Issued by NWS Louisville, KY
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000 FXUS63 KLMK 212308 AFDLMK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LOUISVILLE KY 608 PM EST SAT NOV 21 2009 ...UPDATED AVIATION DISCUSSION... .SHORT TERM (TONIGHT AND SUNDAY)... SFC HIGH PRESSURE CENTERED OVER OHIO WILL MOVE NE INTO THE NEW ENGLAND STATE TONIGHT. EXPECT MOSTLY CLEAR SKIES OVERNIGHT WITH AN INCREASE IN CLOUDS OVER THE SOUTHERN FORECAST AREA (FA) TOWARD SUNRISE AHEAD OF THE NEXT WEATHER SYSTEM. LOW TEMPS WILL BE IN THE UPPER 30S OVER THE BLUEGRASS/SOUTHEAST INDIANA TO LOW 40S ELSEWHERE ACROSS THE REGION. THE NEXT WEATHER SYSTEM SITS TO OUR SOUTH OVER LOUISIANA AND TEXAS. THIS SYSTEM WILL WEAKEN AT THE SFC AND MOVE NORTH UP INTO THE TENNESSEE VALLEY ON SUNDAY. ALTHOUGH MOST MODELS KEEP THE PRECIP SOUTH OF OUR FA...THE 12Z GFS HAS A GOOD HANDLE ON THE CURRENT PRECIP FIELD AND IT DOES BRING SOME UP INTO OUR FAR SOUTHERN COUNTIES SUNDAY AFTERNOON. THEREFORE...WILL CONTINUE A 20% POP IN OUR SOUTHERN COUNTIES ALONG THE TN BORDER FOR THE AFTERNOON HOURS. WITH A NOTABLE AMOUNT OF MORE CLOUDS IN THE SOUTHERN FA...WILL SEE HIGH TEMPS RANGE FROM THE MID 50S OVER SOUTH CENTRAL KY TO UPPER 50S OVER SOUTHERN INDIANA/NORTH CENTRAL KY. .LONG TERM (SUNDAY NIGHT - SATURDAY)... SUNDAY NIGHT THROUGH SATURDAY... SUNDAY NIGHT THROUGH WEDNESDAY NIGHT... IN THE MEDIUM RANGE...THE DETERMINISTIC AND ENSEMBLE MODEL GUIDANCE IS IN GENERAL AGREEMENT WITH THE SYNOPTIC PATTERN ACROSS NORTH AMERICA. CUT OFF 500MB OVER THE MS DELTA REGION IS FCST TO LIFT NORTHEAST AND WEAKEN AS ANOTHER STRONG H5 WAVE DROPS SOUTHEAST OUT OF CANADA AND INTO THE PLAINS. ASSOCIATED WITH THE LIFTING H5 WAVE...A SFC AREA OF LOW PRESSURE LOOKS TO MOVE UP OUT OF THE GULF AND TRACK NE ALONG THE SOUTHEAST COAST. WITH THIS TRACK...SOME LIGHT SHOWER ACTIVITY SEEMS POSSIBLE OVER OUR SOUTHEAST SECTIONS LATE SUNDAY AND EARLY MONDAY BEFORE QUICKLY MOVING OFF THE NORTHEAST. OVERALL...THE TREND IN THE MODEL DATA IS DRIER THAN PREVIOUSLY FCST. LOWS SUNDAY NIGHT LOOK TO DROP INTO THE LOWER 40S IN THE NORTH WITH MID 40S IN THE SOUTH. HIGHS MONDAY SHOULD WARM INTO THE LOWER TO MID 50S. NEXT WEATHER SYSTEM WILL BEGIN TO AFFECT THE REGION BY LATE TUESDAY IN THE FORM OF A LARGE CLOSED LOW PRESSURE SYSTEM ROLLING EASTWARD ACROSS THE PLAINS. ASSOCIATED SFC LOW LOOKS TO MOVE FROM THE PLAINS AND THEN INTO THE GREAT LAKES STATES WITH A LARGE 500 MB GYRE LEFT SPINNING ACROSS THE GREAT LAKES REGION. SHOWER CHANCES LOOK TO