Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 022033
AFDJKL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON KY
333 PM EST MON MAR 2 2015

.SHORT TERM...(THIS EVENING THROUGH TUESDAY NIGHT)
ISSUED AT 332 PM EST MON MAR 2 2015

WHILE UNDER A RIDGE OF HIGH PRESSURE TODAY...WE WILL BE
TRANSITIONING TO THE LEE SIDE OF AN UPPER LEVEL TROUGHING PATTERN
THROUGH THE DAY TOMORROW. THIS WILL BE THE INTRODUCTION TO A
MAJOR TRANSITIONAL PERIOD IN THE WEATHER FORECAST AS WE HEAD INTO
MID WEEK.

TO START OUT...HIGH PRESSURE AT THE SURFACE WILL CONTINUE TO SHIFT E
ACROSS KY THIS AFTERNOON AND EVENING...PULLING OUT OF EASTERN KY BY
LATE THIS EVENING. WHILE IT IS IN CONTROL...EXPECT LIGHT VARIABLE
WINDS AND PARTLY CLOUDY SKIES THROUGH THIS EVENING. THEN...ONCE THE
SURFACE HIGH SHIFTS EASTWARD...A STRONG LOW PRESSURE SYSTEM
CURRENTLY OVER THE 4 CORNER STATES PLAINS WILL MAKE A QUICK SHIFT
EASTWARD TOWARDS THE CENTRAL PLAINS BY 12Z TUESDAY. AHEAD OF THIS
SYSTEM...A WARM FRONT WILL PUSH FROM WEST TO EAST ACROSS THE CWA
FROM 12Z TUESDAY THROUGH 18Z...PULLING IN MOIST BUT GENERALLY LIGHT
SOUTHERLY WINDS ACROSS THE REGION. EXPECT CLOUD COVER TO BEGIN
SPREADING ACROSS KY THIS EVENING...WITH CLOUDS LOWERING THROUGHOUT
THE NIGHT. BETWEEN 9 AND 10Z /GENERALLY/ PRECIP WILL MOVE IN
STARTING IN THE SOUTH AND SPREADING NORTHWARD. WHILE THERE WILL BE A
PUSH OF WARMER AIR...MODELED SURFACE TEMPS CONTINUE TO LAG BEHIND IN
THE LATEST DATA...CREATING A GOOD SCENARIO FOR FREEZING RAIN AT
ONSET. WHILE MOST LOCATIONS WILL LIKELY SEE SOME SORT OF FREEZING
RAIN...MAINLY IN THE NORTHERN HALF OF THE CWA...IT WILL THANKFULLY
BE SHORT LIVED AS SURFACE TEMPS QUICKLY REACT AND RISE ABOVE
FREEZING JUST AFTER 12Z...CHANGING ALL PRECIP OVER TO JUST RAIN.

BETWEEN 18Z TUESDAY AND 0Z WEDNESDAY...THE CWA WILL BE IN BETWEEN
THE EXITING WARM FRONT AND THE APPROACHING COLD FRONT...WITH
CONTINUED STRONG SOUTHERLY FLOW PULLING IN WARM MOIST AIR.
TEMPERATURES WILL RISE INTO THE 50S WITH STRATIFORM LIGHT TO
MODERATE RAIN EXPECTED THROUGHOUT THE DURATION OF THE DAY. THERE
COULD BE ENOUGH ELEVATED INSTABILITY TO PRODUCE A FEW RUMBLES OF
THUNDER...SO WENT AHEAD AND ADDED SLIGHT CHANCE OF THUNDER TO THE
FORECAST THROUGH THE EVENING TUESDAY. AFTER ABOUT 3Z TUESDAY...WE
LOSE SOME OF THE BEST LI/S AND SURFACE TEMPS BEGIN TO DROP SO EXPECT
THUNDER POTENTIAL TO DIE OFF AT THIS POINT.

