Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 200619 AAC
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE JACKSON KY
219 AM EDT MON APR 20 2015

.UPDATE...
ISSUED AT 140 AM EDT MON APR 20 2015

HOURLY GRIDS HAVE BEEN UPDATED BASED ON RECENT RADAR...OBSERVATION
AND SATELLITE TRENDS. SOME SCATTERING OUT OF THE LOW CLOUDS HAS
BEEN OBSERVED IN THE SOUTHWESTERN COUNTIES PER AWOS AND ASOS DATA.
IN FACT...SOME EASTERN VALLEY LOCATIONS IN THE EAST APPEAR TO BE
DECOUPLED WITH LOW DEWPOINT DEPRESSIONS. KI35 HAS BEEN REPORTING
2SM VIS LIKELY FROM SOME LIGHT FOG. DESPITE THE GRADIENT IN
PLACE...SEVERAL ADDITIONAL EASTERN VALLEY LOCATIONS ANY ALSO HAVE
SOME PATCHY FOG DEVELOPMENT OVER THE NEXT 3 TO 5 HOURS...BEFORE
CLOUDS INCREASE IN ADVANCE OF WHAT IS LEFT OF CONVECTION NOW TO
OUR WEST AND SOUTHWEST. ATTM...HELD WITH THE PREVIOUS SLIGHT
CHANCE POPS FOR THIS AND THE PREVIOUS TIMING. FOR THE MAIN
ISSUANCE WE WILL CONSIDER WHETHER OR NOT THUNDER WILL NEED TO BE
INCLUDED WITH THIS VERSUS JUST SHOWERS.

UPDATE ISSUED AT 1044 PM EDT SUN APR 19 2015

AN AREA OF CONVECTION HAS BEEN WORKING ITS WAY EAST THROUGH THE
REGION THIS EVENING...AND A COUPLE OF UPDATES HAVE BEEN SENT TO
PROVIDE UPDATES ON TIMING. HAVE ALSO UPDATED FOR TIMING OF POP ON
MONDAY. 18Z GFS AND NAM WERE IN GOOD AGREEMENT FOR MONDAY...AND
THE 00Z NAM STILL SEEMS TO SUPPORT THE PREVIOUS RUN. REMNANTS OF
CONVECTION CURRENTLY EXITING ARKANSAS WILL PROVIDE A SMALL CHANCE
IN THE MORNING...BUT THE GREATER PROSPECT FOR RAIN LOOKS TO BE
LATE IN THE DAY. DIURNAL DESTABILIZATION COUPLED WITH A WEAK
SHORTWAVE TROUGH ROTATING THROUGH THE LARGER SCALE SYNOPTIC SCALE
TROUGH AND GENERAL COOLING ALOFT SHOULD RESULT I200N SCATTERED TO
NUMEROUS SHOWERS DEVELOPING IN THE AFTERNOON...AND POSSIBLY A FEW
MORE THUNDERSTORMS.

&&

.SHORT TERM...(THIS EVENING THROUGH MONDAY NIGHT)
ISSUED AT 359 PM EDT SUN APR 19 2015

LATEST SURFACE MAP FEATURES BROAD LOW PRESSURE ACROSS IL/IN/KY
WITH A WARM FRONT EXTENDING ESE INTO OUR SOUTHWEST COUNTIES.
FURTHER WEST ACROSS THE PLAINS...A COLD FRONT EXTENDS NORTH TO
SOUTH. ALOFT...AN AMPLIFIED PATTERN IS IN PLACE ACROSS THE HEART
OF THE CONUS...WITH AN UPPER LEVEL LOW WITHIN THE NORTHERN STREAM
LOCATED ACROSS CENTRAL MANITOBA. MEANWHILE...A COUPLE OF WELL
DEFINED SHORT WAVE TROUGHS ARE CHURNING EASTWARD WITHIN THE
SOUTHERN STREAM...ONE CURRENTLY LOCATED ACROSS KS/OK...AND THE
OTHER SWINGING NORTHEAST THROUGH NORTHERN MS/AL.

PLENTY OF CONVECTION IS FIRING UP THIS AFTERNOON...WITH SHOWERS
AND THUNDERSTORMS INITIATING ACROSS WESTERN KY/TN OUT AHEAD OF THE
APPROACHING SHORT WAVE TROUGH AS WELL AS WITHIN THE VICINITY OF
THE SURFACE LOW. THE MAIN PRECIPITATION SHIELD THAT BROUGHT MORE
STEADY RAINS ACROSS EASTERN KENTUCKY THIS MORNING HAS MOVED OFF
TO THE NORTHEAST AND EAST.

