Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 210404
AFDPAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PADUCAH KY
1100 PM CDT MON APR 20 2015

.UPDATE...
ISSUED AT 1100 PM CDT MON APR 20 2015

FOR AVIATION SECTION ONLY.

.UPDATE...
ISSUED AT 922 PM CDT MON APR 20 2015

MINOR UPDATE TO ADDRESS SUBTLE ADJUSTMENTS TO WIND AND CLOUD
COVER. MAY STILL BE TOO HIGH BY 1-2 KNOTS ON WINDS, WHICH MAY
KEEPT TEMPERATURES 1-2 DEGREES HIGHER TONIGHT. HOWEVER, SKY TREND
SHOULD HELP RADIATIONAL LOSS ACCELERATE OVERNIGHT.

THE 18Z MONDAY GFS AND NAM-WRF, AS WELL AS THE 00Z HRRR, STILL
KEEP ANY CHANCES OF RAIN WEST OF THE WFO PAH FORECAST AREA THROUGH
AT LEAST 15Z. THE GFS REMAINS TOO PERSISTENT AND FURTHER SOUTH
WITH PRECIPITATION TOMORROW AFTERNOON AND TOMORROW NIGHT, GIVEN
THE CURRENT FORECAST POSITION IN THE GRIDDED FORECAST. WILL NOT
ADJUST POP/WEATHER AT THIS TIME.

THE CAPE ASSOCIATED WITH CONVECTION TOMORROW AFTERNOON IS MARGINAL
OVER THE WFO PAH FORECAST AREA, HOWEVER MOST OF IT IS EXPECTED
TO BE EXPENDED BETWEEN 22Z TUESDAY AND 03Z WEDNESDAY OVER
SOUTHEAST MISSOURI AND SOUTHERN ILLINOIS. DO NOT PLAN TO MAKE ANY
CHANGES TO CURRENT THUNDERSTORM FORECAST GIVEN SPC TIMING OF
STRONG TO SEVERE POTENTIAL OVER PART OF OUR AREA.

&&

.SHORT TERM...(TONIGHT THROUGH WEDNESDAY NIGHT)
ISSUED AT 235 PM CDT MON APR 20 2015

THE PARENT LOW PRESSURE SYSTEM THAT DRAGGED A COLD FRONT THROUGH THE
REGION EARLY TODAY HAS BEEN STEADILY MOVING STRAIGHT NORTH ACROSS
MICHIGAN TODAY. WHILE THE MAIN BAND OF DEEPER MOISTURE CONTINUES TO
PUSH EAST OF THE AREA...ANOTHER BAND OF LOW LEVEL MOISTURE IS
STREAMING SOUTHEAST ACROSS IA/MO PRODUCING MORE CLOUDINESS. THIS LOW
LEVEL MOISTURE IS EXPECTED TO SHIFT EAST DURING THIS EVENING. BUT
BEFORE THE MOISTURE TOTALLY PUSHES OUT OF THE AREA...WE COULD SEE A
FEW SPOTTY SHOWERS BEFORE SUNDOWN. HOWEVER...NOTHING HAS DEVELOPED
AS OF THIS WRITING...WILL CONTINUE TO MONITOR.

COLD AIR ADVECTION HAS BEEN ONGOING TODAY (WITH PLACES STRUGGLING TO
EVEN REACH 60 DEGREES) WITH 850MB TEMPS DROPPING DOWN INTO THE LOW
SINGLE DIGITS. AS WE CLEAR OUT TONIGHT...READINGS WILL DROP INTO THE
LOW 40S. WINDS SHOULD STAY UP ENOUGH TO PRECLUDE TEMPS FROM DROPPING
TOO FAR. BUT...SOME OF OUR NORTHERN AREAS MAY SEE A FEW READINGS IN
THE UPPER 30S. SFC HIGH PRESSURE OVER TEXAS WILL MOVE EAST SOUTHEAST
OVER THE NEXT 24 HOURS. THIS WILL ALLOW WINDS TO SHIFT TO
SOUTHWESTERLY OVERNIGHT TONIGHT. AS WE HEAD THROUGH THE
EVENING...WARM AIR ADVECTION WILL COMMENCE AND WE SHOULD BE ABLE TO
GAIN SEVERAL DEGREES OF WARMTH FOR TOMORROW.

