FXUS63 KLMK 071732
AFDLMK
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
1232 PM EST MON DEC 7 2009
...UPDATED AVIATION DISCUSSION...
...FORECAST UPDATE #2...
LIGHT SNOW HAS ENDED OVER THE AREA THIS MORNING WITH ONLY LIGHT
PATCHY DRIZZLE LEFT. EXPECT THIS DRIZZLE TO CONTINUE THROUGH EARLY
AFTERNOON BEFORE WE COMPLETELY DRY OUT. THE COLD FRONT ASSOCIATED
WITH THIS LOW PRESSURE SYSTEM STILL SITS OUT OVER ILLINOIS AND
MISSOURI SO IT WILL BE LATE AFTERNOON/EARLY EVENING BEFORE IT PASSES
THROUGH OUR AREA. PREVIOUSLY FORECASTED HIGH TEMPS IN THE LOW TO
MID 40S WITH A FEW UPPER 30S LOOK ON TRACK FOR THIS AFTERNOON.
...FORECAST UPDATE #1...
UPDATED THE FORECAST TO MOVE PRECIP OUT A LITTLE QUICKER. THE LAST
OF THE LIGHT SNOW/SLEET WILL MOVE THROUGH THE BLUEGRASS AND LAKE
CUMBERLAND REGIONS OVER THE NEXT HOUR. THEN ONLY LIGHT DRIZZLE OR
FLURRIES TO FOLLOW AFTER THAT THROUGH EARLY AFTERNOON. DRIVERS
SHOULD CONTINUE TO USE CAUTION ON THE ROADWAYS THIS MORNING AS THERE
ARE MANY SLICK SPOTS AND SEVERAL WRECKS HAVE ALREADY OCCURRED.
.SHORT TERM (TODAY AND TONIGHT)...
A VERY FAST ZONAL FLOW ACROSS THE CONUS CURRENTLY IS DIVIDING ARCTIC
AIR ACROSS THE NORTHERN HALF OF THE COUNTRY FROM MILD AIR ACROSS THE
GULF STATES. A NOSE OF A JET MAX WILL QUICKLY ZIP ACROSS SOUTHERN
INDIANA AROUND DAWN THIS MORNING. ASSOCIATED WITH THIS IS A WEAK
INVERTED SURFACE TROUGH NOW ACROSS SOUTHERN ILLINOIS. THIS WILL MOVE
INTO SOUTHERN OHIO BY LATE MORNING.
EARLIER THIS MORNING AT 3 AM...ISENTROPIC LIFT WAS BRINGING WIDESPREAD
LIGHT MIXED PRECIPITATION ACROSS WESTERN KENTUCKY AND SOUTHERN
ILLINOIS. MOSTLY SNOW HAS BEEN FALLING ALONG AND NORTH OF INTERSTATE
64 WITH MIXED PRECIP NOTED SOUTH OF THIS INTERSTATE. PADUCAH HAS HAD
JUST A COLD RAIN. THE 00Z MESO-NAM INITIALIZED THE CURRENT PRECIP
WELL AND WILL USE AS A GUIDE FOR THIS MORNING'S PRECIP EVOLUTION.
EXPECT LIGHT SNOW TO MOVE ACROSS SOUTHERN INDIANA DURING THE
PRE-DAWN HOURS AND LINGER PERHAPS THROUGH SUNRISE. MIXED
PRECIPITATION IS EXPECTED ACROSS NORTH CENTRAL KENTUCKY ALONG AND
SOUTH OF INTERSTATE 64. SOUTH OF A OHIO TO MADISON COUNTY
LINE...TEMPERATURES HAVE WARMED ENOUGH TO LIKELY BRING JUST RAIN
WITH A FEW ICE PELLETS MIXED IN.
WITH THIS FAST MOVING SYSTEM...ONLY LIGHT QPF IS EXPECTED WITH
LIQUID EQUIVALENT PRECIPITATION EXPECTED TO AVERAGE UP AROUND A TENTH
OF AN INCH ALONG THE OHIO RIVER WEST OF LOUISVILLE...WITH LESSER
AMOUNTS SOUTH AND EAST. SNOW MAY ACCUMULATE UP TO AN INCH AT MOST
ACROSS SOUTHWEST INDIANA BEFORE ENDING AT OR SHORTLY AFTER DAWN.
