Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 031729
AFDLMK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
129 PM EDT MON AUG 3 2015

...UPDATED AVIATION DISCUSSION...

...FORECAST UPDATE...
ISSUED AT 1138 PM EDT MON AUG 3 2015

OUTFLOW BOUNDARY FROM EARLY MORNING CONVECTION CONTINUES TO SURGE TO
THE SOUTHWEST THIS MORNING.  THE BOUNDARY IS CURRENTLY LOCATED FROM
ABOUT HANCOCK COUNTY SOUTHEASTWARD TO NEAR SOMERSET.  LATEST DATA
FROM SATELLITE AND RADAR SUGGEST THAT THIS OUTFLOW IS MIXING OUT AS
IT HEADS SOUTHWEST.  WE EXPECT THIS BOUNDARY TO BE A FOCUS FOR
AFTERNOON CONVECTION ACROSS OUR WEST AND SOUTHWEST THIS AFTERNOON.
IN ADDITION, COLD FRONT MOVING IN FROM THE NORTH WILL ALSO FIRE OFF
CONVECTION TO OUR NORTH WHICH MAY DROP SOUTHWARD INTO THE REGION
LATE THIS AFTERNOON/EVE.  ORGANIZED SEVERE WEATHER THREAT STILL
REMAINS MARGINAL, GIVEN WEAK MID-LEVEL FLOW.  HOWEVER, INSTABILITY
WILL BE PRESENT AND SOME GUSTY WINDS AND HAIL MAY ACCOMPANY THE
STRONGEST STORMS.  CURRENT FORECAST HAS THIS COVERED.  DID TWEAK THE
GRIDS A BIT TO BRING IN LINE WITH CURRENT OBSERVATIONS.

UPDATE ISSUED AT 744 AM EDT MON AUG 3 2015

WEAKENING CONVECTION HAS MADE IT INTO THE BLUEGRASS REGION OF OUR
CWA SO HAVE INCREASED POPS TO LIKELY AND CATEGORICAL FOR THE NEXT
HOUR OR TWO. LATEST IR SATELLITE SHOWS CLOUD TOP WARMING AND RADAR
TRENDS SHOW SIGNIFICANT WEAKENING, SO EXPECT COVERAGE TO QUICKLY
DIMINISH OVER THE NEXT 1 TO 2 HOURS. STORMS ARE ALSO MOVING INTO A
DRIER AND MORE STABLE ENVIRONMENT PER THE LATEST MESOANALYSIS.
OUTFLOW BOUNDARY WILL SPREAD SW THROUGH THE DAY AND WILL HAVE TO
WATCH ITS PROGRESS FOR REDEVELOPMENT THIS AFTERNOON.

.SHORT TERM (NOW THROUGH TUESDAY)...
ISSUED AT 325 AM EDT MON AUG 3 2015

AS THE DAY PROGRESSES, ABUNDANT SUNSHINE WILL ALLOW US TO BECOME
VERY WARM AND VERY UNSTABLE BY THIS AFTERNOON WITH MODERATE 850HPA
THETA-E RIDGING OVERHEAD. A COLD FRONT REACHING FROM LAKE HURON
THROUGH CHICAGO TO KANSAS CITY DURING THE PRE-DAWN HOURS WILL SLIDE
SLOWLY SOUTHWARD TODAY, CROSSING THE OHIO RIVER SOMETIME DURING THE
MID OR LATE AFTERNOON HOURS. THERE WILL ALSO BE THE POSSIBILITY OF
AN OUTFLOW BOUNDARY IN THE AREA FROM THE STORMS TO OUR NORTH THIS
MORNING. TIME HEIGHTS AND SOUNDINGS SUGGEST MOISTURE WILL BE
LACKING, BUT PRECIPITABLE WATER AMOUNTS ARE EXPECTED TO POOL AT
SLIGHTLY ELEVATED LEVELS JUST AHEAD OF THE SURFACE BOUNDARIES. SO,
CONVECTION CAN BE EXPECTED BUT IT WILL PROBABLY REMAIN SCATTERED.
MIDLEVEL LAPSE RATES WILL BE STEEP AND WITH THE AVAILABLE
INSTABILITY AND BOUNDARIES, STRONG TO SEVERE STORMS WILL DEFINITELY
BE A POSSIBILITY. THE MAIN THREATS WILL BE HAIL, WITH WET BULB ZERO
HEIGHTS OF 10K-11K`, AND WIND GUSTS WITH DCAPE PROGGED IN THE 1000-
1500 J/KG RANGE. THERE STILL APPEARS TO BE ONLY MARGINAL DEEP SHEAR,
SO STORMS MAY DEVELOP QUICKLY, DUMP LOCALLY HEAVY DOWNPOURS (AND
ASSOCIATED STRONG WIND GUSTS FROM PRECIPITATION CORES STRIKING THE
GROUND), AND THEN WEAKEN AS OTHER STORMS GO UP.

