Area Forecast Discussion
Issued by NWS Sterling, VA

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878
FXUS61 KLWX 120236
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
936 PM EST THU FEB 11 2016

.SYNOPSIS...
HIGH PRESSURE BUILDS IN ACROSS THE REGION THROUGH FRIDAY. A
STRONG COLD FRONT WILL CROSS THE REGION FRIDAY NIGHT WITH ARCTIC
HIGH PRESSURE BUILDING IN ITS WAKE FOR THE WEEKEND. LOW PRESSURE
WILL IMPACT THE AREA MONDAY AND TUESDAY.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
SURFACE HIGH NOW SITTING OVER THE OHIO VALLEY THIS EVENING. MID-
ATLANTIC SLOWLY COMING UNDER ANTI-CYCLONIC FLOW THOUGH LONG-WAVE
TROUGH STILL OVER EASTERN N AMERICA. HEIGHTS GRADUALLY RISING AND
BL MOISTURE STILL THINNING AS EVIDENT IN RECENT SATELLITE.
GENERALLY EXPECT MOSTLY CLEAR SKIES OVERNIGHT. THE GUSTY WINDS
WILL ALSO CONTINUE TO SLOWLY DIMINISH DURING THE REST OF THE
EVENING AND OVERNIGHT...THOUGH THIS HAS BEEN A LITTLE SLOWER THAN
EXPECTED.

THE HIGH SLIPS TO THE SOUTH OVERNIGHT. BASICALLY JUST A COLD
NIGHT WITH LOWS IN THE TEENS IN MOST LOCATIONS. WIND CHILLS WILL
BE LESS OF A CONCERN WITH THE DECREASING WINDS.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY NIGHT/...
SFC HIGH PRESSURE QUICKLY SLIDES OFFSHORE EARLY FRIDAY WITH RETURN
FLOW BRINGING SLIGHTLY HIGHER TEMPERATURES (BUT STILL ON EITHER SIDE
OF FREEZING)...AS WELL AS INCREASING CLOUDS/MOISTURE. ONE LOW
PRESSURE CENTER ASSOCIATED WITH AN ARCTIC FRONT WILL BE MOVING
THROUGH THE GREAT LAKES...WHILE ANOTHER TAKES SHAPE NEAR THE
CAROLINA COAST IN RESPONSE TO A SOUTHERN VORT MAX. MAJORITY OF
GUIDANCE KEEPS THE COASTAL LOW EFFECTS TO OUR SOUTHEAST...BUT DID
BUMP UP THE LOW END POPS ACROSS SOUTHERN MD.

THE MORE IMPORTANT WEATHER FEATURE FOR OUR AREA WILL BE A PAIR OF
BOUNDARIES TRAILING THE NORTHERN LOW CENTER. INCREASING SIGNAL IN
MODEL GUIDANCE OF A BAND OF SNOW SHOWERS DEVELOPING AHEAD OF THE
FIRST BOUNDARY AND HAVE THUS INCREASED POPS ACROSS THE AREA WITH
SUFFICIENT MOISTURE AVAILABLE. STILL SOME DIFFERENCES ON TIMING AND
COVERAGE...WITH GUIDANCE TENDING TO FAVOR A LATER ARRIVAL...BUT
THERE REMAINS POTENTIAL FOR THESE SNOW SHOWERS TO REACH THE METRO
AREA DURING PORTIONS OF EVENING RUSH HOUR. WITH THE ANTECEDENT
COLD CONDITIONS...ANY SNOW WOULD STICK ON UNTREATED ROADS.
CERTAINLY A SITUATION TO PAY ATTENTION TO.

THIS WILL ALSO MARK THE BEGINNING OF A PERIOD OF UPSLOPE
SNOW...HEAVIEST FRIDAY AFTERNOON AND NIGHT...BUT LASTING THROUGH
SATURDAY. WINTER WX ADVISORY POSSIBLE AS SEVERAL INCHES OF SNOW
EXPECTED.

