000 FXUS63 KLMK 232015 AFDLMK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LOUISVILLE KY 315 PM EST MON NOV 23 2009 .SHORT TERM (TONIGHT AND TUESDAY)... THE UPPER WAVE THAT BROUGHT SCATTERED SPRINKLES AND A FEW LIGHT RAIN SHOWERS TO THE REGION TODAY WILL HAVE MOVED OFF TO THE EAST BY 00Z THIS EVENING. RADAR TRENDS SHOW THE RAIN BECOMING LIGHTER AND MORE SPARSE. SO...WILL HAVE DRY CONDITIONS IN THE FORECAST TONIGHT AFTER 00Z. PERSISTENT CLOUDS...ESPECIALLY SOUTH OF THE OHIO RIVER...COMBINED WITH VERY WEAK SOUTHEASTERLY FLOW WILL KEEP TEMPERATURES FROM FALLING MUCH. GIVEN THAT AND CURRENT DEW POINTS IT APPEARS MET IS TOO COLD AND WILL SIDE MORE TOWARD THE WARMER MAV GUIDANCE FOR LOWS TONIGHT. MOSTLY CLOUDY CONDITIONS WILL CONTINUE ON OUR TUESDAY AS LOW LEVEL MOISTURE GETS TRAPPED OVERHEAD. SOME EARLY MORNING FOG WILL BE POSSIBLE...ESPECIALLY IN ANY SPOTS THAT GOT A FEW RAINDROPS TODAY AND CAN DEVELOP ANY BREAKS IN THE CLOUD COVER TONIGHT...BUT AT THIS TIME WIDESPREAD DENSE MORNING FOG APPEARS UNLIKELY. THE NEXT SYSTEM APPROACHING FROM THE PLAINS...DISCUSSED IN GREATER DETAIL IN THE LONG TERM DISCUSSION BELOW...MAY COME CLOSE ENOUGH TO THROW AN ISOLATED SHOWER INTO THE FAR WEST BY EARLY TUESDAY EVENING...GENERALLY WEST OF A LINE FROM SALEM TO HARDINSBURG TO RUSSELLVILLE. .LONG TERM (TUESDAY NIGHT - MONDAY)... TUESDAY NIGHT THROUGH THURSDAY NIGHT... LATEST MODEL RUNS OF THE 23/12Z GFS AND EURO ARE A LITTLE FASTER THAN THE 23/00Z RUNS WITH THE VERTICALLY STACKED LOW PRESSURE SYSTEM MOVING FROM THE MIDWEST INTO THE GREAT LAKES. INITIAL H5 LOW ASSOCIATED WITH THE MAIN SFC LOW LOOKS TO WEAKEN AS IT MOVES INTO THE GREAT LAKES. HOWEVER...A SECOND AND MORE POTENT H5 LOW WILL QUICKLY MOVE INTO THE NORTHERN OHIO VALLEY ON THURSDAY AND THEN LIFT OUT BY FRIDAY. OVERALL...THE PRECIPITATION PROBABILITIES CONTINUE TO FLUCTUATE WITH EACH MODEL RUN. AT THIS TIME...IT APPEARS THAT OUR BEST SHOT OF SHOWERS WILL COME TUESDAY NIGHT WITH THE INITIAL COLD FRONT. A DRY PUNCH WILL ALLOW A TEMPORARY LULL IN THE PRECIPITATION ON WEDNESDAY THEN WE SHOULD SEE PRECIPITATION RAMP UP AS THE SECOND AND MORE POTENT UPPER LOW MOVES IN BY THANKSGIVING DAY AND INTO THURSDAY NIGHT. TEMPERATURE STRUCTURE IN THE MODELS CONTINUES TO SHOW TRENDS OF WARMING OVER THE LAST SEVERAL RUNS. LOWS TUES NIGHT SHOULD BOTTOM OUT IN THE LOWER 40S WITH HIGHS ON WEDNESDAY WARMING INTO THE UPPER 40S TO THE LOWER 50S. THE COOL DOWN STILL LOOKS ON TARGET FOR WED NIGHT AND THURSDAY WITH LOWS DROPPING INTO THE UPPER 30S WED NIGHT AND HIGHS ON THANKSGIVING WARMING INTO THE LOWER 40S IN THE NORTH AND MID 40S ACROSS THE SOUTH. CRITICAL THICKNESSES AND LOWER PBL TEMPERATURES HAVE CONTINUED TO WARM AS WELL WITH EACH SUCCESSIVE RUN AND THEREFORE THE RISK OF A WINTRY MIX OF RAIN AND SNOW SEEMS MUCH LESS LIKELY FOR THANKSGIVING DAY. HOWEVER...AS THE UPPER LOW APPROACHES THURSDAY NIGHT...CRITICAL THICKNESSES WILL LOWER SIGNIFICANTLY THAT A MIX OF RAIN AND SNOW SHOWERS IS MUCH MORE LIKELY. A FULL CHANGE OVER TO ALL SNOW SHOWERS IS LIKELY FOR EARLY FRIDAY MORNING. OVERNIGHT LOWS ARE EXPECTED TO DROP TO NEAR FREEZING BY FRIDAY MORNING. SNOW ACCUMULATIONS ARE NOT ANTICIPATED FOR TWO REASONS. FIRST...RECENT CO-OP DATA STILL SHOWS 4IN SOIL TEMPS IN THE MID-UPPER 50S...AND SECOND...THE INTENSITY OF THE SNOW SHOWERS IS LOOKS TO BE GENERALLY LIGHT IN NATURE. THOUGH WITH TEMPERATURES NEAR THE FREEZING MARK...SOME BRIDGES AND ELEVATED OVERPASSES MAY DEVELOP SOME SLICK