FXUS63 KJKL 222015 AAA
AFDJKL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON KY
315 PM EST TUE DEC 22 2009

.SHORT TERM.../TONIGHT THROUGH THURSDAY/...UPDATED

19Z SFC ANALYSIS SHOWS WEAK HIGH PRESSURE FURTHER RETREATING TO THE
EAST OUT OF KENTUCKY AHEAD OF A LARGE AND DEVELOPING AREA OF LOW
PRESSURE OVER THE SOUTHERN PLAINS. HIGH CLOUDS ARE PUSHING INTO THE 
OHIO VALLEY FROM THIS LOW WHILE OTHERS ARE MOVING OUT OF THE AREA TO 
THE NORTHEAST FROM A PASSING...FLAT...SHORT WAVE. A GOOD AMOUNT OF 
SUNSHINE TODAY HAS RESULTED IN GOOD MELTING OF THE SNOW COVER. IN 
LOCATIONS WITHOUT MUCH SNOW...LIKE MONTICELLO AND SOMERSET... 
TEMPERATURES CLIMBED TOWARD 50 DEGREES THIS AFTERNOON...ELSEWHERE 
READINGS MADE IT TO THE LOWER AND MIDDLE 40S. DEWPOINTS REMAIN 
FAIRLY MOIST...GENERALLY IN THE MIDDLE 30S. 

THE MODELS ARE IN DECENT AGREEMENT ALOFT WITH RIDGING BUILDING OVER 
THE REGION TONIGHT AND WEDNESDAY IN RESPONSE TO A DEEP DIVING TROUGH 
CURLING INTO THE TEXAS PANHANDLE. IT IS AFTER THIS POINT...00Z 
THURSDAY...THAT LARGER DIFFERENCES CROP INTO THE SOLUTIONS WITH THE 
NAM SIGNIFICANTLY SLOWER MOVING THE DEVELOPING UPPER LOW EAST 
COMPARED TO THE GFS AND NEW ECMWF. AS SUCH...IT HAS BEEN DISCOUNTED 
AFTER ABOUT 24 HOURS. FOR THURSDAY...THE UPPER LOW PULLS IN A 
TRAILING AND ALSO QUITE STRONG CLOSED LOW TO BEGIN ITS DESTINED 
CONSOLIDATION INTO A DEEP CLOSED LOW OVER THE EASTERN PLAINS. AS 
THIS TRANSITION TAKES PLACE...THE ECMWF IS FURTHEST EAST AND A BIT 
STRONGER WITH THE LEAD LOW THAN THE GFS WHILE THE GFS/S FOLLOWING 
AND REINFORCING LOW ARRIVES A BIT QUICKER IN ITS SCENARIO. 
REGARDLESS OF HOW THESE FEATURES COMBINE THE END RESULT IS NEARLY 
THE SAME WITH A POWERFUL AND DEEP UPPER LOW DOMINATING THE HEART OF 
THE COUNTRY BY FRIDAY MORNING. FOR THE LATTER PART OF THE SHORT TERM 
PORTION OF THE FORECAST...FOLLOWED A BLEND OF THE GFS AND ECMWF WX 
SPECIFICS OWING TO THEIR PREFERRED UPPER LEVEL SOLUTIONS. 

