Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 270235 AAA
AFDLWX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
935 PM EST WED NOV 26 2014

.SYNOPSIS...
COASTAL LOW PRESSURE WILL MOVE AWAY FROM THE AREA TONIGHT. AN
UPPER- LEVEL DISTURBANCE WILL PASS THROUGH THE AREA THURSDAY AND
HIGH PRESSURE WILL BUILD OVERHEAD FRIDAY. THE HIGH WILL MOVE OFF
THE COAST DURING THE WEEKEND.

&&

.NEAR TERM /THROUGH THURSDAY/...
COASTAL LOW PRESSURE WILL CONTINUE TO RACE NORTHEAST OFF THE SOUTHERN NEW
ENGLAND COAST TONIGHT. SUBSIDENCE BEHIND THE DEPARTING LOW HAS
LARGELY KICKED INTO PLACE ACROSS THE REGION EXCEPT FOR A FEW
PASSING FLURRIES/SPRINKLES OVER EASTERN SECTIONS OF THE AREA.

THE NEXT WEAK SHORTWAVE TROUGH WILL APPROACH FROM THE WEST
TONIGHT. FORCING WILL BE WEAK WITH THIS SYSTEM BUT
NONETHELESS...THERE WILL BE A CHANCE FOR LIGHT UPSLOPE SNOW
SHOWERS OVER THE POTOMAC HIGHLANDS OVERNIGHT. DECENT SNOW PACK AND
LOW LEVEL MOISTURE WILL LEAD TO FOG DEVELOPMENT
OVERNIGHT...PRIMARILY WEST OF THE BLUE RIDGE MOUNTAINS. SOME OF
THE FOG COULD BE LOCALLY DENSE. WILL CONTINUE MENTION IN THE HWO.
TEMPERATURES WILL FALL BELOW FREEZING IN MOST PLACES EXCEPT THE
METRO CENTERS. THIS WILL LEAD TO REFREEZING CONCERNS ON SECONDARY
ROADWAYS OR UNTREATED SURFACES OVERNIGHT INTO EARLY THURSDAY.

THE UPPER-LEVEL DISTURBANCE WILL MOVE AWAY FROM THE AREA THURSDAY
AFTERNOON AND HIGH PRESSURE WILL BUILD TOWARD THE REGION FROM THE
OHIO VALLEY. A STRAY RAIN OR SNOW SHOWER CANNOT BE RULED OUT WITH
AN UPPER-LEVEL TROUGH OVERHEAD...BUT MOST AREAS WILL BE DRY AND
CHILLY WITH SOME SUNSHINE. MAX TEMPS WILL RANGE FROM THE 20S AND
LOWER 30S IN THE MOUNTAINS TO THE LOWER AND MIDDLE 40S IN CENTRAL
VIRGINIA.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/...
SFC HIGH PRES CONTINUES TO BUILD EAST OVER THE AREA THROUGH
FRIDAY. NWLY FLOW WILL CONTINUE TO CAUSE UPSLOPE SNOW WEST OF THE
ALLEGHENY FRONT INTO LATE THURSDAY NIGHT BEFORE TAPERING OFF AS
THE SATURATED LAYER DECREASES. SHOULD JUST BE WAVE CLOUDS EAST OF
THERE SINCE THE UPR TROUGH AXIS MOVES EAST OF THE AREA THURSDAY
EVENING. NWLY FLOW GUSTS PERIODICALLY TO 20 TO 25 MPH THURSDAY
NIGHT IN COLD AIR ADVECTION...THEN MIXES DOWN AGAIN ACROSS THE
AREA FRIDAY. GRADIENT SLACKENS THROUGH FRIDAY AFTERNOON.

