Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 200607
AFDJKL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON KY
107 AM EST SAT DEC 20 2014

.UPDATE...
ISSUED AT 106 AM EST SAT DEC 20 2014

JUST UPDATED THE FORECAST GRIDS WITH THE LATEST HOURLY OBSERVATIONAL
DATA TO ESTABLISH NEW TRENDS. THE FORECAST IS HOLDING TRUE SO FAR
WITH REGARD TO TEMPERATURES AND CLOUD COVER. THE LATEST SURFACE OBS
ARE SHOWING LITTLE IN THE WAY OF PRECIPITATION REACHING THE GROUND
ANYWHERE IN OUR SOUTHERN COUNTIES. BASED ON THE RETURNS SHOWING UP IN
RADAR...HOWEVER...AM HOPEFUL THAT WET BULBING WILL ALLOW FOR RAIN AND
OR SNOW TO BEGIN REACHING THE GROUND IN OUR COUNTIES SOUTH OF THE HAL
ROGERS PARKWAY.

UPDATE ISSUED AT 1047 PM EST FRI DEC 19 2014

CURRENT CONDITIONS ACROSS THE AREA FEATURE CLOUD COVER FINALLY
STARTING TO OVERSPREAD THE AREA ALONG WITH SOME WEAK RADAR RETURNS
FINALLY MAKING IT INTO SOUTHEASTERN KENTUCKY. ADJUSTED THE FORECAST
TO INCREASE THE CLOUD COVER FOR THE SYSTEM MOVING INTO THE AREA. THE
ONLY OTHER FACTOR THAT NEEDED ADJUSTED WAS THE TEMPERATURES. STILL A
FEW BREAKS IN THE CLOUD COVER HANGING AROUND TILL A BIT LATER IN THE
NIGHT HAS RESULTED IN SOME OF THE VALLEYS DROPPING OFF A BIT LOWER
AND HAVE ADJUSTED LOW TEMPS FOR TONIGHT. WITH THIS...SNOW FROM THE
INCOMING SYSTEM FROM THE SOUTHWEST WILL LAST A LITTLE LONGER INTO THE
AFTER DAWN HOURS. THIS PRECIP IS STILL EXPECTED TO BE LIGHT SO
ACCUMULATIONS WILL STILL BE A DUSTING AT MOST. AS OF 0330Z...IN
WESTERN KY...PRECIP IS DEVELOPING A BIT FURTHER NORTH AND MOVING
NORTHEAST...AT THIS POINT...NOT A LOT OF THAT IS REACHING THE SURFACE
AND MODELS STILL HAVE THIS ACTIVITY FIZZLING OUT BEFORE IT MAKES IT
INTO NORTHEASTERN KENTUCKY SO WILL CONTINUE TO LEAVE PRECIP OUT IN
THE NORTH BUT THIS AREA OF PRECIP NEEDS TO BE MONITORED. A NEW ZFP
HAS BEEN ISSUED FOR THESE UPDATES.

UPDATE ISSUED AT 639 PM EST FRI DEC 19 2014

SO FAR THIS EVENING THE MAIN FORECAST CHALLENGE LOOKS LIKE IT WILL BE
HOW FAR TEMPS WILL FALL IN THE FIRST PART OF TONIGHT BEFORE THE MID
AND UPPER LEVEL CLOUD COVER ASSOCIATED WITH A SYSTEM TRACKING TO THE
SOUTH AND EAST OF EASTERN KY MOVE OVER THE AREA. THIS OCCURRENCE WILL
LIKELY CAUSE TEMPS TO BECOME STEADY AND HOLD NEAR THE FREEZING MARK
FOR LOWS OVERNIGHT. FOR NOW...THESE LOW TEMPS SEEM TO BE ON TRACK BUT
WILL NEED TO MONITOR FOR DRASTIC CHANGES IN TEMPS ALONG WITH THE
POSSIBILITY OF PRECIP TOWARDS DAWN. THIS EVENINGS UPDATE WILL NOT
REQUIRE A NEW ZFP.

