Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 031144
AFDLMK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
744 AM EDT MON AUG 3 2015

...FORECAST 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)...
ZCZC SDFWRKLNG 030701
TTAA00 KSDF DDHHMM

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 (12Z TAF UPDATE)...
ISSUED AT 646 AM EDT MON AUG 3 2015

A GUST FRONT AHEAD OF STORMS BETWEEN LEX AND CVG WILL IMPACT LEX
BEFORE THE BEGINNING OF THE TAF PACKAGE WITH NNE WINDS AROUND 15KT
GUSTING TO 25KT. WILL ACCOUNT FOR THAT IN THE FIRST HOUR OR SO OF
THE TAF. THE ACTUAL STORMS BEHIND THE GUST FRONT HAVE BEEN
WEAKENING...ALBEIT SLOWLY. FOR NOW WILL JUST HAVE VCTS IN THE TAF IN
THE HOPE THAT THEY WILL BE SCATTERED BY THE TIME THEY GET AS FAR
SOUTH AS LEX.

THE STORMS SHOULD NOT AFFECT SDF, THOUGH WE WILL HAVE TO WATCH TO
SEE IF THE GUST FRONT MAKES IT THAT FAR WEST WITH SIGNIFICANT WIND
SPEEDS. FOR NOW WILL COUNT ON THE GUST FRONT BECOMING DIFFUSE AND
SPEEDS LIGHT ENOUGH TO KEEP IT OUT OF THE TAF.

BWG WILL NOT BE AFFECTED BY THIS MORNING`S STORMS.

THE REST OF THE TAF PACKAGE REMAINS UNCHANGED. A COLD FRONT WILL
SINK SOUTHWARD INTO THE REGION TODAY, ALONG WITH THE OLD OUTFLOW
BOUNDARY FROM THIS MORNING`S CONVECTION. THOUGH MOISTURE IS NOT
PLENTIFUL, THESE BOUNDARIES WILL HELP TO SPARK SCATTERED
THUNDERSTORMS. THOSE STORMS COULD BECOME STRONG, AND WILL HAVE TO BE
WATCHED CLOSELY.

THIS EVENING THE STORMS WILL SLOWLY DIMINISH, WITH RELATIVELY QUIET
OVERNIGHT HOURS INTO TUESDAY MORNING.

NON-THUNDERSTORM WINDS WILL COME IN FROM THE WSW TODAY AND COULD GET
A LITTLE GUSTY, TO AROUND 20 KNOTS AT TIMES ESPECIALLY AT SDF AND
LEX.

&&

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

$$

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


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