SECOND BOUNDARY WILL MOVE THROUGH LATE FRIDAY NIGHT AND MARK THE
LEADING EDGE OF THE COLDEST AIRMASS. EVEN THOUGH CHANCES DECREASE A
BIT...SOME SNOW SHOWERS COULD STILL MAKE IT ACROSS ESPECIALLY
NORTHERN PARTS OF THE AREA. TEMPERATURES WILL FALL INTO THE TEENS IN
MOST AREA AND WINDS INCREASE SUBSTANTIALLY WITH GUSTS OF 20-30 MPH
BEHIND THE FRONT. THIS MAY NECESSITATE WIND CHILL ADVISORIES IN THE
HIGHER ELEVATIONS. ALSO OF NOTE IS THE SIGNIFICANT PRESSURE SURGE
JUST AFTER THE BOUNDARY LATE FRIDAY NIGHT WHICH MAY RESULT IN A
BURST OF STRONG GUSTY WINDS POTENTIALLY CLOSE TO 45 MPH.

SATURDAY-SATURDAY NIGHT WILL BE THE COLDEST OF THE STRETCH WITH 850
MB TEMPS BELOW -20C AND STIFF WINDS. HIGHS ON SATURDAY WILL ONLY BE
IN THE TEENS AND 20S WITH LOWS SATURDAY NIGHT IN THE SINGLE
DIGITS...AND BELOW ZERO IN THE POTOMAC HIGHLANDS. WIND GUSTS OF AT
LEAST 30-40 MPH WILL OCCUR SATURDAY...AND THERE IS A CHANCE OF WIND
ADVISORY CRITERIA (I.E. 45-50 MPH). THE WINDS WILL ONLY DIMINISH
SLIGHTLY SATURDAY NIGHT. WIND CHILLS MAY FAIL TO RISE ABOVE +10F
ON SATURDAY IN MUCH OF THE AREA...AND FALL BELOW ZERO SATURDAY
NIGHT. WIND CHILL ADVISORY CRITERIA (-5F) WILL LIKELY BE MET OVER
MOST OF THE AREA...AND WIND CHILL WARNINGS (-25F) ARE POSSIBLE
ALONG THE ALLEGHENIES.

OTHER ISSUE FOR SATURDAY WILL BE A CONTINUED CHANCE OF SNOW SHOWERS
AND STREAMERS ACROSS THE NORTHERN PART OF THE AREA. SNSQ PARAMETER
IN THE NAM AND GFS...AND EVEN 12Z GFS QPF OUTPUT...PLACE THE FAVORED
AREA ACROSS NORTH CENTRAL MD INCLUDING BALTIMORE.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
LATEST MODEL GUIDANCE IS SUGGESTING A PRETTY QUICK EROSION OF AN
IMPRESSIVELY COLD AIRMASS BEGINNING LATE SUNDAY AND INTO EARLY NEXT
WEEK. NORMALLY THIS TYPE OF QUICK EROSION WOULD FORCE SOME KIND OF
PRECIPITATION...AND AS SUCH A LOT OF THE GUIDANCE IS TRYING TO BRING
SOME PRECIPITATION OVER THE AREA SUNDAY NIGHT INTO MONDAY.

A STRONG UPPER-LEVEL DISTURBANCE WILL FORCE A SURFACE LOW OVER THE
SOUTHEASTERN CONUS...WHICH WILL THEN MOVE NORTHEAST NEAR OR OVER THE
AREA. GUIDANCE DIVERGES GREATLY ON SURFACE LOW TRACK AND HOW MUCH
COLD AIR IS LEFT IN PLACE. BEST CHANCE FOR PROLONGED WINTRY
PRECIPITATION WOULD BE WEST OF THE BLUE RIDGE MOUNTAINS. EAST OF
THERE PRECIPITATION MAY VERY WELL CHANGE TO RAIN BY TUESDAY. THERE
WILL LIKELY BE SOME WINTRY PRECIPITATION EARLY NEXT WEEK...BUT
AMOUNTS ARE HIGHLY UNCERTAIN AT THIS TIME.