.LONG TERM...(TUESDAY NIGHT THROUGH SUNDAY)
ISSUED AT 430 AM EST MON MAR 2 2015

THE EXTENDED FORECAST PERIOD BEGINS ON TUESDAY NIGHT WITH A
RATHER ACTIVE AND HIGH AMPLITUDE PATTERN IN PLACE. UNDERWAY AND
ALREADY IMPACTING THE OH VALLEY AT THIS TIME FRAME IS AN
ENLONGATED LONGWAVE TROUGH OVER THE CENTRAL CONUS WITH THE TROUGH
AXIS EXTENDING SOUTHWEST INTO THE FOUR CORNERS REGION WHERE A
CLOSED LOW LIES ENTRENCHED OVER THE BAJA REGION. DURING THIS
TIME...A STRONG AN ACTIVE JET CORE EXTENDS FROM OVER THE SOUTHWEST
TO THE GREAT LAKES REGION WITH THE HIGHEST SPEEDS WITH THE JET MAX
OVER THE WESTERN GREAT LAKES OF 140 TO 160 KNOTS. HEADING INTO THE
DAY ON WEDNESDAY...THE MENTIONED LOW OVER THE BAJA EJECTS INTO THE
SOUTHERN PLAINS WHILE THE ENLONGATED TROUGH MOVES THROUGH THE
CENTRAL CONUS. THE DEVELOPED LIFT AND DYNAMICS OVER THE MS VALLEY
AND INTO THE OH VALLEY IS QUITE SUBSTANTIAL AT THIS TIME AS THE
MID AND UPPER LEVEL FLOW TAKE A SOUTHWEST TO NORTHEAST TRAJECTORY.
THIS SETS THE STAGE FOR PRETTY EFFICIENT RAINFALL AT ONSET OF THE
FIRST SYSTEM INTO TUESDAY NIGHT AND THROUGH THE DAY ON WEDNESDAY
AND THEN ANOTHER POSSIBLE WINTER STORM LIKE EVENT INTO MID WEEK.
THIS UNFORTUNATELY EXACERBATES THE CONCERN FOR FLOODING IN
CONJUNCTION WITH THE SNOWMELT AND POSSIBLY EVEN MORE SNOW ON TOP
OF THAT.

CONCERNING THE LOWER LEVELS...HIGH PRESSURE CENTERED JUST OFF
SHORE IN THE ATLANTIC NUDGING INTO THE SOUTHERN PORTIONS OF THE
SOUTHEASTERN CONUS THROUGH THE MID WEEK WILL KEEP A NEARLY STALLED
SOUTHWEST TO NORTHEAST ORIENTATION OF A SURPRISINGLY STRONG
GRADIENT SURFACE COLD FRONT. THE DEVELOPMENT OF SEVERAL WAVES IN
THE MID LEVELS ALONG THIS FRONT TUESDAY NIGHT INTO WEDNESDAY AND
THROUGH THURSDAY WILL KEEP A SIGNIFICANT QPF OVER THE AREA. THIS
WILL ONCE AGAIN KEEP FLOODING A THREAT WITH THE AMOUNT OF PRECIP
EXPECTED. AN ADDITIONAL SHOT OF MOISTURE CONTINUES AS THE LAST
WAVE RIDES NORTHEAST ALONG THE FRONT AND THIS FEATURE FINALLY
KICKS THE SURFACE LOW OUT TO SEA BY THURSDAY NIGHT. IT IS WORTH
MENTIONING...THAT THIS PATTERN DOES NOT HAPPEN OFTEN...ESPECIALLY
POSTFRONTAL HEAVY SNOWFALL DURING THE LAST HALF OF THE WINTER
SEASON. HOWEVER...THERE DOES SEEM TO BE SOME CONSISTENCY IN THE
MODELS AND NOW THE NAM AND SREF AS THIS EVENT HAS COME INTO THAT
TIME PERIOD. ENSEMBLE MEANS SHOWN FROM WWD PRODUCTS ARE INDICATING
MUCH MORE IN THE WAY OF SNOW AND HAVE AT LEAST COLLABORATED WITH
WWD TO COME UP WITH SOME SLIGHTLY LOWER SNOW VALUES AND SNOWFALL
FORECASTS ARE IN LINE WITH THOSE TRENDS OF COLLABORATION. ANOTHER
HELPFUL INDICATOR OF AT LEAST THE BLOCKING NEEDED FOR THAT
SOUTHWEST TO NORTHEAST ORIENTATION OF THE NEARLY STALLED FRONT IS
THE ENSEMBLE MEAN OF THE NAO. A SHARP DROP IN VALUES FROM THE NAO
PRODUCT ARE OCCURRING DURING THE TIME OF THIS SYSTEMS SET UP.
WHILE NOT NECESSARILY A SHARP DROP INTO NEGATIVE VALUES...THIS
INDICATION WOULD BE ENOUGH FOR SOME BLOCKING OVER THE ATLANTIC AND
IS ENOUGH TO HAVE SOME CONFIDENCE IN THE QPF AND SNOWFALL VALUES
DISPLAYED IN THE FORECAST. IT IS VERY POSSIBLE TO BE GOING
STRAIGHT FROM A FLOOD CONCERN TO A SNOWFALL CONCERN IN A MATTER OF
24 HOURS.

