Severe Thunderstorm Warning 63, NWS Pittsburgh, PA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
245 PM EDT TUE JUN 25 2013

.SYNOPSIS...
WARM AND HUMID CONDITIONS WILL CONTINUE. IN ADDITION...SEVERAL
UPPER LEVEL DISTURBANCES WILL BRING THE CHANCE FOR SHOWERS AND
THUNDERSTORMS UNTIL A COLD FRONT PASSES ON THURSDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
LOOKS LIKE CONVECTION WILL CONTINUE TO DEVELOP IN THE VICINITY OF
THE TRAILING OUTFLOW BOUNDARY THAT IS CURRENTLY SET UP ROUGHLY
ALONG THE I-80 CORRIDOR. WHILE THE MESOSCALE ANALYSIS SUGGESTS
PLENTY OF INSTABILITY...WITH CAPE IN EXCESS OF 2500-3000
J/KG...SHEAR CONTINUES TO REMAIN MARGINAL AT BEST. THIS HAS LEAD
TO VERY DISORGANIZED STORMS THUS FAR.

HOWEVER...SEVERAL OF THE HI RES MODELS ARE CONTINUING TO SUGGEST A
BIT MORE ORGANIZATION BY LATE THIS AFTERNOON. BOTH THE HRRR AND
4KM NAM SUGGEST THAT A MCS WILL DEVELOP AND PROPAGATE ALONG THIS
SLOWLY SINKING BOUNDARY MENTIONED ABOVE...CROSSING THE FORECAST
AREA BY 8PM. NOT COMPLETELY SOLD ON MCS DEVELOPMENT BUT...SINCE THE
DETERMINISTIC MODELS CONTINUE TO SHOW A BREAK DOWN IN THE RIDGE AS
A WEAK SHORTWAVE MOVES ACROSS THE GREAT LAKES THIS
EVENING...BELIEVE THIS COULD BE ENOUGH TO AT LEAST HELP SOME STORMS
REACH STRONG TO SEVERE LEVELS. FOR NOW...CONTINUED THE SCATTERED
COVERAGE WORDING FOR THUNDERSTORMS AND WILL CONTINUE TO MONITOR
UPSTREAM TRENDS.

A SIMILAR SCENARIO REMAINS IN PLACE FOR WEDNESDAY. MODEL
SOUNDINGS CONTINUE TO SUGGEST A BRIEF NORTHWESTERLY WIND COMPONENT
AT MID LEVELS COULD POSSIBLY HELP SUPPORT STRONGER STORMS WEDNESDAY
AFTERNOON...BUT COVERAGE REMAINS UNCERTAIN.

A PERSISTENCE FORECAST FOR TEMPERATURES WAS MAINTAINED THROUGH THE
PERIOD.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
STRONG AGREEMENT AMONGST NCEP CHAIN ON A MODEST MID LVL WAVE
CROSSING THE WESTERN GREAT LAKES WED NGT INTO THUR.  CONFIDENCE HAS
INCREASED TO RAISE POPS FURTHER INTO THE CATEGORICAL RANGE.  TIME OF
DAY DOES NOT LEND ITSELF TO HAZARDOUS WEATHER...SO PRESENT THINKING
IS WE EXPERIENCE A WELCOME RAIN WITH SCATTERED SUB-SEVERE STORMS.
PROGRESSIVE PATTERN WITH IMPULSES CROSSING EVERY 18 TO 24 HOURS DOES
NOT LEND ITSELF MUCH TIME FOR INSERTION OF DRY WEATHER.  CONTINUED
WITH CHANCE POPS THE BALANCE OF SHORT TERM AS INHERITED DATASET
PRESENTLY ILLUSTRATES.

THERMODYNAMIC PARAMETERS ARE NOT IMPRESSIVE FRIDAY FOR A SEVERE
THREAT DESPITE A STRONG KINEMATIC ENVIRONMENT.  SBCAPES PUSH 2.0
KJKG-1 W OF I-77 ALONG WITH BETTER BL EQUIV POT TEMP ADV...BUT MID
LVL LAPSE RATES ARE MARGINAL /AROUND 5CKM-1 OR LESS/.

AS H5 CYCLONE COILS UP ACRS EASTERN CANADA...ASSOCIATED HEIGHT FALLS
WILL BRING COOLER AND LESS HUMID WEATHER OVER THE WEEKEND.
INTERSECTION OF INSTABILITY AND LIFT WILL COINCIDE ON THE LEADING
EDGE OF H7-H3 DCVA SUPPORTING RW/TRW DEVELOPMENT CLOSER TO LAKE
ERIE.  A COLD FRONT ENCROACHES SAT NGT BUT LIMITED MOISTURE
ACCOMPANIES IT.

DUE TO STAGNANT PATTERN LEANED HEAVILY ON BIAS CORRECTED MOSGUIDE
GRIDS FOR TEMPS WHICH HAVE PREFORMED WELL RECENTLY.

