Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 221858
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
258 PM EDT TUE JUL 22 2014

.SYNOPSIS...
HIGH PRESSURE WILL NEAR THE EASTERN SEABOARD TODAY AND TONIGHT. A
COLD FRONT WILL APPROACH FROM THE WEST WEDNESDAY...AND MOVE
THROUGH THE REGION WEDNESDAY NIGHT INTO EARLY THURSDAY. HIGH
PRESSURE IS EXPECTED TO RETURN TO THE REGION TO END THE WORK WEEK.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
HIGH PRESSURE PERSISTS ALONG THE MID-ATLANTIC COAST LATE THIS
AFTERNOON. S-SE WINDS HAVE SET UP OVER THE FORECAST AREA...WITH
MOIST AIR ADVECTING INTO THE REGION. ISOLATED TO SCATTERED SHOWERS
HAVE POPPED UP...AND WILL CONTINUE TO AFFECT PORTIONS OF THE AREA
THIS AFTERNOON. 12Z SOUNDINGS INDICATED A WARM NOSE AROUND
600MB...AND THIS APPEARS TO BE HOLDING IN PLACE AS SHOWERS HAVE
HAD LITTLE VERTICAL EXTENT WITH TOPS REACHING NOT FAR ABOVE THE
FREEZING LEVEL. THIS WILL MINIMIZE THE POTENTIAL FOR THUNDERSTORM
ACTIVITY...ALTHOUGH ISOLATED TSTMS WILL REMAIN POSSIBLE OVER SOME
OF THE MOUNTAINS TODAY. OTHERWISE EXPECT SOME ISOLATED TO
SCATTERED SHOWER ACTIVITY TO CONTINUE...MAINLY ALONG AND WEST OF
THE BLUE RIDGE/CATOCTINS...WITH A FEW SPOTS RECEIVING BRIEF HEAVY
RAINFALL. HIGH TEMPS GENERALLY IN THE M80S ACROSS THE FORECAST
AREA.

SHOWER ACTIVITY DECREASES THIS EVENING...WITH DRY CONDITIONS
EXPECTED IN THE OVERNIGHT HOURS. WITH MOIST AIR IN PLACE...SOME
FOG IS POSSIBLE...MOST LIKELY IN THE SHELTERED VALLEYS. MET/MAV
GUIDANCE ARE IN GOOD AGREEMENT TONIGHT. LOWS IN THE 60S FOR
MOST...WITH LOW 70S IN URBAN AREAS AND NEAR MARINE ZONES.

WEDNESDAY STARTS WITH HIGH PRESSURE EXTENDING FROM THE OFFSHORE
WATERS AND INTO THE CAROLINAS...WITH A COLD FRONT EXTENDING ACROSS
THE LOWER GREAT LAKES AND OHIO VALLEY. THE COLD FRONT WILL
APPROACH DURING THE DAY...WHILE A 500MB TROUGH STRENGTHENS OVER
THE THE SAME REGION. COMBINATION OF INSTABILITY...LIFT AND
MOISTURE IS EXPECTED TO SUPPORT SHOWERS AND THUNDERSTORMS...WITH
ACTIVITY MORE LIKELY OVER NORTHERN AND WESTERN PORTIONS OF THE
FORECAST AREA THAT WILL BE CLOSER TO THE APPROACHING FRONT.
ISOLATED SEVERE STORMS WILL ALSO BE POSSIBLE ACROSS WESTERN MD AND
THE EASTERN WV PANHANDLE...WHICH SHOULD BE IN THE RIGHT ENTRANCE
REGION OF THE JET STREAM BY LATE IN THE DAY. DAMAGING WINDS IS
LIKELY TO BE THE MAIN THREAT.

WEDNESDAY WILL BE THE WARMEST DAY OF THE WEEK...WITH HIGHS IN THE
LOW 90S AT MOST LOCATIONS.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/...
THE COLD FRONT IS EXPECTED TO MOVE THROUGH MOST OF THE FORECAST
AREA WEDNESDAY NIGHT...AND SHOULD BE EAST OF THE I-95 CORRIDOR BY
THURSDAY MORNING. SHOWER/TSTM ACTIVITY SHOULD SHIFT EWD
ACCORDINGLY. SEVERE THREAT IS UNCERTAIN...AS BETTER DYNAMICS WILL
BE OFFSET BY LOWER NIGHTTIME INSTABILITY. LOWS RANGE FROM THE MID
60S OVER EASTERN WV...BEHIND THE FRONT...TO THE MID 70S ALONG AND
EAST OF I-95.

COLD FRONT MOVES EAST OF THE REGION ON THURSDAY...WHILE AN UPPER
TROUGH APPROACHES FROM THE WEST. SHOWER/TSTM CHANCES CONTINUE WITH
COOLER AIR ALOFT...BUT WITH A N-NW FLOW CHANCE OF SEVERE WX IS
UNLIKELY AT THIS TIME. TEMPS WILL BE COOLER WITH HIGHS RANGING
FROM THE UPPER 70S OVER HIGHER ELEVATIONS TO THE MID 80S ELSEWHERE.