ON TUESDAY...WE WILL REMAIN IN CYCLONIC FLOW AS THE MAIN UPPER LEVEL
LOW ROTATES ACROSS THE UPPER GREAT LAKES REGION. WEAK IMPULSES IN
THE FLOW ALONG WITH SOME RETURN MOISTURE ON THE BACKSIDE OF THE SFC
HIGH...WILL RESULT IN SHOWER AND POSSIBLE THUNDERSTORM CHANCES
RETURNING THE AREA MAINLY TUESDAY AFTERNOON/EVENING. MODELS SHOW
SOME ELEVATED INSTABILITY AND STEEP LAPSE RATES...WHICH WILL WARRANT
THE INCLUSION OF THUNDER CHANCES. IN FACT...THE NEWEST DAY 2 HAS A
MARGINAL RISK FOR SEVERE WEATHER IN PARTS OF SEMO...DUE TO THE THE
AFOREMENTIONED PARAMETERS ALONG WITH STRONG UNIDIRECTIONAL WIND
SHEAR. FOR NOW THE COVERAGE OF ACTIVITY LOOKS TO BE SCATTERED SO
WILL KEEP WITH THE CHANCY TYPE POPS. THIS STRONG WIND SHEAR WILL
ALSO LEAD TO SOME PRETTY GUSTY CONDITIONS AT THE SFC AS WELL...WITH
GUSTS 25 TO 30 MPH AT TIMES ESPECIALLY IN THE I-64 CORRIDOR.

A FRONTAL BOUNDARY WILL BE ADVANCING TOWARD THE REGION FROM THE
NORTH TUESDAY EVENING/NIGHT. THIS BOUNDARY WILL PASS THROUGH THE
AREA ON WEDNESDAY MORNING. THEREFORE...CLOUDS AND PRECIPITATION
CHANCES WILL LINGER IN THE FORECAST UNTIL WEDNESDAY EVENING...WHEN
WE SHOULD BE GRADUALLY CLEARING THINGS OUT AS HIGH PRESSURE BUILDS
IN. SO...AFTER WE SEE HIGH TEMPERATURES JUMP INTO THE MID TO UPPER
60S ON TUESDAY...HIGHS IN MANY PLACES (MAINLY ACROSS THE NORTHERN
HALF OF THE AREA) ON WEDNESDAY WILL BE BACK DOWN INTO THE LOWER
60S.

.LONG TERM...(THURSDAY THROUGH MONDAY)
ISSUED AT 235 PM CDT MON APR 20 2015

THE DOMINANT FEATURES IN THE LONG TERM...ONE DEEP VORTEX OVER
SOUTHEAST CANADA THAT WILL GRADUALLY MOVE EAST...AND ANOTHER
SETTLING INTO THE GULF OF ALASKA REGION. WEAKER SYSTEMS WILL
AFFECT THE LOWER 48. THE FIRST ONE OF INTEREST...SHOULD BE A MID
LEVEL TROF/LOW MOVING FROM THE SW U.S. INTO THE CENTRAL PLAINS
FROM 00Z FRI TO 00Z SAT...TURNING ESE AND WEAKENING ACROSS OUR
REGION SATURDAY. AFTER THAT...THE FOCUS IS ON ANOTHER WAVE MOVING
ESE FROM THE PLAINS LATE SUNDAY AND ACROSS OUR AREA MONDAY.

THE OPERATIONAL MODELS CONTINUE TO EXHIBIT RUN TO RUN CONSISTENCY
ISSUES. THIS IS LIKELY DUE TO THE WEAKER FLOW REGIME ACROSS THE
CONUS BELOW THE TWO SIGNIFICANT VORTICES. THIS MEANS WE WILL
PARALLEL WPC`S IDEA OF BLENDING THE ENSEMBLE MEAN SOLUTIONS FOR
HANDLING THE TIMING OF THE AFOREMENTIONED FEATURES...AND RESULTANT
HIGHER POP PERIODS. WE REMOVED POPS THURSDAY AND THURSDAY NIGHT.
ADJUSTED POPS FRIDAY MOVING IN FROM THE WEST...AND PEAKED POPS
FRIDAY NIGHT WITH THE WAVE COMING IN FROM THE PLAINS AND AFFECTING
THE REGION. SHOULD SEE POPS TAIL OFF BY SATURDAY NIGHT AS THE
UPPER WAVE HEADS ESE AWAY FROM THE AREA. LULL SUNDAY...THEN SLIGHT
CHANCE POPS SUNDAY NIGHT THROUGH MONDAY NIGHT. WILL MAINTAIN A
LIMITED THUNDER CHANCE FRIDAY THROUGH SATURDAY. MAX AND MIN TEMPS
WERE A BLEND OF MOS AND EXISTING NUMBERS. MODEL PREFERENCE WAS A
ENSEMBLE MEAN BLEND OF THE GFS/EC/NAEFS.

&&

.AVIATION...
ISSUED AT 1100 PM CDT MON APR 20 2015

THERE MAY BE A FEW MID CLOUDS OVERNIGHT. GUSTY SOUTHWEST WINDS OVER
20KTS WILL REDEVELOP TUESDAY MORNING WITH MID CLOUDS INCREASING FROM
THE WEST IN ASSOCIATION WITH A MID LEVEL WAVE. NO OTHER OPERATIONAL
CONCERNS EXPECTED.

&&

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

$$

UPDATE...SMITH


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