AFDAKQ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WAKEFIELD VA
433 PM EDT THU JUL 7 2011

.SYNOPSIS...
AN UPPER LEVEL TROUGH OF LOW PRESSURE WILL REMAIN TO OUR WEST
TONIGHT...THEN AMPLIFY ON FRIDAY AS IT MOVES CLOSER TO THE REGION.
THIS WILL PUSH A COLD FRONT THROUGH THE MID ATLANTIC STATES FRIDAY
NIGHT INTO SATURDAY. DRIER CONDITIONS WILL MOVE INTO THE AREA FROM
SATURDAY AFTERNOON THROUGH SUNDAY...AS HIGH PRESSURE BUILDS IN
FROM THE NORTHWEST.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
LATEST SFC ANALYSIS SHOWS A WEAK TROUGH EXTENDING FROM N OF DC
SOUTHWEST TO ROANOKE. SCATTERED CONVECTION HAS DEVELOPED ALONG AND
AHEAD OF THE FRONT...HAVING REACHED THE CONVECTIVE TEMP (UPPER
80S)...SUPPORTED BY A FVRBL LLVL THERMODYNAMIC SETUP (SFC BASED
CAPES BTWN 3000-3500 J/KG. TOTAL-TOTALS IN THE MID-UPR 40S ARE
INDICATIVE OF THE MEAGER MID LVL LAPSE RATES (5.5 TO 6 C/KM BTWN
700-500 MB)...HOWEVER...K INDICES IN THE 20S WITH WET BULB ZERO
HEIGHTS AROUND 11500 KFT (SOME 3000 KFT LOWER THAN THE FREEZING
LEVEL) ARE INDICATIVE OF FAIRLY PRONOUNCED DRY AIR AT MID LEVELS.
THIS MAY PROVIDE SOME BRIEF GUSTY TSTM WIND GUSTS AND POTENTIALLY
SOME SMALL HAIL...DESPITE (AGAIN) THE WEAK LAPSE RATES AND LIGHT
WINDS ALOFT (<25 KT).

OVERNIGHT...MID/UPR LEVELS MOISTEN UP ONCE AGAIN AHEAD OF THE
APPROACHING MID LVL SHORTWAVE...WITH DEEP LAYER SW FLOW AS THE
WARM CONVEYOR BELT (WCB) EXPANDS BACK ACROSS THE MID ATLC REGION.
PWATS CLIMB BACK CLOSE TO 2" BY EARLY FRI MORNING...WITH K INDICES
INTO THE MID 30S OVER WRN PTNS. MODELS SHOW MINIMAL FORCING
OVERNIGHT TO FOCUS ANY ADDITIONAL CONVECTION...THOUGH DO INDICATE
VERY WEAK (SUBTLE) LOW-MID LEVEL QVECTOR CONVERGENCE AND SLIGHTLY
STRENGTHENING LLVL FGEN. SO...WITH THIS ALONG WITH DEEPENING MOIST
LAYER...WILL MAINTAIN A MENTION OF ISOLATED-SCATTERED POPS OVERNIGHT.
MIN TEMPS GENERALLY AROUND 70-LOWER 70S.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/...
MODELS REMAIN IN GOOD AGREEMENT WITH MID/UPPER LEVEL PATTERN OF AN
AMPLIFYING TROUGH OVER THE OHIO/TN VALLEYS ON FRI...CROSSING THE
MTNS FRI NIGHT INTO SAT MORNING. DYNAMICS WITH THIS SYSTEM IS RATHER
IMPRESSIVE FOR EARLY JULY...WITH A DECENT SWATH OF RRQ UPPER JET
FORCING (70-75 KT JET CORE AT 300 MB)...WITH THE ATTENDANT LOW-MID
LEVEL FGEN AND QVECTOR CONVERGENCE. MEANWHILE...DEEP LAYER
MOISTENING CONTINUES AHEAD OF THE FRONT...AS PWATS CLIMB TO OR
JUST ABOVE 2.25". THEREFORE HAVE CONTINUED WITH THE HIGH (>50%)
POPS WITH THE FRONTAL PASSAGE...AS WELL AS WITH THE LOCALLY HEAVY
RAIN MENTION DURING THIS PERIOD. WILL ALSO HIGHLIGHT THE RISK OF
LOCALLY HEAVY (LOCALIZED FLOODING) IN THE HWO. ALSO...SHEAR
INCREASES LATER FRI SO THERE WILL BE AN ENHANCED RISK FOR SEVERE
STORMS FRI AFTN/EVENING. LIMITING FACTOR WILL BE HOW MUCH SUN WE
CAN GET ON FRI...MAIN THREATS WILL BE WET MICROBURSTS AND LARGE
HAIL. HIGHS FRI WILL BE HELD DOWN SOMEWHAT BY CLOUDS...MAINLY IN
THE MID-UPPER 80S.