INCREASE TUESDAY AFTERNOON AHEAD OF THE SFC COLD FRONT WHICH LOOKS TO PUSH THROUGH THE REGION TUE NIGHT/EARLY WEDNESDAY. HERE WE`LL BE RUNNING THE HIGHEST POP CHANCES FOR THIS FORECAST PERIOD. AS INITIAL LOW MOVES OFF THE NORTHEAST...LARGE LOBE OF VORTICITY WILL DROP DOWN OUT OF THE UPPER MIDWEST AROUND THE PERIPHERY OF THE LARGE H5 CIRCULATION IN THE LAKES. THIS WILL LEAD TO ADDITIONAL CHANCES OF LIGHT PRECIPITATION INTO WEDNESDAY NIGHT. TEMPS WILL START OFF TUESDAY IN THE LOWER TO MID 40S WITH HIGHS TOPPING OUT IN THE LOW-MID 50S. MUCH COOLER WEATHER WILL MOVE INTO THE REGION WEDNESDAY WITH OVERNIGHT LOWS IN THE MID-UPPER 30S AND HIGHS ON WEDNESDAY IN THE UPPER 40S TO THE LOWER 50S. LOWS WED NIGHT LOOK TO DROP INTO THE MID 30S. THANKSGIVING DAY THROUGH SATURDAY... VERY LARGE H5 CUT OFF LOW IS FCST TO MOVE SLOWLY EASTWARD THROUGH THE GREAT LAKES REGION. SFC LOW WILL LOOKS TO BE STACKED RIGHT UNDERNEATH OF THE UPPER LOW WITH MUCH OF OUR REGION BEING LOCKED INTO A NORTHWEST FLOW SITUATION. LOTS OF LOW-LEVEL MOISTURE LOOKS TO STAY IN THE REGION...SO THANKSGIVING DAY LOOKS TO BE VERY CLOUDY AND COOL WITH SOME SHOWERS MOVING THROUGH THE REGION. TEMPERATURES WILL CONTINUE TO COOL WITH HIGHS IN THE UPPER 30S TO THE LOWER 40S IN THE NORTH AND MID 40S DOWN SOUTH. THE RAW MODEL DATA IS COOLER...AND THE TREND IN THE DATA CONTINUES TO GO DOWN. SO FURTHER ADJUSTMENTS TO TEMPS MAY BE REQUIRED IN SUBSEQUENT FCSTS. NORTHWEST FLOW LOOKS TO CONTINUE THU NIGHT AND INTO FRIDAY. ENOUGH MOISTURE LOOKS TO BE AVAILABLE THU NIGHT FOR SOME LIGHT RAIN SHOWERS EARLY...WITH A TRANSITION TO SNOW SHOWERS POSSIBLE LATE THU NIGHT OR FRIDAY MORNING. SFC AND UPPER LEVEL LOWS LOOK TO PULL OUT QUICKLY FOR FRIDAY AND SATURDAY WITH A DRYING TREND EXPECTED. HIGHS FRIDAY/SAT WILL RANGE FROM THE UPPER 30S-LOWER 40S IN THE NORTH TO THE MID 40S IN THE SOUTH. AGAIN THE RAW MODEL GUIDANCE IS COOLER AND THE TREND IS COOLER...SO FURTHER ADJUSTMENTS DOWNWARD MAY BE REQUIRED. && .AVIATION (00Z TAF ISSUANCE)... AN AREA OF LOW PRESSURE MOVING ACROSS THE GULF COAST STATES WILL BE RESPONSIBLE FOR GRADUALLY INCREASING CLOUDS SUNDAY AND AN EAT TO SOUTHEAST FLOW. WITH CLEAR SKIES AND CALM WINDS FOR MOST OF THE NIGHT WILL WILL CONTINUE TO MENTION MVFR AND OCCASIONAL IFR VSBYS WITH FOG BEING THE RESTRICTION. OTHERWISE EXPECT SOME MID LEVEL CLOUDS TO OVERSPREAD THE AREA AFTER 16Z. && .LMK WATCHES/WARNINGS/ADVISORIES... KY...NONE. IN...NONE. && $$ SHORT TERM........AML LONG TERM.........MJ AVIATION..........JA
