Severe Thunderstorm Warning 177, NWS Louisville, KY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
526 PM EDT MON JUL 19 2010

...MESOSCALE UPDATE...

BROKEN LINE OF CONVECTION WITH WELL ESTABLISHED COLD POOL IS NOW
MAKING ITS WAY INTO THE NORTHWEST CWA. UPSTREAM...NUMEROUS SEVERE
WIND GUSTS HAVE BEEN RECORDED WITH SEVERAL REPORTS OF DAMAGE AS
WELL. STORMS ARE MOVING INTO A FAVORABLE ENVIRONMENT THROUGH THE REST
OF THE EVENING HOURS AS LATEST RUC MESOANALYSIS SHOWS 3500 TO 4000
J/KG OF MIXED LAYER CAPE ALONG AN AXIS FROM CAMPBELLSVILLE TO
LOUISVILLE TO JASPER. STRONGEST PORTIONS OF THE LINE HAVE NOW SEEMED
TO SURGE FORWARD ON THIS AXIS OF INSTABILITY AND APPEAR TO BE
TRAVELING TOWARD THE LOUISVILLE METRO AREA. ALSO...AREAS SOUTH OF
THE WATCH BOX ALONG THE TENNESSEE BORDER COULD SEE MORE ACTIVITY
THAN ORIGINALLY THOUGHT AS SOUTHERN END OF THE LINE HAS
RE-STRENGTHENED AND BEGAN DIVING SOUTH.

LATEST LAPS SOUNDINGS DO SHOW A BIT OF AN STABLE LAYER BETWEEN H9
AND H8...HOWEVER EXPECT THAT AS STRONG AS THE RADAR SIGNATURES ARE
AND AS MUCH INSTABILITY AS THERE IS...WILL BE ABLE TO OVERCOME THIS
EASILY. MAIN POINTS WITH THIS DISCUSSION...THE BOWLING GREEN AREA
NOW LOOKS TO GET INTO THE ACTION MORE...BETWEEN 7 PM AND 10
PM...WITH STRONG TO SEVERE STORMS POSSIBLE. STAY TUNED FOR POSSIBLE
WATCH EXTENSIONS. ALSO...THIS STORM HAS PRODUCED A LOT OF DAMAGE
UPSTREAM INCLUDING A 60 MPH WIND GUST JUST NORTHWEST OF JASPER...SO
AREAS DOWNSTREAM IN THE WATCH BOX SHOULD TAKE THESE STORMS AND
WARNINGS VERY SERIOUSLY.

BEST DEEP LAYER SHEAR IS NORTH OF THE AREA IN THE GREAT LAKES
REGION...SO POTENTIAL FOR SUPERCELLS OR ANY TORNADO POTENTIAL IS
LOW.

.SHORT TERM (TONIGHT AND TUESDAY)...

LOOKS TO BE A BUSY NIGHT AS CONVECTIVE COMPLEX OVER CENTRAL ILLINOIS
IS STEAMING TOWARD THE NORTHERN CWA THIS AFTERNOON. CURRENTLY...HAVE
ARRIVAL TIME IN SOUTHERN INDIANA COUNTIES TO THE OHIO RIVER BETWEEN
7 AND 10 PM...WELL FASTER THAN MODEL SOLUTIONS SUGGEST. HAVE
INCREASED POPS TO LIKELY IN THE SOUTHERN INDIANA AND NORTHERN
KENTUCKY THIS EVENING TO ACCOUNT FOR THE COMPLEX. ONGOING STORMS
WILL BE FEEDING OFF HIGHLY UNSTABLE AIRMASS WITH MOST UNSTABLE CAPE
VALUES UP TO 4000 J/KG FROM TERRE HAUTE IN SOUTHEASTWARD TO
LOUISVILLE. CURRENT SOUNDINGS SHOW THAT INSTABILITY IS A BIT
ELEVATED...HOWEVER WATER VAPOR IMAGERY SHOWS A SHORTWAVE CURRENTLY
OVER MISSOURI AND RAPIDLY APPROACHING. THIS SHOULD HELP PROVIDE
EXTRA DYNAMIC FORCING ALONG WITH STEEPER MID LEVEL LAPSE RATES.
WOULD NOT BE SURPRISED TO SEE OUR AREA ADDED TO SPC RISK WITH NEXT
UPDATE. THE MAIN THREATS WITH THESE STORMS WILL BE DAMAGING WINDS
AND LARGE HAIL...ALONG WITH HEAVY RAINFALL AND EXCESSIVE LIGHTNING.

WILL BE A BIT MORE CONCERNED ABOUT FLOODING THREAT IN THE NORTH
TONIGHT AS WE HAVE BEEN HIT BY SCATTERED HEAVY RAIN OVER THE
WEEKEND. AREAS THAT HAVE SEEN A LOT OF RAINFALL WILL HAVE TO BE
MONITORED FOR HYDRO PROBLEMS. WILL MENTION THREAT IN HWO ALONG WITH
SEVERE THUNDERSTORM THREATS.

