Area Forecast Discussion
Issued by NWS Paducah, KY

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000
FXUS63 KPAH 141135
AFDPAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PADUCAH KY
635 AM CDT TUE APR 14 2015

.UPDATE...
ISSUED AT 635 AM CDT TUE APR 14 2015

THE AVIATION SECTION HAS BEEN UPDATED FOR THE 12Z TAF ISSUANCE.

&&

.SHORT TERM...(TODAY THROUGH THURSDAY)
ISSUED AT 340 AM CDT TUE APR 14 2015

THE UPPER LOW THAT WAS CENTERED JUST SOUTH OF THE FOUR CORNERS
REGION OF THE DESERT SOUTHWEST PART OF THE U.S. IS NOW LOCATED
NEAR CHILDRESS TEXAS (EASTERN PANHANDLE OF TEXAS). THIS FEATURE
WILL BE THE COMPLICATED FEATURE FOR A RELATIVELY DRY FORECAST FOR
TUESDAY. DRIER AIR IS IMPINGING TO THE SOUTH OF THE WFO PAH
FORECAST AREA AT LOWER/MIDDLE LEVELS OF THE ATMOSPHERE AND SHOULD
HELP TO DIMINISH THE WIDESPREAD COVERAGE OF PRECIPITATION
CURRENTLY COVERING THE SOUTHERN TWO-THIRDS OF THE WFO PAH FORECAST
AREA EAST OF THE MISSISSIPPI RIVER. DESPITE THE REDUCTION OF THE
MAIN PRECIPITATION SHIELD EAST OF THE AREA BY NOON, THE
COMBINATION OF A WEAKENING DEFORMATION ZONE ALOFT AND APPROACHING
POSITIVE DIFFERENTIAL ADVECTION AHEAD OF THE LOW AS IT MOVES INTO
EASTERN KANSAS/WESTERN MISSOURI. RATHER CAN KEEP COMPLETELY DRY
CONDITIONS IN PLACE, KEPT A MENTION OF ISOLATED SHOWERS ACROSS THE
WFO PAH FORECAST AREA THROUGHOUT THE DAY AND INTO THE EVENING. A
GREATER COVERAGE OF SHOWERS WILL REMAIN IN PLACE OVER SOUTHEAST
MISSOURI, AS OPEN WAVE (FORMER LOW) MOVES INTO EASTERN IOWA
TONIGHT.

JUST ABOUT THE TIME THE INFLUENCE OF THIS SHORTWAVE LEAVES THE
AREA, THE INFLUENCE OF THE INTERMOUNTAIN TROUGH AND DEEPENING
CLOSED LOW DAMPENS ANY RIDGING (AND GREATER STABILITY) BETWEEN THE
TWO SYSTEMS. THEREFORE, RAIN CHANCES RETURN AGAIN FROM THE WEST ON
WEDNESDAY. THERE WILL BE SOME ELEVATED INSTABILITY WEDNESDAY
NIGHT, EXTENDING INTO THURSDAY, SO A MAINLY DIFFERENTIAL MENTION
OF THUNDERSTORMS WAS ADDED TO THE FORECAST FOR THURSDAY.

WITH THE PROXIMITY OF THE SURFACE, LOW LEVEL FRONTAL BOUNDARY,
DIFFERENTIAL FORCING ALOFT AND DIFFERENTIAL HEATING AT THE SURFACE
DUE TO CLOUD COVER, THE TEMPERATURE FORECAST WILL BE CHALLENGING
FROM ONE LOCATION TO ANOTHER. UNTIL A DISTINCT AIRMASS CHANGE WILL
TAKE PLACE, THE DIURNAL TEMPERATURE RANGE MAY NOT EXCEED 10-12
DEGREES FOR MOST OF THE FORECAST AREA TODAY, WITH A RANGE OF 15-20
DEGREES POSSIBLE ON WEDNESDAY, ESPECIALLY OUTSIDE OF GREATER RAIN
COVERAGE.

LEANED CLOSER TO THE CANADIAN AND THE NAM-WRF ARW AND NMM GUIDANCE
FOR TEMPERATURES, DEWPOINTS, AND WINDS. POPS UTILIZED A GREATER
INFLUENCE OF THE HRRR/RAP IN THE VERY NEAR TERM AND THE NAM-WRF IN
OUTER PERIODS, COMPLEMENTED BY THE CANADIAN GUIDANCE.

