FXUS61 KCTP 111204 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 704 AM EST THU MAR 11 2010 .SYNOPSIS... A BROAD UPPER LEVEL CIRCULATION OVER THE CENTRAL PLAINS WILL SLOWLY MOVE EAST INTO THE CENTRAL APPALACHIANS...INDUCING A STRONG LOW PRESSURE SYSTEM ALONG THE MIDDLE ATLANTIC COASTAL PLAIN THIS WEEKEND. THIS SYSTEM WILL LIKELY BE ACCOMPANIED BY AREAS OF HEAVY RAINFALL. THE COMBINATION OF HEAVY RAIN...ANTECEDENT CONDITIONS AND RESIDUAL SNOW MELT MAY RESULT IN FLOODING. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... SKIES CLEARING OUT BEHIND A POOR ATTEMPT TO MOISTEN UP THE LOW/MID LAYERS FROM ABOVE BY A MINOR SPOKE OF UPPER ENERGY. IN ABSENCE OF ANY LOW CLOUD UNTIL SRN WV...WILL DELAY THE ONSET OF LOWER CLDS THRU THE MORNING AND INTO THE AFTN. MSTR SHOULD INCREASE AND PILE UP FIRST ALONG THE RIDGES OF THE CENTRAL MTS/RIDGE AND VALLEY REGION. BUT THIS WILL WAIT UNTIL THE FLOW CAN GO ERLY. THE FIRST INDICATIONS OF THIS FROM HIGHER-RESOLUTION LOCAL WRF AND NAM12 SHOW MSTR BECMG THICK ENUF OVER THOSE AREAS LATE THIS AFTN. WILL THEREFORE PUSH TIMING BACK A BIT MORE. EXPECT NOTHING MORE THAN SPRINKLE OVER ANY OF THE REGION TODAY...WITH MAX TEMPS JUST AS HIGH AS WED. THIS WILL CONTINUE TO HELP THE SLOW AND STEADY SNOW MELT OFF BENIGN-LY TODAY. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM FRIDAY/... UPPER RIDGE GIVES UP AFTER A VALIANT FIGHT AND GETS PINCHED TO THE N/E OF THE REGION. THE EVENING SHOULD BE MILD AND INCREASINGLY HUMID...WITH DEEP ERLY FLOW FINALLY BEGINNING OVER THE SRN TWO- THIRDS OF THE AREA. CLOUDS SHOULD THICKEN UP WHERE THEY HAVE NOT DURING THE AFTN/EARLY EVENING...EXCEPT FOR THE NRN TIER/NW COS WHERE IT WILL TAKE A BIT LONGER. DRIZZLE/SPRINKLES COULD BEGIN OVER THE HIGHER ELEVS/SE- FACING SLOPES AROUND/AFTER MIDNIGHT. A MORE-SYNOPTIC FEATURE IN THE FORM OF A VERY WEAK S/WV COMES ALONG LATE AT NIGHT...WHICH IS A FURTHER /AND PERSISTENT/ DELAY FROM EARLIER MDL RUNS. STILL...QPF AT THIS POINT IS BARELY MEASURABLE BEFORE 12Z FRI...WITH HUNDREDTHS IN GENERAL FROM MANY SREF MEMBERS...AND EVEN THE 00Z GFS OVER THE SWRN COS. NAM IS NOT SURPRISINGLY ALMOST-DRY. AT MOST A TENTH OR SO COULD FALL IN THE SC MTS AND LAURELS BY SUNRISE. WILL THEREFORE KEEP POPS AT CHCS FOR MUCH OF THE AREA...BUT LIKELIES IN THE SC/SW MTS LATE TONIGHT. MINS WILL RUN MILD - MORE LIKE NORMAL MAXES THAN ANYTHING FOR MID MARCH. