Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 300059
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
859 PM EDT FRI AUG 29 2014

.SYNOPSIS...
HIGH PRESSURE OVER OHIO WILL MOVE OFFSHORE THIS WEEKEND. A WARM FRONT
WILL LIFT NORTH THROUGH THE AREA LATE SATURDAY. A COLD FRONT WILL
APPROACH DURING THE FIRST PART OF THE NEW WEEK.

&&

.NEAR TERM /THROUGH SATURDAY/...

A BEAUTIFUL EVENG COURTESY OF HIGH PRES CENTERED NEAR ACK. TEMPS
IN THE U60S/L70S...DWPTS IN THE 50S. TOUGH TO BEAT THAT ENTERING A
HOLIDAY WKND.

WL DVLP A LGT SELY FLOW TNGT...ENUF TO BRING IN SOME LWR CLDS
AFTR MIDNGT. WL KEEP PATCHY FOG REFERENCE TO THE CENTRAL SHEN VLY
AND CENTRL FOOTHILLS. AM NOT REAL CONFIDENT THAT WL TAKE PLACE.
THE ANTICIPATED MSTR ADVCTN SHUD BUMP DEWPTS TO NEAR 60F... AND
THUS MIN-T LWR-MID 60S REASONABLE W/ THE XCPTN OF THE WARMER
CITIES.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/...
BELIEVE THAT THE RDGG ALOFT WL BE THE PRIMARY WX INFLUENCE SAT.
GDNC SUGGESTING THAT A WMFNT WL ENTER CWFA MID-LT AFTN.
SUBSEQUENTLY INSTBY INCREASES BHD FNT. GFS CURIOUSLY ATTEMPTING TO
FIRE OFF TSRA ALONG WMFNT WHILE STRONG MID-LVL DIVERGENCE
/SUBSIDENCE/ DOMINATES. SHEAR NIL. INSTEAD...BELIEVE THAT PRIMARY
FOCUS FOR ANY STORMS WUD BE OROGRAPHICALLY INDUCED. HV BKN OR NEARLY
BKN CLDS FOR THE DAY...BUT FOCUSED POPS ON THE MTNS. SINCE CAPE
BUILDS THRU THE EVNG...CHC TSRA WL LINGER LATER INTO THE NGT.

THE RDGG STARTS TO BREAK DOWN SUNDAY...W/ DEEPER SWLY FLOW
PREVAILING. THAT WL SUPPORT A STREAM OF PWAT AOA 2 INCHES TO RIDE
THRU CWFA COINCIDENT W/ DECENT INSTBY. WHILE EXACT CORRIDOR OF
CAPE/MSTR LKLY WL ADJUST W/ FUTURE MODEL RUNS...SUSPECT THE MAIN
IDEA WL REMAIN THE SAME. HENCE...XPCT DECENT CVRG OF TSRA...1ST
IN THE MTNS BY MIDDAY...AND DROPPING INTO A DVLPG LEE TROF ALONG
THE I-95 CORRIDOR BY END OF THE AFTN INTO THE EVNG. HV LKLY POPS
IN GRIDS...AND PSBL HVY RAIN WORDING IN HWO.

TEMPS WL BE MODERATING ON SAT. WL BE STAYING W/ THE WARMER MAX
MAXT. MOS MEAN MAXT NOT FAR OFF FM GOING FCST SUN...AND CHGS
MINIMAL. SIMILARLY...CHGS TO MIN-T SAT AND SUN NGT MINOR. HIGHS IN
THE M80S

WHILE IT WL BE HOT BY SUN...W/ DEWPTS AOA 70F...RESULTING
HEAT INDEX VALUES SHUD REMAIN UNDER 100F. THEREFORE...DO NOT
ANTICIPATE ANY HEAT HEADLINES...EVEN THO ITS A HOLIDAY WKND.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
THE UPPER LEVEL SUBTROPICAL HIGH OVER THE SOUTHEAST WILL MIGRATE
WESTWARD TO OVER THE MISSISSIPPI VALLEY MONDAY. THIS WILL CHANGE THE
DIRECTION OF THE UPPER LEVEL FLOW LOCALLY TO BE A BIT MORE
NORTHEASTERLY...WHICH WILL RESULT IN A MARGINAL ENHANCEMENT OF
INSTABILITY MONDAY EVENING. AT THE SURFACE...A WELL DEFINED LEE
TROUGH FORMING IN MOIST SOUTHERLY FLOW WILL FURTHER PROMOTE
INSTABILITY...ESPECIALLY ALONG THE VA AND MD PIEDMONT REGIONS. PWATS
MONDAY WILL BE SLIGHTLY LESS THAN SUNDAY...BUT WITH VALUES STILL
AROUND 2 INCHES AND PLENTY OF INSTABILITY LOCALIZED FLASH FLOODING
REMAINS A THREAT. DESPITE A NICELY CURVED HODOGRAPH...WEAK
SHEAR...0-6 KM SHEAR VALUES OF LESS THAN 20 KTS...SHOULD KEEP THE
SEVERE POTENTIAL LOW MONDAY EVENING. THUNDERSTORMS SHOULD BEGIN TO
DIE OUT AFTER SUNSET AS THEY LOOSE THEIR DIURNAL ENHANCEMENT.