WILL LINGER POPS SAT MORNING...ESPECIALLY EAST...WITH DRIER AIR
MOVING IN BY AFTN FROM THE NW. HIGHS SAT 85-90...COOLEST EAST
WHERE CLOUDS HANG AROUND THE LONGEST. COOLER SAT NIGHT WITH LOWS
INTO THE 60S OVER NW 1/2 OF CWA...AROUND 70 SE. DRY ON SUN WITH
SEASONABLY WARM TEMPS (HIGHS FROM THE MID 80S ALONG THE ATLC COAST
TO THE LOWER 90S FARTHER INLAND).

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
GOING WITH A COMBINATION OF THE 12Z GFS/ECMWF FOR THE EXTENDED
PERIOD. HI PRES MOVING OFF THE NRN MID ATLC CST WILL MAINTAIN DRY WX
SUN NGT AND MON. A COLD FRNT WILL APPROACH FM THE NNW LATE MON NGT
THEN PUSH INTO AND ACRS THE REGION TUE INTO WED. THIS WILL RESULT IN
ANOTHER SLGT OR SML CHC OF SHOWERS AND TSTMS. HI PRES WILL BLD BACK
IN FM THE NNE FOR LATE WED THRU THU.

MIN TEMPS WILL BE IN THE UPR 60S TO LWR 70S MON MORNG...IN THE LWR
TO MID 70S TUE AND WED MORNGS...AND IN THE MID 60S TO LWR 70S THU
MORNG. MAX TEMPS WILL BE IN THE UPR 80S TO MID 90S MON...IN THE UPR
80S TO LWR 90S TUE...IN THE MID 80S TO NEAR 90 WED...AND IN THE MID
TO UPR 80S THU.

&&

.AVIATION /20Z THURSDAY THROUGH TUESDAY/...
MAINLY VFR CONDITIONS EXPECTED ACRS THE AREA FOR THE TAF
PERIOD...WITH JUST ISLTD CONVECTION AND MVFR CIGS/VSBYS POSSIBLE.
MOST OF THIS ACTIVITY SHUD REMAIN OVR NC. HAVE NOT INCLUDED A CB
GROUP ATTM...DUE TO UNCERTAINTY IN TIMING/LOCATION OF ANY CONVECTION.

OUTLOOK...SCTD CONVECTION LIKELY FM MIDDAY FRI THRU SAT WITH AREAS
OF MVFR/IFR POSSIBLE...AS COLD FRNT/AREAS OF LO PRES PUSH ACRS THE
REGION. MAINLY VFR/DRY CONDITIONS THEN EXPECTED SUN AND MON.

&&

.MARINE...
NO HEADLINES IN THE SHRT TERM TNGT THRU SAT. HI PRES WILL BE WELL
OFF THE MID ATLC/SE CST TNGT. A FRNTL BNDRY WITH AREAS OF LO PRES
MOVNG ALNG IT...WILL PUSH ACRS THE AREA FRI THRU SAT. HI PRES WILL
BLD BY TO OUR NNE AND OFF THE CST FOR LATE SAT THRU MON. ANOTHER
COLD FRNT WILL DROP INTO THE REGION DURING TUE. WND SPDS/WAVES/SEAS
WILL REMAIN BELOW SCA LVLS THRU THE PERIOD.

&&

.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
NC...NONE.
VA...NONE.
MARINE...NONE.

&&

$$
SYNOPSIS...BKH