Flash Flooding and Flooding in Kentucky, August 18, 2010

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON KY
259 AM EDT WED AUG 18 2010

.SHORT TERM.../TODAY THROUGH FRIDAY/...UPDATED

THERE HAS BEEN ENOUGH RUN TO RUN INCONSISTENCIES AND MODEL
DIFFERENCES TO KEEP MY CONFIDENCE A BIT LOW IN HOW THE MODELS ARE
HANDLING THIS WEATHER PATTERN. ON TOP OF THAT...THE MODELS DID NOT
HAVE A GOOD HANDLE ON INITIALIZING THE AREAS WHERE PRECIPITATION WAS
FALLING. THIS MORNING...THE QUASI STATIONARY FRONT WAS DRAPED ACROSS
EASTERN KENTUCKY WITH A SHORT WAVE UPSTREAM. EXPECT THIS SHORT WAVE
TO FROM A WAVE ON THE FRONT WHICH WILL THEN MOVE ACROSS EASTERN
KENTUCKY DURING THE LATE MORNING TO EARLY AFTERNOON. THE MODEL
SOUNDINGS ARE NOT SHOWING MUCH INSTABILITY...HOWEVER THEY ARE SHOWING
A SOUNDING WHICH SHOULD BE CONDUCIVE TO EFFICIENT RAIN PRODUCERS. THE
QPF THAT I FORECAST IS WELL BELOW THE FLASH FLOOD GUIDANCE...HOWEVER
I CAN ENVISION THAT THERE WILL BE SOME STORMS THAT TRAIN ALONG THE
FRONTAL BOUNDARY WHICH COULD PRODUCE SOME LOCALIZED HIGH WATER IN
DITCHES AND LOW WATER CROSSINGS...AND MAYBE EVEN A VERY LOCALIZED FLASH
FLOOD. THE THREAT FOR FLASH FLOODING IS SO ISOLATED...THAT I WILL
JUST MENTION IT IN THE HWO AND THEN WE WILL MONITOR TO SEE WHAT
EVENTUALLY TRANSPIRES. LOWERED THE MAX TEMPS FOR TODAY PER MOS
GUIDANCE AND MODEL TRENDS. TWEAKED THE REST OF THE TEMPS TOWARD MODEL
TRENDS...BUT DID NOT MAKE ANY SIGNIFICANT CHANGES.

.LONG TERM.../FRIDAY THROUGH TUESDAY/

THE MODELS HAVE COME INTO BETTER AGREEMENT ALOFT FOR THE LONG TERM
PORTION OF THE FORECAST WHEN COMPARED TO 24 HOURS AGO. THEY DEPICT
TROUGHING EXITING THE EASTERN OHIO VALLEY ON THURSDAY INTO THURSDAY
NIGHT WITH A BRIEF INTRUSION OF RIDGING FOLLOWING IN ITS WAKE. THE
OLD ECMWF TOOK THE TROUGH EAST A TAD QUICKER THAN THE GFS AND IT IS
ALSO STRONGER WITH THE FOLLOW UP RIDGE CROSSING THE TENNESSEE VALLEY
AND INTO THE SOUTHERN APPALACHIANS ON FRIDAY. FOR THE OHIO VALLEY
THIS RIDGE GETS TOPPED BY ANOTHER TROUGH MOVING FROM THE UPPER
MIDWEST INTO THE GREAT LAKES BY SATURDAY MORNING. THE GFS IS WEAKER
AND QUICKER...BUT FURTHER SOUTH WITH THIS SHORTWAVE THAN THE OLD
ECMWF...BUT THEIR UPPER PATTERNS ARE FAIRLY SIMILAR OVER KENTUCKY. A
COUPLE OF MINOR WAVES CROSS THE AREA...IN CONJUNCTION WITH THE
DEEPER TROUGH PASSING TO THE NORTH...THROUGH THE WEEKEND. HEADING
INTO THE START OF THE NEW WORK WEEK...ALL THE MODELS AMPLIFY THE
EASTERN TROUGH WHILE RIDGING BUILDS DRAMATICALLY TO THE WEST...OVER
THE HIGH PLAINS. THE OLD ECMWF IS STRONGER AND FURTHER SOUTH WITH THE
LOW DEEPENING TO OUR NORTHEAST INTO TUESDAY THAN THE GFS...BUT THE
TREND SEEMS TO BE SUPPORTING A MOVE TO THE DEEPER AND MORE
RETROGRADED SOLUTION. AS A RESULT...THE SHORTWAVES SUPPORTING THIS
TROUGH DEVELOPMENT WILL MOVE OVER EAST KENTUCKY THROUGH TUESDAY
WHILE STRONG RIDGING HOLDS OVER THE WESTERN PART OF THE STATE. THE
GENERAL SIMILARITY OF THE UPPER PATTERN THROUGH THE LONG TERM LENDS
ITSELF TO A CONSENSUS SOLUTION AND...AS SUCH...WEATHER SPECIFICS
FROM THE GFS AND SOMEWHAT TO A LESSER EXTENT THE OLD ECMWF WERE
BLENDED FOR GRID EDITING PURPOSES FROM THURSDAY INTO TUESDAY.

