Severe Thunderstorm Warning 221, NWS Paducah, KY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PADUCAH KY
315 PM CST WED OCT 17 2007

.SHORT TERM...TONIGHT THROUGH SATURDAY NIGHT.
MAIN CONCERN CONTINUES TO BE SEVERE STORM POTENTIAL TONIGHT THROUGH
THURSDAY.

THE SHORT RANGE MODELS HAVE COME INTO AGREEMENT IN EMPHASIZING THE
06Z-12Z TIMEFRAME AS THE MAIN SEVERE THREAT. MAJOR MID/UPPER LEVEL
IMPULSE PUSHING OUT OF THE TX/OK PANHANDLES THIS AFTERNOON WILL
ROTATE NORTHEAST INTO SOUTHEAST MISSOURI BY 09Z. IN RESPONSE TO THIS
IMPULSE A LLJ OF 75KTS AT 850MB IS EXPECTED TO DEVELOP.
THEREFORE...WITH THE LIFT EXPECTED WITH THE MID/UPPER LEVEL SYSTEM
AND EXTREME LOW-LEVEL SHEAR...LINE SEGMENTS WITH BOWING SEGMENTS CAN
BE EXPECTED...ALONG WITH A THREAT OF TORNADOES OUT OF ANY CONVECTIVE
MODE. THE STORMS WILL LIKELY OUTRUN THE BEST DEEP LAYER SHEAR...BUT
IF THEY ARE SLOWER TO SWEEP THROUGH THE AREA...THE DEEP LAYER SHEAR
MAY CATCH UP TO THEM AND THERE MAY BE SOME BETTER THREAT OF MORE
ISOLATED SUPERCELL STRUCTURES. THE WORST SEVERE WEATHER WOULD
ACCOMPANY THESE ISOLATED STORMS...BUT AGAIN THAT IS UNLIKELY.

FOR THURSDAY...THE OVERNIGHT CONVECTION WILL LIKELY BE SOMEWHERE
ACROSS SOUTHERN ILLINOIS AND WEST KENTUCKY AT SUNRISE...AND SHOULD
MOVE QUICKLY NORTHEAST OUT OF THE AREA BY 15Z. THE WIND FIELDS AND
INSTABILITY WILL NOT BE QUITE AS GOOD EAST OF THE MISSISSIPPI
RIVER...SO SEVERE THREAT WILL NOT BE QUITE AS GOOD THERE.

THE NEXT QUESTION IS WHETHER THERE WILL BE ANY DEEP CONVECTION
REDEVELOPING NEAR THE DRYLINE/TROUGH IN EASTERN SECTIONS IN THE LATE
AFTERNOON AND EVENING HOURS. BOTH THE 12Z NAM AND GFS BRING A MAJOR
DRY SLOT WITH MID-LEVEL WARMING INTO THE AREA EARLY THURSDAY...WHICH
EFFECTIVELY PUTS A LID ON ANY DEEP CONVECTION. THE MODELS DO
GENERATE SOME SHALLOW SHOWERY CONVECTION THURSDAY EVENING...WHICH
SEEMS BELIEVABLE...SO WILL HAVE TO KEEP A CHANCE POP IN THE EAST
THURSDAY NIGHT.

IN GENERAL...THE 12Z NAM EVOLUTION WAS FOLLOWED CLOSELY THROUGH
THURSDAY NIGHT. WILL HAVE CATEGORICAL POPS WITH SEVERE MENTION
THROUGHOUT THE AREA TONIGHT...AND KEEP GOOD CHANCE POPS THURSDAY
MORNING IN THE EAST WITH SLIGHTS OVER SOUTHEAST MISSOURI. WILL GO
DRY OVER SOUTHEAST MISSOURI THURSDAY AFTERNOON...AND RAMP UP TO JUST
30S IN THE EAST.