AN ACTIVE PATTERN MAY PERSIST INTO THE MIDDLE PART OF NEXT WEEK BUT
DETAILS ARE FUZZY GIVEN THE UNCERTAIN EVOLUTION OF THE EARLY WEEK
SYSTEM.

&&

.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
PRIMARY ISSUE AFFECTING THE TERMINAL THROUGH THE WEEKEND WILL BE
WIND. WNW GUSTS UP TO 20 KT ARE SLOWLY DIMINISHING THIS EVENING
AND MID CIGS AROUND 5KFT HAVE DISSIPATED. VFR THROUGH THE BULK OF
FRIDAY WITH LIGHT SW WINDS. WILL HAVE TO WATCH FOR SNOW SHOWERS
AHEAD OF AN ARCTIC COLD FRONT LATE FRIDAY AFTERNOON INTO EVENING.
NOT HIGH ENOUGH CONFIDENCE TO PUT IN THE EXTENDED TAFS NOW...BUT
THESE COULD CAUSE BRIEF IMPACTS WITH SHORT PERIODS OF IFR CIGS AND
VIS.

WINDS INCREASE SHARPLY BEHIND FRONT...WITH NW GUSTS 25-35 KT
CONTINUING THROUGH SATURDAY AND ONLY GRADUALLY DIMINISHING SATURDAY
NIGHT. COULD BE A FEW GUSTS IN EXCESS OF 40 KTS. THERE WILL BE A
LINGERING THREAT OF ISOLD/SCT SNOW SHOWERS THROUGH
SATURDAY...ESPECIALLY BWI/MTN.

SUB-VFR PSBL SUN NGT OR MON AS PRECIP DEVELOPS. WINDS LIGHT SUN
NGT BCMNG GNLY ELY MON.

&&

.MARINE...
W/NW WINDS CONTINUING TO GUST TO 20-25 KT THIS EVE ARE ONLY SLOWLY
DROPPING OFF. THE SCA OVER THE MORE PROTECTED WATERS WAS EXTENDED
TO 11 PM. WILL HAVE TO WATCH GUSTS AS IT MAY NEED ANOTHER
EXTENSION. STILL THINK WINDS SHOULD LIGHTEN BY MORNING. LIGHT SW
FLOW TO START FRIDAY BUT THAT WILL QUICKLY CHANGE DURING THE
EVENING AS ARCTIC FRONT MOVES THROUGH WITH CHANCE FOR SNOW
SHOWERS. W/NW WINDS WILL INCREASE IMMEDIATELY. THIS MAY NEED TO
BE UPGRADED TO A GALE WARNING GIVEN IMPRESSIVE PRESSURE SURGE JUST
BEHIND FRONT LATE FRIDAY NIGHT...BUT CONFIDENCE NOT HIGH IN THAT
OCCURRING JUST YET. GALES THEN APPEAR LIKELY SATURDAY AND A
PORTION OF SATURDAY NIGHT. THE STRONG WINDS AND COLD TEMPERATURES
OVER THE RELATIVELY WARM WATERS WILL LIKELY RESULT IN A FREEZING
SPRAY THREAT.

WINDS DROP BELOW GALE RELATIVELY QUICKLY SUNDAY...AND
REMAIN RELATIVELY LIGHT INTO MONDAY.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EST FRIDAY FOR ANZ530>534-
     537>543.
     SMALL CRAFT ADVISORY FROM 6 PM FRIDAY TO 6 AM EST SATURDAY FOR
     ANZ530>543.
     SMALL CRAFT ADVISORY UNTIL 11 PM EST THIS EVENING FOR ANZ535-
     536.

&&

$$
SYNOPSIS...ADS/RCM
NEAR TERM...ADS/RCM
SHORT TERM...ADS/RCM
LONG TERM...DFH/RCM
AVIATION...ADS/DFH/RCM
MARINE...ADS/DFH/RCM



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