Flash Flood Warning 34, NWS State College, PA

CENTRAL PENNSYLVANIA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
155 AM EST FRI JAN 9 1998

...ZONE SUGGESTIONS...
TODAY...WRN MTN ZONES... SHRA... FEW MORN TSRA. SHRA IN AFTRN TO
ACCOUNT FOR UPSLOPE. SC/C PA...MORN SHRA WITH FEW AM TSRA. BREEZY
AND COOLER AFTRN.
ERN ZONES... MORE SHRA LIKELY AND A FEW TSRA...THEN BREEZY AND
COOLER.
TONIGHT...MO CLDY NRN/WRN ZONES... PC SERN ZONES. CHC FLURRIES IN
MTNS.
SAT...MO CLDY NRN ZONES... PS CNTRL/SRN ZONES. CHC FLURRIES MTNS.

...DISCUSSION...
WILL FOCUS ON SHORT-TERM (NEXT 12-18 HOURS). 0600Z SFC ANYLS SHOWS
A FRNTL BNDRY W-E ACRS NRN PA WITH A LO PRES ACRS FAR ERN OH AND A
CD FRNT SOUTH THRU ERN OH VLLY. MUCH OF SRN/CNTRL PA REMAINS IN
THIS MEMORABLE JANUARY WARM-SECTOR WITH DWPTS RUNNING IN THE MID TO
UPR 50S OR EVEN 60 IN A FEW PLACES! SATL SHOWS IMPRESSIVE DYNAMICS
HEADING TWD PA IN ASSCTD WITH AN UPR LVL WAVE. ANOTHER SRLY WARM
CONVEYOR BELT-LIKE FEATURE WAS AGAIN FEEDING NORTH TWD PA AS PER
IR/WV CHANNELS AHEAD OF THE UPR LVL WAVE. THE PRECIP WITHIN THIS
"CONVEYOR" ON SATL WAS LESS WIDESPREAD THAN LAST NGT. UPR AIR
SOUNDINGS FROM 0000Z REVEAL QUITE A BIT OF DRY AIR AT MID-LVL/S
WHICH MAY BE PRECLUDING WIDESPREAD RAINS TO THE S AND W OF PA AT
THIS POINT.

HOWEVER... THIS DRIER MID-LVL AIR MASS WAS FUELING JANUARY
THUNDERSTORMS WITH A BONA-FINE MCS WORKG N ACRS ERN OH. KCCX AND
KPBZ 88D/S HAD SCTRD SHRA AND SOME TSRA. AS THE UPR LVL WAVE PUSHES
E TWD PA BY 12Z... IT WILL PROVIDE LIFTG OVR THIS RELATIVELY UNSTBL
AIR MASS OVR PA. MODELS STEEPEN LAPSE RATES AS A RESULT TO GREATER
THAN 7C/KM BTWN 850 AND 500 MB ACRS MUCH OF CNTRL/ERN PA WHICH IS
VERY HEALTHLY! THINK SOME CONVECTIVE OVERTURNING WILL TAKE PLACE AS
THIS UPR LVL WAVE PRESSES INTO PA TWD DAWN. THIS SHUD SUPPORT (AT
LEAST) ANTHR BATCH OF SHRA WITH SCTRD EMBEDDED TSRA THIS AM. THINK
THIS ACVTY WILL BE GONE BY AFTRN WITH PASSAGE OF UPR LVL WAVE. WUD
GO EITHER LIKELY OR CAT POPS FOR SHRA ALL ZONES THIS AM. WILL ALSO
BE MONITORING FOR PTNL SVR TSRA IN CWA...ESP W/ HISTORY OF SVR TO
THE SW OF CWA... STRG MID-LVL WIND FIELDS PRESENT AND LOW-LVL BNDRY
ACRS NRN PA. DRY MID-LVL AIR ALSO INDICATES THAT SOME HAIL CUD BE
A PROBLEM... LARGE HAIL ALSO TO THE SW OF PA ERLR THIS EVE.

NEXT QUESTION IS... DO WE NEED MORE FFA/S? STREAMS/CREEKS RUNNING
VERY HI AND RIVERS STILL RISING. HYDROLOGICALLY WE ARE VERY
VULNERABLE TO FLOODING WITH ADDTNL RAINS. ONLY PROBLEM IS ASSESSING
HOW WIDESPREAD THE SHRA BECOME AND WHERE TO PUT FFA/S. I THINK WE
PROBABLY WILL NEED MORE FFA/S BUT WE SHUD WAIT ANTHR HOUR OR SO AND
LOOK FOR RADAR TRENDS TO THE S TO BETTER PIN-POINT WHERE WATCHES
ARE NEEDED. IF A WIDESPREAD LIGHT/MOD RAIN DVLPS... FFA/S WILL
DEFINITELY BE NEEDED AGAIN MANY AREAS! WILL COORD WITH PHL AND PIT
LATER ON THIS BEFORE ZONE ISSUANCE TIME.

THE UPR LVL WAVE PASSES E OF C-PA BY 1800 UTC AND SUPPORTS A CD
FRNT TO QUICKLY PASS INTO ERN PA. STRG CAA TAKES PLACE BEHIND THIS
FRNT WITH SIGNIFICANT COLD-AIR SC STREAMING INTO PA BY AFTERNOON.
A TYPICAL CAA DAY WILL SET-UP ACRS PA THIS AFTRN/EVE WITH MORE
CLDS/SHRA IN WRN MTNS AND LESS CLDS/NO PRECIP IN SUS VLLY. THINK IT
WILL BECOME QUITE WINDY AS COLD AIR INVADES REGION AND THIS SHUD BE
MENTIONED IN ZONES FOR AFTRN/EVE. WUD KEEP SHRA IN WRN MTN ZONES
FOR AFTRN TOO GIVEN UPSLOPING... MIX W/ SNOW LATE IN DAY? INV GETS
SQUASHED DOWN TO BLO 850 MB TONIGHT AND SHUD PRECLUDE MUCH PRECIP
IN UPSLOPE REGIONS... MAYBE A FEW FLURRIES.

NICOSIA