116  
FXUS63 KLMK 302331  
AFDLMK  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE LOUISVILLE KY  
731 PM EDT THU MAR 30 2017  
   
..UPDATED AVIATION DISCUSSION
 
 
   
MESOSCALE UPDATE
 
 
ISSUED AT 625 PM EDT THU MAR 30 2017  
   
..SEVERE WEATHER RISK CONTINUES IN THE OHIO VALLEY
 
 
WHILE THE TORNADO THREAT IS LOOKING LESS IMPRESSIVE WITH THE WARM  
FRONT WELL TO OUR NORTH, A LINE OF STORMS CONTINUES ITS MARCH ACROSS  
WESTERN KENTUCKY. WE'RE ALSO SEEING A SMATTERING OF CONVECTION OVER  
SOUTH-CENTRAL KENTUCKY, BUT NOTHING IS GETTING VERY STRONG OR  
ORGANIZED JUST YET AS DEWPOINTS HAVE MIXED DOWN INTO THE LOWER 50S  
AND SHEAR IS MOSTLY UNIDIRECTIONAL.  
 
HOWEVER, LATEST SPC MESOANALYSIS SHOWS DOWNDRAFT CAPE MAXED OUT OVER  
CENTRAL KENTUCKY AT 800-900 J/KG. WITH THIS SOMEWHAT FAVORABLE  
ENVIRONMENT, ANY STORMS THAT CAN ACTUALLY GET UP WILL BE FAIRLY  
STRONG COMING DOWN. SO THE NEXT FEW HRS WILL REPRESENT A NARROWING  
WINDOW FOR MAINLY PULSE-SEVERE WINDS.  
 

 
   
SHORT TERM
 
(THIS EVENING THROUGH FRIDAY NIGHT)  
ISSUED AT 347 PM EDT THU MAR 30 2017  
 
IN THE NEAR TERM, PARTLY TO MOSTLY CLOUDY SKIES WERE NOTED ACROSS  
THE REGION. STREAM OF MID-HIGH LEVEL CLOUDINESS CONTINUED TO MOVE  
NORTHEASTWARD ACROSS THE AREA. TEMPERATURES WERE WARM WITH  
TEMPERATURES IN THE LOW TO MID 70S ACROSS SOUTHERN INDIANA AND MID-  
UPPER 70S ACROSS KENTUCKY. A FEW SPOTS ACROSS SOUTHEAST AND EAST KY  
HAVE TOPPED 80 DEGREES. IN GENERAL, WE EXPECT THE WEATHER TO REMAIN  
RATHER QUIET FOR THE NEXT FEW HOURS WITH TEMPERATURES REMAINING  
GENERALLY STEADY.  
 
FOR THIS EVENING AND TONIGHT, MAIN CONCERN REMAINS AROUND STRONG TO  
SEVERE THUNDERSTORMS IMPACTING THE REGION. PREVIOUS THINKING WAS  
THAT A STRONG LINE OF STORMS WOULD MOVE IN FROM THE WEST AND SWING  
THROUGH THE REGION THIS EVENING. THAT STILL LOOKS TO BE ON TRACK,  
BUT THE OVERALL CONFIDENCE IN CONVECTIVE EVOLUTION AND STRENGTH OF  
THE STORMS IS IN QUESTION. WHILE THE EARLIER MODEL RUNS HAD BEEN  
SUGGESTING A DESTABILIZING ATMOSPHERE THIS AFTERNOON, THE CIRRUS  
SHIELD ALOFT HAS KEPT TEMPERATURES DOWN. PROXIMITY SOUNDINGS ARE  
NOT AS MOIST AS THE MODELS SUGGESTED AND MID-LEVEL LAPSE RATES ARE  
NOT ALL THAT STEEP. SURFACE MOISTURE IS ALSO NOT AS HIGH AS THE  
MODELS PROGGED EITHER. CURRENT DEWPOINTS RANGE FROM THE UPPER 40S  
IN THE EAST TO THE LOWER 50S IN THE WEST.  
 
