Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 010103
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
903 PM EDT TUE SEP 30 2014

.SYNOPSIS...
LOW PRESSURE OVER THE GREAT LAKES WILL TRACK EAST ACROSS THE
MIDDLE ATLANTIC REGION TONIGHT AND WEDNESDAY. HIGH PRESSURE WILL
RETURN TO THE EAST COAST LATER WEDNESDAY AND REMAIN IN PLACE UNTIL A
COLD FRONT APPROACHES THE AREA FRIDAY. A COOLER AND DRIER AIRMASS
WILL FOLLOW FOR THE WEEKEND AND EARLY NEXT WEEK.

&&

.NEAR TERM /THROUGH WEDNESDAY/...

S/WV EJECTING FM H5 LOW SPINNING OVER UPR OHVLY SPREADING SHRA AND
A FEW TSRA ACRS CWFA. THE MORE VIGOROUS TSRA/HIER RAFL RATES SEEM
TO BE IN SRN PA XTNDG INTO MD. THERE WAS A HAIL THREAT ERLR. DUE
TO LWR SUN ANGLE AND SUNSET PRIOR TO 7PM...HVY RA AND WIND GUSTS
15-25 MPH WL MARK THE TOP END OF ACTIVITY. HRRR HAS BEEN DOING A
DECENT JOB TRACKING ACTIVITY...ALTHO PRVS CPL RUNS MAY HV BEEN A
LTL BIT SLOW. LTST RUN HAS ACCOUNTED FOR THIS...AND TAKES ACTIVITY
E OF CWFA BY/SOON AFTER MIDNGT. WL ADJUST DATABASE ACCRDGLY.

BIGGER STORY OVERNIGHT MAY BE THE POTENTIAL FOR FOG DEVELOPMENT.
PM SHRA/TSRA WL ADD TO THE LOW LEVEL MOISTURE IN PLACE. THE QUESTION
IS WHETHER CLDS WL PART ENOUGH FOR RADIATION TO TAKE PLACE. IR
SATPIX ACRS WVA CASTS SOME DOUBT ON THAT. WL CONT W/ THE OVERALL
CONCEPT OF PATCHY FOG AFTR MIDNGT AND AREAS OF FOG PRE-DAWN.
/THERE SHUD BE SOME BINOVC./ HWVR...HV RAISED VSBYS UP A LTL. /ITS
A BIAS OF MOST GDNC./ AM NOT AT ALL CONFIDENT ON DENSE FOG ATTM.

UPPER LOW WILL PULL AWAY TO THE NORTH AND EAST ON WEDNESDAY. FOG
AND LOW CLOUDS WILL MIX OUT BY LATE MORNING/MIDDAY WITH A FEW
AFTERNOON SHOWERS POSSIBLE ESPECIALLY OVER THE HIGH TERRAIN.
AFTERNOON HIGHS FROM THE LOWER TO MIDDLE 70S CAN BE EXPECTED.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/...
HIGH PRESSURE TO THE NORTH NOSING INTO THE REGION WILL KEEP AN
EASTERLY LOW-LEVEL WIND FETCH IN PLACE WEDNESDAY NIGHT INTO
THURSDAY. THIS WILL RESULT IN MORE CLOUDS THAN CLEAR SKY THROUGH THE
PERIOD...ESPECIALLY EAST OF THE BLUE RIDGE MOUNTAINS.

AS THE HIGH PRESSURE MOVES OUT INTO THE NORTHERN ATLANTIC...MID- AND
HIGH-LEVEL CLOUDS APPROACHING FROM THE WEST WILL LOWER AND THICKEN
IN ADVANCE OF AN APPROACHING TROUGH THURSDAY NIGHT. A COUPLE OF
SHOWERS PRECEDING THIS TROUGH COULD APPROACH THE WESTERN SLOPES BY
DAYBREAK FRIDAY...BUT THE BULK OF PRECIPITATION IS EXPECTED TO HOLD
OFF UNTIL FRIDAY AFTERNOON AND NIGHT.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
A SEASONABLY STRONG UPPER TROUGH AND COLD FRONT WILL MOVE TOWARDS
THE MID-ATLANTIC FRIDAY. WIDESPREAD CLOUDS WILL CONTINUE TO LOWER
AND THICKEN THROUGH THE DAY...WITH A BAND OF SHOWERS PRECEDING THE
FRONT EXPECTING TO MOVE ACROSS THE AREA DURING THE AFTERNOON AND
INTO THE OVERNIGHT. MOST AREAS EAST OF THE BLUE RIDGE MOUNTAINS
SHOULD REMAIN PREDOMINANTLY DRY DURING THE DAY. MODELS ARE STILL
DIVERGENT ON TIMING/STRENGTH OF THE TROUGH WHICH WILL DETERMINE
EXACTLY WHO GETS HOW MUCH RAIN AND WHEN. FORCING WITH THE TROUGH IS
STRONG BUT THERE IS NOT MUCH INSTABILITY TO WORK WITH...SO WHILE A
FEW RUMBLES OF THUNDER CANNOT BE RULED OUT THE CURRENT THINKING IS
THAT WIDESPREAD THUNDER IS UNLIKELY. BRIEF HEAVY DOWNPOURS AND
PERHAPS GUSTY WINDS IN STRONGER/HEAVIER BANDS OF RAIN COULD BE
REALIZED ESPECIALLY IF THE TROUGH ENDS UP BEING ON THE STRONGER SIDE.