SENSIBLE WEATHER WILL FEATURE THE SFC WAVE THAT IS EXPECTED TO BRING
RAIN TO THE AREA INTO WEDNESDAY NIGHT MOVING OFF TO THE SOUTHEAST AND
TAKING THE DEEPER MOISTURE ALONG WITH IT. CANNOT RULE OUT POP UP...
DIURNALLY ENHANCED...CONVECTION IN THE WAKE OF THIS INTO THE DAY
THURSDAY...PRIMARILY FAVORING THE FAR SOUTHEAST PART OF THE CWA. HIGH
PRESSURE AT THE SURFACE AND RIDGING ALOFT WILL DRY OUT THE AREA ON
FRIDAY SUPPRESSING THE FRONT AND PCPN CHANCES TO THE SOUTH. THIS
FRONT DOES START TO COME BACK NORTH THAT NIGHT AS THE NEXT UPPER
TROUGH APPROACHES...BRINGING CONVECTION CHANCES BACK INTO EAST
KENTUCKY FROM SOUTHWEST TO NORTHEAST ALONG WITH THE BOUNDARY. A
COMPACT SFC LOW WITH ITS ASSOCIATED COLD FRONT...AND THAT NORTHWARD
LIFTED WARM FRONT...WILL THEN EASE THROUGH THE SOUTHERN GREAT LAKES
ON SATURDAY MAINTAINING A GOOD CHANCE FOR SHOWERS AND THUNDERSTORMS
ACROSS EAST KENTUCKY. THESE CHANCES WILL DIMINISH LATER THAT NIGHT
AND DURING THE DAY SUNDAY...FROM NORTHWEST TO SOUTHEAST AS THE FRONT
AND SFC LOW MOVE THROUGH AND PULL OFF TO THE EAST. FOLLOWING THIS...
THE LOWER SFC PRESSURE HOLDS OFF JUST TO THE NORTHEAST WHILE THE
UPPER PATTERN AMPLIFIES ALOFT. FOR THIS WILL KEEP A SMALL CHANCE OF
SHOWERS AND THUNDERSTORMS IN THE FORECAST FOR THE FAR EASTERN
PORTION OF THE CWA AT DIURNALLY FAVORED TIMES THROUGH TUESDAY.

TEMPERATURES THROUGH THE PERIOD WILL BE NEAR NORMAL OR JUST ON THE
HIGH SIDE WITH HUMIDITIES RUNNING HIGH AS WELL. FOLLOWED A BLEND OF
THE INHERITED GRIDS AND HPC GUIDANCE THROUGH THE EXTENDED WITH MINOR
TERRAIN BASED ADJUSTMENTS AT NIGHT. AS FOR POPS...ENDED UP CLOSEST
TO THE MEX NUMBERS DURING THE LONG TERM...BUT NOT SO HIGH YET FOR
SATURDAY AND SUNDAY.

