Hail and Damaging Winds in Pennsylvania, July 17, 2010

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
207 PM EDT SAT JUL 17 2010

.SYNOPSIS...
A SERIES OF DISTURBANCES WILL CROSS THE REGION THROUGH THE MIDDLE
OF NEXT WEEK...BRINGING CHANCES OF SHOWERS AND THUNDERSTORMS. WARM
AND HUMID CONDITIONS WILL CONTINUE.

&&

.NEAR TERM /THROUGH SUNDAY/...
CUMULUS BUILDUPS PREVAIL ACROSS THE AREA THIS AFTN...WITH SHWRS/TSTMS
DEVELOPING ALONG A SURFACE BOUNDARY ACROSS SOUTHERN ONTARIO.
FURTHER SOUTH...AN ISOLATED SHWR OR TWO IS BEGINNING TO DEVELOP.
CONVECTIVE ACTIVITY WILL INCREASE LATE THIS AFTN AS AN UPPER LEVEL
SHORTWAVE/SURFACE TROUGH MOVES INTO THE REGION. HIGH RESOLUTION
MODELS DEPICT A BAND OF SHWRS/TSTMS DEVELOPING ALONG THE TROUGH
THIS EVENING...DIMINISHING AFTER MIDNIGHT. WILL USE SCATTERED POPS
FOR THIS POTENTIAL. WITH THE GREATEST DEEP LAYER SHEAR REMAINING
TO THE NORTH...DO NOT EXPECT ORGANIZED SEVERE STORMS...BUT AN
ISOLATED STRONGER STORM WITH GUSTY WINDS/HEAVY RAIN CANNOT BE
RULED OUT.

THE NEXT SHORTWAVE IN ZONAL FLOW IS PROGGED TO AFFECT THE AREA
LATE SUNDAY AFTN/NIGHT. AFTER A BREAK FROM PRECIP LATE TNGT
INTO SUNDAY AFTN...SHWRS/TSTMS WILL REDEVELOP AHEAD OF THE
SHORTWAVE/SURFACE FRONT. WILL KEEP POPS LOW...WITH THE BULK
OF THE ACTIVITY REMAINING TO THE NORTH AND WEST THROUGH SUNDAY
AFTN. WARM AND HUMID CONDITIONS WILL CONTINUE.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
LOW PRESSURE AND A COLD FRONT WILL ENTER THE REGION SUNDAY
NIGHT...CROSSING THE AREA MONDAY. WITH DECENT RUN TO RUN CONTINUITY
WITH TIMING...AND GENERAL MODEL AGREEMENT...WILL RAISE POPS MONDAY
TO LIKELY WITH THE FRONTAL PASSAGE. MODELS CONTINUE TO SHOW THE
FRONTAL BOUNDARY HANGING UP ACROSS WEST VIRGINIA...SO WILL KEEP
CHANCE POPS IN THE FCST THROUGH TUESDAY. WITH MORE CLOUDS AND
HIGHER COVERAGE OF PRECIP...DAYTIME TEMPERATURES WILL BE HELD
DOWN SOME...WITH LOWER/MID 80S PREVAILING...BUT HUMID CONDITIONS
WILL PERSIST.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
THE UPPER OHIO VALLEY WILL CONTINUE TO BE IN A PRIMARILY ZONAL
MID-LEVEL FLOW ON THE NORTHERN PERIPHERY OF A DEEP RIDGE CENTERED
ACROSS THE SOUTHEAST. THIS MID-LEVEL LEVEL PATTERN WILL BE
ACCOMPANIED BY A SURFACE FRONTAL BOUNDARY DRAPED ACROSS THE AREA.
GFS/ECMWF ARE IN AGREEMENT WITH THIS PATTERN...LEADING TO A CONTINUED
UNSETTLED WEATHER PATTERN IN THE FORECAST.

THE PERIOD BEGINS WITH A SHORT WAVE ADVECTING EAST OF THE AREA
TUESDAY NIGHT...WITH CHANCE POPS FORECAST. WITH THE UPPER OHIO
VALLEY IN A MOIST AND UNSTABLE AIR MASS...DIURNALLY DRIVEN
CONVECTION CAN BE EXPECTED ON WEDNESDAY...ALTHOUGH POPS ARE
RESTRICTED TO A LOW CHANCE WITH THE LACK OF A FORCING MECHANISM.
POPS ARE HIGHER ON THURSDAY WITH THE GFS INDICATING A SURFACE LOW
PROGGED TO BE ACROSS THE GREAT LAKES. SIMILAR TO WEDNESDAY...LOW
CHANCE POPS ARE FORECAST ON FRIDAY...WITH DIURNALLY DRIVEN
CONVECTION POSSIBLE AS A COLD FRONT APPROACHES FROM THE NORTHWEST.
TEMPERATURES THROUGHOUT THIS PERIOD WILL BE AROUND 5 TO 10 DEGREES
ABOVE NORMAL.

