Area Forecast Discussion
Issued by NWS Paducah, KY

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000
FXUS63 KPAH 261732 AAA
AFDPAH

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PADUCAH KY
1232 PM CDT FRI JUN 26 2015

.UPDATE...
ISSUED AT 1225 PM CDT FRI JUN 26 2015

THE AVIATION DISCUSSION HAS BEEN UPDATED FOR THE 18Z TAF ISSUANCE.

&&

.SHORT TERM...(TODAY THROUGH SUNDAY)
ISSUED AT 433 AM CDT FRI JUN 26 2015

GIVEN THE ANTECEDENT AND UPCOMING WEATHER OVERNIGHT...THIS
DISCUSSION IS SOMEWHAT DELAYED FROM NORMAL ISSUANCE TIME.

THE WFO PAH FORECAST AREA IS CURRENTLY SANDWICHED BETWEEN A
DEPARTING AND APPROACHING MCS (MESOSCALE CONVECTIVE SYSTEM). THE
LATEST OBSERVATIONS AS OF 3 AM CDT SUGGEST MEAN CONVERGENCE
BOUNDARY LOOSELY ASSOCIATED WITH THE STALLED OUT FRONT REMAINS
BETWEEN I-64 AND I-70 IN SOUTHERN ILLINOIS. AS EXPECTED...THE
LARGER SCALE NUMERICAL MODELS ARE GOING TO BE A LITTLE SLOWER TO
RESPOND TO THE MESOSCALE INFLUENCES ALONG THIS BOUNDARY TODAY.

THE 00Z FRIDAY CANADIAN...GFS ENSEMBLE...ECMWF AND GFS GUIDANCE
DID A DECENT JOB OF DEPICTING THE MEAN ZONE OF CONVECTION WITHIN
THE FRONTAL ZONE...BUT HAD TO RELY ON THE HIGHER RESOLUTION HRRR
AND NMM VERSION OF THE 4KM NAM-WRF TO DEPICT HIGHER TEMPORAL
(HOURLY) CONVECTIVE ACTIVITY FOR TODAY AND TONIGHT.

THE BIGGEST CHALLENGE AT THIS TIME IS EVOLUTION OF POPS/WEATHER
FROM NOW THROUGH 15Z. THE CURRENT MCS SPRAWLED ACROSS CENTRAL
MISSOURI SHOULD ENHANCE AGEOSTROPHIC RESPONSE OVER THE
DIFFERENTIAL MOISTURE BOUNDARY ACROSS THE INTERSTATE 64 CORRIDOR
TO GENERATE SOME RAIN IN THAT AREA BEFORE DAYBREAK AHEAD OF THE
MCV BEING CREATED WITH THE MID-MISSOURI MCS.

HOWEVER...THE GUIDANCE SUGGESTS THAT A BRIEF PERIOD OF LOW LEVEL
STABILITY...COINCIDING WITH THE DIURNAL MINIMUM IN TEMPERATURES
AND MINIMAL LLJ...WILL ALSO CONTRIBUTE TO A MINIMUM OF CONVECTIVE
ACTIVITY ACROSS THE AREA BETWEEN 12Z-16Z FRIDAY. AS THE UPPER
LEVEL TROUGH OVER WISCONSIN SHARPENS DURING THE MORNING AND INTO
THE AFTERNOON...THIS TREND WILL REVERSE AND THERMAL/MOISTURE
GRADIENTS WILL ALSO SHARPEN IN RESPONSE TO THE DEEPENING SHORTWAVE
IN THE MEAN TROUGH.

GIVEN THE AMPLE BOUNDARY LAYER MOISTURE INSTABILITY IN PLACE...IT
WILL TAKE LITTLE TO GENERATE CONVECTIVE CLUSTERS ALONG THE FRONTAL
BOUNDARY. THE LACK OF CONVECTIVE INHIBITION WILL ALSO MUDDY THE
LOCATION OF THE EFFECTIVE FRONTAL BOUNDARY THIS AFTERNOON. FOR
NOW...ADDED A MENTION OF GUSTY WINDS TO THE
GRIDDED...TABULAR...TEXT FORECAST TO ACCOUNT FOR LOCAL
OPPORTUNITIES FOR ENHANCED WINDS OUTSIDE SEVERE POTENTIAL.

