Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 080115
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
915 PM EDT TUE JUL 7 2015

.SYNOPSIS...
A COLD FRONT WILL SLIDE SOUTHEAST INTO THE AREA TONIGHT AND
WEDNESDAY. THE FRONT WILL STALL IN THE AREA WEDNESDAY NIGHT AND A
LOW PRESSURE WILL RIDE EASTWARD ALONG THE FRONT ON THURSDAY. THE
FRONT WILL SLIDE SOUTH OF THE AREA FRIDAY AND WEAKEN. HIGH PRESSURE
WILL DOMINATE OVER THE WEEKEND.

&&

.NEAR TERM /THROUGH WEDNESDAY NIGHT/...
S/WV ENERGY HAS SUPPORTED TSRA CROSSING WVA AND INTO THE CWFA. AMS
AHD OF LINE HAS SUFFICIENT INSTBY...ALTHO THAT LVL DIMINISHES
FURTHER EAST. /2000+ J/KG CAPE FROM RNK SNDG BUT LESS THAN 1000
J/KG AT IAD./ SHEAR PROFILES NOT THAT GREAT...PLUS DIURNAL HEATING
HAS BEEN LOST WITH THE SETTING SUN. OVERALL...XPCT TSRA TO BE
NON- SVR...AND WKNG THRU THE EVNG. SOME GUSTY WINDS /30-40 KT/
PSBL NEXT HR OR TWO. HV BUMPED POPS UPWD W OF THE BLURDG ONCE
ALREADY...AND BASED ON LTST TRENDS SUSPECT I/LL BE DOING IT YET
AGAIN. RAP RUNS SUGGEST IT MAY MAKE IT TO DC...ALTHO LTST RAP LESS
EMPHATIC THAN PRVS CYCLES.

COLD FRONT APPROACHES THE REGION WED MORNING...WITH INCRSG
COVERAGE OF PCPN OUT AHEAD OF THE SYSTEM. AS IT SEEMS TO BE WITH
COLD FRONTS THIS SUMMER...THE FLOW ALOFT BECOMES NEARLY
ZONAL...RESULTING IN THE FRONT TAKING A MORE EAST- WEST POSITION
THAN NE-SW. WITH THIS SET UP AS WELL...THE FRONT WILL HAVE MINIMAL
PROGRESSION TO THE SOUTH...WITH IT STALLING NEAR THE MASON-DIXON
WED-WED NIGHT. INSTABILITY LOOKS TO BE MARGINAL FOR MOST OF THE
DAY...BUT ENOUGH TO WARRANT TSTMS IN THE FORECAST. OVERALL
DYNAMICS WOULD KEEP ANY SVR THREAT MINIMAL.

DESPITE THE CLOUD COVER...HIGH TEMPS ON WED EXPECTED INTO THE
UPPER 80S TO LOWER 90S. HEAT INDICES WILL REMAIN BELOW THE CENTURY
MARK.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
WAVE OF LOW PRESSURE WILL RIDE ALONG THE FRONT TO OUR NORTH ON
THURSDAY. THIS WILL ALLOW WARM AIR TO REMAIN AND HIGHS MAY ONCE
AGAIN REACH THE 90S ACROSS MUCH OF THE AREA. MOST OF THE UPPER LEVEL
ENERGY WITH THIS WAVE APPEARS TO STAY NORTH OF US...BUT SUGGEST A
DECENT AMOUNT OF SHEAR AND CAPE...SO A STRAY SEVERE THUNDERSTORM
DOESNT LOOK IMPOSSIBLE. AS THE LOW PASSES TO THE NORTH THE COLD
FRONT WILL SLIDE SOUTHEAST ACROSS OUR AREA THURSDAY
NIGHT...PUTTING AN END TO THE 90S FOR A DAY OR TWO. HUMIDITY WILL
ALSO LOWER AND THE CHANCE OF SHOWERS AND THUNDERSTORMS APPEARS
PRETTY LOW ON FRIDAY...BUT DID NOT COMPLETELY REMOVE THEM FROM THE
FORECAST JUST YET IN CASE FUTURE MODELING IS SLOWER IN DRAGGING
THE FRONT THROUGH.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
COLD FRONT WEAKENS AND MOVES AWAY FROM THE REGION FRI NIGHT AS A
HIGH PRES BUILDS IN FOR SAT. UPPER FLOW TRANSITIONS TO NW INTO SUN
AS A FRONTAL BNDRY LIFTS LATER THAT DAY. UPPER LEVEL DISTURBANCES
AFFECTS THE AREA MON INTO TUE. BEST CHANCE FOR PRECIP APPEARS TO
BE SUN THROUGH TUE. TEMPS WILL BE CLOSE TO NORMAL.

