Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 191154 AAA
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE JACKSON KY
754 AM EDT SUN APR 19 2015

.UPDATE...
ISSUED AT 740 AM EDT SUN APR 19 2015

HOURLY GRIDS HAVE BEEN FRESHENED UP BASED ON RECENT TRENDS IN
OBSERVATION AS WELL AS RADAR AND SATELLITE TRENDS. THIS LED TO
HOLDING OFF ANY THUNDER IN THE WEATHER GRIDS UNTIL ABOUT 14Z...OR
10 AM. UPSTREAM LITTLE IF ANY LIGHTNING HAS BEEN NOTED.
OTHERWISE...RAIN SHOWERS...GENERALLY LIGHT CONTINUE TO GRADUALLY
OVERSPREAD THE REGION. THIS SHOULD CONTINUE OVER THE NEXT COUPLE
OF HOURS. SOME OF THE HEAVIER SHOWERS OR STRONGER RETURNS OVER THE
CUMBERLAND PLATEAU OF TN SHOULD ROTATE UP ACROSS THE LAKE
CUMBERLAND REGION THROUGH MID MORNING. OTHERWISE...THE POTENTIAL FOR
SOME DESTABILIZATION IN THE AFTERNOON AND EVENING LEADING TO A FEW
STRONG TO SEVERE THUNDERSTORMS WILL CONTINUE TO BE MONITORED.
SOME OF THE HIGH RESOLUTION GUIDANCE HAS THUNDERSTORMS DEVELOPING
OVER OR NEAR THE REGION AND WORKING ACROSS MAINLY WESTERN PORTIONS
OF THE AREA INTO THE EVENING. HOWEVER...THIS GUIDANCE SUCH AS THE
HRRR IS NOT CONSISTENT FOR RUN TO RUN WITH THE SFC LOW TRACK. ONE
RUN IT IS CLOSER TO THE AREA AND HAS MORE MID AFTERNOON TO EVENING
ACTIVITY...WHILE THE NEXT IS FURTHER NW WITH THE SURFACE LOW
TRACKS AND KEEPS THE BULK OF THE ACTIVITY TO OUR NORTH AND WEST.

THE POTENTIAL FOR THIS IS HIGHLIGHTED IN THE HWO.

&&

.SHORT TERM...(TODAY THROUGH MONDAY)
ISSUED AT 330 AM EDT SUN APR 19 2015

A CLOSED MID AND UPPER LEVEL LOW IS MOVING EAST INTO THE CENTRAL
PLAINS STATES EARLY THIS MORNING WITH A TROUGH AXIS TRAILING INTO
THE SOUTHERN PLAINS. AN UPPER LEVEL RIDGE AXIS EXTENDED NORTH
FROM THE YUCATAN REGION NORTH INTO FL AND THEN FURTHER NORTH INTO
THE GREAT LAKES REGION. FURTHER WEST ANOTHER RIDGE WAS IN PLACE
OVER PARTS OF THE EASTERN PACIFIC. IN THE NORTHERN STREAM...A
TROUGH WAS WORKING ACROSS THE CANADIAN PLAINS AND NEARING THE
DAKOTAS. THERE WERE A FEW WEAKER SHORTWAVES MOVING WITHIN THE
SOUTHWEST FLOW BETWEEN THE TROUGH AND THE RIDGING OVER THE
SOUTHEASTERN STATES. IN ADVANCE OF THIS TROUGH...AND ASSOCIATED
SFC LOW...MOISTURE WAS RETURNING NORTH AND NORTHEAST ACROSS THE
SOUTHEASTERN STATES AND MS VALLEY REGION. AT THE SFC...PRESSURE
PATTERN SOMEWHAT COMPLEX...WITH A NORTHERN STREAM COLD FRONT
EXTENDING INTO THE NORTHERN PLAINS AND ROCKIES ASSOCIATED WITH
THE NORTHERN STREAM SYSTEM. MEANWHILE...AN AREA OF LOW PRESSURE
OVER THE CENTRAL PLAINS. FURTHER SOUTHEAST ANOTHER AREA OF LOW
PRESSURE WAS OVER THE MS VALLEY REGION...ALONG A QUASI WARM
FRONT THAT EXTENDED SOUTHEAST FROM ORGANIZING LOW PRESSURE OVER
THE PLAINS.

AS THE TROUGH WORKS FURTHER EAST AND A LEAST ONE SHORTWAVE MOVE
NORTHEAST IN THE SOUTHWEST FLOW ALOFT...THE SFC WAVE SHOULD TRACK
TO OR REORGANIZE NEAR THE CONFLUENCE OF THE OH AND MS RIVERS OVER
THE NEXT SEVERAL HOURS. AS THIS OCCURS...THE WARM FRONT WILL
APPROACH EASTERN KY...BEFORE MOVING INTO THE AREA OVER THE
UPCOMING DAY. THE SFC WAVE WILL TRACK BY TO OUR NORTHWEST...WITH
THE WARM FRONT LIFTING INTO WV AND OH BY MID TO LATE EVENING. AS
THE ASSOCIATED SFC LOW MOVES INTO THE GREAT LAKES...THE TRAILING
COLD FRONT SHOULD APPROACH THE REGION LATE SUNDAY TONIGHT AND
CROSS THE AREA ON MONDAY.

