Area Forecast Discussion
Issued by NWS Paducah, KY

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000
FXUS63 KPAH 130823
AFDPAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PADUCAH KY
323 AM CDT MON APR 13 2015

.SHORT TERM...(TODAY THROUGH WEDNESDAY NIGHT)
ISSUED AT 255 AM CDT MON APR 13 2015

A COLD FRONT WILL MOVE THROUGH THE REGION TODAY AS WEAK MID LVL
SHORT WAVE ENERGY LIFTS NE FROM THE SRN PLAINS. AS THIS ENERGY
INTERACTS WITH THE SFC FEATURE LATER THIS MORNING AND THIS
AFTERNOON...A LARGE AREA OF SHOWERS AND THUNDERSTORMS SHOULD
DEVELOP OVER OUR FORECAST AREA...ESP ALONG AND S OF THE OH RIVER.
WIND SHEAR AND INSTABILITY NOT LOOKING TOO IMPRESSIVE WITH THIS
SYSTEM...SO NOT EXPECTING STORMS TO BE TOO STRONG THIS TIME
AROUND. INCREASING PWATS MAY LEAD TO SOME HEAVY DOWNPOURS THO IN
ELEVATED CONVECTION. IT ALSO NOW APPEARS THAT POST FRONTAL PRECIP
WILL CONTINUE INTO TONIGHT...ESP OVER WRN KY.

THE FRONT IS NOW FORECAST TO STALL OUT A BIT CLOSER TO OUR SOUTH
OVER SRN TN OR THE NORTHERN GULF COAST STATES LATER TONIGHT AND
TUESDAY AS HIGH PRESSURE DRIFTS FROM THE MIDWEST INTO THE LOWER
GREAT LAKES AND UPPER OHIO VALLEY. GUT FEELING STILL IS THAT MOST
LOCATIONS WILL STAY RAINFREE TUE AS THE HIGH PRESSURE BRUSHES BY
TO OUR NORTH....BUT THE 00Z ECMWF INSISTS LIGHT PRECIP WILL HANG
AROUND IN THE MORNING OVER WRN KY/SE MO. WILL LEAVE SOME SMALL
POPS IN OVER OUR SOUTHERN COUNTIES TO COVER FOR THIS POSSIBILITY.
00Z GFS MAINTAINS A DRY FORECAST. LEFT OVER CLOUDS AND NORTHEAST
WINDS WILL KEEP DAY TIME TEMPS IN THE 60S.

THINGS WILL LIKELY BECOME A BIT MORE UNSETTLED AGAIN LATER WED AND
WED NIGHT AS A SOUTHERN BRANCH TROF OUT OVER THE DESERT SW OPENS
UP AND BEGINS TO LIFT NE TOWARD THE REGION. NOT MUCH OF A SFC OR
LOW LEVEL REFLECTION WITH THIS SYSTEM TO FOCUS PRECIP. A WEAK
INVERTED TROF MAY END UP SOMEWHERE CLOSE TO WRN KY WED NIGHT. WILL
HIT THAT AREA WITH THE HIGHEST POPS FOR NOW.

.LONG TERM...(THURSDAY THROUGH SUNDAY)
ISSUED AT 255 AM CDT MON APR 13 2015

THE EVOLUTION OF THE LATE WEEK WEATHER SYSTEMS HAS GONE FROM QUITE A
DYNAMIC, COLD CORE LOW SYSTEM IMPINGING ON THE WFO PAH FORECAST AREA
TO A MORE BENIGN WEATHER SYSTEM MOVING INTO NEXT WEEKEND. THAT IS
THE PERIL OF TRANSLATING CLOSED LOW SYSTEMS OVER THE EASTERN PACIFIC
AND MODIFYING THEM OVER A LAND MASS. TO THE CREDIT TO THE MEDIUM
RANGE GUIDANCE TRENDS, THESE SYSTEMS HAVE BEEN WEAKENED WITH TIME TO
A LESS DRAMATIC (AND SEVERE) VERSION.

