Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 141935
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
335 PM EDT MON APR 14 2014

.SYNOPSIS...
HIGH PRESSURE WILL REMAIN OFF THE EAST COAST THIS EVENING. A COLD
FRONT WILL CROSS THE APPALACHIANS LATE TONIGHT AND MOVE THROUGH
THE AREA TUESDAY. HIGH PRESSURE WILL BUILD EAST INTO THE NORTHERN
MID-ATLANTIC WEDNESDAY AND REMAIN OVER THE AREA THROUGH FRIDAY.
LOW PRESSURE MAY IMPACT THE REGION ON SATURDAY.

&&

.NEAR TERM /THROUGH TUESDAY/...
A POWERFUL SPRING STORM SYSTEM HAS BEEN SWINGING ACROSS A BETTER
PART OF THE CONUS YESTERDAY INTO TODAY. A DEEP AND COLD UPPER TROUGH
HAS SPENT MUCH OF TODAY PUSHING DOWN THE LENGTH OF THE PLAINS FROM
CNTRL CANADA...DOWN TO THE TX GULF COAST. TO GET A FEEL FOR WHAT`S
ON THE WAY...EVEN IF THE EFFECTS AREN`T SIMILAR - THE COLD FRONT HAS
BEEN DROPPING TEMPS A SOLID 20-30F DEG IN JUST A FEW HRS ALONG MUCH
OF THE BOUNDARY.

THE PRECIP AMOUNTS W/ THIS LARGE-SCALE HAVEN`T BEEN TOO TERRIBLY
HIGH...MAINLY OVER THE GULF COAST STATES WHERE MOST OF THE MOISTURE
FETCH REMAINS BUT THIS WILL PLAY INTO OUR AREA GETTING MODERATE
AMOUNTS OF QPF ON TUE. THE SFC LOW PRESSURE SYSTEM RESPONSIBLE FOR
THE INITIAL PUSH OF COLD AIR YESTERDAY AND TODAY WILL ESSENTIALLY
TAKE-OFF TOWARD THE NE TONIGHT AND LARGELY AWAY FROM OUR AREA INTO
THE OVERNIGHT HRS. THE SFC LOW HERE IN THE MID AFTN HRS IS ALREADY
MOVING UP THE NRN SIDE OF THE ST. LAWRENCE CHANNEL. THE COLD FRONT
ASSOCIATED W/ THIS STORM SYSTEM WILL ALSO BE TAKEN AWAY W/ THE
PARENT SFC LOW LATER TONIGHT...UNTIL ANOTHER SECONDARY SFC LOW
DEVELOPS OVER THE CNTRL APLCNS OVERNIGHT. THIS FEATURE...IN CONCERT
W/ YET ANOTHER SFC LOW DEVELOPING OVER SRN APLCNS EARLY TUE WILL
THEN BRING A REJUVENATED COLD FRONT ACROSS OUR REGION MIDDAY
TUE...BRINGING A NOTICEABLE AND SWIFT TANKING OF TEMPS TOMORROW.

BEFORE THE SHARP TEMP DROP...WE`LL HAVE PERIODS OF RAIN MOVING
ACROSS THE AREA - STARTING LATE TONIGHT FROM WEST TO EAST. THE MEAN
LAYER SHEAR IS SWLY...WHICH WILL CAUSE THE INITIAL WAVES OF LIGHT TO
MODERATE RAIN FROM SW-TO-NE ACROSS THE HIGHER TERRAIN AND PARTS OF
THE SHENANDOAH VLY TONIGHT. AREAS EAST OF THE BLUE RIDGE TO THE
COAST WILL BE THE LAST TO GET PRECIP MOVING IN...MORE TOWARD
MIDNIGHT OR LATER. MOST OF THE ACTIVITY AFFECTING THE AREA FROM LATE
TONIGHT INTO THE OVERNIGHT WILL BE SCATTERED...SHORT-LIVED...AND
FAIRLY LIGHT. TOWARD THE PREDAWN HRS TUE...MORE WIDESPREAD SHIELD OF
RAIN WILL MAKE THEIR WAY FROM THE SW AND OVER THE CWA...SPREADING
GENERALLY LIGHT TO MODERATE RAIN OVER THE AREA UNDER TEMPS IN THE
50S AND 60S.