&&

.AVIATION /01Z WEDNESDAY THROUGH SUNDAY/...
GENERALLY VFR CONDITIONS THRU THE NGT. LINE OF TSRA CROSSING THE
APLCNS ATTM. XPCT A BIT OF A WEAKENING TREND...BUT A FEW STORMS
LKLY WL MAKE IT TO THE BLURDG. LOW CONFIDENCE WHAT WL HPPN
THEREAFTER. MRB NEAREST STORMS...AND ADDED MVFR TEMPO GROUP TO
TAF. HWVR...A BREAK HAS DVLPD IN THE LINE...AND ITS PSBL THAT EVEN
MRB MAY MISS THIS ACTIVITY. AM WITHHOLDING ANY MENTION DC/BALT
METROS ATTM SINCE CONFIDENCE TOO LOW. WORST CASE SCENARIO WOULD BE
FOR BRIEF AOB IFR W/ GUSTY WINDS 30-40 KT. BASED ON CURRENT
SPEED...EXTRAPOLATION BRINGS PCPN TO MRB BTWN 02-03Z...CHO/IAD
BTWN 03-04Z...AND ELSW AFTR 04Z /ASSUMING IT SURVIVES/.

THE BETTER CHC FOR PCPN IMPACTING THE TERMINALS TOMORROW. COULD
SEE PCPN AS EARLY AS 12Z...BUT INCRSG CHC AFTR 15/16Z...LASTING
THRU THE AFTN...TAPERING OFF WED EVENING. SUB-VFR CONDITIONS PSBL
IN ANY STORM.

WINDS S-SW THIS AFTN 8-12 KTS...BCMG S 5 KTS OR LESS TONIGHT.
WINDS WILL INCREASE AGAIN FROM THE SW AFTR 12Z WED...BCMG
LIGHT/VRB WED NIGHT AS THE FRONT STALLS OVER THE REGION. DEPENDING
ON WHERE THE BOUNDARY ALIGNS...COULD SEE SUB-VFR CONDITIONS WITH
DEVELOPING STRATUS/FOG.

MAIN CONCERN THURSDAY IS POTENTIAL FOR A GUSTY THUNDERSTORM DURING
THE AFTERNOON AND EVENING. CONDITIONS SHOULD OTHERWISE BE VFR WITH
SOUTHWESTERLY WINDS BECOMING NORTHWESTERLY ON FRIDAY.

VFR CONDITIONS EXPECTED FOR FRI NIGHT THROUGH THE WEEKEND.

&&

.MARINE...
SUB-SCA CONDITIONS ON THE WATERS ATTM. AS THE FRONT NEARS
TONIGHT...COULD SEE INCRSG SLY FLOW...RESULTING IN CHANNELING ON
THE CHESAPEAKE BAY. WILL MAINTAIN THE SCA FOR NOW...BUT WL BE
REEVALUATING IT SHORTLY. AS THE WINDS VEER TO THE SW WED...SUB-
SCA CONDITIONS.

LOW PRESSURE PASSING TO THE NORTH MAY BRING SOME SCA-LEVEL WINDS TO
THE WATERS ON THURSDAY. WINDS APPEAR TO DIMINISH BY FRIDAY AFTERNOON
AFTER THE SYSTEM HAS PASSED OUR AREA. THUNDERSTORMS WILL ALSO REMAIN
A CONCERN THURSDAY.

SUB-SCA CONDITIONS EXPECTED FOR FRI NIGHT AND SAT.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 8 AM EDT WEDNESDAY FOR ANZ533-534-
     537-541>543.

&&

$$
SYNOPSIS...SEARS/RCM
NEAR TERM...HTS/SEARS
SHORT TERM...RCM
LONG TERM...IMR
AVIATION...HTS/SEARS/RCM/IMR
MARINE...HTS/SEARS/RCM/IMR



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