AS FOR SENSIBLE WEATHER...EXPECT THE HIGH CLOUDS FROM THE WEST TO 
MOVE IN LATER TONIGHT AND THICKEN...LIKELY LIMITING THE RADIATIONAL 
COOLING IN CONJUNCTION WITH CONTINUED MILD WAA. HOWEVER...THIS IS 
ALSO COUNTERED IN MUCH OF THE CWA BY EXISTING PATCHES...LARGEST IN 
THE EAST...OF SNOW. ACCORDINGLY...THE LOW TEMPERATURE FORECAST WILL 
BE A CHALLENGE TONIGHT WITH ANY RIDGE THAT HAS MANAGED TO LOSE MOST 
OF ITS SNOW ENDING UP THE WARMEST...SOME COLD VALLEY LOCATIONS... 
PARTICULARLY EAST...AND ELSEWHERE LOWS JUST BELOW FREEZING AS 
MELTING OF THE SNOW PACK CONTINUES TO PROVIDE HIGH HUMIDITIES WELL 
THROUGH THE NIGHT. THIS MELTING WILL ALSO LIKELY CONTRIBUTE TO FOG 
DEVELOPING ON THE RIDGETOPS LATE TONIGHT...BUT PROBABLY NOT TO THE 
EXTENT WE SAW EARLY THIS MORNING. EXPECT A DAY SIMILAR TO TODAY ON 
WEDNESDAY WITH WAA CONTINUING TO SUPPORT TEMPERATURES REBOUNDING 
INTO THE UPPER 40S AND LOWER 50S...DESPITE LESS SUNSHINE. LATE IN 
THE DAY AND INTO THE WEDNESDAY NIGHT A FEW STRAY SHOWER WILL BE 
POSSIBLE AS THE LARGE...BECOMING STACKED...SFC LOW SPINS WELL TO OUR 
WEST AND A DEVELOPING WARM FRONT APPROACHES THE AREA. THIS THREAT OF 
ISOLATED TO SCATTERED SHOWERS WEDNESDAY NIGHT WILL COMBINE WITH 
STILL COLD VALLEY LOCATIONS IN THE FAR EAST FOR A VERY SLIGHT CHANCE 
OF FREEZING RAIN TOWARD DAWN FRIDAY. THOUGH THIS WILL NOT BE A 
SIGNIFICANT WEATHER FACTOR...WILL MENTION THE RISK IN THE HWO AND 
HINT AT IT IN THE FAR EAST ZONES THAT CARRY POPS. FOR THURSDAY... 
TEMPERATURES WILL CLIMB INTO THE LOWER AND MIDDLE 50S MOST LOCATIONS 
WITH THE WINDS PICKING UP BETTER FROM THE SOUTH...GUSTY AT 
TIMES...CONTINUING THE MELTING OF REMAINING SNOW. FOLLOWING THE 
BLENDED SOLUTION OF THE GFS AND ECMWF...SHOWERS SHOULD BE PUSHING 
MORE FORCEFULLY INTO THE WESTERN PORTION OF EAST KENTUCKY BY LATE 
AFTERNOON AS THE SYSTEM/S LARGE OCCLUDED/COLD FRONT STARTS TO SWEEP 
EAST THROUGH KENTUCKY WITH INCREASED ALACRITY. 

AS FOR TEMPS...FOLLOWED A BLEND OF THE GUIDANCE THROUGH THE 
PERIOD...BUT WITH SIGNIFICANT MODIFICATION FOR BOTH RELATIVE TERRAIN 
AT NIGHT AND EXISTING SNOW COVER THROUGH AT LEAST WEDNESDAY NIGHT. 
WITH THE POPS...ENDED UP CLOSEST TO THE MAV NUMBERS THROUGH  
WEDNESDAY...THEN WAS MOST SIMILAR TO THE NUMBERS FROM THE MAV INTO 
THURSDAY.  

.LONG TERM.../THURSDAY NIGHT THROUGH TUESDAY/...UPDATED

THE FOCUS FOR THE PERIOD IS ON A STRENGTHENING LOW PRESSURE SYSTEM
OVER THE UPPER MIDWEST WHICH IS EXPECTED TO FORCE A COLD FRONT
THROUGH EASTERN KENTUCKY FRIDAY MORNING. THE MAIN IMPACTS EXPECTED
WITH THIS SYSTEM CONTINUE TO BE A BRIEF PERIOD OF HEAVY RAINFALL AND
GUSTY WINDS.

QPF FROM AVAILABLE MODELS REMAINS LESS THAN AN INCH FOR THE AREA
THURSDAY NIGHT INTO FRIDAY MORNING AND RAIN SHADOWING EFFECT FROM
SOUTHEAST LOW LEVEL WINDS WILL PROBABLY MEAN LESS THAN A HALF INCH
OVER THE UPPER REACHES OF THE CUMBERLAND... KENTUCKY AND BIG SANDY
BASINS IN OUR AREA. DO NOT EXPECT ANY WIDESPREAD WATER PROBLEMS FROM
THIS AMOUNT OF RAIN COMBINED WITH CONTINUED SNOW MELT FROM OUR
RATHER LARGE HIGHER ELEVATION SNOW PACK... ALTHOUGH RIVERS WILL RUN
HIGH.

