Area Forecast Discussion
Issued by NWS Jackson, KY

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000
FXUS63 KJKL 290030 AAA
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE JACKSON KY
830 PM EDT SAT MAR 28 2015

.UPDATE...
ISSUED AT 815 PM EDT SAT MAR 28 2015

23Z SFC ANALYSIS SHOWS HIGH PRESSURE SETTLING INTO THE OHIO
VALLEY. WITH CLEAR SKIES...A DRY AIR MASS...AND WINDS GOING
LIGHT...A GOOD NIGHT FOR RADIATIONAL COOLING IS UNDERWAY. EXPECT
THE VALLEYS TO DECOUPLE SHORTLY AND THEIR TEMPERATURES TO START
TO DROP DRAMATICALLY. CURRENTLY READINGS ARE GENERALLY IN THE LOW
TO MID 30S ACROSS EASTERN KENTUCKY WHILE DEWPOINTS RANGE FROM THE
SINGLE DIGITS NORTH AND ON THE RIDGES TO THE MID TEENS IN THE
SOUTH AND IN SOME VALLEYS. HAVE UPDATED THE FORECAST TO CLEAR THE
SKY COVER AND ALLOW FOR EVEN COLDER TEMPERATURES IN THE VALLEYS
WHERE LOWS MAY BE CLOSER TO 10 DEGREES THAN 20 BY MORNING. THE
UPDATED GRIDS HAVE BEEN SENT TO THE NDFD AND WEB SERVERS ALONG
WITH AN UPDATED SET OF ZONES.

&&

.SHORT TERM...(THIS EVENING THROUGH SUNDAY NIGHT)
ISSUED AT 317 PM EDT SAT MAR 28 2015

THE CENTER OF HIGH PRESSURE...CURRENTLY JUST SOUTH OF LAKE
MICHIGAN...WILL CONTINUE TO TRACK TO THE SE THIS EVENING AND
OVERNIGHT...REACHING EASTERN KY BY 6Z TONIGHT...AND EXITING TO THE
SOUTH CAROLINA COAST BY 18Z TOMORROW. THE INFLUENCE OF THIS HIGH
PRESSURE WILL BE IN PLACE TODAY THROUGH TOMORROW...WITH DRY AND COLD
AIR BEING PULLED IN FROM THE NW. SOME FAIR WEATHER CU HAVE DEVELOPED
ACROSS EASTERN KY...BUT WILL QUICKLY DIE OUT THIS EVENING WITH LOSS
OF DAYTIME HEATING. THE SAME IS TRUE FOR ANY ONGOING WIND GUSTS.

THE BIGGER CONCERN WILL BE TONIGHT AND TOMORROW UNDER THE INFLUENCE
OF SUCH A DRY AIRMASS. WITH A HIGH PRESSURE SURFACE INVERSION
DEVELOPING OVERNIGHT...LIGHT TO CALM WINDS AS THE HIGH PRESSURE
PASSES NEARLY OVERNIGHT...WITH CREATE A SCENARIO FOR MAXIMUM LOSS OF
DAYTIME RADIATIONAL HEATING. TEMPERATURES WILL DROP DOWN TO AROUND
20 DEGREES...WITH MANY OF THE VALLEYS FALLING FURTHER INTO THE MID
TEENS. THIS IS A COUPLE DEGREE FURTHER DROP FROM THE PREVIOUS
FORECAST. THESE TEMPS WILL LIKELY BREAK SEVERAL MIN TEMP RECORDS
ACROSS THE CWA.

THEN FOR TOMORROW...TEMPERATURES WILL RECOVER INTO THE LOW AND MID
50S AS SKIES REMAIN SUNNY AND WINDS SHIFT TO THE SOUTH BEHIND THE
EXITING HIGH PRESSURE. HOWEVER...DRY AIR INFLUENCE WILL STILL BE IN
PLACE...WITH DEW POINTS TAKING MUCH LONGER TO RECOVER. BY
AFTERNOON...WE COULD BE EXPERIENCING SOME CRITICAL RH VALUES DOWN IN
THE LOW TO MID TEENS ACROSS A GOOD PORTION OF THE CWA.