&&

.SHORT TERM...(THIS EVENING THROUGH SATURDAY NIGHT)
ISSUED AT 350 PM EST FRI DEC 19 2014

19Z SFC ANALYSIS SHOWS HIGH PRESSURE STILL IN CONTROL OF THE WX OVER
THE OHIO VALLEY. THE LOWER CLOUDS OVER THE NORTHEAST ARE FINALLY
RESPONDING TO THE DRIER AIR FROM THIS HIGH BY ERODING OFF BENEATH A
LAYER OF HIGH CLOUDS SPREADING IN AND THICKENING FROM THE SOUTHWEST.
TEMPERATURES ACROSS THE AREA VARY FROM THE CHILLY LOW 30S IN THE
NORTH TO THE LOWER 40S IN THE FAR SOUTHEAST. MEANWHILE...WITH LIGHT
WINDS IN PLACE OVER THE AREA...DEW POINTS VARY FROM THE LOW 20S NORTH
TO THE MID 20S SOUTH.

THE MODELS CONTINUE TO BE IN GOOD AGREEMENT WITH A COUPLE OF
DAMPENING WAVES MOVING THROUGH THE REGION OVER THE NEXT 36 TO 48
HOURS. THE FIRST OF THESE WILL PASS TO THE SOUTH LATE TONIGHT AND
INTO SATURDAY MORNING...WHILE A BIT BETTER DEFINED ONE WILL MOVE
JUST NORTH OF EAST THROUGH THE CENTRAL OHIO VALLEY DURING THE DAY
SATURDAY. THE MODELS ALSO CONTINUED THEIR TREND OF THESE WAVES BEING
WEAKER AND OF LESS SUBSTANCE. LATER SATURDAY NIGHT...HEIGHTS WILL
RISE AHEAD OF THE NEXT MORE SIGNIFICANT TROUGH. ACCORDINGLY...HAVE
FOLLOWED A BLENDED SOLUTION AND LEANED MORE CLOSELY TO THE NAM12 AND
HRRR.

SENSIBLE WEATHER WILL FEATURE CLOUDS THICKENING AND LOWERING THROUGH
THE NIGHT WITH A CHANCE OF LIGHT SNOW OR RAIN MOVING INTO OUR
SOUTHERNMOST AREAS AFTER MIDNIGHT. DO NOT EXPECT MUCH IN THE WAY QPF
OUT OF THIS WITH MOST OF THE PCPN FALLING AS JUST VIRGA OR
FLURRIES/SPRINKLES. GIVEN THE DRY DEW POINTS THE PCPN RATE WILL LIKELY
NOT FALL FAST ENOUGH TO CONTRIBUTE TO WETBULBING...KEEPING IT AS
LIQUID LONGER THAN NORMAL IN THESE TYPE OF SITUATIONS. THE WEAK
SOUTHERN WAVE WILL MOVE AWAY FROM KENTUCKY BY NOON SATURDAY WITH EVEN
SOME CLEARING POSSIBLE BEFORE EVENING. THIS WILL MAKE FOR A TRICKY
TEMPERATURE FORECAST INTO SATURDAY WITH A WIDE VARIANCE BETWEEN THE
COOLER MET NUMBERS AND THE MUCH MILDER MAV ONES. AS WE ARE LEANING
MORE TOWARD THE STILL RATHER DRY NAM12 SOLUTION WILL ALSO FAVOR THE
COOLER MET MAX T NUMBERS. ANOTHER COOL NIGHT FOLLOWS INTO SUNDAY
MORNING AS SOME CLEARING WILL BE POSSIBLE FROM THE WEST.

AGAIN USED THE BCCONSSHORT AS A STARTING POINT FOR THE T/TD/WIND
GRIDS FOR THE FIRST 20 HOURS OR SO BEFORE POPULATING WITH THE
SUPERBLEND THEREAFTER. ONLY MINOR ADJUSTMENTS WERE MADE FOR TERRAIN
EFFECTS BOTH TONIGHT AND SATURDAY NIGHT GIVEN THE CLOUDS...BUT DID
DROP THE MAXT DOWN A COUPLE OF DEGREES FROM THE TOO WARM BLEND. AS
FOR POPS...ENDED UP CLOSE TO A BLEND OF THE WETTER MET AND DRY MAV
TONIGHT INTO SATURDAY...AND THEN DRY ON SATURDAY NIGHT.