AS FOR SNOW RATIOS INTO WEDNESDAY NIGHT AND THURSDAY...THERE IS
SOME CONCERN AT ONSET OF THIS SYSTEM THAT SOME WARM AIR ALOFT MAY
CREATE SOME FREEZING PRECIP WHICH WOULD LOWER SNOW TOTALS A BIT.
GIVEN ALL THIS...THE GRADIENT MOVING THROUGH WOULD ENSURE COLD
ENOUGH SURFACE TEMPS AND THEREFORE HAVE GONE WITH A STRONG MENTION
IN THE HWO. QPF VALUES WILL GO FROM 2 TO 2.50 INCHES AND SNOWFALL
IN THE 6 TO 8 INCH RANGE.

THE PATTERN GOES QUITE AFTER THURSDAY WITH SURFACE HIGH PRESSURE
MOVING IN AND A NOTICEABLE LACK OF ARCTIC AIR THAT HAS USUALLY
BEEN FOLLOWING THESE SYSTEMS THIS WINTER...THOUGH STILL BELOW
NORMAL HIGHS FOR FRIDAY. SATURDAY HIGHS FINALLY GET BACK TO NEAR
NORMAL. BY SUNDAY...ANOTHER WAVE DROPPING INTO THE SOUTHERN PLAINS
ASSISTS IN SURFACE LOW DEVELOPMENT AND THIS FEATURE TRACK NORTH
BRINGING ADDITIONAL POSSIBLE WINTER WEATHER TO FAR SOUTHEASTERN
KENTUCKY. OBVIOUSLY...THIS SYSTEM IS WAY TOO FAR OUT TO PIN DOWN
WINTER PRECIP IF ANY. BUT IT DOES CONTINUE TO HIGHLIGHT AN ACTIVE
AND WET PATTERN THROUGH THE EXTENDED.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 1233 PM EST MON MAR 2 2015

A BRIEF AREA OF HIGH PRESSURE WILL KEEP VFR CONDITIONS OVER
EASTERN KY TODAY...WITH GENERALLY LIGHT AND VARIABLE WINDS. AS WE
HEAD INTO TONIGHT...THE AREA OF HIGH PRESSURE WILL BEGIN EXITING
TO OUR EAST...AND A WARM FRONT WILL PUSH IN FROM THE WEST...WITH
WINDS BECOMING GENERALLY SOUTHERLY THOUGH STILL LIGHT. AS THIS
OCCURS...EXPECT HIGH CLOUDS TO THICKEN AND QUICKLY LOWER TO MVFR
BETWEEN 8Z AND 12Z FROM WEST TO EAST. RAIN WILL ALSO QUICKLY MOVE
IN WITH THE CLOUDS...WITH MOST TAF SITES GENERALLY SEEING PRECIP
BETWEEN 9 AND 10Z. A STRONG WARM NOSE JUST ABOVE THE SURFACE
CONTINUES THE INDICATE THE POSSIBILITY OF FREEZING RAIN AT
ONSET...QUICKLY CHANGING OVER TO ALL RAIN AS TEMPERATURES RISE
ABOVE FREEZING AFTER 12Z. UNFORTUNATELY...MODELS ARE POINTING AT
CIGS AND VIS CONTINUING TO LOWER TO LIFR CONDITIONS DURING THE DAY
TOMORROW AS RAIN PERSISTS THROUGH THE REGION.


&&

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

$$

SHORT TERM...JMW
LONG TERM...SHALLENBERGER
AVIATION...JMW



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