FXUS63 KJKL 091756
AFDJKL
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON KY
1256 PM EST WED DEC 9 2009
.SHORT TERM
THE SHORTWAVE MOVING THROUGH THE LOWER OH VALLEY IS LEADING TO
SHOWERS ACROSS PARTS OF MIDDLE TN AND CENTRAL KY. THE LATEST NAM
SUGGESTS LAPSE RATES WILL STEEPEN FOR A WINDOW OF TIME THROUGH ABOUT
17Z OR 18Z. THIS WILL LEAD TO ISOLATED SHOWERS AND AN INCREASE IN THE
STRATOCU AT THE LEAST. ALSO...RECENTLY THE VWP HAS HAD WINDS NEAR
30KT OR HIGHER AT 2KFT MSL....WITH 40KT AT 4KFT MSL AND AT 6KFT
MSL...50 KT. THE 0Z NAM SUGGESTS WINDS AT AROUND 15Z WILL BE THE
HIGHEST AT 850 MB GENERALLY FROM EKQ TO JKL TO HTS AND SE. BY 18Z...
THE NAM FORECASTS 850 MB WINDS FROM ABOUT 45KT SW TO ABOUT 50KT OVER
NEARLY ALL OF THE AREA AT 18Z AND 43 TO 47KT AT 21Z. MEANWHILE...NAM
1000 TO 700 MB LAYER WINDS ARE FORECAST TO BE 45 TO 50 KT AT
15Z...INCREASE TO 46 TO 51Z AT 18Z AND REMAIN 45 TO 50 KT AROUND 21Z.
SINCE MIXING IS EXPECTED TO REACH TO 800 MB OR HIGHER DURING THE 16Z
TO 20Z TIMEFRAME...WINDSPEEDS IN THAT LAYER ARE FORECAST TO BE 53 TO
60KT AT 15Z...49 TO 61KT AT 18Z AND 48 TO 58KT BY 21Z. THIS WILL ALL
LEAD TO THE PEAK WIND GUSTS IN THE 11 AM TO 4 PM TIMEFRAME. DURING
THIS PERIOD GUSTS AROUND 50KT OR ABOUT 60 MPH ARE MOST
LIKELY...THOUGH GUSTS AROUND 50 MPH ARE POSSIBLE OUTSIDE OF THIS
WINDOW THROUGH AS LATE AS 2Z OR SO.
OTHERWISE...TEMPERATURES WILL ALSO FALL THROUGH THIS AFTERNOON LIKELY
DROPPING TO THE MID 40S WEST AND NEAR 50 EAST AROUND 18Z AND THEN TO
THE MID 30S TO AROUND 40 BY 22Z. WRAPAROUND MOISTURE SHOULD ARRIVE
18Z TO 19Z THROUGH 22Z AND LEAD TO SOME ISOLATED RAIN SHOWERS AND
POSSIBLY ISOLATED RAIN AND SNOW SHOWERS 20Z TO 0Z AS THE ATMOSPHERE
CONTINUES TO COOL OFF.
UPDATED GRIDS AND AN UPDATED ZFP AS WELL AS FRESHENED UP HWO AND NPW
HAVE ALREADY BEEN ISSUED.
THE PREVIOUS SHORT TERM FORECAST DISCUSSION FOLLOWS...
/THE REST OF TODAY/
UPDATED TO ACCOUNT FOR THE FRONT STARTING TO MOVE ACROSS THE AREA.
THE FRONT IS NEARING THE INTERSTATE 75 CORRIDOR. THE FRONT THIS FAR
SOUTH HAS BEEN RATHER INACTIVE...BUT WILL LEAVE A SLIGHT CHANCE FOR
SHOWERS EARLY AND THEN HIGHLIGHT ISOLATED SHOWERS RETURNING LATE WITH
THE DRY SLOT IN THE MIDDLE. WINDS WILL TURN TO THE SOUTHWEST IN ALL
AREAS THROUGH 12Z TO 13Z AND INCREASE...ESPECIALLY AS THE SUN COMES
UP AND WE GET INTO THE WARM SECTOR. FALLING TEMPERATURES STILL LOOK
IN STORE LOOKING AT UPSTREAM OBS.
THE PREVIOUS SHORT TERM FORECAST DISCUSSION FOLLOWS...
/TODAY THROUGH THURSDAY NIGHT/
THE PRECIP PART OF THE EVENT ASSOCIATED WITH THE POTENT MIDWEST LOW
NOW OVER WESTERN IL IS WINDING DOWN...BUT NOT BEFORE RAINFALL TOTALS
AVERAGING IN THE 1.5 TO 2.5 INCH RANGE IN MANY AREAS GENERALLY FROM
SME TO JKL TO INEZ AND NORTH TO THE INTERSTATE 64 CORRIDOR AND THEN
ANOTHER AREA FROM SE MCCREARY COUNTY EAST THROUGH MUCH OF HARLAN
COUNTY. SOME AREAS NEAR THE KY 80 CORRIDOR OVER THE S FK KY RIVER
BASIN APPEAR TO HAVE HAD OVER 2 INCHES AS WELL WHEN COMBINING KY
MESONET...IFLOWS AND RAWS AND ASOS/AWOS DATA. THERE IS STILL SOME
THREAT FOR AREAL FLOODING ALONG THE LARGER STREAMS AND CREEKS AS THE
RAIN FROM THE PAST 18 HOURS COLLECTS IN THEM. DOWNSTREAM OF THESE
SIGNIFICANT RISES WILL ALSO OCCUR ON THE AREA RIVERS...ESPECIALLY THE
SOUTH FORK OF THE KY AND THE MAIN STEM AS WELL AS THE RED RIVER AND
POSSIBLY PARTS OF THE UPPER CUMBERLAND.
