Area Forecast Discussion
Issued by NWS Sterling, VA

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS61 KLWX 260754
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
354 AM EDT SUN OCT 26 2014

.SYNOPSIS...
HIGH PRESSURE WILL BUILD OVERHEAD THROUGH TONIGHT BEFORE MOVING
OFF THE COAST MONDAY AND TUESDAY. A COLD FRONT WILL PASS THROUGH
THE AREA WEDNESDAY AND HIGH PRESSURE MAY RETURN FOR THURSDAY INTO
FRIDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
AN ATYPICAL COLD FRONTAL PASSAGE AND ATMOSPHERE OVER THE AREA
ATTM. AS OF 3AM...IAD IS 61F AND LOCATIONS SOME 2-3 COUNTIES TO
THE SOUTH AND EAST ARE 10-15F COOLER. SAME STORY BACK EVEN FURTHER
TO THE NORTH AND WEST - THE OPPOSITE OF WHAT IS TYPICAL NOT ONLY
IN A LATITUDE SENSE BUT ALSO CONSIDERING A COLD FRONT SHOULD HAVE
THE COLD AIR BEHIND IT - NOT OUT AHEAD OF IT. BUT MORE IS GOING ON
THAN JUST A WARM-SECTOR AHEAD OF THE FRONT AND CAA BEHIND. LOW
LEVEL MOISTURE TRAPPED IN A CORRIDOR IN THE LEE OF THE BLUE RIDGE
HAS HELPED CREATE A STABLE LAYER FOR THE INCOMING WINDS FROM THE
WEST. DEWPOINTS W OF THE RIDGE HAVING NO TROUBLE DROPPING WELL
INTO THE 30S BUT TEMPS HAVE ALSO INCREASED BEHIND THE BOUNDARY
INTO THE L60S. FURTHER SOUTH AND EAST OVER THE NRN VA
PIEDMONT...TEMPS HAVE SETTLED DOWN IN THE 40S.

ANOTHER COUPLE OF HRS THOUGH AND TEMPS WILL BEGIN TO DROP BACK DOWN
INTO THE 50S ACROSS THE ENTIRE REGION...FOR THOSE THAT ARE IN THE
60S AS WELL. A FEW WAVE-TYPE CLOUDS THAT ARE MAKING THEIR WAY ACROSS
THE REGIONAL SKIES ATTM WILL DISSIPATE AND PROPAGATE WELL E OF THE
AREA BY THE POST-DAWN HRS. CLEAR SKIES THRU THE DAYTIME HRS TODAY W/
A REBOUND IN TEMPS BACK TOWARD YDA`S LEVELS BUT W/ DRY AND GUSTY
WINDS. BLENDED THE VARIOUS WRF DERIVATIVES FOR HOURLY WINDS FOR
TODAY...SHOWING THE AREAL WAVE-LIKE PATTERN TO THE GUSTS OVER THE
MTNS/FOOTHILLS.

RELATIVELY HIGHER TEMPS...LOW HUMIDITIES AND GUSTY WINDS
ALONG W/ FUEL MOISTURES THAT HAVE BEEN DROPPING OVER THE PAST FEW
DAYS WILL CREATE AN ENHANCE FIRE THREAT...SEE THE FIRE WX SECTION
BELOW FOR FURTHER DETAILS.

