Area Forecast Discussion
Issued by NWS Sterling, VA

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499
FXUS61 KLWX 070228 AAA
AFDLWX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
928 PM EST SAT FEB 6 2016

.SYNOPSIS...
HIGH PRESSURE WILL WEAKEN THROUGH MONDAY. COASTAL LOW PRESSURE
WILL PASS BY WELL TO THE SOUTH AND EAST SUNDAY NIGHT. ANOTHER LOW
PRESSURE SYSTEM WILL DIVE SOUTH INTO THE OHIO VALLEY MONDAY BEFORE
PASSING THROUGH OUR AREA MONDAY NIGHT INTO TUESDAY. HIGH PRESSURE
WILL SLOWLY BUILD TOWARD OUR AREA DURING THE MIDDLE PORTION OF
NEXT WEEK.

&&

.NEAR TERM /THROUGH SUNDAY/...
HIGH CLOUDS OVER THE AREA WILL TEND TO THIN OUT OVERNIGHT LEADING
TO MOSTLY CLEAR SKIES TOWARD MORNING. HOWEVER..HIGH CLOUDS
ASSOCIATED WITH JET STREAK ON EAST SIDE OF UPPER LOW OVER THE GULF
STATES WILL SPREAD NORTHWARD ACROSS THE AREA SUN MORNING WITH
MOSTLY CLOUDY/CLOUDY SKIES EXPECTED SUN ESPECIALLY EAST OF THE
BLUE RIDGE. NO PRECIP IS EXPECTED WITH THIS SYSTEM ANYWHERE IN OUR
FCST AREA BUT DID INCREASE THE SKY COVER SIGNIFICANTLY FOR SUN.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...

UPDATE ON WINTRY WX MON AND TUE...P-TYPE ISSUES EARLY AND LACK OF
A WELL DEFINED LOW-MID LEVEL CIRCULATION AND INFLOW OF GULF OR
ATLC MOISTURE STRONGLY SUGGEST THIS WILL BE A MINOR SNOW EVENT.
LOW-LEVEL TEMPS EAST OF THE BLUE ARE VERY MARGINAL FOR AN ALL SNOW
EVENT MON AND MON NIGHT SO A MIXTURE OF RAIN AND/OR WET SNOW
LIKELY. COLUMN DOES NOT GET SUFFICIENTLY COLD ENOUGH FOR ALL SNOW
UNTIL TUE AND BY THAT TIME THE MOISTURE WILL BE DEPARTING AS WINDS
BECOME WESTERLY. ONE NOTEWORTHY ASPECT OF THIS SYSTEM IS VERY COLD
AIR ALOFT AND STEEP LAPSE RATE ENVIRONMENT WHICH COULD SUPPORT
CONVECTION. SEVERAL STABILITY INDICES SUCH AS K...LIFTED AND
SHOWALTER INDICES SUGGEST THUNDERSTORMS POSSIBLE WHICH MAY ENHANCE
PRECIP RATES. AT THIS TIME...EVERYTHING POINTS OUT TO ADVISORY
LEVEL EVENT WITH MINOR SNOW ACCUMULATIONS.

PREVIOUS DISCUSSION...

BY SUNDAY NIGHT...THE COASTAL LOW WILL BE MOVING OUT TO SEA WHILE A
BROAD UPPER LEVEL LOW MOVES INTO THE GREAT LAKES. THIS VERTICALLY
STACKED SYSTEM WILL MOVE INTO THE OHIO VALLEY BY MONDAY AFTERNOON.
AN ASSOCIATED COLD FRONT WILL PROGRESS EASTWARD MONDAY AND RAIN AND
SNOW SHOWERS WILL MOVE ACROSS THE APPALACHIANS BY MONDAY AFTERNOON.
SFC TEMPS ARE EXPECTED TO RISE INTO THE U30S/L40S AND L30S IN THE
MTNS MONDAY. AS PRECIPITATION MOVES EASTWARD MOST OF IT WILL BE RAIN
WITH THE EXCEPTION OF THE HIGHER ELEVATIONS. THE BROAD UPPER LEVEL
LOW WILL MOVE OVERHEAD MONDAY NIGHT INTO TUESDAY AND SFC LOW
PRESSURE TRANSFERS TO THE MID-ATLANTIC COAST. THERE IS A LARGE
SPREAD IN MODEL GUIDANCE FOR MOISTURE AND QPF FIELDS AND THEREFORE
UNCERNTAINITY EXISTS IN SNOWFALL ACCUMULATIONS.

TEMPS WILL DROP INTO THE 20S AND L30S NEAR I-95 BY TUESDAY MORNING
AND FOR THAT REASON PRECIPITATION WILL TRANSITION TO ALL SNOW INTO
TUESDAY. ACCUMULATION IS EXPECTED WITH 3-6 INCHES NORTH AND WEST OF
I-95 AND 1-3 INCHES ACROSS THE WASHINGTON DC AND BALTIMORE METROS.
AT THIS TIME...THE SNOWFALL ACCUMULATION CONFIDENCE LEVEL IS LOW TO
MEDIUM AS POTENTIAL EXISTS FOR HEAVY BANDS OF SNOW TO FORM
ACROSS THE MID-ATLANTIC PRODUCING MORE ACCUMULATION. AT
THIS TIME...LOCATION OF THESE BANDS COULD EXIST ANYWHERE ACROSS
THE MID-ATLANTIC REGION.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
A NEWLY-DEVELOPED LOW PRESSURE SYSTEM OFF OF THE COAST OF THE
DELMARVA PENINSULA WILL MOVE FARTHER OUT TO SEA TUESDAY AND TUESDAY
NIGHT...BUT NOT BEFORE LEAVING BEHIND A LITTLE MORE SNOW
ACCUMULATION IN EASTERN AREAS ALONG THE CHESAPEAKE BAY. ADDITIONAL
UPPER LEVEL ENERGY IN THE WESTERN ZONES WILL BRING ADDITIONAL SNOW
ACCUMULATION TO THE POTOMAC HIGHLANDS AS WELL.