&&

.AVIATION.../06Z TO 06Z/

A QUASI STATIONARY FRONT EXTENDED MOSTLY EAST TO WEST JUST NORTH OF
THE HAL ROGERS PARKWAY. AT 5Z...AN MCS WAS LOCATED OVER CENTRAL
TENNESSEE AND WAS MOVING SLOWLY TO THE NORTH EAST. THE VARIOUS TAF
MOS AND LAMP GUIDANCE TOOLS WERE ALL OVER THE PLACE TO THE POINT
THAT THEY WERE ABOUT WORTHLESS. THE MODELS IN GENERAL INITIALIZED
VERY POORLY AND DID NOT SEEM TO HAVE A HANDLE ON THE PRECIPITATION
THAT WAS OCCURRING...SO THIS PUT ME IN A LOW CONFIDENCE MODE.
DECIDED TO USE A BLEND OF THE MODEL TIME HEIGHTS IN ORDER TO MAKE UP
THE TAF. EXPECT THE CEILING TO FALL AS THE RAIN BEGINS IN THE
MORNING...BUT THEN SHOULD RISE UP AGAIN AFTER 18Z WHEN THE WAVE MOVES
OFF TO THE EAST. AFTER THE SUN SETS...THE CIGS SHOULD DROP DOWN AGAIN
TO MVFR. IF THE PRECIP DEVELOPS AS EXPECTED...THERE SHOULD BE SOME
VLIFR CIGS AND VSBY AFTER 06Z...BUT THAT WILL BE IN THE NEXT ROUND OF
TAFS.

&&

.JKL WATCHES/WARNINGS/ADVISORIES...NONE.

&&

SHORT TERM...JJ
LONG TERM...GREIF
AVIATION...JJ

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE JACKSON KY
427 AM EDT WED AUG 18 2010

KYZ044-050>052-058>060-068-069-079-080-083>088-104-106>120-191130-
FLEMING-MONTGOMERY-BATH-ROWAN-ESTILL-POWELL-MENIFEE-ROCKCASTLE-
JACKSON-PULASKI-LAUREL-WAYNE-MCCREARY-WHITLEY-KNOX-BELL-HARLAN-
ELLIOTT-MORGAN-JOHNSON-WOLFE-MAGOFFIN-FLOYD-LEE-BREATHITT-KNOTT-
OWSLEY-PERRY-CLAY-LESLIE-LETCHER-MARTIN-PIKE-
427 AM EDT WED AUG 18 2010

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF EASTERN KENTUCKY.

.DAY ONE...TODAY AND TONIGHT.

LOCALLY HEAVY RAIN IS A POSSIBILITY TODAY AND THIS EVENING...ESPECIALLY
SOUTH OF THE MOUNTAIN PARKWAY. ANY SLOW MOVING THUNDERSTORMS WILL BE
CAPABLE OF PRODUCING MINOR FLOODING OF LOW LYING AREAS. ISOLATED
LOCATIONS THAT SEE REPEATED ROUNDS OF THUNDERSTORMS MAY EXPERIENCE
FLASH FLOODING.

THUNDERSTORMS ARE POSSIBLE TODAY AND TONIGHT. THEN AGAIN FROM
THURSDAY THROUGH SUNDAY NIGHT...MAINLY DURING THE LATE AFTERNOON AND
EVENING HOURS.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY.

THUNDERSTORMS ARE POSSIBLE THURSDAY AND THEN AGAIN SATURDAY THROUGH
MONDAY NIGHT...MAINLY DURING THE LATE AFTERNOON AND EVENING HOURS.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT ANTICIPATED.

JJ