AS FOR PRECIPITATION AMOUNTS...THINK THAT HPC QPF WAS OVERDONE FOR
TONIGHT...SO KNOCKED IT DOWN ABOUT 30 PERCENT. 1-2 INCHES WILL BE
POSSIBLE OVER MUCH OF THE AREA...BETWEEN THE SCATTERED CONVECTION
MOVING THROUGH THE AREA THIS AFTERNOON AND EVENING...AND THE
OVERNIGHT/THURSDAY AM CONVECTION. PORTIONS OF SOUTHEAST MISSOURI AND
SOUTHERN ILLINOIS MAY SEE SOME LOCALLY HIGHER AMOUNTS.

GENERALLY FAVORED THE WARMER GUIDANCE FOR TEMPERATURES TONIGHT AND
THURSDAY...THEN STAYED NEAR CONSENSUS THROUGH FRIDAY NIGHT.

.LONG TERM...SUNDAY THROUGH WEDNESDAY.
AFTER A DRY AND PLEASANT SUNDAY...MODELS CONTINUE TO BE ALL OVER THE
PLACE AND INCONSISTENT WITH AN EARLY WEEK WEATHER SYSTEM.  GFS
BRINGS PRECIP ACROSS THE REGION LATE SUNDAY NIGHT INTO MONDAY BEHIND
A COLD FRONT...WHICH IS ABOUT 6 HOURS FASTER THAN ITS PREVIOUS RUN.
THE ECMWF BRINGS PRECIP INTO THE REGION MONDAY AS MOISTURE SURGES
NORTHWARD AHEAD OF AN UPPER LOW OVER THE SOUTHWEST U.S. AND A
SURFACE LOW OVER TEXAS.  THE ECMWF IS VERY SLOW WITH THE PROGRESSION
OF THIS SYSTEM...WITH THE SURFACE LOW FINALLY MOVING OVER THE QUAD
STATE REGION BY 12Z WEDNESDAY.  WHILE THE GFS HAS US DRY BY MONDAY
NIGHT...THE ECMWF LINGERS PRECIP OVER THE REGION THROUGH MID WEEK
DUE TO THE SOUTHWEST UPPER LOW NEVER MOVING.  DGEX IS SOMEWHERE IN
BETWEEN...DEVELOPING AN UPPER LOW OVER THE SOUTHWEST U.S. BUT SLOWLY
MOVING IT NORTHEAST THROUGH MID WEEK.

DUE TO SO MANY UNCERTAINTIES...STAYED VERY CLOSE TO HPC
GUIDANCE...WHICH KEEPS SLIGHT TO LOW CHANCE POPS IN THE FORECAST
SUNDAY NIGHT THROUGH TUESDAY NIGHT.  FOR TEMPERATURES...BASED ON
LEANING MORE TOWARD THE ECMWF GUIDANCE...WENT COOLER THAN THE LATEST
MEX GUIDANCE.

&&

.AVIATION...
SHOWERS AND TSTMS WILL MOVE NE...AFFECTING KCGI BY 20Z...KPAH BY
21Z...AND KEVV AROUND 23Z.  SHOWERS AND STORMS WILL CONTINUE DEVELOP
AND MOVE ACROSS REGION OVERNIGHT. SEVERE STORMS POSSIBLE...WITH VERY
GUSTY WINDS AND HAIL POSSIBLE IN AND NEAR TSTMS.   TSTMS WILL TAPER
OFF AFTER 12Z.  CIGS RANGING FROM BKN015 TO BKN030 WILL SPREAD EAST
AND NORTHEAST THROUGH THE AFTERNOON...WITH BKN010-015 POSSIBLE WITH
TSTMS. S TO SE WINDS GUSTING AROUND 20 KTS TODAY WILL BE 10 TO 15
KTS OVERNIGHT...THEN INCREASE ON THURSDAY FROM THE S TO SW WITH
GUSTS OF 25 TO 30 KTS.

&&

.PAH WATCHES/WARNINGS/ADVISORIES...
KY...NONE.
MO...NONE.
IL...NONE.
IN...NONE.
&&

DRS

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