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195
FXUS61 KCTP 300911
AFDCTP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
511 AM EDT TUE SEP 30 2014

.SYNOPSIS...
A COLD FRONT WILL DROP ACROSS THE REGION THIS AFTERNOON AND
EVENING...BRINGING A CHANCE OF SHOWERS AND THUNDERSTORMS. WHILE
SOME HAIL IS LIKELY TO ACCOMPANY THUNDERSTORMS OVER WESTERN AND
CENTRAL SECTIONS DUE TO COLD AIR ALOFT...STRONG WIND GUSTS ARE
NOT EXPECTED DUE TO RELATIVELY WEAK WINDS ALOFT. UNSETTLED
WEATHER WILL MOVE EAST OF THE REGION LATER WEDNESDAY...WITH DRY
WEATHER EXPECTED THROUGH THE END OF THE WEEK. A STRONGER COLD
FRONT WILL PUSH EAST INTO THE COMMONWEALTH LATE FRIDAY NIGHT AND
SATURDAY.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
SHORTWAVE TROF OVER NORTHERN VIRGINIA TRACKING EASTWARD EARLY THIS
MORNING...TAKING DEEPER LAYER MOISTURE AND AND SHOWER CHANCES
WITH IT FOR NOW. THROUGH EARLY MORNING...MAIN SENSIBLE WEATHER
CONCERN WILL BE AREAS OF FOG...WHICH WILL BE DENSE FROM THE
NORTHWEST MOUNTAINS EASTWARD ACROSS THE NORTH CENTRAL MOUNTAINS
AND SOUTHWARD THROUGH THE LOWER SUSQ RIVER VALLEY...ALREADY LOTS
OF 1/2SM TO 1/4SM VSBYS SHOWING UP SO WILL GO AHEAD AND ISSUE
DENSE FOG HEADLINES FOR THESE AREAS THROUGH 13Z. ACROSS THE
LAUREL HIGHLANDS AND EXTENDING INTO THE WEST CENTRAL AND MOUNTAINS
AND CENTRAL/SOUTH CENTRAL MOUNTAINS...ENOUGH OF A SOUTHERLY
COMPONENT AHEAD OF THE FRONT APPROACHING THE EASTERN GLAKS TO
PREVENT ANY FOG WHICH FORMS FROM BECOMING DENSE...BUT WILL
CONTINUE TO MONITOR THERE.

AFTER MORNING FOG DISSIPATES...AN INTERESTING CONVECTIVE DAY IS IN
STORE. COLD FRONT NOW REACHING THE NORTHERN/WESTERN SHORES OF LAKE
ERIE WILL SLOWLY PUSH EAST OF LAKE ERIE BY EARLY AFTERNOON.
PARAMETERS SETTING UP WELL FOR HAIL TO ACCOMPANY ANY STORMS DURING
MAX HEATING WITH HEALTHY CAPES (MUCAPES IN EXCESS OF 1200 J/KG)
AND WET BULB ZERO BETWEEN 7K FT AND 8.5 FT ACROSS WESTERN AND
CENTRAL PA. BOUNDARY LAYER WINDS ARE WEAK...SO THE MAIN THREAT
WILL BE HAIL. THIS IS OUTLINED IN SPC SEE TEXT AREA OVER NORTHWEST
PA. ADDED SMALL HAIL WX TYPE AS WELL...SOMETHING I USUALLY DON`T
DO ON THE MID SHIFT PRECEDING A CONVECTIVE DAY...BUT GIVEN THERMO
PARAMETERS HAVE HIGH CONFIDENCE IN AT LEAST SMALL HAIL TODAY WEST
AND CENTRAL.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/...
4KM SPC WRF INDICATES AFTERNOON CONVECTION WILL LINGER WELL INTO
THE EVENING HOURS OVER ESPECIALLY CENTRAL AND EASTERN SECTIONS.
AFTER STORMS DIMINISH EARLY THIS EVENING...KEPT SCATTERED SHOWERS
IN THESE AREAS THROUGH LATE EVENING. FOG MAY ONCE AGAIN BECOME AN
ISSUE LATE TONIGHT...ESPECIALLY OVER THE EAST WHERE SFC RIDGE AXIS
BUILDS AND A WEAK INVERSION SETS UP IN LIGHTS WINDS. MINS WILL
RANGE THROUGH THE 50S.

SLOWLY FILLING UPPER TROF WOBBLES SLOWLY EASTWARD ACROSS THE
COMMONWEALTH ON WEDNESDAY. IT LOOKS QUITE CLOUDY GIVEN FAIRLY
STEEP LAPSE RATES...BUT GENERALLY DRY WITH ONLY SLGT CHC POPS
UNDER THE "COOL" CORE ALOFT. AN UNDERWHELMING UPPER LOW OF 571 DM
TRACKS INTO SOUTHERN NEW ENGLAND BY 00Z THU...WITH RISING HEIGHTS
LATE IN THE DAY ACROSS WESTERN AND CENTRAL PA. TEMPS ON WED
HOWEVER WILL BE COOLER THAN RECENT DAYS...DUE TO THE CLOUD COVER.
EXPECT HIGHS TO RANGE FROM THE UPPER 60S NORTH TO THE LOWER 70S
SOUTH.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
PROGRESSIVE UPPER LOW/COMPACT TROF AXIS OVER THE NERN U.S. AT THE
START OF THE PERIOD IS FORECAST TO LIFT OUT BY THE END OF THE
WEEK...AS UPPER RIDGE REBUILDS ACROSS THE REGION INTO THE EARLY
PART OF THE WEEKEND. A SECOND...MUCH STRONGER AND EXPANSIVE UPPER
TROF AXIS EXTENDING SWD FROM AN UPPER LOW ANCHORED OVER NRN
ONTARIO IS FORECAST TO SWEEP ACROSS THE EASTERN U.S. OVER THE
WEEKEND.