THE MODELS ARE IN GOOD AGREEMENT THROUGH THE SHORT TERM...WITH
CONVECTION LIKELY FIRING UP ACROSS EASTERN KENTUCKY IN THE FORM OF
CLUSTERS AND LINE SEGMENTS THROUGH THE REST OF THIS AFTERNOON.
THE SHEAR REMAINS AMPLE...HOWEVER INSTABILITY STILL LOOKS MARGINAL
GIVEN THE PERSISTENT CLOUD COVER. STILL...THERE IS A LITTLE
THINNING TO THE CLOUDS ACROSS CENTRAL TN/KY AND THIS MAY WORK EAST
THROUGH THE REST OF THE AFTERNOON...ALLOWING FOR JUST ENOUGH
INSTABILITY TO SUPPORT A FEW STRONGER STORMS. LOCALLY HEAVY
RAINFALL ALSO REMAINS A CONCERN GIVEN THE SLOWER EASTWARD MOVEMENT
TO THE LINES.

THIS ACTIVITY WILL WIND DOWN FROM SOUTHWEST TO NORTHEAST THROUGH
THE REST OF THIS EVENING...AS THE SHORT WAVE TROUGH EXITS TO THE
NORTHEAST AND DAMPENS. THERE WILL BE A RELATIVE LULL IN THE
CONVECTION OVERNIGHT...BEFORE THE MAIN COLD FRONT AND ANOTHER
SHORT WAVE TROUGH APPROACH TOWARDS DAWN. ANOTHER FAIRLY STOUT LOW
LEVEL JET WILL ENGAGE LATE TONIGHT INTO MONDAY MORNING ACROSS THE
OHIO AND TENNESSEE VALLEYS AS THE UPPER LEVEL TROUGH AMPLIFIES AND
SURFACE LOW PRESSURE DEEPENS AS IT HEADS NORTH INTO THE GREAT
LAKES.

DEPENDING ON THE TIMING OF THE COLD FRONT ON MONDAY...THERE
REMAINS A MARGINAL THREAT FOR STRONG TO SEVERE STORMS...WITH
DAMAGING WINDS BEING THE MAIN THREAT GIVEN THE MORE UNIDIRECTIONAL
FLOW. WILL CONTINUE TO MENTION THIS IN THE HWO. HAVE GONE WITH
CATEGORICAL POPS FOR MONDAY...AS A FEW ROUNDS OF SHOWERS AND
STORMS SHOULD EVENTUALLY HIT MOST LOCATIONS THROUGHOUT THE
DAY...WITH THE COLD FRONT AS WELL AS A COUPLE OF PASSING SHORT
WAVE TROUGHS. SCATTERED SHOWERS WILL WIND DOWN ACROSS THE
SOUTHEAST LATE MONDAY NIGHT...WITH TEMPERATURES COOLING OFF TO THE
40S BY DAWN TUESDAY.

.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 345 PM EDT SUN APR 19 2015