OUR CURRENT THINKING IS THAT CONVECTION WILL START TO DEVELOP IN THE  
21-23Z TIME FRAME IN THE VICINITY OF THE I-65 CORRIDOR OF CENTRAL KY  
AND GROW UPSCALE. AT THE SAME TIME, CONVECTIVE LINE ALONG THE COLD  
FRONT IN WESTERN KY WILL SWEEP EASTWARD. THIS SHOULD RESULT IN A  
RATHER LARGE CONVECTIVE COMPLEX DEVELOPING ACROSS THE CENTRAL PART  
OF THE CWA AND THEN MOVE EASTWARD INTO EASTERN KY OVERNIGHT. THIS  
IDEA IS SUPPORTED BY THE LAST FEW RUNS OF THE OPERATIONAL HRRR,  
EXPERIMENTAL HRRR, AND THE NSSL WRF ARW CAM MODELS. DEPENDING ON  
THE DEGREE OF INSTABILITY THAT DEVELOPS PRIOR TO CONVECTIVE  
DEVELOPMENT, STRONG TO SEVERE CONVECTION STILL LOOKS LIKELY, THOUGH  
THE OVERALL COVERAGE MAY BE LESS THAN PREVIOUSLY THOUGHT.  
NONETHELESS, DAMAGING WINDS AND ISOLATED LARGE HAIL LOOK TO BE THE  
MAIN SEVERE WEATHER THREATS.  
 
IN REGARDS TO THE TORNADO THREAT, INITIAL TORNADO THREAT THIS EVENING  
WILL BE TO OUR NORTH ALONG THE RETREATING WARM FRONT ACROSS CENTRAL  
IN/OH WHERE THE LOW LEVEL FLOW IS MUCH MORE BACKED WHICH IS WHERE  
THE LOW-LEVEL HELICITY IS MAXIMIZED. FORECAST WIND FIELDS IN THE  
LOWER ATMOSPHERE CONTINUE TO SHOW MORE OF A SPEED SHEAR PROFILE  
WITHOUT MUCH IN THE WAY OF TURNING IN THE LOW LEVELS. LATEST MODEL  
PROXIMITY SOUNDINGS DO NOT SUGGEST MUCH IN THE WAY OF LOW-LEVEL  
BACKING PRIOR TO CONVECTION DEVELOPING, SO THE TORNADO THREAT LOOKS  
RELATIVELY LOW IN AREAL COVERAGE. HOWEVER, CAN NOT COMPLETELY RULE  
OUT AN ISOLATED TORNADO WITHIN THE CONVECTIVE LINE, ESPECIALLY WHERE  
SOME LOCALIZED SURFACE WIND BACKING COULD OCCUR.  
 
CONVECTION WILL END FROM WEST TO EAST LATE TONIGHT WITH LOW  
TEMPERATURES FALLING INTO THE UPPER 40S TO THE LOWER 50S. UPPER LOW  
WILL PUSH THROUGH THE REGION ON FRIDAY WHICH WILL RESULT IN A  
COOL/CLOUDY/SHOWERY DAY ACROSS THE REGION. HIGHS WILL LIKELY TOP  
OUT IN THE LOWER 50S WITH LOWS FRIDAY NIGHT COOLING INTO THE UPPER  
30S TO THE LOWER 40S.  
 

 
   
LONG TERM
 
(SATURDAY THROUGH THURSDAY)  
ISSUED AT 320 PM EDT THU MAR 30 2017  
 
THE WEEKEND CONTINUES TO LOOK DRY AND QUIET AS HIGH PRESSURE WILL  
NOSE IN FROM CANADA. SATURDAY WILL LIKELY START OFF CLOUDY WITH A  
SLOW CLEARING TREND THROUGHOUT THE DAY AS THE LOW LEVELS TAKE TIME  
TO DRY OUT. HIGHS WILL RANGE FROM THE UPPER 50S ACROSS SOUTHERN IN  
AND THE NORTHERN BLUEGRASS WITH LOWER 60S ACROSS THE I-65 CORRIDOR  
TO SOUTHERN KY. WITH MORE CLEARING EXPECTED SATURDAY NIGHT,  
TEMPERATURES SHOULD DROP INTO THE UPPER 40S ACROSS SE IN INTO THE  
NORTHERN BLUEGRASS WITH LOWER 40S ELSEWHERE. SOUTHERLY FLOW WILL  
BECOME RE-ESTABLISHED BY SUNDAY WHICH SHOULD ALLOW TEMPERATURES TO  
QUICKLY WARM BACK INTO THE UPPER 60S TO THE LOWER 70S. LOWS SUNDAY  
NIGHT LOOK TO COOL BACK INTO THE 50S.  
 