THE GUSTY S-SWLY WINDS WILL CONTINUE TO SQUEEZE UP THE ERN SEABOARD
AHEAD OF THE STRENGTHENING LOW PRES SYSTEM...EVEN BRINGING SOME
AREAS OF THE I-95 CORRIDOR AND EAST INTO THE L70S BY DAWN. THIS WILL
MAXIMIZE THE CONVECTIVE POTENTIAL DURING THE EARLY MRNG HRS. LOW
CAPE VALUES IN THE COUPLE-FEW HUNDREDS WILL BE AVAILABLE FOR MUCH OF
THE AREA - ESPEC THE SERN SECTION OF THE CWA...ALONG W/ A POTENT
40-50KT LOW LEVEL JET I-95 AND EAST FOR AMPLE LINEAR SUPPORT. THE
CONVECTIVE NATURE OF THE PRECIP WILL THEN LIKELY TURN INTO A MORE
STABLE AND STRATIFORM RAIN AS THE COLD FRONT BEGINS TO BARREL ACROSS
THE AREA FROM THE POTOMAC HIGHLANDS TOWARD THE METRO AREAS LATE
MRNG/EARLY AFTN. WINDS WILL BE GUSTY ANYWAY...BUT THEY`LL TURN FROM
A WARM SLY BREEZE TO DRY AND COLD NW FLOW DIRECTLY BEHIND THE FRONT.
TEMPS WILL START TO DROP SEVERAL DEGREES EACH HR THRU THE
AFTN...DROPPING WELL INTO THE 30S/40S OVER THE WRN ZONES AND INTO
THE 40S/50S E OF THE MTNS.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
COLD FRONT MOVES OFFSHORE THROUGH THE EARLY EVENING HOURS ON
TUESDAY. STRONG COLD AIR ADVECTION CONTINUES TO SUPPORT FALLING
TEMPERATURES. FOLLOWED SREFS FOR POPS DECREASING FROM WEST TO EAST
THROUGH EARLY EVENING. IF COLD AIR CAN CATCH UP TO THE BACK EDGE OF
PRECIP QUICKLY ENOUGH...A FEW WET SNOWFLAKES COULD OCCUR BUT THE
BULK OF THE PRECIP WILL END AS RAIN.

FOCUS THEN TURNS TO THE COLD AIR. WITH COLD ADVECTION...MOMENTUM
TRANSFER WILL KEEP GUSTY NORTHWEST WINDS GOING INTO THE NIGHT. BUT
ITS THESE NORTHWEST WINDS THAT ARE BRINGING IN A MUCH COLDER AIR
MASS AND DESPITE THE WIND TEMPERATURES HAVE THE POTENTIAL TO DROP
BELOW FREEZING BY DAYBREAK ESPECIALLY IN THE SUBURBS. THE GROWING
SEASON WILL BEGIN APRIL 15TH EAST OF THE BLUE RIDGE...WHICH MEANS
THESE AREAS WILL BE CANDIDATES FOR FROST/FREEZE HEADLINES.
CONSIDERING FORECAST MINIMA...WILL BE ISSUING A FREEZE WATCH FOR
TUESDAY NIGHT/WEDNESDAY MORNING.

HIGH PRESSURE BUILDS IN FOR WEDNESDAY. SUNSHINE WILL RETURN BUT
MAXIMA MAY STRUGGLE TO REACH 50. HIGH PRESSURE WEDNESDAY NIGHT
WILL ALSO PAVE THE WAY FOR ANOTHER COLD NIGHT WITH RADIATIONAL
COOLING IN PLAY. ADDITIONAL FREEZE HEADLINES MAY BECOME NECESSARY
WEDNESDAY NIGHT INTO THURSDAY MORNING. MODERATING TREND SHOULD
BEGIN THURSDAY WITH HIGH PRESSURE MOVING OFF THE COAST.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
SURFACE HIGH PRESSURE WILL DEPART INTO THE NORTH ATLANTIC THURSDAY
NIGHT...LEAVING BEHIND A SURFACE RIDGE AXIS WEDGED AGAINST THE
EASTERN SLOPES OF THE APPALACHIANS. THIS WILL RESULT IN A CONTINUED
ONSHORE FLOW THROUGH FRIDAY.

AN UPPER-LEVEL TROUGH AND SURFACE LOW PRESSURE APPROACH THE AREA
FROM THE WEST LATE FRIDAY NIGHT INTO SATURDAY. THE LATEST GUIDANCE
SHOWS A WIDE SPREAD IN THE DEPTH OF THE APPROACHING TROUGH AND
STRENGTH OF LOW PRESSURE AT THE SURFACE. RAIN IS LIKELY FOR AT LEAST
PART OF THE AREA SATURDAY...BUT THERE IS A MODERATE TO HIGH LEVEL OF
UNCERTAINTY IN INTENSITY/COVERAGE.

WEAK RIDGING AND MILDER WEATHER LOOKS TO BUILD INTO THE AREA LATE IN
THE WEEKEND INTO EARLY NEXT WEEK.

&&

.AVIATION /19Z MONDAY THROUGH SATURDAY/...
WE`RE STILL UNDER A HIGH PRESSURE REGIME...BUT THE STRENGTH OF A
POWERFUL STORM SYSTEM OVER THE PLAINS AND UPPER MIDWEST IS CAUSING
SLY WINDS AROUND THE BACKSIDE OF THE HIGH TO REMAIN GUSTY...WELL
INTO THE 20-30KT RANGE. SUSTAINED SFC WINDS ARE ALSO RELATIVELY
HIGH...A SIGN THAT THE LOW LEVELS ARE - AND WILL REMAIN - GUSTY
THROUGHOUT THE REST OF THE DAY AND INTO THE OVERNIGHT.

