WITH THE CENTER OF
THE HIGH SETTLING OVER THE MID ATLANTIC ON SATURDAY. ALOFT...ZONAL
FLOW WILL TRANSITION INTO RIDGING OUT AHEAD OF THE NEXT APPROACHING
DEEPENING TROUGH. OVERALL SYNOPTIC FEATURES THUS LEADING TO A QUIET
AND DRY PERIOD. THE RETURN TO SOUTHERLY FLOW WILL BEGIN THE WARMING
TREND UNDER RISING HEIGHTS ALOFT AND DECENT WAA WHICH WILL PUSH
850MB TEMPS FROM AROUND 15 BELOW ZERO 12Z FRIDAY TO AROUND 2 DEGREES
ABOVE ZERO 12Z SAT.

AFTER THE QUIET START TO THE WEEKEND...ATTENTION TURNS TO A
DEVELOPING LOW PRESSURE SYSTEM WHICH IS EXPECTED TO LIFT A WARM
FRONT THROUGH THE AREA SLOWLY SUNDAY INTO MONDAY. GENERAL CONSENSUS
AMONGST THE 00Z MODEL SOLUTIONS IS DRY WX THRU SAT NIGHT WITH LIGHT
RAIN MOVING IN SOMETIME AFTR 12Z SUN...WITH THE MUCH HIGHER
CONFIDENCE OF PCPN THEN SUN AFTN-MONDAY. GFS MUCH MORE PRONOUNCED
WITH THE UPPER LEVEL ENERGY ASSOCIATED WITH MULTIPLE SHORTWAVES
ROUNDING THE BASE OF THE TROUGH AS WELL AS BEING A BIT QUICKER IN
THE PROGRESSION WHILE THE ECMWF IS TRENDING MORE TO THE BULK OF THE
PCPN SUNDAY NIGHT. AS SUCH...INTRODUCED POPS SUNDAY MORNING THEN
QUICKLY TRANSITIONED TO LIKELY-CATEGORICAL SUNDAY AFTN AND
MAINTAINED THESE POPS THRU THE FIRST HALF OF SUN NIGHT. PCPN BECOMES
MORE SHOWER-LIKE AND PERIODIC IN NATURE MONDAY AS THE COLD FRONT
NEARS THE REGION. WITH THE UPPER LEVEL TROUGH STAYING IN PLACE
THROUGH WED...THE COLD FRONT STALLS NEAR THE AREA...EVENTUALLY
PUSHING TO THE NORTH AND EAST BY WED AS A MUCH DEEPER...STRONGER
TROUGH ALOFT NUDGES IT ALONG.

AS FOR THE PCPN TYPE WITH THIS SYSTEM...STRONG WAA WILL REBOUND
TEMPS BACK TO NEAR NORMAL SUNDAY AND A GOOD 5-10 DEGREES ABOVE
NORMAL FOR MONDAY.AT THE MOMENT...EVERYWHERE LOOKS TO REMAIN RAIN AND
RAIN SHOWERS SUNDAY-TUESDAY. FOR NOW HAVE DRY WX IN PLACE WED...BUT
IF ANY PCPN DOES OCCUR...THIS WOULD BE THE NEXT CHC FOR SEEING SNOW
SHOWERS IN THE HIGHEST ELEVATIONS.

&&

.AVIATION /15Z THURSDAY THROUGH MONDAY/...
VFR AT ALL TERMINALS DURING TAF PERIOD. GUSTY WEST WIND WITH MAX DAYTIME
BOTH TODAY AND FRIDAY...SLACKENING TONIGHT.

VFR CONDITIONS FRI NIGHT THROUGH AT LEAST SUNDAY MORNING. SUB-VFR
CONDITIONS ARE LIKELY BY SUNDAY AFTN AND LASTING THROUGH
MONDAY...WITH IFR PSBL WITH THE HEAVIEST PCPN SUN EVENING-NIGHT.

LLWS MAY BRIEFLY BE A CONCERN SUNDAY NIGHT AS A STRONG LLJ SETS UP
OVER THE TERMINALS. AT THE SFC...SLY FLOW INCREASES AHEAD OF THE
COLD FRONT...WITH GUSTS UP TO 20-25 KTS PSBL MONDAY.

VFR CONDITIONS AND WINDS LESS THAN 10 KTS RETURN BY TUESDAY.

&&

.MARINE...
CONTINUING SCA FOR GUSTY W WINDS THROUGH FRIDAY AFTERNOON. TODAY
WILL SEE HIGH END SCA WITH FROPA.  THERE MAY BE A FEW HOURS BELOW
THRESHOLD TONIGHT...BUT QUICKLY RETURN TO SOLID SCA ON FRIDAY.

SUB-SCA CONDITIONS FRIDAY NIGHT THROUGH SATURDAY NIGHT. GUSTS TO 20
KTS POSSIBLE BY SUNDAY MORNING...WITH HIGHER CONFIDENCE OF
OCCURRENCE BY SUNDAY AFTN. SOLID SCA CONDITIONS WITH GUSTS TO 25 KTS
SUNDAY NIGHT-MONDAY. WINDS WILL DIMINISH AND DROP BELOW SCA CRITERIA
ONCE AGAIN FOR TUES-WED.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EST FRIDAY FOR ANZ530>543.

&&

$$
SYNOPSIS...LEE
NEAR TERM...LEE/HAS
SHORT TERM...SEARS
LONG TERM...SEARS
AVIATION...SEARS/LEE
MARINE...SEARS/LEE






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