NEXT WEATHER SYSTEM IN THE FORM OF A CLOSED UPPER LOW WILL ROLL  
EASTWARD THROUGH THE TN VALLEY MONDAY AND TUESDAY. BULK OF THE  
STRONG STORMS ASSOCIATED WITH THIS FEATURE WILL LIKELY REMAIN TO OUR  
SOUTH. HOWEVER, WIDESPREAD SHOWERS AND POSSIBLY SOME THUNDERSTORMS  
WILL AFFECT THE REGION MONDAY AND INTO EARLY TUESDAY. TEMPERATURES  
WILL REMAIN MILD WITH HIGHS IN THE MID-UPPER 60S WITH OVERNIGHT LOWS  
IN THE LOWER 50S.  
 
A BRIEF PERIOD OF DRY WEATHER LOOKS LIKELY FOR TUESDAY, BUT WITH THE  
FAST PROGRESSIVE FLOW ALOFT, ANOTHER SYSTEM WILL STREAK THROUGH THE  
REGION ON WEDNESDAY BRINGING YET ANOTHER ROUND OF SHOWERS AND  
THUNDERSTORMS TO THE REGION. HIGHS WEDNESDAY WILL BE IN THE UPPER  
60S TO AROUND 70, WITH HIGHS ON THURSDAY ONLY WARMING INTO THE UPPER  
50S TO THE LOWER 60S.  
 
A LOOK AHEAD SHOWS A RATHER LARGE NEGATIVE HEIGHT ANOMALY DEVELOPING  
ALONG THE EASTERN US. BOTH THE GFS AND EURO ARE IN DECENT AGREEMENT  
WITH THIS FEATURE WHICH SHOULD BRING MORE UNSETTLED AND COOLER THAN  
NORMAL WEATHER TO THE REGION.  
 

 
   
AVIATION...(00Z TAF UPDATE)
 
 
ISSUED AT 710 PM EDT THU MAR 30 2017  
 
SCATTERED SHOWERS AND THUNDERSTORMS ONGOING ACROSS THE REGION AT  
THIS TIME. LATEST HIGH-RES MODELS INDICATE THAT THE LINE OF  
CONVECTION ON THE WESTERN FRINGES OF THE CWA WILL BEGIN TO DISSIPATE  
AS IT TRACKS EASTWARD, WHILE NEW CONVECTIVE DEVELOPMENT WILL OCCUR  
ACROSS CENTRAL TN/KY AND MOVE NORTHEASTWARD. THIS WOULD RESULT IN  
WIDESPREAD SHOWERS AND THUNDERSTORMS FOR SEVERAL HOURS THIS EVENING  
BEFORE THE ACTIVITY SHIFTS OFF TO THE NORTHEAST AFTER 07Z. ANY  
STRONG SHOWERS AND THUNDERSTORMS COULD PRODUCE LOCAL MVFR/IFR  
CIGS/VIS FOR A BRIEF PERIOD OF TIME.  
 
AFTER THE SHOWER AND THUNDERSTORM ACTIVITY MOVES NORTHEASTWARD,  
WE'LL HAVE A BRIEF PERIOD OF VFR CIGS/VIS BEFORE MVFR/IFR CIGS MOVE  
IN FROM THE WEST. FORECAST MODEL SOUNDINGS HOLD THE LOW LEVEL  
STRATUS IN PLACE FOR MOST OF THE MORNING AND AFTERNOON TOMORROW.  
WINDS WILL BE BREEZY OUT OF THE SOUTHWEST AND GUSTS COULD APPROACH  
OR EXCEED 20KTS.  
 

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

 
 

 
 
MESOSCALE...RAS  
SHORT TERM...MJ  
LONG TERM...MJ  
AVIATION...DM  
 
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