AFTER MIDNIGHT...EXPECT THE MAJORITY OF CONVECTION TO BE ENDING IN
OUR AREA WITH BEST ACTION TO THE NORTH OF THE AREA IN BETTER CORE OF
MID LEVEL FLOW. ALSO...WITH H5 RIDGING SLOWLY BUILDING IN FROM THE
SOUTHWEST...ACTIVITY SHOULD BE LIFTED NORTHWARD. WILL MAINTAIN
ISOLATED POPS IN THE SOUTH TO SCATTERED POPS IN THE NORTH BASED ON
UNSTABLE AIRMASS ALONE. TOMORROW SHOULD BE A MAINLY DIURNAL EVENT IN
THE NORTHERN CWA AS H5 RIDGING CONTINUES TO BUILD IN FROM THE
SOUTHWEST. WILL KEEP INHERITED FORECAST OF 20 POPS IN SOUTH AND 30
POPS IN NORTH. AS WITH THE POP GRADIENT...TEMPERATURE GRADIENT WILL
BE SIMILAR WITH LOWER 90S IN THE SOUTH AND UPPER 80S IN THE NORTH.
WILL HAVE TO CONTINUE TO BE ON THE LOOKOUT FOR UPSTREAM MCS
ACTIVITY...HOWEVER WITH RIDGE BUILDING IN STRONGER...SHOULD BE LESS
LIKELY TO GET A CONVECTIVE COMPLEX TO COME BARRELING INTO OUR AREA.

.LONG TERM (TUESDAY NIGHT - MONDAY)...

WILL ONLY MAKE SUBTLE CHANGES FOR THE LONG TERM PERIOD WITH OUR
CURRENT FCST/MODEL GUIDANCE/HPC INPUT IN SUPPORT.

FOR TUE NIGHT THRU WED NIGHT...LITTLE CHANGE IN THE UPPER LEVEL
RIDGE NOTED WITH THE CENTER OVER THE TN VLY/NRN GULF STATES. QSTNRY
BNDRY FROM CENTRAL PARTS OF IL/IN SAGS A BIT SWD INTO SRN INDIANA
WED...SO WILL CONTINUE LOW CHC POPS THRU THE PERIOD...HIEST ACRS OUR
NRN FA...CLOSEST TO THE VERY SLOW MOVG FRONT...WHERE
CONVERGENCE/MOISTURE POOLING SHUD BE GREATEST.

BEYOND THAT PERIOD...FROM THU THRU MON...SUBTLE HEIGHT RISES NOTED
THU AND FRI AS THE RIDGE STRENGTHENS A BIT. WITH THE STALLED/SLOW
MOVG FRONT OVER SRN INDIANA ON THU...WILL KEEP SCT TO ISOLD WORDING
FOR STORMS IN THE FCST AND THEN LET THE DRY PERIOD FOR THU NIGHT
THRU FRI NIGHT CONTINUE AS BNDRY TURNS NWD AS A WARM FRONT.

FOR THE REMAINDER OF THE PERIOD...THE SRN EDGE OF THE WLYS DIPS SWD
INTO OUR FA AS SUBTLE UPR LEVEL IMPULSES DROP SEWD ON INCREASING NW
FLO. ASSOCIATED COOL FRONT PROGGED TO APPOACH OUR FA SAT AND STALL
IN THE OH RIVER VCNTY SUN AND MON...TYPICAL OF COOL FRONTS THIS TIME
OF YEAR. WILL INCREASE POPS A BIT FOR THE WEEKEND AND LEAVE ISOLD
WORDING IN MON AS FRONT BASICALLY WASHES OUT.

TEMP AND COMFORT WISE...IT APPEARS LOWER TO MID 90 MAXS WILL
CONTINUE AT LEAST THRU SAT WITH THE OPPRESSIVE HUMIDITY CONTINUING.
HIGHEST TEMPS WILL BE ALONG/WEST OF INTERSTATE 65.

&&

.AVIATION (18Z TAF ISSUANCE)...

STILL EXPECT MAINLY VFR CONDITIONS THROUGH THE FORECAST PERIOD AS
SCT TO BKN STRATOCU FROM THIS MORNING HAS LIFTED WITH MIXING AND HAS
SCATTERED EARLY THIS AFTERNOON. HAVE LOW CONFIDENCE IN THUNDERSTORM
CHANCES AT THE TAF SITES...HOWEVER FEEL SDF HAS THE GREATEST SHOT AT
SEEING THUNDERSTORMS BETWEEN 6 PM AND MIDNIGHT AS CONVECTIVE COMPLEX
FROM UPSTREAM WORKS ITS WAY INTO THE REGION. WATER VAPOR IMAGERY
SHOWS A SHORTWAVE THAT WILL ARRIVE ABOUT THE SAME TIME AS THE
THUNDERSTORM COMPLEX SO EXPECT THAT STORMS COULD BE QUITE STRONG
DURING THIS TIME. HAVE INCLUDED VCTS AT SDF DURING THIS TIME FOR NOW
AND WILL REFINE FORECAST WITH TIMING AND DETAILS AS CONFIDENCE GROWS
IN THIS SCENARIO. CERTAINLY...LOW MVFR OR WORSE CONDITIONS WILL BE
POSSIBLE IF THUNDERSTORM COMPLEX MAKES IT TO THE TERMINAL THIS
EVENING. OTHERWISE...BROAD AND STEADY SOUTHWEST FLOW WILL KEEP
THINGS HOT AND MUGGY. BWG WILL HAVE A SHOT AT RESTRICTED
VISIBILITIES TONIGHT AS WELL. WINDS WILL BE A BIT STRONGER OUT OF
THE SOUTHWEST ON TUESDAY AFTERNOON...WITH SOME GUSTS AROUND 20 MPH
POSSIBLE.

&&

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

MESOSCALE......BJS
SHORT TERM.....BJS
LONG TERM......DK/11
AVIATION.......BJS

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