310  
FXUS63 KLMK 201044  
AFDLMK  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE LOUISVILLE KY  
644 AM EDT THU SEP 20 2018  
   
..UPDATED AVIATION DISCUSSION
 
 
   
SHORT TERM
 
(TODAY AND TONIGHT)  
ISSUED AT 254 AM EDT THU SEP 20 2018  
 
QUIET AND CALM WEATHER ONGOING THIS MORNING THANKS TO A LARGE UPPER  
LEVEL RIDGE CURRENTLY OVER THE TN VALLEY. GOES-16 IR PRODUCTS SHOW  
MOSTLY CLEAR SKIES ACROSS THE REGION, AND VERY PRONOUNCED  
VALLEY/RIVER FOG JUST TO OUR EAST IN THE APPALACHIANS. WINDS HAVE  
GENERALLY BEEN LIGHT TO CALM SO FAR THIS MORNING, SO CAN'T RULE OUT  
SOME PATCHY GROUND FOG DEVELOPING IN THE USUAL FOG-PRONE AREAS LATER  
THIS MORNING BEFORE SUNRISE. ANY FOG THAT DOES FORM SHOULD BURN OFF  
QUICKLY AFTER SUNRISE.  
 
ANOTHER HOT AND MOSTLY SUNNY DAY WILL BE ON TAP, WITH TEMPERATURES  
GENERALLY REACHING THE UPPER 80S TO LOW 90S. WHEN COMBINED WITH  
DEWPOINTS IN THE UPPER 60S TO LOW 70S, HEAT INDICES WEST OF I-65  
COULD APPROACH 100 DEGREES FOR A FEW HOURS THIS AFTERNOON. DOESN'T  
LOOK LIKE WE'LL GET MUCH RELIEF FROM THE HEAT IN THE FORM OF RAIN,  
AS WARM AIR ALOFT DUE TO THE PRESENCE OF THE UPPER LEVEL RIDGE WILL  
KEEP MOST CONVECTION SUPPRESSED. A FEW HIGH-RES MODELS HINT AT SOME  
VERY ISOLATED STORMS DEVELOPING LATE THIS AFTERNOON NORTH OF I-64,  
BUT COVERAGE OF SAID SHOWERS LOOKS TO BE TOO LOW TO INCLUDE IN GRIDS  
AT THIS TIME.  
 
ANOTHER WARM, MUGGY NIGHT WILL BE IN STORE TONIGHT. WINDS WILL PICK  
UP SOME OVERNIGHT AS A WEAK LLJ DEVELOPS AND THE PRESSURE GRADIENT  
TIGHTENS IN RESPONSE TO A DEEPENING LOW NEAR THE GREAT LAKES REGION.  
   
LONG TERM
 
(FRIDAY THROUGH WEDNESDAY)  
ISSUED AT 255 AM EDT THU SEP 20 2018  
 
VIGOROUS STORM SYSTEM MOVING ACROSS THE NORTHERN GREAT LAKES INTO  
ONTARIO ON FRIDAY WILL DRIVE A COLD FRONT SE INTO THE OHIO VALLEY.  
WE'LL HAVE PLENTY OF INSTABILITY AHEAD OF THE FRONT TO SUPPORT  
STRONG UPDRAFTS. STRONGER DEEP-LAYER SHEAR TO ORGANIZE A POTENTIAL  
SQUALL LINE WILL REMAIN TO OUR NORTH AND NORTHEAST, BUT NOT OUT OF  
THE QUESTION THAT WE COULD CATCH THE TAIL END OF THE LINE. MARGINAL  
SVR RISK FOR SOUTHERN INDIANA AND NORTH-CENTRAL KENTUCKY LOOKS TO BE  
REASONABLE, GIVEN THE POTENTIAL FOR A LINE OR PULSE THREAT. THAT  
COULD INCREASE IF THE SHEAR WERE TO EXTEND FARTHER SW.  
 
COLD FRONT BECOMES ORIENTED PARALLEL TO THE UPPER FLOW ON FRIDAY  
NIGHT, AND A WEAK WAVE EJECTING OUT OF THE SOUTHERN PLAINS WILL  
SUPPORT RENEWED PRECIP CHANCES ON SATURDAY, ESPECIALLY ACROSS  
SOUTHERN KENTUCKY. TO THE NORTH OF THAT PRECIP SHIELD, HIGH PRESSURE  
OVER THE GREAT LAKES WILL BRING COOL AND CLOUDY CONDITIONS WITH  
TEMPS MORE TYPICAL OF OCTOBER.  
 
SUNDAY FORECAST WILL BE LARGELY DEPENDENT ON JUST WHERE THE STALLED  
FRONT REMAINS HUNG UP UNDER FLAT UPPER FLOW. ADDITIONAL WAVES OF  
SHOWERS AND STORMS ALONG THE FRONT WILL KEEP AT LEAST SOUTH-CENTRAL  
KENTUCKY UNSETTLED, AND PERHAPS EVEN MORE OF THE AREA IF THE ECMWF  
IS CORRECT IN ITS FRONTAL POSITION, WHICH IS FARTHER NORTH THAN THE  
GFS. THAT FRONT WILL LIFT NORTH ON SUN NIGHT AS UPPER FLOW BACKS SW  
IN RESPONSE TO DOWNSTREAM RIDGING, WITH BROAD AND MOIST SOUTHERLY  
FLOW SETTING UP ON MONDAY. GFS AND ECMWF PAINT A LOT OF QPF, BUT  
THIS IS OFTEN OVERDONE IN THE WARM SECTOR.  
 
UNSETTLED WEATHER CONTINUES TUE-WED AS A LONGWAVE UPPER TROF PUSHES  
A COLD FRONT AT LEAST WELL INTO THE OHIO VALLEY, IF NOT ALL THE WAY  
THROUGH. TOO EARLY TO GET TOO DETAILED WITH SEVERE POTENTIAL, BUT  
THE SYSTEM LOOKS DYNAMIC ENOUGH TO SUPPORT AT LEAST SOME STRONGER  
STORMS. EXPECT ABOVE NORMAL TEMPS AND BORDERLINE SUMMERTIME HUMIDITY  
THROUGH THE FIRST HALF OF NEXT WEEK, WITH CLOUDS AND PRECIP LIMITING  
DIURNAL RANGES.  
 
WIDESPREAD QPF TOTALS OVER THE PERIOD WILL LIKELY AVERAGE 2-3  
INCHES. HOWEVER, DEPENDING ON THE PLACEMENT OF ANY HEAVIER AND/OR  
REPEATED RAINFALL, HIGHER AMOUNTS WILL LIKELY RESULT IN FLOODING  
ALONG SOME STREAMS.  
 

 
   
AVIATION
 
(12Z TAF ISSUANCE)  
ISSUED AT 642 AM EDT THU SEP 20 2018  
 
SOME ISOLATED PATCHY GROUND FOG HAS DEVELOPED THIS MORNING ACROSS  
THE REGION, BUT SHOULD QUICKLY BURN OFF AFTER SUNRISE. VFR  
CONDITIONS ARE THEN EXPECTED FOR THE REST OF THE FORECAST PERIOD. A  
WEAK (~30KT) LLJ NEAR 2KFT IS FORECAST TO DEVELOP AFTER MIDNIGHT,  
BUT LLWS LOOKS TO BE WEAK ENOUGH TO NOT NEED MENTION IN TAFS AT THIS  
TIME.  
 

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

 
 

 
 
SHORT TERM...DM  
LONG TERM...RAS  
AVIATION...DM  
 
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