181
FXUS63 KLMK 041931
AFDLMK
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
245 PM EDT SAT JUL 4 2009
SHORT TERM (TONIGHT AND SUN)
IT APPEARS THAT THE BEST SVR STORM POTENTIAL WILL RESIDE TO OUR SW
THIS EVE...WITH OUR SWRN MOST FA HAVING THE BEST CHC OF BEING PLACED
IN A LATE DAY WATCH. DESTABILIZATION IS HAVING A HARD TIME GETTING
STARTED...THOUGH IT IS ACCELERATING NOW ACRS THE WRN TN VLY AND THE
MO/IL/KY TRI STATE REGION...WHERE DEWPOINTS HAVE REACHED NEAR 70 AND
CAPES NEAR 2000 J/KG.
NRN MO LOW PRES WILL DROP SEWD INTO THE LOWER OH/TN VLYS TNGT. A
BROAD AREA OF SHOWERS AND ISOLD TSTMS AHEAD OF THE LOW AND WEAK MID
LEVEL SHRTWV TROF WILL MOVE ACRS THE NRN HALF OF OUR FA TNGT...WHILE
ADDITIONAL TSTMS DEVELOP ON THE SRN FLANK OF THE SYS...WHERE
INSTABILITY IS GREATER. IT APPEARS THAT A 1 TO 2 INCH SWATH OF RAIN
IS LIKELY ACRS MOST OF OUR FA WITH THE HEAVIEST AMOUNTS IN OUR
CENTRAL/SRN FA WHERE TSTMS SHUD BE MORE NUMEROUS.
WIDESPREAD SHOWERS/STMS SHUD BE EXITING TO OUR EAST BY SUNRISE WITH
SCT SHOWERS PRIMARILY DURG THE FIRST HALF OF THE DAY SUNDAY TO
FOLLOW. IN THE WAKE OF THE LOW...WINDS SHUD SHIFT TO A NLY COMPONENT
ACCOMPANIED BY LOW CLOUDS MUCH OF THE DAY...RESULTING IN ANOTHER
WELL BELOW NORMAL TEMP DAY FOR EARLY JULY.
LONG TERM (SUNDAY NIGHT THROUGH SATURDAY)
AFTER THE SYSTEM PASSING OVER THE FORECAST AREA IN THE SHORT TERM
EXITS...PRECIP CHANCES DROP TO NEAR ZERO FOR MOST OF THE EXTENDED.
OHIO AND TENNESSEE RIVER VALLEYS REMAIN STUCK BETWEEN BROAD UPPER
LEVEL RIDGE OVER THE WESTERN U.S. AND A SERIES OF CLOSED LOWS OVER
EASTERN CANADA AND NEW ENGLAND. RELATIVELY WEAK WEST TO NORTHWEST
FLOW BETWEEN THESE TWO FEATURES NOT SHOWING ANY SIGNS OF GENERATING
A DECENT SHORTWAVE...AND WITH LIMITED MOISTURE AT THE SURFACE AND
ALOFT...LITTLE MORE THAN FAIR WEATHER CU EXPECTED FOR THE WORK WEEK
ALONG WITH GRADUALLY WARMING TEMPERATURES.
THE GOOD NEWS IS THAT BOTH TEMPERATURES AND DEW POINTS WILL REMAIN
WELL BELOW THE LEVELS THEY WERE DURING THE LAST DRY SPELL. WHILE
TEMPERATURES WILL WORK THEIR WAY UP TO AROUND 90 BY THURSDAY...A
WEAK BUT ADVANTAGEOUS SURFACE PRESSURE PATTERN SHOULD KEEP GULF
MOISTURE WELL AWAY...LEAVING DEW POINTS IN THE UPPER 50S AND 60S
THROUGH THE WORK WEEK. THIS WILL ALLOW FOR OVERNIGHT LOWS IN THE
60S UNTIL FRIDAY...WHEN LOWER 70S RETURN TO THE PICTURE FOR
PRIMARILY THE WESTERN AND SOUTHERN PART OF THE FORECAST AREA.
THE FLY IN THE OINTMENT APPEARS TO ARRIVE IN TIME FOR NEXT
WEEKEND...AT LEAST ACCORDING TO THE LATEST GFS MODEL RUN. IT
GENERATES A SIGNIFICANT SHORT WAVE OVER THE MID MISSISSIPPI VALLEY
ON FRIDAY AND DRIVES IT SOUTHEAST INTO THE LOWER OHIO AND TENNESSEE
VALLEYS FRIDAY NIGHT AND SATURDAY IN A NEAR CARBON COPY OF THE LARGE
AREA OF RAIN WORKING ITS WAY THROUGH THE OH VALLEY THIS AFTERNOON.
THE ECMWF ALSO DEVELOPS A VORT LOBE OVER THE WEEKEND...BUT IS SLOWER
AND WEAKER THAN THE GFS. GIVEN THE FAR OUT TIME FRAME AND TIMING
OVER THE WEEKEND...WILL INSERT POPS OF 20 FOR FRIDAY NIGHT AND
SATURDAY AS A PLACEHOLDER FOR FURTHER REFINEMENT IN LATER FORECAST
ISSUANCES.
AVIATION (18Z TAFS)
VFR CONDITIONS WILL DETERIORATE TO IFR TO MVFR AS A MESOSCALE
CONVECTIVE SYS OVERSPREADS OUR REGION LATE TDA AND TNGT. TSTM
DEVELOPMENT ON THE SRN FLANK OF THE SYS WILL PRIMARILY AFFECT THE
BWG VCNTY WHILE SHOWERS DOMINATE OVER SDF AND LEX. LOW PRES FCST TO
MOVE BETWEEN SDF AND BWG...WILL RESULT IN VEERING WINDS AT BWG
TGNT/SUN AND BACKING WINDS AT SDF. WINDS AT LEX SHUD BE SIMILAR TO
SDF.
WIDESPREAD SHOWERS AND TSTMS SHUD EXIT BWG AND SDF BY SUNRISE AND
LEX SHORTLY THEREAFTER AS LOW PRES EXITS TO THE EAST LEAVING CIGS
GENERALLY IN THE 010 TO 020 RANGE.
LMK WATCHES/WARNINGS/ADVISORIES
KY...NONE.
IN...NONE.
SHORT TERM...DK
LONG TERM....JBS
AVIATION.....11
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