HIGH PRESSURE OFF THE COAST WILL RIDGE DOWN ACROSS THE SOUTHEAST US
TUESDAY. MEANWHILE...A DEEP LOW PRESSURE SYSTEM WELL NORTH OF THE
GREAT LAKES WILL SWING A COLD FRONT SOUTH FROM THE OHIO VALLEY TO
THE NEW ENGLAND STATES. THIS FRONT WILL STRUGGLE TO GET INTO THE
MID-ATLANTIC TUESDAY DUE TO THE HIGH BUILDING TO OUR SOUTH. THE
RESULT WILL BE A MORE WESTERLY/DOWNSLOPING COMPONENT TO THE LOW
LEVEL FLOW. THIS SHOULD HELP TO SUPPRESS MOST CONVECTION
TUESDAY...ESPECIALLY COMPARED TO SUNDAY AND MONDAY. IF THUNDERSTORMS
DO FORM...THE MOST LIKELY LOCATION WILL BE ALONG THE
MASON-DIXON...WHERE THE FLOW WILL BE MORE SOUTHERLY THAN ACROSS THE
SOUTHERN PART OF THE CWA.

THE FRONT WILL FINALLY REACH OUR AREA WEDNESDAY...THOUGH WITH LITTLE
MOISTURE LEFT IT SHOULD BE MOSTLY DRY. THE PRIMARY IMPACT FROM THE
FRONTAL PASSAGE...WHICH SHOULD OCCUR FROM NORTH TO SOUTH OVER THE
COURSE OF THE DAY WEDNESDAY...WILL BE A DROP IN HUMIDITY AND
SLIGHTLY COOLER TEMPS FOR THE SECOND HALF OF THE WORKWEEK. EXPECT
HIGHS NEAR 90 MONDAY AND INTO THE LOWER 90S TUESDAY...THE WARMEST
DAY OF THE WEEK...BEFORE DROPPING INTO THE UPPER 80S FOR THE SECOND
HALF OF THE WORKWEEK.

&&

.AVIATION /01Z SATURDAY THROUGH WEDNESDAY/...
VFR THRU MUCH OF THE VALID TAF PD. A LGT SELY FLOW DVLPG AFDK MAY
SUPPORT ADVCTN OF A LOWER CLD DECK AFTR MIDNGT. NOT COMPLETELY
SOLD ON THAT...SPCLY IF THERE WL BE ANY SUBSEQUENT FLGT
RESTRICTIONS. FLLWG LEAD OF PRVS TAF...CONFINING MVFR TO CHO
ONLY. BY AFTN...CIGS LKLY BKN035-040 W/ SELY WNDS AOB 10 KT.

SUN-TUE...SCT-NMRS TSRA...LRGLY DIURNALLY DRIVEN. LCL FLGT
RESTRICTIONS PSBL...BUT CANNOT PINPOINT WHERE ATTM.

WL BE POST-FROPA BY WED. VFR.

&&

.MARINE...

VRBL WINDS AOB 10 KT AS HIPRES OVHD. RDG WL MV E OF THE DELMARVA...
SUPPORTING A SELY FLOW TNGT AND SAT...AND SLY FLOW BY SAT NGT.
WNDS SHUD REMAIN AOB 10 KT THRU SAT. GRADIENT DOES INCR SAT NGT-
SUN...BUT IT DOESNT LOOK LIKE GRADIENT FLOW WL MIX TO THE SFC. HV
CAPPED WNDS AT 15 KT.

HV A TSRA THREAT LT SUN INTO SUN EVE. A HIGH WIND THREAT WL
ACCMPNY THESE STORMS. SPECIAL MARINE WRNGS PSBL...CONTG THRU MON.

&&

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

&&

$$
UPDATE...WOODY!
PRVS...HTS/CEB






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