WARMER WEATHER MAKES A BRIEF RETURN THUR...FRI AND EARLY SAT AS
THE UPPER RIDGE REBUILDS....WITH MAXES AND MINS AT LEAST SEVERAL
DEGREES ABOVE CLIMO NORMALS.

THE ARRIVAL OF THE SECOND TROF WILL SUPPORT A STRONG COLD FRONT
WITH DEEPER CONNECTIONS TO THE GOMEX AND THE ATLANTIC
OCEAN...THUS POTENTIAL FOR MORE WIDESPREAD AND HEAVIER RAINFALL.
PASSAGE OF THE FRONT WILL ALSO BRING NOTICEABLY COOLER TEMPS TO
THE REGION FOR SUNDAY INTO MONDAY. A SHORT WAVE WITHIN THE THEN
EXPECTED CYCLONIC FLOW OVER THE REGION WILL BRING ANOTHER FRONTAL
SYSTEM TO THE REGION WITH AN INCREASED CHANCE OF SHOWERS FOR THE
END OF THE PERIOD.

&&

.AVIATION /09Z TUESDAY THROUGH 06Z WEDNESDAY/...
30/09Z UPDATE...DROPPED BFD/IPT/LNS ALL BELOW AIRFIELD MINS PER
LATEST OBS. UNV/AOO ARE TRENDING LOWER ATTM WITH 5SM AND 7SM
RESPECTIVELY AND WILL MAINTAIN 2SM FM 10-13Z ALTHOUGH CONFIDENCE
IS MARGINAL. MOST SIGNIFICANT CHANGE WAS TO MDT WITH IFR NOW
EXPECTED TO PREVAIL THRU DAWN.

30/06Z...CLR SKIES/LGT WINDS AGAIN SUPPORTING VALLEY FOG
FORMATION ACRS CENTRAL PA. HIGHEST CONFIDENCE IN IFR OR BLW AT
BFD/IPT/LNS (PERSISTENCE) FOLLOWED BY AOO/UNV. MDT HAS YET TO
REALLY GET INTO THE FOG OVER THE LAST SEVERAL DAYS AND WILL CAP
VSBY AT 3-5SM. DEWPT DEPRESSION AT JST SUGGEST FOG IS UNLIKELY
ALTHOUGH DID SHOW SCT015 GROUP TWD DAYBREAK. FOG WILL GIVE WAY TO
VFR FOR THE MORNING HOURS...AHEAD OF COMPACT UPPER LEVEL LOW AND
WEAK COLD FRONT FCST TO SHIFT SEWD FROM THE GRT LKS ACRS PA LATER
TODAY INTO TNGT. MODEL GUIDANCE IS SUPPORTIVE OF VCSH/-SHRA
MENTION AT ALL SITES FROM THIS AFTN INTO EARLY TNGT ALONG WITH A
GENERAL LOWERING TREND IN CIGS/VSBYS. ARRIVAL OF COOLING ALOFT
ASSOCD WITH UPPER LOW FAVORABLY TIMED WITH DAYTIME HEATING SHOULD
SUPPORT ISOLD-SCT TSTM DEVELOPMENT...FOCUSING ALONG/AHEAD OF SFC
COLD FRONT. THE COOL TEMPS ALOFT WILL FAVOR HAIL AS THE PRIMARY
TSTM HAZARD.

OUTLOOK /WEDNESDAY THROUGH SATURDAY/...

WED...UPPER LOW WILL BE SLOW TO MOVE NEWD THEREFORE CHC OF SHOWERS
WILL CONTINUE ON WED. SOME LOW CIGS PSBL AS WELL.

THU...LOW CIGS LKLY EARLY...AND COULD PERSIST THRU MUCH OF THE
DAY OR REFORM THU NGT DUE TO HIGH PRES WEDGE/MARITIME FLOW E OF
THE APPLCHNS.

FRI...SHOWERS AND THUNDERSTORMS LKLY ASSOCD WITH WELL-DEFINED
GUSTY COLD FROPA. LLWS LKLY DUE TO STG SLY WINDS AHEAD OF THE COLD
FRONT.

SAT...AM SHOWERS ERN AREAS. BREEZY WITH IMPROVING CONDITIONS E OF
THE MTNS DUE TO WLY DOWNSLOPE. ISOLD SHOWERS AND LOCAL MVFR
POSSIBLE OVER N/WRN AREAS.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
DENSE FOG ADVISORY UNTIL 9 AM EDT THIS MORNING FOR PAZ004>006-
010>012-028-037-041-042-045-046-049>053-056>059-063>066.

&&

$$
SYNOPSIS...DEVOIR
NEAR TERM...DEVOIR/FITZGERALD
SHORT TERM...DEVOIR/FITZGERALD
LONG TERM...LAMBERT/GARTNER
AVIATION...STEINBUGL




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