748
FXUS63 KLMK 201131
AFDLMK
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
631 AM EST THU FEB 20 2020
..UPDATED AVIATION DISCUSSION
SHORT TERM
(TODAY AND TONIGHT)
ISSUED AT 255 AM EST THU FEB 20 2020
DOMINANT WEATHER PLAYER TODAY IS A 1046MB SFC HIGH CENTERED NEAR THE
SE CORNER OF SOUTH DAKOTA. SOUTHERN STREAM SYSTEM WILL PRODUCE
ACCUMULATING SNOW ACROSS PARTS OF THE TENNESSEE VALLEY, BUT ALL IN
ALL THE HIGH PRESSURE WILL WIN OUT ACROSS INDIANA AND ALL BUT
EXTREME SOUTHERN KENTUCKY. MOST AREAS WILL SEE PLENTY OF MID/HIGH-
LEVEL CLOUD COVER WITH TEMPS A FEW DEGREES BELOW NORMAL, AND THE
MAIN QUESTION MARK WILL BE THE NORTHWARD EXTENT OF ANY PRECIP.
WILL PAINT THE SOUTHERN TIER OF COUNTIES IN KENTUCKY WITH CHANCE
POPS, WHICH MAY BE A BIT ON THE GENEROUS SIDE BUT COULD BETTER
MESSAGE THE TRACE SNOWFALL POTENTIAL. LOW-LEVEL DRY AIR WILL SUPPORT
ENOUGH EVAPORATIVE COOLING TO KEEP IT MOSTLY SNOW, BUT SFC TEMPS
WILL STILL BE SOLIDLY ABOVE FREEZING SO LITTLE OR NO ACCUMULATION IS
EXPECTED.
SKIES WILL CLEAR FROM NW-SE IN THE LATE AFTERNOON AND EARLY EVENING,
SETTING UP FOR DECENT RADIATIONAL COOLING TONIGHT. LIGHT N-NE BREEZE
WILL BE A LIMITING FACTOR, BUT MANY LOCATIONS WILL STILL DIP INTO
THE TEENS BY FRI MORNING.
LONG TERM
(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 255 AM EST THU FEB 20 2020
FRIDAY THROUGH SATURDAY NIGHT...
EXPECT DRY WEATHER FRIDAY AND SATURDAY WITH AMPLE SUNSHINE GIVEN
BENIGN NW FLOW IN THE MID-TROPOSPHERE COMBINED WITH A RIDGE OF HIGH
PRESSURE AT THE SURFACE EXTENDING ACROSS THE OH VALLEY. IT WILL BE
CHILLY FRIDAY WITH AFTERNOON HIGHS MAINLY UPPER 30S AND LOWER 40S.
AFTER A COLD START SATURDAY MORNING IN THE LOWER 20S, AFTERNOON
TEMPS SHOULD MODERATE INTO THE MID 40S TO LOWER 50S, OR ABOUT
AVERAGE FOR MID-LATE FEB.
SUNDAY THROUGH MONDAY...
THE PATTERN ALOFT CHANGES SUNDAY AND MONDAY AS MID-LEVEL FLOW BACKS
TO SW AHEAD OF A VIGOROUS STORM SYSTEM FORECAST TO PUSH EAST ACROSS
THE CENTRAL PLAINS SUNDAY AND MID MS VALLEY MONDAY. THERE IS GOOD
CONSISTENCY IN MODEL GUIDANCE SUGGESTING HIGHER FORECAST CONFIDENCE.
A BAND OF INITIAL WARM ADVECTION/ISENTROPIC LIFT WELL AHEAD OF THIS
SYSTEM SHOULD BRING SOME SHOWERS INTO WEST-CENTRAL KY SUNDAY
AFTERNOON, SPREADING ACROSS THE REST OF CENTRAL KY AND SOUTHERN IN
SUNDAY NIGHT. ADDITIONAL WIDESPREAD SHOWERS WILL SPREAD ACROSS OUR
AREA LATE SUNDAY NIGHT AND MONDAY MORNING. RAINFALL AMOUNTS ARE
EXPECTED TO BE GENERALLY MODEST IN THE 0.25 TO 0.75 INCH RANGE, WITH
ISOLATED HIGHER AMOUNTS POSSIBLE. MODEL SOUNDINGS DO SHOW SOME
STEEPENING OF LAPSE RATES ALOFT MONDAY AFTERNOON AND EVENING, SO
SCATTERED BRIEF HEAVY SHOWERS OR EVEN A RUMBLE OR TWO OF THUNDER ARE
POSSIBLE AT THAT TIME.
TUESDAY THOUGH THURSDAY...
IN THE WAKE OF THE DEPARTING SYSTEM MONDAY NIGHT, EXPECT MAINLY DRY
CONDITIONS TUESDAY WITH SEASONAL AFTERNOON HIGH TEMPS (UPPER 40S TO
MID 50S). LATEST MODEL GUIDANCE THEN SUGGESTS ANOTHER SYSTEM SHOULD
DIVE SOUTHEAST QUICKLY INTO THE MID MS AND OH VALLEYS LATE TUESDAY
NIGHT AND WEDNESDAY, BUT SPREAD (UNCERTAINTY) EXISTS IN THE DETAILS
(STRENGTH, TIMING, TEMP STRUCTURE, AND PRECIP TYPE). OPERATIONAL
RUNS OF THE GFS AND GEM MODELS WOULD SUGGEST SOME SNOW POTENTIAL OR
RAIN CHANGING TO SOME SNOW (WITH A DEFORMATION BAND POSSIBLE), WHILE
THE ECMWF KEEPS SOME SNOW TO OUR NW WITH SOME RAIN SHOWERS HERE. OUR
MORE ROBUST MODEL BLEND SUGGESTS A GOOD CHANCE OF SOME RAIN AND/OR
SOME SNOW WEDNESDAY WITH LOWS IN THE 30S AND AFTERNOON HIGHS IN THE
LOWER-MID 40S. THIS SYSTEM IS ABOUT 6 DAYS OUT, SO NOTHING TO DWELL
TOO MUCH ON AT THIS TIME.
AVIATION
(12Z TAF ISSUANCE)
ISSUED AT 625 AM EST THU FEB 20 2020
RADAR IS LIGHTING UP WITH MID-LEVEL RETURNS OVER SOUTH-CENTRAL
KENTUCKY, BUT LOW-LEVEL DRY AIR WILL PREVENT ANY PRECIP FROM
REACHING THE GROUND EVEN AT BWG. WILL STAY VFR ACROSS THE BOARD WITH
MID-LEVEL CEILINGS FOR MUCH OF THE DAY TODAY, AND GRADUAL CLEARING
BY THIS EVENING. DECENT GRADIENT BETWEEN STRONG HIGH PRESSURE
BUILDING DOWN THE PLAINS AND A DEEPENING LOW OVER THE SOUTHEAST WILL
KEEP N-NE WINDS ABOVE 10 KT FOR MUCH OF THE TAF PERIOD, FINALLY
LAYING DOWN IN THE PLANNING PERIOD AT SDF.
LMK WATCHES/WARNINGS/ADVISORIES
IN...NONE.
KY...NONE.
SHORT TERM...RAS
LONG TERM...TWF
AVIATION...RAS
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