A COLD FRONT IS PROGGED TO FINALLY CLEAR SOUTHEAST OF THE AREA
FRIDAY NIGHT WITH HIGH PRESSURE BUILDING IN FROM THE NORTHWEST. THIS
WILL ALLOW FOR A DRIER AND COOLER AIR MASS TO ADVECT INTO THE
AREA...WITH A DRY FORECAST TO START THE WEEKEND. DESPITE THE FRONTAL
PASSAGE...MORE ABUNDANT SUNSHINE WILL ALLOW TEMPERATURES ON SATURDAY
TO BE AROUND 5 DEGREES ABOVE NORMAL.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
VFR CONDITIONS WILL PREVAIL INTO THE EVENING ALTHOUGH AN ISOLATED
THUNDERSTORM CANNOT BE RULED OUT IN THIS WARM AND MOIST
ENVIRONMENT. SCATTERED TO BROKEN CUMULUS WILL DEVELOP THIS
AFTERNOON WITH SOUTHWESTERLY WINDS GUSTING TO 20KTS. MORE
ORGANIZED CONVECTION WILL DEVELOP ALONG A SURFACE TROUGH ACROSS
LAKE ERIE LATE THIS AFTERNOON...ADVANCING SOUTHEASTWARD TO
KFKL/KDUJ AROUND 00Z. TEMPO GROUPS ARE FORECAST AT KFKL/KDUJ AFTER
AROUND 00Z. AS THE LINE ADVANCES FURTHER SOUTHEASTWARD...DIURNALLY
LESS FAVORABLE TIMING HAS DICTATED ONLY CB GROUPS ACROSS THE REST
OF THE TERMINALS AS CONVECTION SHOULD WEAKEN AND DECREASE IN
COVERAGE.

LINGERING CONVECTION WILL DIMINISH BY 06Z...WITH PATCHY MVFR FOG
DEVELOPING AT MOST OF THE TERMINALS NEAR DAWN. VFR CONDITIONS WILL
PREVAIL FOR THE MAJORITY OF SUNDAY BEFORE CONVECTION APPROACHES FROM
THE WEST IN THE LATE EVENING HOURS.

SHOWER AND THUNDERSTORM CHANCES ALONG WITH THE POTENTIAL FOR NEAR
DAWN RESTRICTIONS WITH FOG WILL CONTINUE MONDAY THROUGH THURSDAY AS
A SERIES OF DISTURBANCES CROSS THE UPPER OHIO VALLEY.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
OH...NONE.
PA...NONE.
WV...NONE.

&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE PITTSBURGH PA
1055 AM EDT SAT JUL 17 2010

MDZ001-OHZ039>041-048>050-057>059-068-069-PAZ007>009-013>016-020>023-
029>032-WVZ001>004-012-021>023-041-181800-
GARRETT-TUSCARAWAS-CARROLL-COLUMBIANA-COSHOCTON-HARRISON-
JEFFERSON OH-MUSKINGUM-GUERNSEY-BELMONT-NOBLE-MONROE-MERCER-VENANGO-
FOREST-LAWRENCE-BUTLER-CLARION-JEFFERSON PA-BEAVER-ALLEGHENY-
ARMSTRONG-INDIANA-WASHINGTON-WESTMORELAND-GREENE-FAYETTE-HANCOCK-
BROOKE-OHIO-MARSHALL-WETZEL-MARION-MONONGALIA-PRESTON-TUCKER-
1055 AM EDT SAT JUL 17 2010

THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN MARYLAND...EAST
CENTRAL OHIO...NORTHWEST PENNSYLVANIA...SOUTHWEST
PENNSYLVANIA...WEST CENTRAL PENNSYLVANIA...NORTHERN WEST VIRGINIA
AND NORTHERN PANHANDLE OF WEST VIRGINIA.

.DAY ONE...TODAY AND TONIGHT.

SCATTERED THUNDERSTORMS WILL DEVELOP THIS AFTERNOON AND EVENING.
A FEW OF THE STORMS WILL PRODUCE GUSTY WINDS AND LOCALLY HEAVY
RAIN.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY.

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SUNDAY AFTERNOON
AND NIGHT. THE PRIMARY SEVERE WEATHER THREAT WILL BE DAMAGING
THUNDERSTORM WINDS.

.SPOTTER INFORMATION STATEMENT...

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.