Area Forecast Discussion
Issued by NWS Paducah, KY

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000
FXUS63 KPAH 300319 AAA
AFDPAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PADUCAH KY
1019 PM CDT FRI MAY 29 2015

.MESOSCALE DISCUSSION...
ISSUED AT 1019 PM CDT FRI MAY 29 2015

UPDATE...THE COMBINATION OF LOW LEVEL CONVERGENCE AND WIND FIELDS IN
THE CONVECTION OVER NORTHERN PERRY COUNTY IL (NORTH OF
PINCKNEYVILLE) SUGGEST SOME INITIAL DEVELOPMENT OF A SMALL MESO-
VORTEX. THIS MAY HELP TO MAINTAIN ELEVATED CONVECTION ALONG THE
WESTERN EDGE OF THE COLD POOL WEST OF JEFFERSON COUNTY IL.

A RATHER BROAD MESO-HIGH CENTERED OVER SOUTHEAST ILLINOIS
NORTHWEST OF CISNE IN WAYNE COUNTY ILLINOIS. THIS HAS MODFIED THE
SURFACE FLOW AND SHUNTED THE EFFECTIVE SURFACE BASED CAPE TOWARD
THE SHAWNEE HILLS IN SOUTHERN ILLINOIS. BETWEEN THE PREVIOUS
CONVECTION OVER THE FOOTHILLS OF SOUTHEAST MISSOURI AND PERSISTENT
SHOWERS AND THUNDERSTORMS OVER SOUTHWEST ILLINOIS THIS AFTERNOON
AND THIS EVENING...A SHARP CAPE GRADIENT HAS DEVELOPED SOUTH OF
THE BROAD COLD POOL AROUND THE MESO-HIGH. CAPES GREATER THAN 200
J/KG2 STRETCH FROM PERRYVILLE MO TO PRINCETON IN AS OF 9 PM CDT.

THE EAST-NORTHEASTERLY BOUNDARY LAYER FLOW AROUND THE MESO HIGH IS
HELING TO GENERATE SOME UPSHEAR COLD POOL CONVECTION FROM GALATIA
TO MURHPYSBORO IL...WHERE CONVERGENT FLOW IS SUPPORTING ENOUGH
VORTICITY FOR UPDRAFTS. FURTHER TO THE NORTH...CONVECTION HAS DIED
OFF GIVEN THE LACK OF DECENT MOIST INFLOW NEAR THE UPPER LEVEL OF
THE PLANETARY BOUNDARY LAYER. THIS SHOULD CONTINUE TO WEAKEN THE
COVERAGE AND INTENSITY OF SHOWERS AND THUNDERSTORMS FURTHER NORTH.
THIS IS ALSO SUGGESTED BY THE HRRR GUIDANCE THROUGH MIDNIGHT.

ANTICIPATE SOME MAINTENANCE OF CONVECTION OVER PERRY...WILLIAMSON
AND JEFFERSON COUNTIES FOR ANOTHER HOUR OR SO.

THE CAPE GRADIENT FURTHER SOUTH OVER THE REST OF THE WFO PAH
FORECAST AREA WILL SERVE AS A GOOD DIFFERENTIAL THETA-E BOUNDARY
AND HEATING BOUNDARY FOR SATURDAY AND MAY SERVE AS A FOCAL POINT
FOR SUSTAINED CONVECTION ON SATURDAY.

&&

.SHORT TERM...(THIS EVENING THROUGH SUNDAY NIGHT)
ISSUED AT 132 PM CDT FRI MAY 29 2015

THE HRRR PICKS UP ON CONVECTION TO OUR WEST IF OVERDONE A TAD. IT
BASICALLY MIGRATES SCATTERED CONVECTIVE ELEMENTS INTO OUR SEMO
OZARK COUNTIES TONIGHT. IT DOS NOT MODEL ACCURATELY THE WIDELY
SCATTERED ACTIVITY IN OUR EAST...BUT DOES SUGGEST SIMILAR TREND
THERE INTO THE EARLY EVENING HOURS.

OVER TIME...SYNOPTIC MODELING IS THE SAME...DRAWING FRONT IN AND
THIS WEEKEND WITH PASSAGE AND HIGH POP EVENT. LACKING STRONG
FORCING...IT APPEARS TO BE MAINLY A HEAVY RAIN THREAT...WITH
PERHAPS PULSE MAINLY HEAT OF DAY STORMS BEARING WATCH ON THEIR
INTENSITY. POPS PEAK ALONG/AHEAD OF PASSING BOUNDARY SATURDAY INTO
SATURDAY NIGHT.