WILL ISSUE A SPECIAL WEATHER STATEMENT THIS MORNING AS PRECIPITATION
AMOUNTS EXPECTED TO GENERALLY REMAIN LESS THAN ONE INCH.
MIXED PRECIPITATION WILL BE ENDING BY NOON ACROSS OUR EASTERN
COUNTIES. DESPITE DRIER AIR MOVING IN ALOFT THIS AFTERNOON...A
SATURATED BOUNDARY LAYER WILL LIKELY MEAN LOW CLOUDS PERSISTING MUCH
OF THIS AFTERNOON. LIGHT SOUTH WINDS THIS MORNING WILL SWITCH TO THE
SOUTHWEST AT 5 TO 10 MPH AFTER THE INVERTED TROUGH PASSES LATER THIS
MORNING. TEMPS TODAY WILL STRUGGLE TO REACH 40 ACROSS THE NORTH WITH
LOW 40S POSSIBLE ACROSS THE SOUTH. EXPECT CLOUDY SKIES TONIGHT WITH
LOWS NEAR FREEZING.
.LONG TERM (TUESDAY - SUNDAY)...
THE MUCH ADVERTISED MID WEEK STORM SYSTEM IS STILL ON TRACK TO
AFFECT THE LOWER OHIO VALLEY TUESDAY AND WEDNESDAY WITH A COLD END
TO THE WEEK.
TUESDAY AND WEDNESDAY...
A STRONG UPPER LEVEL JET MAXIMUM LOCATED AT THE BASE OF A FOUR
CORNERS TROUGH WILL STEAK ACROSS THE CENTRAL UNITED STATES AND
STRENGTH AS IT ENTERS THE LOWER OHIO VALLY. THE ASSOCIATED TROUGH
WILL BECOME NEGATIVELY TILTED AS IT MOVES FROM THE MID MISSISSIPPI
VALLY INTO THE GREAT LAKES REGION. IN THE LOWER LEVELS OF THE
ATMOSPHERE A LOW WILL TRACK FROM THE FOUR CORNERS TO NORTHERN
INDIANA FROM 12Z TUESDAY THROUGH 12Z WEDNESDAY. THE PRESSURE
GRADIENT WILL TIGHTEN UP ACROSS THE REGION WITH INCREASING WINDS.
THE FIRST ISSUE WILL BE TIMING OF PRECIPITATION INTO THE REGION
TUESDAY. MODELS ARE GENERALLY SLOW WITH MOISTURE RETURN ON A STRONG
ISENTROPIC SURFACE SO WE WILL MENTION PRECIPITATION BEGINNING AT 12Z
TUESDAY. IF THIS OCCURS SOME OF THE PRECIPITATION MAY BEGIN AS A
BRIEF PERIOD OF SNOW ACROSS THE NORTHERN PORTION OF CENTRAL KENTUCKY
AND SOUTH CENTRAL INDIANA. WE HAVE UPPED POPS TUESDAY AFTERNOON INTO
THE CATEGORICAL RANGE AND WILL CONTINUE WITH CATEGORICAL POPS
TUESDAY NIGHT. WE WILL ALSO CONTINUE TO MENTION ELEVATED
THUNDERSTORMS TUESDAY NIGHT. 850MB WINDS TUESDAY NIGHT WILL RANGE
FROM 60-75 KNOTS DEPENDING ON THE MODEL. GIVEN THE STABLE LAYER JUST
ABOVE THE SURFACE IT WILL BE DIFFICULT TO REALIZE A WIDESPREAD
SEVERE WEATHER OUTBREAK...BUT SHOULD ANY STORMS BECOME STRONG ENOUGH
WE MAY SEE THE WINDS ALOFT MIX DOWN TO THE SURFACE LATE TUESDAY
NIGHT. EVEN WITHOUT STORMS...EXPECT ENOUGH LOW-LEVEL MOMENTUM
TRANSFER TO PRODUCE A WINDY NIGHT.