WITH SFC DEWPOINTS FIRMLY HOLDING IN THE 30S OVERNIGHT...TEMPS WILL
MAKE A SIMILAR DROP TONIGHT. MANY AREAS WILL DROP WELL INTO THE 40S
AND MUCH OF THE PIEDMONT/SHELTERED VLYS WILL REACH THE M-U30S FOR
OVERNIGHT LOWS. PATCHY FROST WILL BE POSSIBLE IN AREAS THAT DO REACH
THESE LOWER TEMP VALUES AND CAN HAVE WINDS DECOUPLE AFTER A BREEZY
DAY. MOST OF THE AREA SHOULD SEE WINDS DROP OFF SHORTLY AFTER
SUNSET...BUT A FEW RESIDUAL GUSTS EXPECTED INTO THE EARLY MRNG HRS.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY/...
MONDAY WILL BE MUCH LIKE SATURDAY - A PLEASANT TRANSITION DAY W/
HIGH PRESSURE REBOUNDING FROM THE DEEP SOUTH AFTER GETTING PUSHED
OUT OF THE AREA TODAY. A CHANGE IN THE WIND FIELD WILL TURN OUR SFC
WINDS TO SLY...BRINGING BACK SOME WARMTH AND INCREASING LOW LEVEL
MOISTURE. THE HIGHLANDS WILL BENEFIT THE MOST FROM THIS REGIME...W/
TEMPS CLIMBING WELL INTO THE 70S - SOME LOCALES NEAR 80F IN THE
SHELTERED APLCN VLYS. A BIT MORE OF A COMPLEX SOLUTION FOR THE
PIEDMONT/COASTAL AREAS...W/ TEMPS ALSO CLIMBING INTO THE SEASONAL
AVG`S BUT THE COOLER AIR WILL RESIDE OVER EXTREME NERN MD.
BIAS-CORRECTED MAV/MEX SEEMED TO HAVE THE BEST HANDLE ON THIS - W/
SOME EURO CONTRIBUTIONS AS WELL. CLOUD-FREE AND DRY FOR THE
MONDAY...W/ SOME CIRRUS MOVING IN FROM THE NW LATER IN THE DAY.

HIGH PRESSURE WILL MOVE INTO THE ATLANTIC OCEAN MONDAY NIGHT AND
TUESDAY WHILE A COLD FRONT APPROACHES FROM THE WEST. A SOUTHERLY
FLOW WILL INCREASE BETWEEN THESE SYSTEMS. THIS WILL ALLOW FOR
MILDER CONDITIONS MONDAY NIGHT COMPARED TO SUNDAY NIGHT...AND
TUESDAY WILL TURN OUT QUITE WARM FOR THIS TIME OF YEAR AS THE
SOUTHERLY FLOW STRENGTHENS. MAX TEMPS TUESDAY WILL RANGE FROM THE
MID AND UPPER 70S NEAR WASHINGTON AND BALTIMORE...TO THE LOWER 80S
IN CENTRAL VIRGINIA.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
THE COLD FRONT WILL SLOWLY PASS THROUGH THE AREA LATE TUESDAY
NIGHT AND WEDNESDAY. CLOUDS WILL INCREASE AHEAD OF THIS SYSTEM AND
A FEW SHOWERS ARE POSSIBLE DURING THIS TIME.
HOWEVER...PRECIPITATION AMOUNTS SHOULD BE LIGHT SINCE LITTLE
MOISTURE WILL BE ASSOCIATED WITH THE BOUNDARY.

HIGH PRESSURE WILL RETURN FOR WEDNESDAY NIGHT AND
THURSDAY...BRINGING A RETURN OF DRY AND SEASONABLY COOL
CONDITIONS. AN UPPER-LEVEL TROUGH WILL SWING THROUGH THE AREA
FRIDAY INTO SATURDAY. UNCERTAINTY IN THE STRENGTH AND TIMING OF
THIS SYSTEM REMAIN HIGH. THERE WILL BE A CHANCE FOR SHOWERS DURING
THIS TIME...AND THERE MAY BE ENOUGH COLD AIR FOR SOME SNOW SHOWERS
ALONG THE RIDGE TOPS.

&&

.AVIATION /07Z SUNDAY THROUGH THURSDAY/...
VFR CONDS THRU THE CURRENT TAF PERIOD...BUT A CHALLENGING SITUATION
CREATED BY AN INCOMING COLD FRONT. WEST OF THE BLUE RIDGE...BOUNDARY
LAYER WINDS HAVE BEEN ABLE TO NEAR-FULLY FIX DOWN...CREATING THE
20-30KT GUSTS THAT HAVE BEEN APPEARING IN MANY POTOMAC HIGHLAND OBS
IN RECENT HRS. EAST OF THE BLUE RIDGE...A MORE STABLE ATMOS HAS CUT
DOWN SUBSTANTIALLY ON THESE GUSTS BUT MORE RECENTLY THIS LAYER HAS
SHOWN SIGNS OF MIXING-OUT. THRU 12Z...LOCALES ACROSS THE I-95
CORRIDOR AND NEARBY TAF SITES SHOULD PREPARE FOR BRIEF GUSTS IN THE
20-30KT RANGE W/ INTERMITTENT PERIODS OF LIGHTER WINDS.