UPPER TROUGH MOVES THROUGH THURSDAY NIGHT...WITH DRY CONDITIONS
EXPECTED EXCEPT POSSIBLY OVER SRN MD AND PORTIONS OF THE PIEDMONT.
LOWS DROP INTO THE 50S AND 60S.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
A RIDGE OF HIGH PRESSURE WILL BUILD IN FROM THE NORTHWEST FRIDAY AND
FRIDAY NIGHT TO ALLOW COOLER AND DRIER AIR TO PUSH INTO THE REGION
THROUGH SATURDAY.

WITH THE HIGH MOVING TO THE COAST AND OFFSHORE DURING THE DAY
SATURDAY...SOUTHEAST TO SOUTHERLY WINDS WILL EVOLVE...THUS PERHAPS
SPAWNING A SHOWER IN THE POTOMAC HIGHLANDS WITH THE UPSLOPE
COMPONENT.

DISTURBANCES IN THE UPPER LEVELS WILL ROTATE IN FROM THE OHIO VALLEY
AND LOWER GREAT LAKES SATURDAY NIGHT AND SUNDAY...THUS...BRINGING
THE CHANCE FOR SHOWERS AND THUNDERSTORMS.

AS FOR SUNDAY NIGHT THROUGH TUESDAY...A POTENT UPPER LEVEL STORM
SYSTEM WILL LINGER ACROSS THE GREAT LAKES REGION. SEVERAL WAVES OF
ENERGY WILL ROTATE AROUND IT AND ACROSS THE MID ATLANTIC REGION. THE
CHANCE OF SHOWERS AND THUNDERSTORMS...ONCE AGAIN...WILL BECOME A
NUISANCE TO THE REGION.


&&

.AVIATION /19Z TUESDAY THROUGH SUNDAY/...
ISOLATED SHOWER OR MAYBE A BRIEF TSTM PSBL THIS AFTERNOON. WINDS
FROM THE S-SE...LESS THAN 10KT.

VFR MOST OF THE NIGHT...BUT MVFR VSBYS WITH FOG IS POSSIBLE LATE
TONIGHT INTO THE EARLY MORNING HOURS WITH MOIST AIR OVER THE REGION.

SCATTERED SHOWERS AND TSTMS POSSIBLE WED AFTN INTO EARLY THU. AN
OFFSHORE HIGH WILL PUSH UP THE HEAT/HUMIDITY BEFORE TSTMS
ARRIVE/DEVELOP...WHILE A COLD FRONT APPROACHES FROM THE NW. THE
FRONT WILL LIKELY MOVE ACROSS THE AREA LATE WED INTO EARLY
THU...SWEEPING THIS ACTIVITY OFF THE COAST BY LATE THU AFTN.

VFR CONDITIONS WITH LIGHT AND VARIABLE WINDS EXPECTED FRIDAY
THROUGH SATURDAY AT ALL TERMINALS.

&&

.MARINE...
WINDS BLO SCA VALUES TDA/TGNT WITH SOUTHERLY WINDS AROUND 10KT.

LIGHT S-SW FLOW WILL CONTINUE WEDNESDAY AND MAXIMIZE JUST BEFORE THE
PASSAGE OF A COLD FRONT EARLY THU. SHOWERS AND TSTMS POSSIBLE WED
EVE INTO THE OVERNIGHT.

NO MARINE HAZARDS EXPECTED FRIDAY THROUGH SATURDAY.

&&

.TIDES/COASTAL FLOODING...
THE DAYTIME HIGH TIDE CYCLE IS THE LOWER OF THE TWO
ASTRONOMICALLY...HENCE THERE WL BE NO NEED FOR AN ADVISORY DURG THE
DAY. WILL CONTINUE TO MONITOR FOR POTENTIAL MINOR FLOODING AT HIGH
TIDE EARLY WEDNESDAY MORNING.

&&

.CLIMATE...
YDA WAS ONE MONTH SINCE THE SUMMER SOLSTICE. WE`RE A LTL OVR
HALFWAY THRU WHAT IS CONSIDERED MET SUMMER. HOW DOES THIS SUMMER
SHAPE UP SO FAR TEMP-WISE? LOOKING AT THE PAST 30 YRS...

6/1-7/21...1984-2014...

STATION AVG MAX  RANK AVG MIN RANK AVG DAILY RANK

DCA       87     12TH    70   6TH     78.5    9TH
BWI       84.3   23RD    64.3 15TH    74.5    19TH
IAD       83.6   23RD    63.6 12TH    73.6    20TH

AN INTERESTING STAT - DCA...AVG LOW TEMPS FOR THE PAST 30 YRS...
FIVE OF THE TOP SIX WARMEST HV BEEN 2010 THRU 2014. RANKINGS:

1 2010 72.1
2 2013 71.6
3 2011 71.0
4 1994 70.9
5 2012 70.2
6 2014 70.0
7 2008 68.9

EVEN IF YOU XTND TO THE ENTIRE DC RECORD - SINCE 1871...2014 RANKS
#7 FOR WARMEST AVG LOW TEMPS FOR THE PD 6/1-7/21.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...NONE.

&&

$$
SYNOPSIS...KCS
NEAR TERM...KCS
SHORT TERM...KCS
LONG TERM...KLW
AVIATION...KCS/KLW
MARINE...KCS/KLW
TIDES/COASTAL FLOODING...WOODY!/KCS
CLIMATE...WOODY!






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