THE EXTENDED PORTION OF THE FORECAST WILL ALTERNATE BETWEEN COOL AND
DRY PERIODS AND COOL AND WET PERIODS. THE BEGINNING THE EXTENDED
WILL BE MARKED BY RIDGE OF HIGH PRESSURE THAT WILL BE SLOWLY
RETREATING SOUTHEASTWARD AHEAD OF AN APPROACHING COLD FRONT. BOTH
THE GFS AND ECMWF MODELS WERE IN GOOD AGREEMENT ON THIS. THE
CONSENSUS IS FOR TUESDAY AND TUESDAY TO BE DRY AHEAD OF THE
FRONT...WITH ISOLATED TO SCATTERED RAIN SHOWERS OVERSPREADING THE
AREA TUESDAY NIGHT AS THE FRONT MOVES THROUGH. BASED ON THE EAST
WEST ORIENTATION OF THE FRONT...AND THE NEARLY ZONAL FLOW ALONG
IT...IT APPEARS THE FRONT WILL GET HUNG UP A BIT AS IF MOVES OUT OF
THE OHIO VALLEY AND INTO THE TENNESSEE VALLEY. THIS WOULD LEAD TO
SCENARIO WHERE THE FRONT REMAINS IN PLACE THROUGH WEDNESDAY
EVENING...BEFORE FINALLY PUSHING OFF TO THE SOUTHEAST ONCE THE WINDS
BEHIND THE BOUNDARY SHIFT TO THE NORTHWEST. IN SPITE OF THE
LINGERING NATURE OF THE FRONT...THE ONE ISSUE WITH THE SET UP WILL
BE LACK OF MOISTURE OFF THE GULF AND GOOD LIFT ALONG THE FRONT.
THEREFORE...THE FORECAST AT THIS TIME WILL FEATURE SCATTERED RAIN
SHOWERS ALONG THE FRONT AND NO THUNDER DUE TO LACK OF INSTABILITY.
DUE TO UPLIFT AND LINGERING MOISTURE BEHIND THE FRONT...WE COULD SEE
RAIN SHOWERS IN THE AREA THROUGH THURSDAY AFTERNOON BEFORE EXITING
OUR FAR SOUTHEASTERN COUNTIES. ANOTHER RIDGE OF HIGH PRESSURE IS
THEN PROGGED TO SETTLE OVER THE REGION THURSDAY NIGHT AND MOST OF
FRIDAY...BEFORE ANOTHER WEATHER SYSTEM MOVES IN FROM THE SOUTHWEST
LATE FRIDAY AFTERNOON. ONCE AGAIN ONLY RAIN SHOWERS ARE EXPECTED
DUE TO LACK OF INSTABILITY AND COOL TEMPERATURES. THIS SECOND
AROUND OF PRECIPITATION WILL LAST A COUPLE OF DAYS AS WELL...WITH
THE LAST RAIN SHOWERS EXITING THE AREA EARLY SUNDAY
MORNING...SHOULD THE GFS HOLD TRUE TO ITS CURRENT LATE PERIOD
SOLUTION ANYWAY.

TEMPERATURES DURING THE UPCOMING WORK WEEK WILL LIKELY BE WELL BELOW
NORMAL FOR EVERYDAY BUT WEDNESDAY...DUE TO THE PRESENCE OF COOLER
THAN NORMAL AIR...CLOUD COVER AND THE TWO ROUNDS OF RAIN SHOWERS.
HIGHS EACH DAY ARE FORECAST TO MAX OUT IN THE UPPER 50S AND LOWER
60S FOR MOST LOCATIONS EACH DAY BUT WEDNESDAY. ON WEDNESDAY A PERIOD
OF SOUTHERLY TO SOUTHWESTERLY FLOW MAY BE ENOUGH TO ALLOW
TEMPERATURES TO PEAK NEAR NORMAL VALUES SOUTH OF THE MOUNTAIN
PARKWAY. OVERNIGHT LOWS WILL GENERALLY BE IN THE 40S. THE EXCEPTION
MAY BE FRIDAY NIGHT...WHEN MOSTLY CLEAR TO PARTLY CLOUDY SKIES AND
LIGHT NORTHWEST WINDS MAY ALLOW MIN TEMPS TO DIP INTO THE UPPER 30S
ACROSS THE AREA. WE MIGHT EVEN SEE SOME PATCHY FROST IN THE DEEPER
AND MORE SHELTERED VALLEYS IN OUR EAST AND NORTHEAST BY EARLY
SATURDAY MORNING.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY NIGHT)
ISSUED AT 200 AM EDT MON APR 20 2015

SOME SCATTERING OUT OF THE LOW CLOUDS HAS OCCURRED AND SHOULD
TRANSLATE NORTHEAST ACROSS THE AREA FOR SOME TIMES OF VFR OVER THE
NEXT 3 TO 5 HOURS AT THE TAF SITES. AFTER THAT...ANOTHER ROUND OF
SHOWERS AND POSSIBLY A STRAY THUNDERSTORM MAY MOVE THROUGH FROM
WEST TO EAST BETWEEN ABOUT 09Z AND 14Z. A BETTER SHOT AT
SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS WILL COME
GENERALLY BETWEEN 18Z TO 00Z. ANY OF THE STRONGER SHOWERS OR
THUNDERSTORMS WILL BE CAPABLE OF DROPPING CONDITIONS BELOW MVFR
AT LEAST FOR A TIME. OTHERWISE...MAINLY VFR OR MVFR IS EXPECTED
THROUGH THE PERIOD. WINDS WILL PICK UP OUT OF THE WEST AROUND 16Z
AND AFTER...WITH SOME GUSTS TOPPING 20 KTS.

&&

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

$$

UPDATE...JP
SHORT TERM...GEOGERIAN
LONG TERM...AR
AVIATION...JP


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