Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 300011
AFDJKL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON KY
711 PM EST THU JAN 29 2015

.UPDATE...
ISSUED AT 711 PM EST THU JAN 29 2015

EVERYTHING BEING REPORTED JUST UPSTREAM THIS EVENING CONTINUES TO BE
MAINLY DRIZZLE. THIS WOULD BE SUPPORTED BY MODEL SOUNDINGS SUGGESTING
VERY LITTLE ICE IN THE CLOUDS THROUGH THE EVENING. MODEL SOUNDINGS
COOL ENOUGH (TO INTRODUCE ICE INTO THE CLOUDS) TOWARDS MIDNIGHT TO
FINALLY SEE SOME SNOW ENTERING THE PICTURE. ADJUSTED WEATHER THROUGH
THE EVENING TO REFLECT MORE DRIZZLE, BEFORE GOING WITH RAIN SHOWERS
LATE EVENING...BEFORE QUICKLY MIXING WITH OR CHANGING TO SNOW. SUB-
FREEZING TEMPERATURES ARE STILL WELL UPSTREAM AND WILL TAKE A GOOD
CHUNK OF THE NIGHT TO SEE THEM GET HERE...BUT IT LOOKS LIKE SOMETIME
AFTER 2 AM WE SHOULD SEE THOSE SUBFREEZING TEMPS WORKING INTO OUR
AREA.

&&

.SHORT TERM...(THIS EVENING THROUGH FRIDAY NIGHT)
ISSUED AT 358 PM EST THU JAN 29 2015

A SURFACE COLD FRONT WAS ENTERING THE JKL FORECAST AREA FROM THE NW
AT MID AFTERNOON. AS IS OFTEN THE CASE...COLD AIR ADVECTION WILL
LEAD TO STEEP LOW LEVEL LAPSE RATES...AND WHEN COMBINED WITH UPSLOPE
FLOW...SHALLOW CONVECTIVE PRECIP SHOULD DEVELOP. IT WILL BE FURTHER
AIDED BY THE SUPPORT OF THE MID/UPPER LEVEL TROUGH AXIS PASSING OVER
TONIGHT AND EARLY FRIDAY. INITIALLY...THE TEMPERATURE PROFILE
SUPPORTS PRECIP IN THE FORM OF RAIN THIS EVENING. AS THE COLUMN
COOLS...SURFACE TEMPS WILL COOL ENOUGH TO ALLOW SNOW...AND THE
UPPER PART OF THE MOISTURE COLUMN WILL EVENTUALLY REACH -10C AND
COLDER...AND PRECIP WILL CHANGE TO SNOW. THE PRECIP AMOUNTS WILL BE
LIGHT...BUT THE PROBABILITY IS FAIRLY HIGH. SNOWFALL WILL GENERALLY
BE A HALF INCH OR LESS...BUT SOME AMOUNTS OF AROUND AN INCH MAY OCCUR
AT HIGHER ELEVATIONS IN THE SOUTHEAST. THE LAST OF THE SNOW SHOWERS
WILL TAPER OFF DURING THE DAY FRIDAY AS HIGH PRESSURE BUILDS IN AND
UPSLOPE FLOW IS LOST. MOSTLY CLEAR SKIES ARE EXPECTED AS THE SURFACE
HIGH PASSES OVER ON FRIDAY NIGHT.

.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 358 PM EST THU JAN 29 2015

THIS PERIOD STARTS OUT QUIET WITH HIGH PRESSURE OVERHEAD AND
TEMPERATURES NEAR 40 DEGREES...THANKS IN PART TO SOUTHWESTERLY
WINDS. SKIES WILL BE MOSTLY CLEAR IN THE MORNING WITH INCREASING
CLOUDS IN THE AFTERNOON AS THE NEXT STORM SYSTEM APPROACHES THE
REGION.

