000
FXUS61 KLWX 041917
AFDLWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
317 PM EDT FRI JUL 4 2008
.SYNOPSIS...
A STATIONARY FRONT WILL LINGER ACROSS MARYLAND...VIRGINIA AND WEST
VIRGINIA THROUGH THE WEEKEND AS A SEQUENCE OF UPPER DISTURBANCES
IMPACTS THE MID ATLANTIC. MOISTURE WILL REMAIN IN PLACE THROUGH
NEXT WEEK...WITH UNSETTLED WEATHER TO CONTINUE THROUGH AT LEAST
MID WEEK.
&&
.NEAR TERM /UNTIL 8 PM THIS EVENING/...
A SOLID SHIELD OF 5-7KFT STRATUS W/ EMBEDDED CB/S OVERLAID ACROSS
THE WRN HALF OF THE CWA. THE POTOMAC HILANDS WILL CONTINUE W/
STRATIFORM SHRA THRU THE AFTN/EVNG. THE ERN EDGE OF THIS LIGHT/MOD
PRECIP MOVING ENE INTO NRN MD OVR THE COURSE OF THE EARLY
AFTN...WHICH WILL CONT TO LIMIT INSTABILITY FOR THE POTOMAC RIVER
VALLEY INTO THE DC METRO AREA. DWPNTS REMAIN IN THE MID 60S W/
LITTLE BNDRY LAYER MIXING OCCURRING THIS MRNG. THE ERN HALF OF THE
CWA W/ THE MOST CLEARING...THO FAIRLY HAZY AND LIMITED TIME LEFT
BEFORE THE WRN ACTIVITY OVERTAKES THE PIEDMONT REGION. IN-SITU
LAPS CAPE VALUES INCR ACROSS ERN MD AND INTO THE PIEDMONT OF N CNTL
VA /UPWARD OF 1500-2000 J/KG/ BTWN THE BLUE RIDGE AND I-95.
COMBINATION INDICES TARGET THE SRN PORTION OF THE BLUE RIDGE NEAR
KCHO...INTO THE REGION S OF I-66.
WEAK LOW LEVEL FLOW NOT FAVORABLE FOR MOISTURE CONVERGENCE...EVEN
ACROSS THE STNRY BNDRY ACROSS N CNTL VA. WEAK LAPSE RATES AS THE
COLUMN HAS REMAINED FAIRLY MOIST. OUTFLOW FROM OROGRAPHIC CONVTN
WILL HAVE TO BE THE MECHANISM FOR SUBSEQUENT ACTIVITY FURTHER
EAST. PSBL MESOSCALE DYNAMICS MAY AID IN DEVELOPMENT AS A MID
LEVEL MCV BEGINNING TO SHAPE UP OVER CNTL WV...STEERING PORTIONS
OF THE ACTIVITY ACROSS THE MID ATLNC. ALREADY SHOWING SOME WEAK
LEFT-MOVING STORMS. SO EVEN W/ THE WEAK AND FAIRLY UNFAVORABLE IN-
SITU CONVTVE PARMS...THE APRCHNG DYNAMICS MAY PROVIDE NECESSARY
STEERING/FORCING TO MAXIMIZE THE AVAILABLE INSTABILITY.
&&
.SHORT TERM /8 PM THIS EVENING THROUGH 6 PM SATURDAY/...
THE QUESTION MARKS FOR THE NIGHTTIME HRS REMAIN...AS THE CONVTN FROM
THIS AFTERNOON WILL DETERMINE THE COVERAGE OF SHRA ACTIVITY DURING
THE NIGHTTIME HRS. THE NRN HALF OF THE CWA LOOKS TO HAVE THE MOST
COVERAGE AND LONGEST TIME PERIOD OF INTERMITTENT RAINFALL
OVERNIGHT...INTO THE EARLY MRNG HRS. LIKELY POPS TO COVER MUCH OF
THE REGION THRU SAT. THE ACTIVITY EXPTD TO REMAIN SCT/D ACROSS THE
SRN HALF OF THE CWA AS THE SFC BNDRY BEGINS TO PUSH N/WRD AS A WEAK
WARM FRONT. PWATS WILL CONT TO REMAIN FAIRLY HIGH THRU THE DAY...W/
SIMILAR CHARACTERISTICS FROM FRIDAY IN TERMS OF SVR/TSTM CHNCS.