OVER THE NEXT SEVERAL HOURS...AS THE WARM FRONT LIFTS NORTH
ACROSS THE TN VALLEY REGION AND INTO THE LOWER OH VALLEY AND
APPALACHIAN REGION...A BAND OF SHOWERS WITH SOME POSSIBLE EMBEDDED
THUNDERSTORMS IS EXPECTED TO WORK NORTH FROM THE SOUTHEASTERN
STATES FROM NEARER TO DAWN AND LIFT ACROSS THE AREA THIS MORNING
THROUGH MID AFTERNOON. IN ADVANCE OF THIS BAND OF SHOWERS...SOME
MORE ISOLATED TO SCATTERED SHOWER ACTIVITY IS EXPECTED TO
CONTINUE.

SOME MID LEVEL DRYING IS ANTICIPATED IN THE WARM SECTOR DURING THE
LATE MORNING AND AFTERNOON OVER CENTRAL KY AND MIDDLE TN. THIS
SHOULD EXTEND INTO EASTERN KY AS WELL...STARTING EARLY THIS
AFTERNOON IN THE FAR SOUTHWEST AND THE GRADUALLY SPREADING NORTH
AND EVENTUALLY EAST. SOME DESTABILIZATION SHOULD ALSO OCCUR DURING
THE AFTERNOON TO EARLY EVENING. THIS SHOULD LEAD TO MORE SCATTERED
SHOWERS AND SOME THUNDERSTORMS...ESPECIALLY ACROSS THE WESTERN
HALF OR SO OF THE AREA CLOSER TO THE ACTUAL SFC LOW TRACK.
INSTABILITY IS NOT EXPECTED TO BE ALL THAT HIGH...WITH
CAPE SOMEWHAT LIMITED. MODEL FORECAST SOUNDINGS INDICATE SBCAPE
MAY REACH THE 1000 TO 1500 J/KG RANGE WITH SOMEWHAT STRONG FLOW
ALOFT. THIS COULD SUPPORT SOME STRONGER THUNDERSTORMS WITH LOCALLY
HEAVY RAIN...GUSTY WINDS AND POSSIBLY HAIL. A STRAY STORM OR TWO
COULD BECOME SEVERE WITH STRONG WINDS THE PRIMARY THREAT...PENDING
HOW UNSTABLE OR NOT THE REGION EVENTUALLY BECOMES. SPC HAS PLACED
THE ENTIRE REGION IN A MARGINAL RISK FOR SEVERE THUNDERSTORM WITH
THE HIGHER RISKS REMAINING WELL SOUTH AND SOUTHWEST OF EASTERN KY.
EAST OF THE SFC LOW TRACK...THERE MAY BE A EVER SO SLIGHTLY HIGHER
PROBABILITY FROM MIDDLE TN NORTH INTO CENTRAL AND NORTHERN KY.

WITH THE LOSS OF DAYTIME HEATING AND WEAK MID LEVEL RIDGING
PROGGED TO WORK ACROSS THE REGION OVERNIGHT...THERE SHOULD BE A
LULL IN SHOWER AND ANY THUNDERSTORM ACTIVITY FROM LATE EVENING
THROUGH MUCH OF SUNDAY NIGHT. THE CHANCES FOR ACTIVITY SHOULD
INCREASE AGAIN TOWARD DAWN AND PEAK ON MONDAY AS THE COLD FRONT
WORKS ACROSS THE AREA. IF SOME HEATING CAN OCCUR ACROSS EASTERN
SECTIONS OF THE AREA IN ADVANCE OF THE FRONT...A COUPLE OF STRONG
TO POSSIBLY SEVERE THUNDERSTORMS WOULD BE POSSIBLE WITH STRONG
WINDS BEING THE MAIN THREAT. THE PRECIPITATION CHANCES WILL BEGIN
TO DECREASE FROM WEST TO EAST BY EARLY ON MONDAY EVENING.