&&

.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
A SERIES OF SHRTWVS WL CONT TO DROP SE ACRS THE GT LKS RGN THRU
MOST OF THE PD. THIS WL SPPRT SHWR/TSTM CHCS AT LEAST THRU SAT.
MOISTURE MORE IN QUESTION BY SUN SO ONLY MENTIONED SLGT CHC POPS
THEN. OTRW...WENT NO HIGHER THAN CHC POPS ATTM DUE TO TIMING
UNCERTAINTIES IN INDIVIDUAL SHRTWVS. EXP TEMPS NR OR A SLGTLY ABV
SEASONAL AVGS UNTIL HIGH PRES BLDS IN LT IN THE PD WITH SLGTLY BLO
AVG READINGS.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
VFR CONDS CURRENTLY. BECOMING MORE UNSTABLE AS THE HEATING
CONTINUES. DISTURBANCE MOVING ALONG THE OUTFLOW BOUNDARY FROM THE
OVERNIGHT MCS WILL BE THE FOCUS OF THE NEXT CLUSTER OF STORMS THAT
WILL MOVE THROUGH THE TAF SITES EARLY THIS EVENING WITH MVFR
RESTRICTIONS IN TSRA. PTCHY MVFR IN BR IS PSBL FOR MANY TAF SITES
DURING THE SUNRISE HOURS ON WEDNESDAY.

OUTLOOK.../WEDNESDAY THROUGH SATURDAY/...
VFR IS EXPD MUCH OF THE TIME...ALTHOUGH A SERIES OF DISTURBANCES
WL BRING DAILY CHCS OF SHWRS/TSTMS WITH THE HIGHEST CHC BEING
THU/THU NGT.

&&

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

&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE PITTSBURGH PA
929 AM EDT TUE JUN 25 2013

MDZ001-OHZ039>041-048>050-057>059-068-069-PAZ007>009-013>016-020>023-
029-031-073>076-WVZ001>004-012-021>023-041-261330-
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-GREENE-WESTMORELAND-WESTMORELAND RIDGES-
FAYETTE-FAYETTE RIDGES-HANCOCK-BROOKE-OHIO-MARSHALL-WETZEL-MARION-
MONONGALIA-PRESTON-TUCKER-
929 AM EDT TUE JUN 25 2013

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.

SLIGHT RISK FOR SEVERE STORMS LATE THIS AFTERNOON AND EVENING. THE MAIN
THREAT WILL BE LARGE HAIL AND DAMAGING WINDS.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY.

SLIGHT RISK FOR SEVERE STORMS WEDNESDAY. THE MAIN THREAT WILL BE LARGE
HAIL AND DAMAGING WINDS.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED.

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE PITTSBURGH PA
1159 AM EDT TUE JUN 25 2013

PAZ016-251615-
JEFFERSON PA-
1159 AM EDT TUE JUN 25 2013

...A STRONG THUNDERSTORM WILL AFFECT EAST CENTRAL JEFFERSON COUNTY...

AT 1155 AM EDT...A STRONG THUNDERSTORM WAS LOCATED 4 MILES SOUTHEAST
OF BROCKWAY...MOVING EAST AT 40 MPH.

WIND GUSTS TO 50 MPH ARE POSSIBLE WITH THIS STORM.

  LOCATIONS IMPACTED INCLUDE...
  BROCKWAY...

PLEASE REPORT SIGNIFICANT WEATHER BY CALLING...412-262-1988...POSTING
TO THE NWS PITTSBURGH FACEBOOK PAGE...OR USING TWITTER
@NWSPITTSBURGH.

LAT...LON 4120 7871 4119 7877 4113 7880 4114 7884
      4129 7879 4126 7873 4124 7874 4123 7870
      4120 7870

34

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE PITTSBURGH PA
300 PM EDT TUE JUN 25 2013

OHZ040-041-251930-
CARROLL OH-COLUMBIANA OH-
300 PM EDT TUE JUN 25 2013

...A STRONG THUNDERSTORM WILL AFFECT COLUMBIANA AND NORTHEASTERN
CARROLL COUNTIES...

AT 257 PM EDT...A STRONG THUNDERSTORM WAS LOCATED 2 MILES WEST OF
AUGUSTA...MOVING EAST AT 30 MPH.

WIND GUSTS TO 40 MPH AND PENNY SIZE HAIL ARE POSSIBLE WITH THIS
STORM.

  LOCATIONS IMPACTED INCLUDE...
  AUGUSTA...            EAST ROCHESTER...     MECHANICSTOWN...
  MILLPORT...           SALINEVILLE...
  GUILFORD LAKE STATE PARK...                 SALEM...
  LISBON...             LEETONIA...

PLEASE REPORT SIGNIFICANT WEATHER BY CALLING...412-262-1988...POSTING
TO THE NWS PITTSBURGH FACEBOOK PAGE...OR USING TWITTER
@NWSPITTSBURGH.

LAT...LON 4091 8081 4091 8074 4064 8060 4057 8112
      4073 8119 4073 8110 4080 8109 4091 8082

34