SPOTS EARLY FRIDAY MORNING. WE WILL BE HIGHLIGHTING THIS THREAT IN THE HWO PRODUCT THIS AFTERNOON. FRIDAY THROUGH MONDAY... COLD NORTHWEST FLOW STILL LOOKS ON TAP AS LARGE UPPER LEVEL LOW MOVES TO OUR NORTHEAST. ABUNDANT LOW-LEVEL MOISTURE STILL LOOKS TO REMAIN IN PLACE FOR SCT SNOW SHOWERS ACROSS THE EASTERN 2/3RDS OF THE FCST AREA ON FRIDAY. THESE SNOW SHOWERS WILL LIKELY TAPER OFF DURING THE AFTERNOON AS THE UPPER LEVEL LOW PULLS OUT AND MOISTURE BECOMES MORE SCANT. SFC 2M TEMPS FROM THE RAW GFS CONTINUE TO TREND WARMER AND WE/VE RAISED TEMPS SLIGHTLY FOR THIS FCST PACKAGE. A GRADIENT OF TEMPERATURE WILL BE NOTED WITH HIGHS IN THE MID 40S IN THE SW TO THE LOWER 40S IN THE NE. DRY CONDITIONS ALONG WITH CLEARING IS EXPECTED FOR FRIDAY NIGHT WITH LOWS DROPPING INTO THE UPPER 20S IN THE NE TO AROUND 30 IN THE SW. AS WE MOVE INTO THE SAT-MON TIME PERIOD...MODEL SOLUTIONS BEGIN TO DIVERGE SIGNIFICANTLY. IN GENERAL...THE MODELS ARE IN REASONABLE AGREEMENT FOR SATURDAY WITH A DRY FCST AS H5 HEIGHTS RISE IN RESPONSE TO THE DEPARTING UPPER LEVEL LOW TO OUR NORTHEAST...AND A DEVELOPING TROUGH IN THE WESTERN U.S. HIGHS SAT WILL MODERATE WITH HIGHS IN THE LOWER 40S IN THE NE TO THE MID AND UPPER 40S IN THE CENTRAL SECTIONS AND AROUND 50 IN THE SE. LOWS SAT NIGHT SHOULD DROP INTO THE LOWER 30S IN THE EAST AND MID 30S IN THE WEST. BY SUNDAY...LARGE DIFFERENCES IN THE MODELS ARE GOING TO LEAD TO A LOWER CONFIDENCE FCST HERE. THE EURO HAS BEEN INSISTENT ON DROPPING A LARGE TROUGH INTO THE WEST WITH SFC CYCLOGENESIS OCCURRING OVER TX. THE GFS KEEPS MORE STRENGTH IN THE NORTHERN STREAM WHICH RESULTS IN A FASTER MOVING SYSTEM UP THROUGH THE NATIONS MID-SECTION AND INTO THE GREAT LAKES...A SIMILAR STORM TRACK THAT WE SAW THROUGH MUCH OF OCTOBER 2009. WE HAVE SIDED WITH THE EUROPEAN RUN FOR THIS PORTION OF THE FCST PD WHICH RESULTS IN A SLOWER AND DEEPER SYSTEM THAT WILL AFFECT THE REGION SUNDAY AND MONDAY. WARM AIR ADVECTION AND ISENTROPIC LIFT WILL LEAD TO A DEVELOPING RAIN SHIELD TO OUR WEST EARLY ON SUNDAY AND THEN GRADUALLY SPREAD EASTWARD AND NORTHEASTWARD AS THE SFC LOW DEVELOPS MOVES UP THROUGH LA/MS/TN. THIS SHOULD BRING A GOOD SHOT OF RAIN TO MUCH OF THE REGION...WITH PERHAPS A LITTLE BIT OF A WINTRY MIX ON THE BACKSIDE IF THE COLDER AIR CAN GET INTO THE REGION BEFORE THE PRECIPITATION MOVES OUT. HIGHS SUNDAY SHOULD WARM INTO THE UPPER 40S TO THE LOWER 50S WITH MONDAY`S HIGHS RANGING FROM THE MID-UPPER 40S IN THE NORTH AND LOWER 50S ACROSS THE SOUTHEAST. LOWS SUN NIGHT LOOK TO DROP INTO THE UPPER 30S TO THE LOWER 40S...WITH LOWS MONDAY NIGHT DROPPING TO NEAR FREEZING BY TUE MORNING. && .AVIATION (18Z TAF ISSUANCE)... A STORM SYSTEM DIGGING INTO THE GREAT PLAINS WILL KEEP MOST RAINFALL OFF TO OUR WEST FOR THIS FORECAST PACKAGE...OTHER THAN A FEW STRAY SPRINKLES OR LIGHT RAIN SHOWERS EARLY THIS AFTERNOON THAT SHOULD BE OF LITTLE CONSEQUENCE TO AVIATION. WINDS WILL REMAIN LIGHT FROM THE SOUTH AND SOUTHEAST. LOW LEVEL MOISTURE WILL STAY TRAPPED IN THE REGION THROUGHOUT THE PERIOD...RESULTING IN MOSTLY MVFR CEILINGS WITH SOME AREAS OF IFR. AT THIS TIME IT APPEARS THAT THE LOW STRATUS WILL BE THE PRIMARY CHALLENGE TO AVIATION...WITH ANY SURFACE VISIBILITIES REMAINING AT OR ABOVE 2 MILES. IF HOLES CAN DEVELOP IN THE OVERCAST TOWARDS MORNING THEN SOME LOWER VISIBILITIES COULD DEVELOP. && .LMK WATCHES/WARNINGS/ADVISORIES... KY...NONE. IN...NONE. && $$ SHORT TERM........13 LONG TERM.........MJ AVIATION..........13