HIGHS TODAY WILL BE QUITE WARM AROUND 90 DEGREES, BUT RELATIVELY LOW
DEW POINTS WILL PREVENT THE AFTERNOON FROM BEING TOO OPPRESSIVE.

CONVECTION WILL GRADUALLY WANE WITH THE SETTING OF THE SUN THIS
EVENING, WITH TEMPERATURES DROPPING INTO THE MID 60S TO AROUND 70.

ON TUESDAY THE SURFACE WON`T GET QUITE AS UNSTABLE AS IT DOES TODAY,
AND MID-LEVEL LAPSE RATES WON`T BE QUITE AS STEEP. DCAPES ARE
PROGGED TO BE A LITTLE LOWER AND WET BULB ZERO HEIGHTS A LITTLE
HIGHER, AND ONCE AGAIN MOISTURE DOES NOT APPEAR PLENTIFUL. NO STRONG
TRIGGERS WILL BE IN THE AREA, BUT THE REMNANTS OF TODAY`S COLD FRONT
WILL LIKELY BE LURKING AROUND, AND WE`LL HAVE SOME UPPER LEVEL
DIVERGENCE ASSOCIATED WITH A JET STREAK CROSSING THE LOWER GREAT
LAKES AND A SMALL JETLET MOVING OVER THE MID MISSISSIPPI VALLEY. SO,
WILL HAVE THUNDERSTORMS IN THE FORECAST BUT WILL KEEP POPS IN THE
ISOLATED TO LOW CHANCE CATEGORY. AFTERNOON HIGHS WILL BE IN THE
UPPER 80S TO LOWER 90S.

.LONG TERM (TUESDAY NIGHT THROUGH SUNDAY)...
ISSUED AT 255 AM EDT MON AUG 3 2015

THE MAIN FORECAST CONCERN IN THE LONG TERM IS STORM CHANCES AND
THREATS WEDNESDAY THROUGH THURSDAY NIGHT AS A SERIES OF WEATHER
SYSTEMS INTERACT WITH A STATIONARY SURFACE BOUNDARY OVER THE LOWER
OHIO VALLEY.

THE SYNOPTIC PATTERN TUESDAY NIGHT AND WEDNESDAY IS EXPECTED TO
FEATURE UPPER LEVEL RIDGING OVER THE WESTERN CONUS WITH A TROUGH
POSITIONED OVER THE GREAT LAKES REGION. AT THE SURFACE...THE STALLED
OUT BOUNDARY WILL LIKELY BE ALONG THE TN/KY LINE BEFORE SLOWLY
MOVING NORTH AS A WARM FRONT. AS THE FIRST MID-LEVEL SHORTWAVE
TROUGH PIVOTS THROUGH TUESDAY NIGHT...SCATTERED SHOWERS AND STORMS
MAY SPREAD IN FROM THE WEST...INTERACTING WITH THE LOW-LEVEL JET.
THE DYNAMICS WITH THIS FEATURE ARE WEAK...AND MOISTURE TRANSPORT IS
NOT THAT IMPRESSIVE...SO FOR NOW HAVE KEPT POPS IN THE 20-30 PERCENT
RANGE.