ALTHOUGH SOMEWHAT MARGINAL AT THIS TIME...ADDED A SPECIFIC MENTION
OF HEAVY RAIN TO GRIDDED...TABULAR AND TEXT FORECAST FOR THE AREA
COVERED BY THE FLASH FLOOD WATCH IN PLACE UNTIL 11 PM TONIGHT.
STILL FEEL THAT THE I-64 CORRIDOR AND SOUTHWEST INDIANA WILL HAVE
THE BEST POTENTIAL FOR ANY FLASH FLOOD PRODUCING RAINS THIS
AFTERNOON AND EARLY THIS EVENING.

WITH RESPECT TO TEMPERATURES...WINDS...DEWPOINTS...UTILIZED THE
HRRR AND 4KM NAM-WRF TO HANDLE THE SUBTLE CHANGES DUE TO THE
MOVEMENT OF MESOSCALE SYSTEMS THROUGH THE WFO PAH FORECAST AREA IN
THE NEAR TERM.

THERE SHOULD BE A SHARP CUTOFF IN PRECIPITATION AFTER MIDNIGHT
TONIGHT FROM WEST TO EAST...WITH DRY AND COOLER CONDITIONS ON
SATURDAY INTO SUNDAY.

.LONG TERM...(SUNDAY NIGHT THROUGH THURSDAY)
ISSUED AT 433 AM CDT FRI JUN 26 2015

THE DOMINANT PATTER FOR THE EXTENDED FORECAST PERIOD WILL BE A
WESTERN U.S. RIDGE CENTERED ON THE ROCKIES AND A EASTERN U.S.
TROUGH CENTERED IN THE UPPER CENTRAL GREAT LAKES REGION.

FOR THE WFO PAH FORECAST AREA...THIS PLACES THE LOCAL AREA IN A
PERSISTENT NORTHWEST FLOW ALOFT...WITH A SERIES OF CHANNELED
SHORTWAVE ROTATING OUT OF CANADA ACROSS THE AREA THROUGH THE
PERIOD.

DIURNAL AND NON-DIURNAL SHOWERS AND THUNDERSTORMS WILL BE THE RULE
AS SYSTEMS MOVE ACROSS THE AREA. THE FIRST SYSTEM WILL MOVE
THROUGH SUNDAY NIGHT THROUGH MONDAY NIGHT...WITH THE NEXT SYSTEM
POISED TO MOVE THROUGH WEDNESDAY INTO THURSDAY. TEMPERATURES
THROUGH THE PERIOD WILL REMAIN BELOW NORMAL FOR THIS TIME OF
YEAR...OWING TO THE PATTERN FLOW...PERIODIC CLOUDINESS AND
INTERMITTENT WAVES OF COLD AIR ADVECTION ACROSS THE AREA.

&&

.AVIATION...
ISSUED AT 1225 PM CDT FRI JUN 26 2015

AS A FRONTAL SYSTEM APPROACHES FROM THE WEST...CLOUDINESS AND
PRECIPITATION CHANCES WILL INCREASE WITH IFR/MVFR CIGS/VSBYS IN
TSRA...ESPECIALLY BETWEEN 20-01Z. A FEW STORMS COULD BECOME
SEVERE WITH LARGE HAIL AND DAMAGING WINDS BEING THE PRIMARY
THREATS. IN THE WAKE OF THE STORMS...SHOWERS MAY LINGER INTO THE
OVERNIGHT HOURS...THEN CIGS ARE EXPECTED TO BECOME MVFR IN THE
WRAP AROUND MOISTURE AND CONTINUE THROUGH THE END OF THE PERIOD.
VARIABLE WINDS AOB 5 KNOTS WILL GRADUALLY VEER AROUND TO THE
NORTHWEST TO NORTH BUT SHOULD REMAIN AOB 10 KNOTS.

&&

.PAH WATCHES/WARNINGS/ADVISORIES...
IL...FLASH FLOOD WATCH UNTIL 11 PM CDT THIS EVENING FOR ILZ075>078-
     080>087.

MO...NONE.
IN...FLASH FLOOD WATCH UNTIL 11 PM CDT THIS EVENING FOR INZ081-082-
     085>088.

KY...FLASH FLOOD WATCH UNTIL 11 PM CDT THIS EVENING FOR KYZ014-
     018>020.

&&

$$

SHORT TERM...SMITH
LONG TERM...SMITH
AVIATION...JP


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