FXUS63 KPAH 190948 AFDPAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PADUCAH KY 348 AM CST TUE FEB 19 2013 .SHORT TERM...(TODAY AND THURSDAY NIGHT) ISSUED AT 347 AM CST TUE FEB 19 2013 THE FORECAST SIGNAL IN THE NUMERICAL GUIDANCE FOR THE UPCOMING WEATHER EVENT HAS BEEN CONSISTENT DURING THE LAST FOUR DAYS...MAINLY IN THE PLACEMENT OF ANY BRIEF WINTRY MIX ACCUMULATION LATE WEDNESDAY NIGHT /AFTER MIDNIGHT/ THROUGH NOON ON THURSDAY. THE HEADACHE HAS BEEN ASSOCIATED WITH THE THERMAL PROFILES /SOUNDINGS/ TIED TO THE AREA IMPACTED BY THE WINTRY MIX. THE INITIAL COMPLICATION COMES FROM THE FACT THAT THE CRITICAL CLOSED LOW THAT WILL BE IMPACTING THE REGION IS STILL IN THE EASTERN PACIFIC. ALTHOUGH THE REMOTE SENSING RETRIEVAL FROM THE GOES AND POES SATELLITES CAN GET A GOOD ESTIMATE OF TEMPERATURES ALOFT...A DETAILED SAMPLING OF UPPER AIR SOUNDINGS/SURFACE OBSERVATIONS IS INVALUABLE. UNTIL THIS LOW PRESSURE CENTER MOVES ON SHORE LATE TONIGHT AND ADEQUATELY SAMPLED IN THE 00Z AND 12Z WEDNESDAY UPPER AIR SOUNDINGS. THE NUMERICAL MODEL GUIDANCE THE LAST FEW DAYS HAS BEEN A LITTLE WARMER AT THE 925/850 MB LEVELS /BY 1-1.5 DEGREES CELSIUS/...MAINLY WITH THE DETERMINISTIC GFS GUIDANCE. ON MONDAY...THE NAM-WRF INITIALIZED BETTER WITH THE MANDATORY UPPER AIR LEVELS...WITH THE ECMWF SLIGHTLY CLOSER TODAY VERSUS THE GFS OR NAM-WRF. WITH THIS PACKAGE LEANED CLOSER TO THE COLDER ECMWF SOLUTION FOR THE INITIAL UPPER AIR PROFILE WITH THE ONSET AND DEVELOPMENT OF MIXED PRECIPITATION TYPES LATE WEDNESDAY NIGHT INTO THURSDAY. AT THIS TIME...GIVEN THE MODEL RESOLUTION AND UNCERTAINTY OF THE UPPER AIR PROFILE...IT REMAINS DIFFICULT TO PRODUCE A DIFFERENTIAL PROBABILITY FOR PRECIPITATION TYPES. THAT IS...FOR EXAMPLE TO HAVE A LIKELY OR DEFINITE CHANCE FOR RAIN AND A CHANCE OR SLIGHT CHANCE OF SLEET. FOR NOW...WILL STILL NEED TO KEEP A MATCHING PROBABILITY OF LIQUID...FREEZING...FROZEN WHERE MIXED PRECIPITATION IS FORECAST. AT THIS TIME...THE FOCUS FOR THE CHANCE PROBABILITY OR BETTER OF A WINTRY MIX WILL START OUT IN WESTERN SECTIONS OF SOUTHEAST MISSOURI CLOSE TO MIDNIGHT...REACHING THE MISSISSIPPI RIVER BY 3 AM CST...MOVING EAST OF THE OHIO AND WABASH RIVER BETWEEN 6-7 AM CST. THE LOW LEVEL WIND FIELD AIDING A LARGER GRADIENT OF WARM ADVECTION WILL NOT LIKELY KICK IN UNTIL THE 15-18Z TIME FRAME. BETWEEN 3 AM AND 9 AM CST...LOW LEVEL COLD AIR DAMMING ALONG AND NORTH OF CRAWLEYS RIDGE/SHAWNEE HILLS WILL KEEP TEMPERATURES COLD ENOUGH TO FORCE MOST OF THE INITIAL PRECIPITATION TO FALL AS A MIXTURE OF SLEET AND SNOW...CHANGING OVER TO SOME FREEZING RAIN AND SLEET OVER THE SOUTHEAST MISSOURI FOOTHILLS...AS DEEPER SOUTHERLY FLOW MOVES INTO THE AREA LATER IN THE MORNING. AT THIS TIME...THE MAIN CONCERN FOR ANY ACCUMULATION REMAINS JUST TO THE WEST OF THE WFO PAH FORECAST AREA. IF THE ORIENTATION AND TRACK OF THE UPPER LOW IS FASTER AND FURTHER SOUTH THAN EXPECTED...SOME ICE POTENTIAL COULD MOVE INTO THE FOOTHILLS OF SOUTHEAST MISSOURI. THIS WILL NEED TO BE MONITORED CLOSELY DURING THE NEXT 24-36 HOURS IN THE MODELS PRIOR TO THE EVENT. FROM A MODEL PERSPECTIVE...THE SHORT RANGE ENSEMBLE FORECAST /SREF/ GUIDANCE APPEARED TO BE SUPERIOR IN THE INITIALIZATION AND PROBABILITY OF THE WINTRY PRECIPITATION TYPES FOR THIS EVENT. MOST OF THE FORECAST CLOSELY MATCHES THE 03Z TUESDAY SREF GUIDANCE OUTPUT SURPRISINGLY. AS WITH