MODELS ARE IN BETTER AGREEMENT BY LATER SATURDAY AFTER THE FRONT
MOVES THROUGH. A MUCH COOLER AND DRIER AIRMASS WILL MOVE INTO THE
REGION AND STICK AROUND FOR THE REMAINDER OF THE WEEKEND...WITH
TEMPERATURES FALLING TO SEVERAL DEGREES BELOW NORMAL...PERHAPS
ISOLATED FREEZING TEMPERATURE READINGS ALONG THE WESTERN RIDGES
SATURDAY NIGHT IF WINDS SLACKEN A TAD QUICKER THAN GUIDANCE IS
CURRENTLY SUGGESTING.

THE NEXT STORM SYSTEM APPROACHES THE AREA FROM THE WEST EARLY NEXT
WEEK BUT MODELS ARE HIGHLY DIVERGENT ON WHEN IT AND ITS IMPACTS
REACH THE AREA.

&&

.AVIATION /01Z WEDNESDAY THROUGH SUNDAY/...
VFR CONDS ACRS ALL TERMINALS ATTM. A LINE OF SHRA/TSRA ALIGNED W/
BLURDG ATTM WL TRACK EWD ACRS HUBS THRU 03Z. STABILITY MARGINAL.
SUSPECT ACTIVITY WL WEAKEN FURTHER AS IT APPROACHES. BRIEF FLGT
RESTRICTIONS LKLY DURING ITS PASSAGE...MOSTLY MVFR. WL ATTEMPT TO
PLACE 1 HR TEMPOS IN TAFS SHORTLY.

LOW CIGS AND FOG A GOOD BET OVERNIGHT....MIXING OUT BY LATE
MORNING OR MIDDAY WEDNESDAY. WENT A TOUCH MORE OPTIMISTIC THATN
PRVS FCST CYCLE...BUT STILL HV SUB-IFR CIGS FOR MRNG PUSH.

CIG AND PSBL VSBY RESTRICTIONS LATE WED NIGHT-THU AM AND AGAIN THU
NIGHT INTO FRI AM WITH MOIST ONSHORE FLOW PORTRAYED IN ALL THE
GUIDANCE. CLIMO IS FAVORABLE FOR FOG/STRATUS THIS TIME OF THE YEAR
SO THAT LENDS TO MODERATE CONFIDENCE. SHWRS/ISO TSTMS IN ONE OR MORE
BANDS AHEAD OF A COLD FRONT PSBL W/ GUSTY WINDS FRI-FRI NIGHT. VFR
SAT AS WINDS TURN OUT OF THE W OR NW.

&&

.MARINE...
WINDS ARE EXPECTED TO REMAIN BELOW SCA CRITERIA THE REMAINDER OF
TODAY THROUGH THURSDAY.

SOLID SCA CONDITIONS LOOKING INCREASINGLY LIKELY LATE THIS WEEK INTO
THIS WEEKEND BOTH AHEAD OF /SOUTHERLY FLOW/ AND BEHIND
/NORTHWESTERLY FLOW/ A SEASONABLY STRONG COLD FRONT. WINDS/SEAS
GRADUALLY ABATE AS THE WEEKEND PROGRESSES.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...NONE.

&&

$$
SYNOPSIS...KRW
NEAR TERM...HTS/KRW
SHORT TERM...DFH
LONG TERM...DFH
AVIATION...HTS/KRW/DFH
MARINE...HTS/KRW/DFH







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