FRIDAY NIGHT...SFC HIGH CENTER CROSSES THE AREA WITH CLEAR AND
CALM AND MIN TEMPS BACK BELOW FREEZING. PLACES WITH A REMAINING
SNOWPACK OF MORE THAN A FEW INCHES (HIGHER ELEVATIONS) WILL SEE A
MARKED DROP IN TEMPERATURES...POSSIBLY INTO THE TEENS. LOW 30S
ALONG THE SHORE LINE.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
HIGH PRESSURE WILL MOVE OFFSHORE THIS WEEKEND SETTING UP A SOUTHERLY
RETURN FLOW. TEMPERATURES WILL RETURN TO NEAR NORMAL UNDER THIS
REGIME. A FRONT WILL BUMP INTO THIS HIGH LATE IN THE WEEKEND THEN
STALL NEAR THE AREA NEXT WEEK. IT LOOKS WARM ENOUGH FOR RAIN SHOWERS
ALONG THIS FRONT MONDAY. HIGH PRESSURE WILL MOVE BY TO THE NORTH
BEHIND THE FRONT...BUT DEPENDING ON HOW FAR SOUTH THE FRONT GETS IT
MAY NOT GET MUCH COOLER. MODELS DISAGREE ON THIS PLACEMENT SO
TEMPERATURE FORECAST IS UNCERTAIN DURING THE MIDDLE OF NEXT WEEK.

&&

.AVIATION /03Z THURSDAY THROUGH MONDAY/...
MOSTLY VFR EXPECTED AT THE TERMINAL SITES OVERNIGHT. SOME PATCHY
FOG COULD DEVELOP ESPECIALLY WHERE SNOW PACK EXISTS. SOME OF THE
FOG COULD BE LOCALLY DENSE.

AN UPPER-LEVEL DISTURBANCE MAY BRING A RAIN OR SNOW SHOWER LATE
TONIGHT THROUGH THURSDAY...BUT MOST AREAS WILL BE DRY. VFR
CONDITIONS WITH NORTHWEST WINDS ARE EXPECTED FOR MOST OF THURSDAY.

NWLY FLOW GUSTS 20 TO 25 KT THURSDAY NIGHT AND FRIDAY AS HIGH
PRES BUILDS (VFR CONDS). HIGH OVERHEAD FRIDAY NIGHT WITH CONTINUED
VFR.

MAINLY VFR THROUGH THE WEEKEND W/ WIND BECOMING S AROUND 10 KT.

&&

.MARINE...
SMALL CRAFT CONDITIONS WILL CONTINUE FOR A SHORT TIME BEFORE WINDS
DIMINISH BEHIND THE DEPARTING COASTAL LOW PRESSURE SYSTEM.

NORTHWEST WINDS ARE EXPECTED THURSDAY...BUT SPEEDS SHOULD REMAIN
BELOW SCA CRITERIA. SURGE OF NWLY FLOW THURSDAY EVENING WITH 20 TO
25 KT GUSTS OVER MOST OF THE WATERS (SCA FOR ALL BUT UPPER TIDAL
POTOMAC...PATAPSCO AND PATUXENT)...THEN ACROSS THE WATERS FRIDAY.
WINDS WILL QUICKLY DIMINISH WITH SUNSET AS GRADIENT SLACKENS. HIGH
PRESSURE OVERHEAD FRIDAY NIGHT WITH SLY FLOW BEGINNING SATURDAY
MORNING.

SOUTHERLY FLOW TO SMALL CRAFT ADVISORY LEVELS POSSIBLE AHEAD OF A
FRONT OVER THE WEEKEND INTO EARLY NEXT WEEK.

&&

.CLIMATE...
RECORDS FOR EARLIEST MEASURABLE SNOW ALREADY PASSED A FEW WEEKS
AGO...BUT BELOW IS A LIST OF DAILY MAXIMUM SNOWFALL RECORDS
SPECIFIC TO THE DATE OF NOVEMBER 26TH. THE SNOWFALL REPORTED AT
DULLES SO FAR TODAY HAS BEEN 1.6 INCHES /AS OF 3 PM/ AND THIS
BREAKS THE OLD RECORD BELOW OF 1.1 INCHES SET IN 1978. DCA/BWI
RECORDS ARE SAFE.

DCA   2.2" (1898)
BWI   4.5" (1898)
IAD   1.1" (1978)

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR ANZ530>534-
     536>543.
     SMALL CRAFT ADVISORY FROM 7 PM THURSDAY TO 6 PM EST FRIDAY FOR
     ANZ530>534-536-537-539>541-543.
     SMALL CRAFT ADVISORY FROM 8 AM TO 6 PM EST FRIDAY FOR ANZ535-
     538-542.

&&

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






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