THE PREVIOUS EARLY MORNING FORECAST ISSUANCES...AN ADJUSTMENT TO ALL RAIN HAS HAD TO BE MADE AS SURFACE TEMPERATURES RISE UNDER SOUTHERLY FLOW AT THE SURFACE AND ALOFT...AS A WARM FRONT MOVE NORTH. THE WARM NOSE OF TEMPERATURES WIDENS DURING THIS TIME AND ANY PRECIPITATION LOADING ALOFT WILL ONLY AID IN THE WARMING OF THE SURFACE LAYER AND THE EROSION OF SUB-FREEZING SURFACE TEMPERATURES TO THE NORTH. THE SNOWFALL/ICE PELLET ACCUMULATION EARLY THURSDAY MORNING BECOMES ACADEMIC...AS THE RAIN WILL QUICKLY MELT AWAY ANY TRACES OF ACCUMULATION DURING THE AFTERNOON. THE EFFECTIVE ICE CRYSTAL PRODUCTION LAYER LOSES ANY EFFECTIVE MOISTURE BY THURSDAY EVENING...LEAVING ONLY A TRACE OR NEAR TRACE PRECIPITATION EVENT. ALSO AT THIS TIME...THE LOCAL FORECAST IS SOMEWHAT AT ODDS WITH THE HPC SNOW/SLEET/ICE FORECAST. HOPEFULLY...THERE WILL BE SOME SYNERGY ONCE THE UPPER LOW MOVES ONTO THE WEST COAST LATER TONIGHT. .LONG TERM...(FRIDAY THROUGH MONDAY) ISSUED AT 347 AM CST TUE FEB 19 2013 IN THE WAKE OF A WEATHER SYSTEM FORECAST TO CROSS THE REGION THURSDAY INTO THURSDAY NIGHT...THERE MAY BE PATCHY DRIZZLE OVER THE FAR EASTERN SECTIONS OF THE CWA FRIDAY MORNING BEFORE THE LOW LEVEL MOISTURE GETS SCOURED OUT...BUT DECIDED TO LEAVE IT OUT. WITH NO DISCERNABLE UPSTREAM SHORT WAVE TO HOLD UP OR SLOW THE DEPARTING SYSTEM...CHANCES ARE THE PRECIP WILL BE OVER BY 12Z FRIDAY ANYWAY. HIGH PRESSURE SHOULD KEEP THE REGION DRY WITH SLIGHTLY BELOW NORMAL TEMPERATURES THROUGH SUNDAY. SATURDAY NIGHT THE GFS...IN RESPONSE TO A SHARP H5 TROUGH MOVING EASTWARD ACROSS THE SOUTHERN PLAINS... DEVELOPS A SURFACE LOW OVER THE DEEP SOUTH AND TRACKS IT JUST TO THE SOUTH AND EAST OF OUR CWA WHILE PAINTING MINOR QPF OVER THE FAR SOUTHEAST SECTIONS OF OUR CWA. THE ECMWF AND CANADIAN DO NOT PICK UP ON THE H5 TROUGH AND KEEP ALL QPF ALONG THE GULF COAST...SO DECIDED TO GO WITH THE MAJORITY FOR NOW. BEYOND THAT...THE NEXT CHANCE FOR PRECIPITATION WILL BE SUNDAY NIGHT INTO MONDAY AS THE NEXT STORM SYSTEM CROSSES THE REGION. PRECIPITATION SHOULD REMAIN ALL LIQUID WITH THIS SYSTEM AND THERE SHOULD BE JUST ENOUGH INSTABILITY TO WARRANT SMALL THUNDER CHANCES ON MONDAY. MODELS NOT IN GOOD AGREEMENT ON THIS ONE EITHER. THE GFS IS FASTER AND HAS THE EVENT VIRTUALLY OVER BY MIDDAY MONDAY WHEREAS THE ECMWF JUST GETS THINGS STARTED MONDAY MORNING AND KEEPS PRECIP CHANCES OVER THE AREA THROUGH MONDAY NIGHT. HOPEFULLY WITH TIME MODELS WILL GET A BETTER GRIP ON THIS ONE. && .AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT) ISSUED AT 515 PM CST MON FEB 18 2013 LINGERING SHOWERS MAY IMPACT KOWB FOR ANOTHER HOUR OR SO. WIND SHIFT TO THE WEST/NORTHWEST IS ALREADY UNDERWAY AT KCGI/KPAH/KEVV AND THE SHIFT WILL TAKE PLACE AT KOWB WITHIN THE NEXT HOUR OR TWO. STRONG GUSTY SOUTH/SOUTHWEST WINDS WILL PERSIST BEFORE THAT HAPPENS THOUGH. MEANWHILE...MVFR CIGS ARRIVE WITH THE WIND SHIFT AND ARRIVAL OF AN UPPER LEVEL TROUGH. HOWEVER...LOOKING AT SATELLITE...THE LOW CLOUDS MAY NOT LAST TOO LONG AT KCGI/KPAH. MVFR CIGS MAY LINGER AT KEVV/KOWB LONGER INTO THE DAY ON TUESDAY...BUT ALL TERMINALS SHOULD BE SKC BY 18Z. WINDS WILL STAY UP FOR MOST OF THE NIGHT AND INTO MOST OF TUESDAY. BY 00Z WEDNESDAY...THE WIND SHOULD SUBSIDE. && .PAH WATCHES/WARNINGS/ADVISORIES... IL...NONE. MO...NONE. IN...NONE. KY...NONE. && $$ SHORT TERM...SMITH LONG TERM...JAP AVIATION...JAP