WITH THAT SAID, THE BETTER INITIALIZING NUMERICAL MODEL GUIDANCE
WITH THE NORTHERN MEXICO/WESTERN TX LOW AND THE OFFSHORE LOW NEAR
THE PACIFIC NW/SOUTHWEST CANADA COASTLINE WERE BEST INITIALIZED BY
THE CANADIAN/NAM-WRF GUIDANCE, FOLLOWED BY THE DETERMINISTIC GFS.

THE CANADIAN AND GFS 00Z MONDAY DETERMINISTIC GUIDANCE WERE FAIRLY
SIMILAR IN THE LOCATION OF THE DEEP CLOSED LOW OVER THE FOUR CORNERS
REGION OF THE DESERT SOUTHWEST U.S. THROUGH 12Z (7 AM CDT)THURSDAY
TIME FRAME. BEYOND THAT TIME, THE GFS RECURVES THE UPPER LOW TOO FAR
NORTH, BRINGING HEIGHTS, THICKNESSES, AND INSTABILITY TOO FAR NORTH
AHEAD OF THIS LOW. IN ADDITION, THE DETERMINISTIC GFS PRECIPITATION
PARAMETERIZATION SCHEME WAS WAY TO AGGRESSIVE.

WITH THIS IN MIND, A BLEND, WEIGHTED TOWARD THE CANADIAN WAS USED
INTO NEXT WEEKEND, LEANING TOWARD A DRIER SOLUTION WITH TIME. THE
CANADIAN APPEARS TO KEEP THE NORTHERN STREAM A LITTLE MORE DOMINANT
THAN DEPICTED BY THE GFS, WHICH MAKES THE SOUTHERN STREAM (CLOSED
LOW) THE DOMINANT FEATURE WITH TIME. WITH THE ABSENCE OF CANADIAN
DATA NEXT WEEKEND, ATTEMPTED TO BLEND THE AVAILABLE GFS DATA TOWARD
THE CANADIAN WEATHER TRENDS. THE NORTHERN STREAM PHASES WITH AND
WEAKENS THE SOUTHERN STREAM CLOSED UPPER LOW INTO A SHARPER WAVE BY
THE END OF NEXT WEEKEND.

GIVEN THESE TRENDS, THE OVERALL POP/WEATHER FORECAST WITH THIS
PACKAGE IS LESS AGGRESSIVE THAN RECENT DAYS, WITH THE BEST CHANCES
OF RAIN MORE CLOSELY TIED TO THE SOUTHERN 1/3-1/4 OF THE WFO PAH
FORECAST AREA FOR THE MAJORITY OF THE FORECAST PERIOD.

THIS SHOULD ALLOW FOR SLIGHTLY WARMER MAX/MIN TEMPERATURES THAN
PREVIOUSLY FORECAST, BUT WITHIN TOLERANCE WITH PREVIOUS SOLUTIONS.

&&

.AVIATION...
ISSUED AT 1140 PM CDT SUN APR 12 2015

MID AND HIGH CLOUDS WILL PREVAIL DURING THE EARLY PART OF THE
OVERNIGHT WITH LOWER VFR CIGS DEVELOPING TOWARD MORNING. MVFR
CIGS ALONG WITH RAIN/ISOLD THUNDER BECOME POSSIBLE DURING THE
MORNING HOURS BUT BECOME MORE LIKELY AS WE HEAD INTO THE AFTERNOON
HOURS. THIS THREAT FOR PRECIP CONTINUES INTO THE EVENING HOURS.
WINDS WILL START OUT AS SOUTH OR SOUTHEASTERLY AND THEN SWITCH
AROUND TO NORTH OR NORTHEAST AND INCREASING... BY THE LATTER HALF
OF THE FORECAST PERIOD.


&&

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

$$

SHORT TERM...GM
LONG TERM...SMITH


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