FORCING WILL BE ORIENTED MORE SW-NE AS THE UPPER TROF SLOWLY DIGS
S/WRD INTO THE OHIO RVR VALLEY...PUSHING THE WAA REGIME UP THE ERN
SEABOARD. STEADY CLOUD COVER MAY INHIBIT MAX HEATING AND MAX INSTAB
PARMS...THO FORCING AND LL HELICAL VALUES WILL IMPROVE W/ THE
BETTER APRCHNG DYNAMICS.
&&
.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
ELONGATED UPR TROF TO REMAIN W AND SW OF FCST AREA THRU THE
WEEKEND AMID RELATIVELY WEAK MID LVL FLOW...WITH STATIONARY BNDRY
TO LINGER THRU SAT EVE.
INCRG SWLY MID LVL FLOW WILL AID IN DVLPMT OF WEAK LEE TROFFING...
WHICH WILL YIELD RETURN TO LGT SLY WINDS SUN AND MON...AND NWD MVMT
OF BNDRY. WITH QUALITY MSTR TO REMAIN IN AREA AND SVRL SHRTWV
TROFS TO MOVE ACRS THRU THE WEEKEND...PDS OF SHRA AND TSTMS APPEAR
LKLY SAT EVE THRU SUN EVE. POPS HIGHEST SUN THRU SUN EVE AS UPR
TROF DECOMPOSES AND EJECTS ACRS FCST AREA.
DP UPR LOW OVER N CNTRL CONUS/CNTRL CANADA MOVES EWD TWD GTLKS
REGION TUE THRU THU. APPEARS THAT SHRTWV RDGG SHOULD PROVIDE FOR
LWR CHCS PCPN TUE AND TUE EVE...AND WILL CARRY ONLY SLGT CHC POPS
MOST ZONES...SPCLY TUE EVE.
ZONAL TO SWLY FLOW ALOFT WILL DPN LEE TROF...INCR SLY SFC FLOW...
AND REINFORCE MSTR. ALSO...TREND IN MODELS HAS BEEN TO SLOW MVMT
OF THE UPR SYSTEM...AND HENCE ARRIVAL OF CDFNT HAS BEEN DELAYED TO
COINCIDE WITH PASSAGE OF ASSOCIATED SHRTWV TROF ON THU AFTN. HAVE
INCRD POPS THU AND THU EVE AS INTRUSION OF CDFNT XPCTD TO AID IN
TSTM DVLPMT.
MAXIMA WILL BE LIMITED BY CLOUD CVR IN SHRT TERM...WITH INCRG MAX
TEMPS BY MID WEEK.
&&
.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
FOR THE LATE AFTN HRS...I-95 TAF SITES STILL A FEW HRS OFF FROM
THE APRCHNG/DEVLPNG TSTMS. TSTM ACTIVITY WILL CONT TO BE OF SCT/D
NATURE...SO VCTS KEPT IN TAFS AS ORGANIZED CONVTN EXPTD TO HOLD-OFF
BEFORE TSTMS DECR IN INTENSITY AND BECOME AREAS OF STRATIFORM
RAINFALL INTO THE LATE NIGHT HRS AND OVERNIGHT. WEAK SFC WINDS AND
INCR MOISTURE OVERNIGHT WILL LIKELY DROP SITES INTO THE MVFR/IFR
CATS FOR THE EARLY MRNG HRS SAT.
TSTMS REMAIN IN FCST THRU EXTENDED PDS...AS MSTR CONTS IN PLACE
AND SVRL SHRTWV TROFS WILL PASS THRU THE MID ATLANTIC.
&&
.MARINE...
REMAINING FAIRLY QUIET ON THE WATERS THRU THE AFTN. TSTM ACTIVITY
ACROSS THE SHNDH VALLEY WILL CONT E/WRD DRNG THE LATE AFTN. BY LATE
EVNG AND OVERNIGHT...DEVELOPING TSTMS AND WIDESPREAD RAINFALL WILL
LIKELY OVERTAKE THE CHESPKE BAY REGION. WINDS EXPTD TO REMAIN FAIRLY
LIGHT AND BELOW SCA CONDS THRU SAT.
TSTMS REMAIN IN FCST THRU EXTENDED PDS...AS MSTR CONTS IN PLACE
AND SVRL SHRTWV TROFS WILL PASS THRU THE MID ATLANTIC.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...NONE.
&&
$$
SCHOOR/KRAMAR
NWS LWX Office Area Forecast Discussion
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