A STRONG COLD FRONT WILL SWEEP ACROSS THE REGION WEDNESDAY. BEHIND
THE FRONT WESTERLY WINDS WILL REMAIN STRONG WITH GUSTS TO 40 MPH
POSSIBLE. THE GUSTY WINDS WILL ALSO USHER IN MUCH COLDER AIR AND
RESIDUAL MOISTURE WILL CHANGE TO LIGHT SNOW SHOWERS WEDNESDAY
AFTERNOON.
THURSDAY THROUGH SUNDAY...
FLOW ALOFT WILL BECOME ZONAL BEHIND THIS SYSTEM...AND GENERALLY
REMAIN THAT WAY THROUGH THE REST OF THE PERIOD. THURSDAY WILL SEE
MODERATE BREEZES AS THE PRESSURE GRADIENT WEAKENS AND THEN BY EARLY
FRIDAY THE HIGH CENTER WILL BE CLOSE TO THE REGION. WITH THE WIND
EXPECT THURSDAY MORNING TO FEEL THE COLDEST OF THE PERIOD...WITH
WIND CHILL READINGS POSSIBLY GETTING INTO THE SINGLE DIGITS.
FRIDAY MORNING'S LOWS SHOULD BE SIMILAR TO THURSDAY...BUT WINDS
SHOULD BE LIGHT. HIGH CLOUDS MAY MOVE IN WITH AN UPPER LEVEL SYSTEM
OVERNIGHT...AND THAT WOULD PREVENT TEMPERATURES FROM DROPPING TOO
FAR. SOUNDINGS ALSO INDICATE PLENTY OF MOISTURE IN THE SNOW-GROWTH
ZONE THROUGH THE DAY FRIDAY...BUT DRY LOW LEVELS SHOULD DISSIPATE
ANY PRECIP UNTIL PERHAPS LATE IN THE DAY/EVENING OVER THE NORTHERN
CWA.
THE NEXT WEEKEND LOOKS DRIER THAN IN PREVIOUS FORECASTS DESPITE A
SERIES OF UPPER LEVEL DISTURBANCES MOVING ACROSS THE CWA WITHIN THE
ZONAL FLOW. GIVEN THE FAST MOVING NATURE OF THE FLOW AND DIFFICULTY
IN PREDICTING THESE SMALLER DISTURBANCES OUT TO DAY 6-7...WILL LOWER
SNOW CHANCES TO SLIGHT FOR FRIDAY NIGHT AND NOT MENTION ANY
PRECIPITATION SATURDAY AND SUNDAY.
&&
.AVIATION (18Z TAF ISSUANCE)...
WE/LL START OFF THE TAF PERIOD WITH LIFR/IFR CIGS. THESE SHOULDN/T
LAST MUCH LONGER AS A PATCH OF SCT CLOUDS OVER SOUTHERN ILLINOIS AND
WESTERN KENTUCKY MOVES THIS WAY THIS AFTERNOON. BY 21Z...EXPECT
CIGS TO SCT OUT AND VSBYS TO IMPROVE TO VFR.
SOME FEW-SCT LOW CLOUDS WILL HANG AROUND TONIGHT. IN ADDITION...A
COLD FRONT SITTING OVER ILLINOIS AND MISSOURI WILL MOVE EAST ACROSS
THE AREA SWINGING WINDS AROUND BRIEFLY TO THE NW AND THEN QUICKLY
OVER TO EAST AS THE NEXT WEATHER SYSTEM APPROACHES. WITH THE
REDUCED CLOUD COVER...FAIRLY LIGHT WINDS (3-4KTS)...AND ABUNDANT LL
MOISTURE...WE SHOULD SEE SOME MVFR BR DEVELOP AROUND 6Z.
THE NEXT LOW PRESSURE SYSTEM WILL START TO PUSH OVERRUNNING PRECIP
INTO OUR AREA TOMORROW MORNING AFTER 13Z. LIGHT TO MODERATE RAINS
WILL BE IN STORE FOR TOMORROW AFTERNOON WITH FLIGHT RESTRICTIONS
DROPPING TO IFR POSSIBLY LIFR BY MID-LATE AFTERNOON.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
KY...NONE.
IN...NONE.
&&
$$
UPDATE.........AML
SHORT TERM.....JSD
LONG TERM......JA
AVIATION.......AML
