-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KPBZ 222302
AFDPBZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
702 PM EDT WED MAY 22 2013

.SYNOPSIS...
SHOWER AND THUNDERSTORM CHANCES WILL CONTINUE UNTIL A COLD FRONT
PASSES THROUGH THURSDAY EVENING. HIGH PRESSURE RETURNS FOR THE
WEEKEND.

&&

.NEAR TERM /THROUGH THURSDAY/...
-- Changed Discussion --
RECENT MESO DATA SHOWS ML CAPES AVG 500-1000 J/KG OVR WV INTO WRN
PA. STILL PSBL FOR AN ISOLD SVR TSTM OVR THE NEXT HOUR OR TWO
UNTIL INSTAB FADES. ANOTHER SURGE OF MOISTURE SEEN ON STLT IS EXP
TO MOVE NWD KEEPING SHWR CHCS INTO THE OVRNGT PD. STILL A CHC OF A
TSTM WITH SOME ELEVATED INSTAB BUT SVR THREAT SHOULD END. A CDFNT
WL APRCH FM THE WEST THU BRINGING ADDNL SHWRS/TSTMS. MDL PROGS
SHOW INSTAB SHOULD BE MINIMAL AND THIS SEEMS REASONABLE GIVEN EXPD
CLD COVER.
-- End Changed Discussion --

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
A RAPID TRANSITION TO MUCH COLDER CONDITIONS TAKES PLACE DURING
THIS PERIOD AS THE CONSENSUS OF THE MORE RELIABLE GLOBAL MODEL
SYSTEMS SUGGESTING THE MID-LEVEL SYSTEM TRACKING THROUGH THE
REGION SHOULD CLOSE OFF AS IT MOVES OVER PITTSBURGH AND SLOWLY
OOZES SOUTHEASTWARD. THE CLOSED SOLUTIONS FAVORED BY THE MORE
RELIABLE MODELS END UP TRENDING TOWARD THE SLOWER END OF THE
GUIDANCE PACK WITH THIS SYSTEM...WHICH MAKES SENSE GIVEN THE
HIGHER LONG WAVE AMPLITUDE. AS SUCH...THE SYSTEMS DEPARTURE WAS
SLOWED IN THE FORECAST WHICH RESULTED IN INCREASING POPS INTO
FRIDAY.

WHILE ITS DEPARTURE IS SLOWER...MUCH DRIER AIR DOES WORK INTO THE
AREA BY FRIDAY NIGHT WITH THE CONSENSUS OFFERING EXTREMELY LEAN
LAYER RH PROFILES AND WEAKENING NORTHWEST COLD ADVECTION. THIS
SETS THE STAGE FOR STELLAR RADIATIONAL COOLING GOING INTO SATURDAY
MORNING. GRIDDED GUIDANCE SUGGESTS WIDESPREAD 30S ACROSS THE
AREA...WHICH WITH 850 MB TEMPERATURES FALLING TOWARD -2C IS NOT TOO
SHOCKING. FROST WAS ADDED TO THE GRID TO ACCOMMODATE LOWS
GENERALLY IN THE MID 30S ACROSS VAST TRACTS OF THE CWA...AND
FROST/FREEZE HEADLINES SEEM POSSIBLE AT THIS POINT. THESE
TEMPERATURES AT 850 MB FAIL TO MODERATE DURING THE DAY SATURDAY
MUCH...SO TEMPERATURES WILL LIKELY ONLY WANDER FOR HIGHS FROM THE
UPPER 50S FRIDAY TOWARD THE LOWER 60S SATURDAY. FRIES

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
SIMILAR CONDITIONS PERSIST THROUGH THE REST OF THE WEEKEND AND
EVEN POSSIBLY INTO MONDAY MORNING WITH VERY DRY CONDITIONS AND
LIGHT WINDS FAVORING SUPERIOR RADIATIONAL COOLING EACH NIGHT. AS
SUCH...LOWS CONTINUE TO LOOK TO HEAD TOWARD THE 30S EACH
NIGHT...WITH A FEW LOCATIONS INEVITABLY DROPPING BELOW FREEZING.
ONCE AGAIN...FROST WAS ADDED TO THE FORECAST INTO THE
OVERNIGHT/EARLY MORNINGS THIS WEEKEND...AND FROST/FREEZE HEADLINES
AGAIN SEEM QUITE POSSIBLE.

OTHERWISE...VERY GRADUAL MODERATION OF LOW LEVEL TEMPERATURES WILL
BE LIKELY AS THE CLOSED SYSTEM DEPARTS EASTWARD BUT DRY CYCLONIC
NORTHWESTERLY FLOW ALOFT REMAINS THE LARGE CONTROLLING FACTOR FOR
OUR WEATHER. THIS IS THANKS IN PART TO THE FACT THAT THE MODEL
CONSENSUS KEEPS THE LARGE SCALE RIDGE AXIS LARGELY TO OUR WEST
THROUGH THE MIDDLE OF NEXT WEEK. AS A RESULT...CONDITIONS SHOULD
REMAIN GENERALLY DRY WITH VERY SLOW MODERATION OF TEMPERATURES
THROUGH THE WEEK. FRIES

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
-- Changed Discussion --
TSTMS BEGINNING TO DCRS THIS EVE...AND THIS SHOULD CONT. SHOULD
STILL BE SCT SHWRS ARND INTO THE OVRNGT HOURS BUT GENL VFR WEA IS
EXP. A BRF PD OF MVFR CIGS IS PSBL THU MRNG BEFORE VFR CU/STRATOCU
RETURNS. A CDFNT WL MOVE ACRS THE RGN LATE THU BRINGING MVFR SHWRS
NEAR OR JUST AFT THE END OF THE TAF PD. A TSTM IS PSBL BUT
PROBABILITY LOOKS LOW ATTM.

.OUTLOOK.../THURSDAY NIGHT THROUGH MONDAY/...
RESTRNS ARE LIKELY IN SHWRS THU NGT AFT FROPA. HIGH PRES AND VFR
CONDS EXPD FRI THRU MON.
-- End Changed Discussion --

&&

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

&&

$$

07