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... A CLOSED MID LEVEL LOW/EXTENSIVE LONGWAVE TROUGH OVER THE PLAINS WILL PIVOT AND EVOLVE EAST-SOUTHEAST INTO THE OHIO VALLEY AND CENTRAL APPALACHIANS THIS WEEKEND. SURFACE LOW DEVELOPMENT IS PROGGED ALONG THE MIDDLE ATLANTIC COASTAL PLAIN...WITH A HIGHLY ANOMALOUS ONSHORE EASTERLY FETCH OF ABOVE NORMAL PWAT/MARITIME AIR WRAPPING NORTH/WEST OF THE LOW CENTER. 850MB U WIND ANOMALIES ARE FORECAST TO EXCEED 4 TO 5SD...A CLEAR SIGNAL THAT HEAVY TO PERHAPS EXCESSIVE RAINFALL IS LIKELY WITH THIS SYSTEM. DETERMINISTIC MODEL DIFFICULTIES IN RESOLVING THE TRAJECTORY OF THE INLAND MOISTURE FLUX...COMBINED WITH ONGOING CONVECTIVE GRID- SCALE FEEDBACK HAVE STEERED GRIDDED QPF FORECASTS TOWARD A COMPROMISE SOLUTION...RESULTING IN STORM TOTALS OF GENERALLY 2 TO 3 INCHES OVER MUCH OF THE CWA. THIS MAY ACTUALLY HEDGE ON THE LOW END OF THE DISTRIBUTION GIVEN THE MAGNITUDE OF THE ANOMALY FIELDS AND CONSULTATION OF THE WETTEST GEFS/SREF PLUME MEMBERS. THERE IS GOOD AGREEMENT IN THE PERIOD OF HEAVIEST RAIN FROM SATURDAY THROUGH SUNDAY. CONSIDERED EXPANDING THE FLOOD WATCH FURTHER EAST THIS PACKAGE WITH GUIDANCE BEGINNING TO ZERO-IN ON A QPF MAXIMA ALONG THE NJ COAST AND POINTS WESTWARD INTO THE SUSQ RIVER VALLEY. BUT BASED ON A 5TH PD START TIME OF THE HEAVY RAIN WILL ALLOW THE DAYSHIFT TO DIGEST ANOTHER ROUND OF MODEL DATA AND EVENTUALLY MAKE THE FINAL CALL ON WHETHER/WHERE TO EXPAND THE FLOOD WATCH. OCCASIONAL LIGHT RAIN MAY LINGER INTO EARLY MONDAY BEFORE CONDITIONS IMPROVE THROUGH THE MIDDLE OF THE WEEK. THE LONGER TERM LOOKS MAINLY DRY AS HIGH PRESSURE BUILDS SOUTH FROM THE NORTHERN PLAINS INTO THE MS VALLEY. STILL NO COLD AIR IN SIGHT AS THE STRETCH OF GENERALLY ABOVE NORMAL TEMPERATURES CONTINUES. && .AVIATION /12Z THURSDAY THROUGH MONDAY/... VFR SKIES WILL RULE THROUGH MOST OF THE DAY...WITH ONLY HIGH CLOUDS. LOWER CLOUDS MAY START TO FORM LATE THIS AFTN...AFT 18Z BUT COULD BE BEFORE 00Z AS MSTR INCREASES AS THE ERLY FLOW STARTS OVER THE SE FIRST...THEN SPREADS WEST AND NORTH. MAJOR SYSTEM WILL WRAP UP TO THE WEST TODAY AND FRIDAY...AND SHOULD PRODUCE LOW CIGS AND VSBYS OVER C PA THRU MOST IF NOT ALL OF THE WEEKEND...AS THE ERLY FLOW CONTINUES WITH THE REGION N OF THE WARM FRONT MOST OF THE TIME. RAIN SHOULD BECOME WDSPD ON FRIDAY AND BEGIN A PROLONGED TIME OF RAINFALL...IFR TO LIFR CIGS AND FOG. OUTLOOK... FRI-SUN...GENERALLY IFR CIGS/VSBY OCNL RA. MON...DRYING/IMPROVEMENT TO VFR PSBL. && .CTP WATCHES/WARNINGS/ADVISORIES... FLOOD WATCH FROM THIS EVENING THROUGH LATE SATURDAY NIGHT FOR PAZ024-033. && $$ SYNOPSIS...STEINBUGL NEAR TERM...DANGELO SHORT TERM...DANGELO LONG TERM...STEINBUGL AVIATION...DANGELO