.LONG TERM...(THURSDAY NIGHT THROUGH TUESDAY)
ISSUED AT 340 AM CDT TUE APR 14 2015

THE 00Z GFS...ECMWF...AND GEM ARE IN AGREEMENT IN TAKING THE MID
/UPPER-LEVEL TROUGH...CURRENTLY COMING ONSHORE THE PACIFIC
NORTHWEST...SOUTHEAST INTO THE SOUTHERN ROCKIES BY 00Z FRIDAY. THE
MODELS ARE ACTUALLY IN DECENT AGREEMENT IN TIMING IMPULSES IN THE
NORTHERN STREAM ALONG THE CANADIAN BORDER THROUGH SATURDAY...BUT
DIFFER IN HOW THE SOUTHERN ROCKIES SYSTEM INTERACTS WITH THE
NORTHERN STREAM FLOW.

THE GFS APPEARS TO BE THE OUTLIER IN KEEPING ITS SOUTHERN ROCKIES
SYSTEM SEPARATED FROM THE NORTHERN STREAM FLOW LONGER...AND PUSHING
IT FARTHER EAST FASTER THAN THE ECMWF AND GEM. THIS RESULTS IN SOME
TIMING DIFFERENCES IN BETTER POPS ACROSS OUR REGION. ALL 3
OPERATIONAL RUNS DO EMPHASIZE SUNDAY FOR AT LEAST A GOOD CHANCE
POP...AS THE REMNANTS OF THE SOUTHERN ROCKIES SYSTEM MOVE OVERHEAD.
THE ECMWF AND GEM WOULD WARRANT ONLY LOW POPS OUTSIDE OF SUNDAY AND
SUNDAY NIGHT.

WILL HAVE BETTER CHANCES IN THE FRIDAY THROUGH SATURDAY PERIOD JUST
IN CASE THE GFS HAS A CLUE. OTHERWISE...PUSHED THE FORECAST TOWARD
THE DRIER ECMWF/GEM FORECAST. SUSPECT THAT MONDAY WILL BE DRY...AND
NEXT TUESDAY SHOULD DEFINITELY BE SO...AS SURFACE HIGH PRESSURE
FINALLY BUILDS ACROSS THE REGION.

THE GFS HAS EITHER ELEVATED OR SURFACE-BASED INSTABILITY AVAILABLE
THROUGH NEXT WEEKEND...SO WILL MENTION A CHANCE OF THUNDERSTORMS
THROUGHOUT THE PERIOD. WITH GENERALLY WEAK SOUTHWEST FLOW ALOFT
THROUGH THE PERIOD...SEVERE WEATHER SEEMS UNLIKELY AT THIS TIME.
LOCALLY HEAVY RAINFALL WOULD BE THE PRIMARY CONCERN LATE THIS WEEK
AND NEXT WEEKEND.

THE GFS AND ECMWF ARE IN DECENT AGREEMENT IN DEVELOPING A
SIGNIFICANT UPPER LOW OVER ONTARIO...WITH CYCLONIC FLOW OVER MOST OF
THE COUNTRY EAST OF THE ROCKIES. THIS SHOULD RESULT IN COOLER AND
DRIER CONDITIONS ACROSS THE REGION FOR THE FIRST HALF OF NEXT
WEEK...AND POSSIBLY LONGER.

TEMPERATURES WILL GENERALLY BE MILD THROUGH THE WEEKEND...BUT WITH
PLENTY OF CLOUD COVER AND PRECIPITATION CHANCES...IT IS NOT LIKELY
TO GET OUT OF THE 70S. A COOL DOWN IS LIKELY EARLY NEXT WEEK.

&&

.AVIATION...
ISSUED AT 635 AM CDT TUE APR 14 2015

A SURFACE LOW LIFTING NORTHEAST THROUGH MIDDLE TENNESSEE WILL
DRAG THE LIGHT TO MODERATE RAINS EAST OF THE AREA THIS MORNING.
MVFR CONDITIONS IN RAIN ARE THE WORST THAT CAN BE EXPECTED AT KEVV
AND KOWB FOR THE FIRST FEW HOURS OF THE FORECAST. IN
ADDITION...NORTHEAST WINDS WILL OCCASIONALLY GUST OVER 20KTS THIS
MORNING AND INTO THE EARLY AFTERNOON. PERSISTENT NORTHEAST WINDS
UNDER 10KTS AND VFR CEILINGS WILL BE THE NORM AT ALL SITES FROM
MID AFTERNOON THROUGH THE END OF THE PERIOD. IF WINDS WERE TO DIE
OFF COMPLETELY LATE TONIGHT...SOME MVFR VISIBILITIES IN FOG WOULD
BE POSSIBLE...BUT THAT IS NOT LIKELY.

&&

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

$$

UPDATE...DRS
SHORT TERM...SMITH
LONG TERM...DRS
AVIATION...DRS


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