THERE IS STILL A LOT OF UNCERTAINTY WITH THIS LATE WEEKEND SYSTEM
DUE TO THE MODEL RUN TO RUN DIFFERENCES. BOTH THE ECMWF/GFS MODELS
BRING SOUTHERN STREAM ENERGY FROM THE SOUTHWESTERN US LOW AND TRY TO
PHASE IT WITH THE NORTHERN STREAM ENERGY AS IT CROSSES THE TENNESSEE
VALLEY. HOWEVER... THE TRACK AND STRENGTH OF THE SFC LOW THAT
DEVELOPS IN THE MODELS IS WHERE THERE ARE SUBSTANTIAL RUN TO RUN
DIFFERENCES....ESPECIALLY WITH THE LATEST 12Z/29 GFS RUN WHICH
DEEPENS THE SFC LOW AND TAKES IT UP ACROSS MASSACHUSETTS. ONE THING
THE MODELS DO HAVE IN COMMON IS THE AMOUNT OF QPF THEY SHOW. ANOTHER
QUESTION THAT REMAINS IS HOW MUCH COLD AIR STAYS IN PLACE AND THIS
WILL HEAVILY DEPEND ON THE TRACK OF THE SFC LOW. THAT BEING SAID...
HAVE LEANED A BIT TOWARD A COLDER SOLUTION ON SUNDAY. MODEL
SOUNDINGS HAD MOST OF THE MOIST COLUMN BELOW ZERO WITH SFC TEMPS
JUST ABOVE FREEZING UNTIL LATE SUNDAY NIGHT. OVERALL CONFIDENCE IN
THIS SYSTEM REMAINS LOW. THOUGH...STILL BELIEVE THERE IS A
REASONABLE CHANCE FOR MEASURABLE SNOW SUNDAY INTO MONDAY.

AS THE SYSTEM DEPARTS HIGH PRESSURE ONCE AGAIN BUILDS INTO THE
REGION...ALONG WITH A COLD AIR MASS. THIS SHOULD ALLOW TEMPERATURES
TO GENERALLY BE FALLING THROUGHOUT THE DAY ON MONDAY. LOWS MONDAY NIGHT
COULD REACH THE SINGLE DIGITS IN SPOTS BUT SHOULD MAINLY BE IN THE
LOW TO MID TEENS. TEMPERATURES SHOULD REBOUND ON TUESDAY INTO THE
MID TO UPPER 30S IN RESPONSE TO SOUTHERLY FLOW FROM THE GULF
USHERING IN WARMER AIR. WEDNESDAY ANOTHER SYSTEM MOVES INTO KENTUCKY
BRINGING ANOTHER CHANCE FOR A MIXED PRECIP EVENT ENDING ON THURSDAY.
AN ARCTIC AIR MASS ADVECTS IN BEHIND IT... DROPPING TEMPS ONCE
AGAIN INTO THE LOW TEENS AND SINGLE DIGITS. FRIDAY WILL BE A CHILLY
BUT QUIET DAY WITH HIGHS WELL BELOW NORMAL.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING)
ISSUED AT 711 PM EST THU JAN 29 2015

CIGS ARE ALREADY COMING DOWN TO MVFR IN THE WAKE OF A COLD FRONT
EXITING TO THE SOUTHEAST. THESE MVFR CIGS WILL CONTINUE THROUGH THE
REST OF THE NIGHT AND LIKELY THROUGH TOMORROW. NOT SURE WHEN WE MIGHT
RETURN TO VFR...BUT AT THE EARLIEST IT WOULD BE MID AFTERNOON
TOMORROW. WINDS WILL REMAIN A BIT GUSTY THROUGH THE EVENING OUT OF
THE NORTHWEST...BUT SHOULD LOSE THE GUSTINESS AS WE HEAD THROUGH THE
NIGHT. IN ADDITION...UPSLOPE FLOW AND THE LOW LEVEL MOISTURE IN PLACE
WILL SET THE STAGE FOR SOME DRIZZLE THIS EVENING...TRANSITIONING TO
LIGHT RAIN OR SNOW SHOWERS LATE TONIGHT. AT THIS TIME...ANY
ACCUMULATIONS WILL BE UNDER HALF AN INCH AND MAINLY IN SOUTHEAST
KENTUCKY.

&&

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

$$

UPDATE...KAS
SHORT TERM...HAL
LONG TERM...JVM
AVIATION...KAS





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