THE STORM SYSTEM TO OUR WEST WILL MAKE A COUPLE OF LARGE-SCALE
TRANSITIONS BEFORE MOVING ACROSS THE REGION EARLY TUE - BUT ONCE IT
DOES...A STRONG COLD FRONT WILL MOVE THRU AREA REGION FROM LATE
MRNG INTO EARLY AFTN...W/ PERIODS OF RAIN OUT AHEAD OF AND ALONG
W/ THE FRONT. WINDS WILL ALSO SHIFT FROM SLY TO NWLY W/ THE SAME
POTENCY OF GUSTS IN THE 25-30KT RANGE.

HIGH PRESSURE BUILDS IN FOR LESS WIND WEDNESDAY. NO SIGNIFICANT WX
EXPECTED TO END THE WEEK.

&&

.MARINE...
WINDS IN SOLID SCA RANGE THIS AFTN WILL ESSENTIALLY STAY IN THE
20-30KT RANGE THROUGHOUT THE EVE AND OVERNIGHT HRS OUT OF THE SOUTH.
A STRONG COLD FRONT WILL THEN SWING ACROSS THE WATERS BY LATE AFTN
TUE...SPREADING NEAR GALE GUSTS ON TUE AFTN. HIGHEST CONFIDENCE IN
GALES IS BEHIND THE FRONT WITH A NORTHWEST SURGE AND GALE WARNING
HAS BEEN ISSUED FOR THIS PERIOD.

HIGH PRESSURE BUILDS IN FOR WEDNESDAY. SMALL CRAFT ADVISORY
LEVEL WIND GUSTS ARE POSSIBLE FOR PARTS OF THE WATERS THURSDAY
NIGHT...AND AGAIN OVER THE WEEKEND DEPENDING ON THE EVOLUTION OF
LOW PRESSURE MOVING NEAR THE AREA.

&&

.TIDES/COASTAL FLOODING...
POSITIVE TIDAL ANOMALIES REMAIN IN THE 1/2-3/4 FOOT RANGE FOR THE
WRN SHORES OF THE MD CHSPK BAY. THE STEADY AND GUSTY SLY WINDS WILL
KEEP THESE LEVELS STEADY INTO THE OVERNIGHT HRS AND THRU EARLY
TUESDAY MRNG. A FULL MOON UPCOMING...LIKELY HELPING WATER LEVELS TO
APPROACH MINOR FLOOD CRITERIA AT THE MORE SENSITIVE LOCATIONS AROUND
TIMES OF THE HIGHER HIGH TIDES EARLY TUESDAY MRNG. CBOFS GUIDANCE
HOWEVER FCSTS TIDAL LVLS BELOW MINOR COASTAL FLOODING THRESHOLDS AT
ALL SITES.

&&

.CLIMATE...
UNUSUALLY WARM CONDITIONS WERE OBSERVED ACROSS THE AREA EARLY THIS
MORNING. LOW TEMPERATURES WERE AROUND 20 DEGREES ABOVE NORMAL.
DEPENDING ON HOW LOW TEMPERATURES GET THIS EVENING...RECORD DAILY
HIGH MINIMUM TEMPERATURES COULD BE TIED OR BROKEN AT DCA...BWI AND
IAD. BELOW IS A TABLE OF RECORDS FOR THE DAY AND LOW TEMPERATURES
OBSERVED SO FAR.

SITE...PREVIOUS RECORD...LOW SO FAR...
DCA....63 F IN 1896......65 F.........
BWI....62 F IN 1896......62 F.........
IAD....58 F IN 1972......63 F.........

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...FREEZE WATCH FROM LATE TUESDAY NIGHT THROUGH WEDNESDAY MORNING
     FOR DCZ001.
MD...FREEZE WATCH FROM LATE TUESDAY NIGHT THROUGH WEDNESDAY MORNING
     FOR MDZ004>007-009>011-013-014-016.
VA...FREEZE WATCH FROM LATE TUESDAY NIGHT THROUGH WEDNESDAY MORNING
     FOR VAZ036>040-042-050>057-501-502.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EDT TUESDAY FOR ANZ530>543.
     GALE WARNING FROM 6 PM TUESDAY TO 6 AM EDT WEDNESDAY FOR
     ANZ530>543.

&&

$$
SYNOPSIS...BPP
NEAR TERM...GMS
SHORT TERM...BPP
LONG TERM...DFH
AVIATION...GMS/BPP/DFH
MARINE...GMS/BPP/DFH
TIDES/COASTAL FLOODING...GMS
CLIMATE...DFH







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