ON THE BACK SIDE OF THE FRONT BEGINNING SUNDAY INTO SUNDAY
NIGHT...POPS MAY LINGER BUT DRIER AIR STARTS TO WORK DOWN THE
COLUMN. WE`LL SEE SOME DEW POINTS DROPPING BACK INTO THE 50S THEN
AND EFFECTIVELY THIS WILL WORK TOWARD ENDING POPS FROM NORTHWEST
TO SOUTHEAST WITH TIME.

SUMMER LIKE WARMTH/HUMIDITY 80S/60S CONTINUES UNTIL FROPA...AFTER
WHICH THE MOVE BACK INTO THE 70S/50S COMMENCES SUNDAY-SUNDAY
NIGHT.

.LONG TERM...(SUNDAY NIGHT THROUGH FRIDAY)
ISSUED AT 153 PM CDT FRI MAY 29 2015

A WEAK UPPER-LEVEL FLOW PATTERN WILL CONTINUE THROUGH THE LONG
TERM...WHICH SHOULD BECOME MORE FREQUENT AS WE HEAD INTO THE SUMMER
MONTHS. EARLY IN THE WEEK...WEAK TROUGHING OVER THE LOWER OHIO
VALLEY WILL BRING SOMEWHAT COOLER AND DRIER CONDITIONS. BROAD
RIDGING WILL FOLLOW IN THE WAKE OF THE TROUGH FOR MID TO LATE WEEK.
THIS WILL RESULT IN A GRADUAL INCREASE IN WARMTH AND HUMIDITY.

AS FAR AS THE SPECIFICS...MONDAY THROUGH TUESDAY NOW LOOK MAINLY DRY
AND A LITTLE COOLER. THE MODELS HAVE TRENDED DRIER AND A BIT COOLER.
POPS WILL BE REMOVED FOR MUCH OF THE AREA...BUT A SLIGHT CHANCE OF
SHOWERS WILL BE KEPT FOR PARTS OF WESTERN KENTUCKY. WITH THE COOLER
AND DRIER AIR...INSTABILITY LOOKS TOO LIMITED FOR THUNDER. LINGERING
CLOUDS SHOULD KEEP HIGHS IN THE 70S ON MONDAY. EVEN WITH LOTS OF SUN
ON TUESDAY...HIGHS SHOULD GENERALLY BE AROUND 80 DEGREES. AS FOR
OVERNIGHT LOWS...HIGH PRESSURE OVER THE GREAT LAKES WILL BRING DRIER
AIR AND LIGHT WINDS...WHICH SHOULD ALLOW MOST PLACES TO FALL INTO
THE 50S.

WEDNESDAY THROUGH FRIDAY...LOW LEVEL WINDS WILL VEER FROM THE EAST
INTO THE SOUTH AS THE HIGHS RETREATS TO THE EAST COAST. LOW LEVEL
MOISTURE WILL SLOWLY CREEP UP. WITH THE INCREASING MOISTURE WILL
COME A SMALL CHANCE OF DIURNALLY INDUCED SHOWERS AND
STORMS...ESPECIALLY THURSDAY AND FRIDAY. HIGHS WILL INCH BACK INTO
THE LOWER AND MID 80S...AND OVERNIGHT LOWS WILL BE IN THE 60S.

&&

.AVIATION...
ISSUED AT 607 PM CDT FRI MAY 29 2015

PRIOR TO THE EFFECTIVE ISSUANCE OF THE 00Z SATURDAY WFO PAH TAF
FORECAST PACKAGE...A SMALL CLUSTER OF SHOWERS AND THUNDERSTORMS
ARE EXPECTED TO MOVE NORTHWEST OF THE KCGI TAF SITE...SO DID NOT
INCLUDE PRECIPITATION AT THE BEGINNING OF THE FORECAST. THE
OVERALL CLUSTER OF SHOWERS AND THUNDERSTORMS MAY PERSIST BRIEFLY
WITH THE DEVELOPMENT OF A WEAK LOW LEVEL JET...SO ADDED A MENTION
OF RAIN IN THE 03Z-07Z TIME FRAME AT KCGI.

THE BULK OF CONVECTION SHOUSL HOLD OFF UNTIL TOMORROW AFTERNOON.
ATTEMPTED TO KEEP VFR CEILINGS AND VISIBILITIES FOR MOST OF THE
TAF SITES IN PLACE PRIOR TO THE ONSET OF CONVECTION ON SATURDAY.


&&

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

$$

MESOSCALE...SMITH
AVIATION...SMITH


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