MEANWHILE...A SURFACE LOW PRESSURE SYSTEM...POISED TO BE LOCATED
JUST NORTH OF LAKE SUPERIOR AROUND 18Z TOMORROW...WILL CONTINUE TO
SHIFT EASTWARD...PULLING A COLD FRONT ACROSS KY BETWEEN AROUND 3Z
AND 12Z SUNDAY NIGHT/MONDAY MORNING. GIVEN THE FAST MOVING NATURE OF
THIS SYSTEM...AND THE AMOUNT OF DRY AIR IN PLACE...EXPECT MINIMAL
IMPACTS FOR ASSOCIATED POPS AND QPF. TEMPERATURES WILL REMAIN WARM
ENOUGH FOR ANY PRECIP TO FALL AS LIGHT RAIN...BUT GENERALLY ONLY
BETWEEN 0.1 AND 0.2 INCHES ARE EXPECTED BEFORE TAPERING OFF DURING
THE MORNING HOURS MONDAY.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 245 PM EDT SAT MAR 28 2015

THE FORECAST PERIOD WILL BE ACTIVE WITH SEVERAL SHORT WAVES MOVING
FAIRLY QUICKLY THROUGH ZONAL FLOW...WITH RAIN CHANCES INCREASING
DURING THE LATTER HALF OF THE WEEK. THE ZONAL FLOW WILL RESULT IN
MILD TEMPERATURES...AND AS INSTABILITY INCREASES LATER IN THE WEEK
THUNDERSTORMS WILL ALSO BECOME POSSIBLE. THERE IS GOOD MODEL
AGREEMENT TO START THE PERIOD...BUT SIGNIFICANT DIFFERENCES DEVELOP
BY LATE IN THE WEEK.

AT THE START OF THE PERIOD SURFACE HIGH PRESSURE WILL BE NOSING EAST
FROM THE MID MS VALLEY...WHILE A SHORT WAVE AND ASSOCIATED SURFACE
LOW MOVE INTO THE NORTHERN PLAINS. THIS LOW WILL TRACK INTO THE
GREAT LAKES ON TUESDAY...BRINGING A WARM FRONT ACROSS THE AREA THAT
WILL THEN BE QUICKLY FOLLOWED BY A COLD FRONT. HOWEVER...MOISTURE
LOOKS TO BE LIMITED AND THE MODEL BLEND KEEPS THE FORECAST DRY FOR
TUESDAY...WITH ONLY A SLIGHT CHANCE OF RAIN TUESDAY NIGHT. WILL
FOLLOW NEIGHBORING WFOS TO N...E AND W...AND LOWER PROBABILTIES
SLIGHTLY FOR TUESDAY NIGHT...THUS RESULTING IN NO MENTION OF RAIN
FOR TUESDAY NIGHT. ANOTHER SHORT WAVE AND SURFACE LOW LOOK TO TRACK
ACROSS ONTARIO ON THURSDAY...WITH ASSOCIATED FRONTS MOVING ACROSS
OUR AREA AND BRINGING BETTER RAIN CHANCES. THE TRAILING COLD FRONT
WITH THIS SYSTEM LOOKS TO STALL SOMEWHERE FROM THE GREAT LAKES OR OH
VALLEY INTO THE SOUTHERN PLAINS...WITH LOW PRESSURE DEVELOPING OVER
THE SOUTHERN PLAINS THURSDAY NIGHT. IT IS AT THIS POINT THAT THE
MODELS BEGIN TO SHOW SIGNIFICANT DIFFERENCES. THE ECMWF IS VERY
AGGRESSIVE WITH PHASING THE NORTHERN AND SOUTHERN STREAMS AS WE MOVE
TOWARDS THE WEEKEND...WITH THE SOUTHERN PLAINS SURFACE LOW DEEPENING
RAPIDLY AS IT MOVES TOWARDS THE GREAT LAKES ON FRIDAY. THE GFS IS
MUCH WEAKER ALOFT AND AT THE SURFACE...WITH THE SURFACE LOW TRACKING
MORE EASTWARD IN FLATTER FLOW. BOTH SCENARIOS RESULT IN SHOWER AND
THUNDERSTORM CHANCES FOR OUR REGION...BUT THE ECMWF SOLUTION WOULD
RESULT IN A SEVERE WEATHER THREAT AS WELL. THIS WILL NEED TO BE
WATCHED AS WPC NOTES THE CANADIAN AND GFS ARE BEGINNING TO TREND
TOWARDS MORE AMPLIFIED SOLUTIONS...BUT WPC AND WE ARE NOT YET
COMMITTED TO THE FULLY PHASED ECMWF SOLUTION.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SUNDAY EVENING)
ISSUED AT 830 PM EDT SAT MAR 28 2015

HIGH PRESSURE WILL MOVE ACROSS THE OHIO RIVER VALLEY DURING THE
BULK OF THE FORECAST PERIOD. THIS WILL MEAN CLEAR SKIES AND LIGHT
WINDS OVERNIGHT. AN APPROACHING COLD FRONT FROM THE NORTHWEST WILL
BRING MORE IN THE WAY OF CLOUDS BACK INTO THE AREA FOR SUNDAY
AFTERNOON. THIS FRONT WILL ALSO TURN THE WINDS TO THE SOUTH AND
ALLOW THEM TO PICK UP TO BETWEEN 10 AND 15 KTS BY LATE AFTERNOON.

&&

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

$$

UPDATE...GREIF
SHORT TERM...JMW
LONG TERM...SBH
AVIATION...GREIF



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