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 351 PM EST FRI DEC 19 2014

ACTIVE PATTERN CONTINUES TO BE THE STORY FOR MUCH OF THE LONG TERM
PERIOD. SUNDAY DOES LOOK QUIET FOR THE BEGINNING OF THE PERIOD WITH
MOSTLY CLEAR CONDITIONS...HOWEVER CLOUDS WILL INCREASE FROM SOUTH TO
NORTH THROUGH THE DAY INTO SUNDAY NIGHT. THIS IS SYSTEM ONE WHICH
WILL COME FROM THE SOUTHERN BRANCH AND WILL BRING BEST CHANCES OF ALL
RAIN SUNDAY NIGHT INTO MONDAY. THIS SYSTEM IS EXPECTED TO PROGRESS NE
BUT THERE IS QUESTIONS AS TO THE PHASING OF THIS SOUTHERN AND
IMPENDING NORTHERN BRANCH SYSTEM. GIVEN SOME UNCERTAINTY WILL KEEP
SLIGHT CHANCE OF PRECIP MONDAY INTO TUESDAY.

THEN FOCUS SHIFTS TO THE NORTHERN SYSTEM AS UPPER LEVEL LOW AND
SURFACE LOW APPROACHES THE GREAT LAKES MONDAY NIGHT. THE MODELS ARE
STILL NOT IN AGREEMENT ON WHAT HAPPENS WITH THIS SYSTEM IN TERMS OF
TIMING AND EVOLUTION. THE GFS DEVELOPS A SECONDARY LOW LATER THAT
MOVES NE ACROSS THE MIDDLE ATLANTIC WEDNESDAY...WHILE THE ECMWF
DEVELOPS A LOW ACROSS TN AND OH VALLEY THEN MOVES IT STRAIGHT NE
TUESDAY NIGHT. THESE TIMING AND EVOLUTION ISSUES WILL PLAY A ROLE IN
HOW MUCH PRECIP AND PRECIP TYPES. EITHER WAY THINKING WEDNESDAY WE
WILL SEE RAIN/SNOW TO SNOW AS WE MOVE THROUGH THE DAY INTO THE NIGHT
ACROSS PORTIONS OF THE REGION...HOWEVER IT DOES LOOK LIKE IT WILL BE
MORE WRAP AROUND LATER WEDNESDAY. THE WRAP AROUND SNOW SHOWERS
SHOULD DIE DOWN AS WE MOVE THROUGH THE DAY THURSDAY WITH SYSTEM
TRACKING INTO THE FAR NE US BY THURSDAY NIGHT. SURFACE HIGH PRESSURE
OFF TO THE SOUTH AND UPPER LEVEL RIDGING WILL BUILD EAST ACROSS THE
SE US THURSDAY NIGHT INTO FRIDAY. THIS WILL LEAD TO RETURN FLOW AND
HIGH TEMPERATURES WARMING INTO THE LOWER 50S BY FRIDAY.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)
ISSUED AT 106 AM EST SAT DEC 20 2014

TAF FORECAST REMAINS A CHALLENGE IN REGARDS TO PRECIPITATION ONSET
NEAR LOZ AND SME AND THE NORTHWARD EXTENT OF ANY PRECIP THAT DOES
FORM. BASED ON SURROUNDING OBS AND THE LATEST MODEL DATA...IT APPEARS
THAT MVFR CONDITIONS WILL THE WORST WE SEE AT ANY OF THE TAF SITES
OVERNIGHT AND THROUGH THE DAY ON SATURDAY.

&&

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

$$

UPDATE...AR
SHORT TERM...GREIF
LONG TERM...DJ
AVIATION...AR






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