Flash Flood Warning 29, NWS State College, PA

CENTRAL PENNSYLVANIA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
230 AM EDT THU APR 22 1999

DIFFICULT FORECAST FOR THE NEXT 48 HOURS. MODELS STILL AT ODDS WITH
PLACEMENT OF THE SURFACE WARM FRONT.

IN THE SHORT TERM...GOOD AMOUNT OF CONVECTION FIRING ALONG WHAT
APPEARS TO BE A DEVELOPING MID LEVEL (850 MB) FRONTAL BOUNDARY. THE
BOUNDARY IS DEVELOPING IN THE UPPER LEVEL CONFLUENCE ZONE...IN
RESPONSE TO AN UPPER LEVEL SHORT WAVE SLIDING NORTH OF THE REGION.
MODEL FGEN FIELDS SUPPORT WHAT IS DEPICTED IN THE 850 THETA-E
FIELDS...THAT IS A DEVELOPING/LIFTING BOUNDARY NOW EXTENDS ACROSS
NRN IN/OH INTO WRN NYS...THEN BECOMES MORE DIFUSE ACROSS CENTRAL AND
EASTERN PA.

EXPECT THIS BOUNDARY TO CONTINUE TO SHARPEN UP OVERNIGHT...AND ACT
AS THE FOCUS FOR OVERNIGHT CONVECTION. THE BOUNDARY WILL CONTINUE TO
REMAIN STATIONARY WEST OF THE STATE...BUT LIFT NORTH/DEVELOP
NORTHWARD AS THE OVERNIGHT PROGRESSES ACROSS PA. DEEPEST TSRA AGAIN
FOCUSING JUST AT THE NOSE OF THE 850 JET...WHERE IT INTERSECTS THE
NEARLY E-W THETA-E GRADIENT. LUCKILY...AS TSRA MOVE EAST...THEY ARE
ENCOUNTERING MUCH MORE STABLE AIR EAST OF THE MOUNTAINS (CTP CWA)
AND LOSING THEIR PUNCH.

AM INCLINED TO FOLLOW ALONG THE LINES OF PREVIOUS FORECAST...AND
KEEP EITHER LOW OR NO POPS FOR SOUTHERN AREAS TODAY...INCREASING TO
LIKELY IN THE NORTH. BUT EVEN HERE...STRESSING MAINLY MORNING HOURS
FOR THE PCPN.

STILL MUCH DISCREPANCY ABOUT THE POSITION OF THE SURFACE WARM FRONT
FOR TODAY. MY SURFACE ANALYSIS IS BEGINNING TO SHOW A REFLECTION OF
THE AFOREMENTIONED FRONT DEVELOPING ACROSS LAKE ERIE INTO CENTRAL
NY. REAL SURFACE WARM FRONT LIES WELL SOUTH ACROSS KY AND SOUTHERN
VA.

EXPECT WARM FRONT TO NEVER ADVECT NORTH TODAY...BUT RATHER CENTRAL
PA TO REMAIN IN A NEBULOUS AIRMASS BETWEEN THE NORTHERN AND SOUTHERN
FRONTS. COULD STILL GET PRETTY WARM TO THE SOUTH...BUT TEMPERATURES
WILL BE HELD IN CHECK OVER MOST AREAS.

REAL CONCERN IS TONIGHT. QUASI-STATIONARY UL JET OF 110 KTS OVER THE
NIAGARA PENINSULA WILL KEEP A 50+ KNOT LLJ POISED OVER OHIO. THE
SAME MECHANISM WHICH HAS BEEN FIRING TSRA THE LAST FEW NIGHTS WILL
BE IN PLACE AGAIN...THIS TIME HOWEVER FARTHER EAST AND NORTH.
ENVISION THE POSSIBILITY OF A TRAINING CONVECTIVE EVENT...AND MAY
ISSUE AN ESF STATEMENT...STRESSING THE POSSIBILITY OF HEAVY RAIN
OVERNIGHT.

FRIDAY LOOKS WET AS FRONTAL SURFACE PUSHES SOUTH. ETA MOST
AGGRESSIVE DEVELOPING FRONTAL WAVE THAT TRACKS ACROSS THE STATE.
OTHER MODELS... ALTHOUGH LACKING THE DEFINITION OF THIS SURFACE
FEATURE...SHOW ABUNDANT MOISTURE AS WELL.

.CTP...NONE.

JUNG