THE WIND THREAT ALSO LOOKS MINIMAL AS TIGHTEST PRESSURE GRADIENT
REMAINS TO OUR NORTHWEST THURSDAY NIGHT AND FRIDAY. THIS IS A
FAVORABLE SETUP FOR MOUNTAIN WAVE ACTIVITY OFF BLACK MOUNTAIN THOUGH
LATE THURSDAY NIGHT WITH A POTENT (50-KT PLUS) 850 MB JET PROGGED
AND PERPENDICULAR FLOW AT MOUNTAIN TOP LEVEL. LOCALIZED ADVISORY
CRITERIA WINDS OR GREATER WILL THUS BE POSSIBLE ACROSS EXTREME
SOUTHEAST KENTUCKY... BUT WILL HAVE TO MONITOR FUTURE MODEL RUNS TO
BETTER DEFINE THE THREAT.

OTHERWISE... PROGS REMAIN CONSISTENT IN BRINGING IN A MUCH COLDER
AIR MASS BEHIND THIS SYSTEM LATE FRIDAY THROUGH MONDAY AT LEAST.
LATEST GUIDANCE IS SLOWER IN EJECTING THE UPPER LOW TO OUR NORTHEAST
WITH OPERATIONAL GUIDANCE DEEPER AND FURTHER SOUTH THAN NAEFS MEAN.
NONETHELESS... A PERIOD OF MUCH BELOW NORMAL TEMPERATURES APPEARS
LIKELY THROUGH THE WEEKEND. PROGGED WEST TO SOUTHWEST MEAN LOW-LEVEL
FLOW IS NOT FAVORABLE FOR UPSLOPE SNOW SHOWER ACTIVITY... BUT WE
WILL MAINTAIN AT LEAST A 20 POP FROM FRIDAY NIGHT THROUGH MONDAY AS
PINWHEELING SHORTWAVES AROUND UPPER LOW TO THE NORTH WILL LIKELY
BRING A SNOW SHOWER FROM TIME TO TIME.

THE UPPER LOW IS EXPECTED TO FINALLY WEAKEN/MOVE TO OUR NORTHEAST
EARLY NEXT WEEK. SURFACE HIGH PRESSURE MAY EVEN HAVE A CHANCE TO
BUILD INTO THE AREA BY TUESDAY WITH A BIT OF A WARM UP EXPECTED.
ANOTHER SOUTHERN STREAM SYSTEM IS THEN PROGGED TO BEGIN ORGANIZING
TO OUR SOUTHWEST... BUT ITS IMPACTS ON OUR AREA... IF ANY... WILL
LIKELY NOT BE FELT UNTIL NEXT WEDNESDAY OR LATER.

&&

.AVIATION.../18Z TO 18Z/

VRF CONDITIONS SHOULD PREVAIL WELL INTO THE EVENING. HOWEVER...DO
ANTICIPATE A REPEAT OF LAST NIGHT...JUST TO A LESSER EXTENT...AS WAA
CONTINUES AND AN INVERSION HELPS TO SET UP A LOW DECK OF CLOUDS OVER
THE SNOW COVERED AREAS...INCLUDING THE TAF SITES. ALSO ANTICIPATE
THE DEVELOPMENT OF BR...WORSE ON THE HIGHER RIDGES LIKE JKL BUT STILL
LIKELY NOT ANYWHERE NEAR AS BAD AS LAST NIGHT. EVEN SO...MVFR
CONDITIONS WILL LIKELY BE FOUND THROUGH THE REST OF THE NIGHT AND
INTO THE EARLY MORNING HOURS OF WEDNESDAY BEFORE AGAIN MIXING OUT
AROUND 14Z. DID ALSO ADD A TEMPO FOR IFR CONDITIONS AT JKL DURING THE
PREDAWN HOURS. AFTER THE LOW CLOUDS AND BR MIX OUT WEDNESDAY VFR
CONDITIONS WILL ONCE AGAIN BE THE RULE. WINDS THROUGH THE PERIOD
WILL BE RELATIVELY LIGHT FROM THE SOUTH.

&&

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

&&

$$
SHORT TERM...GREIF
LONG TERM...ABE
AVIATION...GREIF