.LONG TERM...(MONDAY NIGHT THROUGH SATURDAY)
ISSUED AT 334 AM EDT SUN APR 19 2015

PERIOD WILL BEGIN WITH RAIN SHOWERS MAINLY ACROSS THE SE
PORTIONS...AS A COLD FRONT AND UPPER LEVEL SHORT WAVE PULL OUT OF
THE REGION. HIGH PRESSURE WILL BUILD TO THE SOUTH OF THE REGION
WITH COOLER AND DRIER AIR BUILDING INTO EASTERN KY. AFTER A WARM
WEEKEND HIGHS ON TUESDAY WILL GENERALLY BE IN THE LOWER 60 UNDER
SUNNY SKIES...WHICH WILL BE NEARLY 10 DEGREES BELOW NORMAL. THIS
HIGH WILL MOVE EAST AND BRING SOME RETURN FLOW TO THE REGION
TUESDAY NIGHT. HOWEVER TEMPS THROUGH THE PERIOD WILL STAY BELOW
NORMAL. ALSO A WEAK FRONT AND WEAK UPPER LEVEL WAVE ROUNDING THE
BASE OF THE UPPER LEVEL LOW CENTERED NEAR THE GREAT LAKES. THIS
WILL BRING SLIGHT TO CHANCE POPS TUESDAY NIGHT INTO WEDNESDAY.
HOWEVER THERE IS STILL SOME DIVERGENCE WITH THIS SETUP IN THE
GUIDANCE...SO DID LEAN TOWARD THE BLEND MORE AT THIS POINT. THE
ECMWF IS A BIT MORE INLINE WITH THE GFS THAN PREVIOUS RUNS FROM
YESTERDAY...BUT REMAINS SLOWER THAN THE GFS IN THE LATEST RUNS.
THE RAIN CHANCES DO WANE AS WE MOVE WEDNESDAY NIGHT INTO THURSDAY
AS FRONT DROPS SOUTH OF THE REGION.

THIS FRONT WILL BRING ANOTHER SHOT OF COLD AIR WITH 850 TEMPS IN
THE 0 TO -4 RANGE THURSDAY NIGHT. THIS COUPLED WITH CLEARING SKIES
COULD LEAD TO FROST DEVELOPMENT OVERNIGHT THURSDAY INTO FRIDAY
MORNING ESPECIALLY ACROSS THE BLUEGRASS WHERE HIGH PLACEMENT IS
BETTER. RIGHT NOW THE CONFIDENCE IS LOWER...SO WILL LEAVE OUT OF
THE GRIDS FOR NOW. DID OPT TO LEAN TOWARD A RAW MODEL BLEND WHICH
DID INTRODUCE SOME MID TO UPPER 30S ACROSS THE REGION. THIS HIGH
PRESSURE IS EXPECTED MOVE EAST ACROSS THE REGION FRIDAY WITH
INCREASING CLOUDS ACROSS THE CUMBERLAND VALLEY LATE FRIDAY AS NEXT
SYSTEM APPROACHES. BOTH THE GFS AND ECMWF WANT TO KEEP A
DEVELOPING SURFACE LOW TO THE SOUTH OF THE REGION. THIS WOULD
SUPPRESS THE BETTER DYNAMICS WITH FORECAST SOUNDINGS SHOWING
FAIRLY MEAGER INSTABILITY. DO INTRODUCE CHANCE POPS WITH BETTER
CHANCES ACROSS THE SOUTHERN PORTIONS OF EASTERN KY. ALSO KEPT WITH
PREVIOUS FORECAST IN TERMS OF NO THUNDER SATURDAY GIVEN THAT THE
WARM SECTOR AND BETTER DYNAMICS WILL BE WELL SOUTH GIVEN LOW
PLACEMENT.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z MONDAY MORNING)
ISSUED AT 750 AM EDT SUN APR 19 2015

LOW AND MID LEVELS CONTINUE TO GRADUALLY SATURATE ACROSS THE
REGION...BUT AS OF 11Z...CIGS AND VIS WERE STILL VFR AT ASOS AND
AWOS SITES IN EASTERN AND SOUTH CENTRAL KY. AS FURTHER SATURATION
OCCURS THROUGH THE 15Z TO 16Z TIMEFRAME...THESE SHOULD LOWER
FURTHER TO MVFR...EXCEPT PERHAPS A TAD LATER AT SJS. AN AREA OF
SHOWERS SHOULD WORK ACROSS THE REGION THROUGH ABOUT 19Z. IF ANY OF
THESE ARE HEAVY ENOUGH CIGS COULD BE REDUCED AT TIMES TO
IFR...ESPECIALLY AT SME AND LOZ. THE DETERIORATION INTO MVFR SHOULD
ARRIVE FIRST AT WESTERN LOCATIONS...WITH EASTERN LOCATIONS HOLDING
OFF LONGER DUE TO INITIAL LOW LEVEL DOWNSLOPE FLOW OFF THE HIGH
TERRAIN TO OUR SE. THUNDERSTORMS WITH GUSTY WINDS AND VIS TO IFR
AND POSSIBLY BRIEFLY NEARING AIRPORT MINS WILL ALSO BE
POSSIBLE...MAINLY 18Z AND LATER WEST OF INTERSTATE 75...WITH
CHANCES POSSIBLY SPREADING NORTHEAST AS FAR AS SYM AND SJS BY 23Z
OR SO. CHANCES FOR PRECIP SHOULD DIMINISH FROM SW TO NORTHEAST
22Z TO 3Z IN SOME DRY SLOTTING BETWEEN THE WARM FRONT AND AN
APPROACHING COLD FRONT. VIS AND CIGS SHOULD RETURN TO THE VFR
RANGE FOR SEVERAL HOURS IN MANY LOCATIONS DURING THE LAST 12 HOURS
OF THE PERIOD.

&&

.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...JP
SHORT TERM...JP
LONG TERM...DJ
AVIATION...JP



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