POST-SUNRISE...THE MORE STEADY AND WIDESPREAD GUSTS IN THE 20-30KT
RANGE WILL BEGIN AND CONTINUE WELL INTO THE AFTN HRS. BY LATE THIS
AFTN/EVE...THE TOP-END GUSTS WILL SUBSIDE BACK TOWARD 15-20KT THEN
DROP OFF AFTER SUNSET. HIGH PRESSURE WILL BUILD BACK INTO THE AREA
ON MONDAY...ALLOWING SFC WINDS TO SWITCH TO SLY THRU THE DAYTIME HRS
AND CLEAR SKIES FOR ALL SITES TODAY INTO MONDAY.

VFR CONDITIONS ARE EXPECTED MOST OF THE TIME MONDAY NIGHT THROUGH
THURSDAY. GUSTY SOUTHWEST WINDS ARE POSSIBLE TUESDAY AFTERNOON. A
COLD FRONT WILL BRING A CHANCE FOR SHOWERS LATE TUESDAY NIGHT AND
WEDNESDAY. CIGS/VSBYS MAY APPROACH MVFR LEVELS DURING THIS TIME.

&&

.MARINE...
A COLD FRONT PUSHING ACROSS THE AREA WILL EVENTUALLY SPREAD SOLID
SCA GUSTS ACROSS THE WATERS IN THE COMING HRS AND CONTINUE
THROUGHOUT THE DAY. A FEW NEAR-GALE GUSTS IN THE U20KT RANGE WILL BE
POSSIBLE AT ISOLATED LOCALES DURING THIS TIME PERIOD BUT THE
OVERWHELMING RANGE WILL BE A GENERAL 20-25KT. HIGH PRESSURE WILL
BUILD INTO THE AREA AGAIN STARTING LATER THIS AFTN...SLOWLY DROPPING
WINDS BACK DOWN INTO THE 5-10KT AND SWITCH THE FLOW TO SLY HEADING
INTO MONDAY.

A COLD FRONT WILL APPROACH THE WATERS MONDAY NIGHT AND TUESDAY.
SOUTHERLY WINDS WILL INCREASE TUESDAY. A SMALL CRAFT ADVISORY MAY
BE NEEDED FOR PORTIONS OF THE WATERS TUESDAY INTO TUESDAY NIGHT.
THE COLD FRONT WILL PASS THROUGH THE WATERS WEDNESDAY. HAVE CAPPED
GUSTS AROUND 15 KNOTS FOR NOW DUE TO THE RELATIVE WEAK PRESSURE
GRADIENT. HOWEVER...A PRESSURE SURGE MAY CAUSE WIND GUSTS TO
EXCEED SCA CRITERIA WEDNESDAY NIGHT INTO THURSDAY FOR PORTIONS OF
THE WATERS.

&&

.FIRE WEATHER...
GUSTY WINDS ARE EXPECTED BEHIND A COLD FRONT TODAY. THE GUSTY
WINDS ALONG WITH LOW RELATIVE HUMIDITY AND LOW FUEL MOISTURE WILL
ENHANCE THE THREAT FOR THE SPREAD OF WILDFIRES LATE THIS MORNING
AND AFTERNOON. WILL CONTINUE WITH A SPECIAL WEATHER STATEMENT FOR
THE ENHANCED THREAT ACROSS THE CENTRAL SHENANDOAH VALLEY INTO THE
POTOMAC HIGHLANDS OF VIRGINIA. THE RELATIVE HUMIDITY WILL BE
LOWEST ACROSS THESE AREAS. ELSEWHERE...THE RELATIVE HUMIDITY MAY
BE A BIT HIGHER BUT WINDS WILL BE GUSTY.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 2 AM EDT MONDAY FOR ANZ530>534-537-
     539>541-543.
     SMALL CRAFT ADVISORY UNTIL 6 PM EDT THIS EVENING FOR ANZ535-
     536-538-542.

&&

$$
SYNOPSIS...BJL
NEAR TERM...GMS
SHORT TERM...BJL/GMS
LONG TERM...BJL
AVIATION...BJL/GMS
MARINE...BJL/GMS
FIRE WEATHER...BJL/GMS







USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.