THE MAIN UPPER LEVEL TROUGH OF LOW PRESSURE WILL PIVOT ACROSS THE
REGION LATER IN THE DAY WEDNESDAY INTO WEDNESDAY NIGHT. ADDITIONAL
UPSLOPE SNOW EXPECTED IN THE POTOMAC HIGHLANDS...WHILE GRADUAL
CLEARING SKIES ARE EXPECTED TO THE EAST. AN OCCASIONAL DAYTIME SNOW
SHOWER OR TWO ARE POSSIBLE IN THE EASTERN ZONES DUE TO DIURNAL
DIFFERENCES. FOR NOW...IT IS A SLIGHT CHANCE OF SNOW SHOWERS. MUCH
COLDER AIR WILL BE ON THE HEELS OF THIS UPPER TROUGH WEDNESDAY NIGHT
AS A COLD DOME OF HIGH PRESSURE BUILDS IN FROM THE WEST.

HIGH PRESSURE WILL DOMINATE THURSDAY AND THURSDAY NIGHT WITH VERY
COLD AND DRY AIR ACROSS THE REGION. TEMPERATURES WILL BE 10 TO 15
DEGREES BELOW NORMAL.

AS THE HIGH FLATTENS OUT LATE THURSDAY NIGHT INTO FRIDAY...AN AREA
OF LOW PRESSURE SHOULD SCOOT ACROSS THE TENNESSEE VALLEY. THIS LOW
SHOULD JUST SPREAD ADDITIONAL CLOUD COVER ACROSS THE SOUTHERN HALF
OF OUR REGION. A BRIEF PERIOD OF LIGHT SNOW CANNOT BE RULED OUT.
VERY COLD TEMPERATURES WILL CONTINUE FRIDAY INTO FRIDAY NIGHT WITH
TEMPERATURES ABOUT 10 TO 15 DEGREES BELOW NORMAL.

BEHIND THE AREA OF LOW PRESSURE...THE MAIN UPPER LEVEL TROUGH OF
SUPPORT WILL PIVOT EAST WITH A FIRM RIDGE OF HIGH PRESSURE QUICKLY
TO FOLLOW IT. ASIDE FROM DIURNAL CLOUD COVER SATURDAY...THIS TROUGH
WILL MAINLY SUPPORT ARCTIC AIR SURGING INTO THE MID ATLANTIC
SATURDAY.

&&

.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
VFR CONDITIONS EXPECTED THROUGH MONDAY. WINDS WILL BECOME NE BY
SUNDAY AFTERNOON AS A COASTAL LOW MOVES SOUTH OF THE REGION. A
COLD FRONT WILL APPROACH THE REGION MONDAY AND RAIN OR SNOW IS
EXPECTED MONDAY BECOMING ALL SNOW BY TUESDAY MORNING. VSBY AND
CIGS RESTRICTIONS EXPECTED BY MONDAY NIGHT. &&

MVFR TO BRIEFLY IFR CONDITIONS TUESDAY WITH A CHANCE OF LIGHT
SNOW...POSSIBLY MIXING WITH RAIN. WINDS NORTHWEST 5 TO 10 KNOTS.
MVFR CONDITIONS TUESDAY NIGHT WITH AN OCCASIONAL SNOW SHOWER IN
PARTS OF THE REGION. WINDS NORTHWEST BECOMING WEST 10 TO 15 KNOTS
WITH HIGHER GUSTS.

.MARINE...
HIGH PRESSURE ACROSS THE REGION WILL KEEP WINDS BELOW SCA
CONDITIONS. WINDS WILL BECOME NE BY SUNDAY AFTERNOON. WINDS ARE
EXPECTED TO INCREASE AND GUSTY WINDS WILL BEGIN SUNDAY NIGHT INTO
MONDAY AS A COASTAL LOW MOVES TO THE SOUTH AND EAST. A SCA MAY BE
NEEDED.

NO MARINE HAZARDS TUESDAY. WINDS NORTHWEST 5 TO 10 KNOTS. SMALL
CRAFT ADVISORY CONDITIONS POSSIBLE TUESDAY NIGHT. WINDS NORTHWEST
BECOMING WEST 10 TO 15 KNOTS GUSTS 20 KNOTS.

&&

.MARINE...

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 6 PM SUNDAY TO 6 AM EST MONDAY FOR
     ANZ533-534-537-543.

&&

$$
SYNOPSIS...LFR
NEAR TERM...LFR
SHORT TERM...LFR
LONG TERM...KLW
AVIATION...HAS/KLW
MARINE...HAS/KLW



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