UPPER LEVEL FORCING WILL CONTINUE TO BE FAVORABLE FOR THUNDERSTORM
DEVELOPMENT WEDNESDAY...WITH HIGHER COVERAGE EXPECTED DURING THE
AFTERNOON/EARLY EVENING HOURS THANKS TO RESIDUAL BOUNDARIES ACROSS
THE AREA AND PEAK HEATING PROVIDING MODEST INSTABILITY. DEEP LAYER
SHEAR OVER THE AREA IS NOT IMPRESSIVE BUT NOT ABSENT EITHER /25 TO
30 KTS/...SO ANY PERKIER STORM THAT DOES MANAGE TO GROW COULD PUT
DOWN GUSTY WINDS. PWATS WILL BE TRENDING UPWARD THROUGH THE WEEK AS
HIGHER MOISTURE POOLS AROUND THE FRONT. AS SUCH...BRIEF HEAVY
RAINFALL WILL ALSO BE A THREAT.

03.00Z GUIDANCE IN REASONABLE AGREEMENT SHOWING A STRONGER MID-LEVEL
SHORTWAVE TROUGH ARRIVING LATE WEDNESDAY NIGHT INTO THURSDAY
AFTERNOON. A SURFACE LOW LOOKS TO DEVELOP TO OUR WEST...THOUGH
MODELS VARY CONSIDERABLY ON ITS PLACEMENT AND STRENGTH. WITH THE
WARM FRONT / STATIONARY BOUNDARY STILL IN PLAY AND THE MORE
FAVORABLE UPPER LEVEL FORCING...THERE IS LIKELY TO BE HIGHER
COVERAGE OF STORMS ACROSS THE AREA DURING THIS PERIOD. LOW LEVEL
SHEAR COULD END UP BEING MORE FAVORABLE FOR ORGANIZED STORM
DEVELOPMENT...BUT CONFIDENCE IS STILL TOO LOW AND DETAILS TOO
UNCERTAIN THIS FAR OUT. TRAINING WEST/EAST THUNDERSTORMS MAY BE THE
BIGGER PLAYER...AND OVER THE COURSE OF THE WEEK...SOME LOCATIONS
COULD PICK UP BETWEEN 1 AND 3 INCHES. POPS IN THE 60 TO 70 PERCENT
RANGE LOOK GOOD AT THIS TIME.

IN THE WAKE OF THURSDAY`S SYSTEM...SURFACE HIGH PRESSURE BUILDS IN
FROM THE NORTHWEST FOR FRIDAY AND THE WEEKEND...PROVIDING A FEW
DRIER DAYS TO LOWER OHIO VALLEY. HUMIDITY WILL DROP TO MORE
COMFORTABLE LEVELS AS WELL...AND TEMPERATURES WILL TREND SEVERAL
DEGREES BELOW NORMAL. A MODEL CONSENSUS PUTS HIGHS IN THE UPPER 70S
TO LOW 80S AND MORNING TEMPERATURES IN THE LOW/MID 60S. THE TYPICAL
COOL SPOTS MAY DIP INTO THE MID TO UPPER 50S SATURDAY AND SUNDAY
MORNINGS.

&&

.AVIATION (18Z TAF UPDATE)...
ISSUED AT 128 PM EDT MON AUG 3 2015

A SURFACE COLD FRONT WILL SINK SOUTHWARD INTO THE REGION THIS
AFTERNOON.  WHILE MOISTURE IS NOT ALL THAT PLENTIFUL, THE FRONT AND
REMNANT OUTFLOW BOUNDARY FROM THIS MORNINGS CONVECTION WILL LIKELY
SPARK ISOLATED-SCATTERED CONVECTION THIS AFTERNOON.  HIGHEST CHANCES
LOOK TO BE AT KSDF AND KLEX WITH A LESSER THREAT AT KBWG.  STORMS
ARE EXPECTED TO BE DIURNAL IN NATURE AND DISSIPATE AFTER SUNSET.
VFR CONDITIONS ARE EXPECTED OVERNIGHT, THOUGH A PERIOD OF MVFR VSBYS
AT KBWG LOOK INCREASINGLY LIKELY DUE TO PATCHY FOG.  WINDS THIS
AFTERNOON WILL BE GUSTY OUT OF THE SOUTHWEST AND THEN SHIFT TO THE
NORTHWEST AFTER FRONTAL PASSAGE TONIGHT.  WINDS ARE EXPECTED TO BE
LIGHT AND VARIABLE OVERNIGHT AND INTO THE DAY ON TUESDAY.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
KY...NONE.
IN...NONE.
&&

$$

UPDATE.........MJ
SHORT TERM.....13
LONG TERM......ZBT
AVIATION.......MJ


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