THE MAIN CONCERN HOWEVER FOR TODAY IS WITH THE WEST SOIL DUE TO
RECENT HEAVY RAIN COMBINED WITH THE POTENT POST FRONTAL SUSTAINED
WINDS AND WIND GUSTS ANTICIPATED STARTING ALONG THE FRONT BETWEEN
NOW AND ABOUT 12Z TO 13Z WHEN IT CLEARS THE EASTERN CWA AND THEN FOR
SEVERAL HOURS TODAY THROUGH ABOUT MID AFTERNOON. DURING THIS PERIOD
WIND GUSTS OF 50KT OR HIGHER ARE ANTICIPATED FOR A FEW HOURS. HOWEVER...
STRONG WINDS WILL REMAIN ALOFT EVEN EARLY IN THE EVENING...AND SO
WILL THE POTENTIAL FRO GUSTS AS THE LOW DEPARTS TO THE NE AND HIGH
PRESSURE BUILDS TOWARD THE TN AND OH VALLEY. THE PRESS GRADIENT
BETWEEN THE SYSTEMS WILL REMAIN RATHER TIGHT EVEN INTO MIDDAY ON THU
WHEN HEIGHT RISES AND HIGH PRESS WORK INTO THE REGION. IN SUMMARY...THE
HIGH WIND WARNING APPEARS WELL WARRANTED AND WILL BE CONTINUED WITH
THE EXPIRATION TIME AS IS.
ON THE STRONG AND GUSTY POST FRONTAL WINDS TODAY...A COLDER AIRMASS
WILL ADVECT INTO THE REGION WITH HIGHS IN THE 12Z TO 15Z TIMEFRAME
AND THEN FALLING TEMPS AFTER THAT. THE WIND GUSTS AS MENTIONED ABOVE
WILL MIX DOWN LIKELY MOST READILY IN THE DRY SLOT EVIDENT ON THE WV
AND IR IMAGERY OVER MUCH OF EASTERN ARKANSAS DON INTO LA AND NE INTO
CENTRAL KY. THE FRONT HAS BEEN RATHER INACTIVE RECENTLY AS FAR AS
SHOWER ACTIVITY WITH THE SYSTEM SHEARING TO THE NE. WE HELD ONTO SOME
SLIGHT TO LOW END CHANCE POPS JUST IN CASE FOR EARLY IN THE MORNING.
THE WRAPAROUND MOISTURE COMBINED WITH COLDER TEMPS ALOFT WILL ARRIVE
THROUGH THE AFTERNOON TO EARLY EVENING AND LEAD TO A SLIGHT CHANCE TO
CHANCE FOR SHOWERS AGAIN LATER IN THE DAY. AS TEMPS COOL ALOFT AND AT
THE SFC...SOME SNOW MAY MIX WITH THE RAIN FROM WEST TO EAST...WITH
ANY PRECIP PRIMARILY SNOW ALONG THE WESTERN TIER BY 22Z OR SO. THERE
COULD BE SOME ENHANCEMENT ALONG THE ESCARPMENT AND OTHER N TO SOUTH
ORIENTED RELATIVE RIDGE-LINES ACROSS THE AREA WITH THE SNOW SHOWER
ACTIVITY THAT SHOULD BE AT ITS HEIGHT BETWEEN 0Z AND 6Z. RATHER LOW
PW OF 0.25" OR LESS AND SHALLOW LAYER FOR CONVECTION SHOULD LIMIT ANY
AMOUNTS AND DURATION OF THIS EVENT...BUT A LIGHT DUSTING OF THE WHITE
STUFF IS POSSIBLE...ESPECIALLY RIDGETOPS. TEMPS WILL CONTINUE TO FALL
THROUGH TONIGHT WITH THE COLD ADVECTION WITH THE WEST AND HIGH
TERRAIN THE COLDEST AND BIG SANDY VALLEY THE WARMEST.
8H TEMPS OF -12C TO -15C EVEN WITH A DRY AIRMASS MOVING IN ASSOCIATED
WITH THE RIDGING SHOULD LEAD TO TEMPS STRUGGLING TO REACH 30 IN MANY
AREAS OR BELOW MOS VALUES. WITH THE RIDGE OF HIGH PRESSURE AND SFC HIGH
TO BUILD IN AND SLACKENING GRADIENT ON THU NIGHT ALONG WITH DEWPOINTS
OF AROUND 10 OF LESS EXPECTED TEMPS WILL LIKELY FALL BELOW MOS
VALUES AND SOME UPPER SINGLE DIGIT READINGS CANNOT BE RULED OUT
ACROSS THE HIGHER TERRAIN AND IN NORMALLY COLDER SPOTS.
.LONG TERM.../THURSDAY THROUGH TUESDAY/
MODELS HAVE DIVERGED A BIT IN THEIR RESPECTIVE SOLUTIONS OVER THE
PAST 24 HOURS...ESPECIALLY WITH RESPECT TO LOWER LEVEL FEATURES.
MAIN CHANGES TO THE EXTENDED PORTION OF THE FORECAST WERE TO TREND
TOWARDS LATEST ECMWF WHILE KEEPING SOME CONTINUITY WITH NATIONAL
GUIDANCE. IN GENERAL OUR AREA REMAINS UNDER THE INFLUENCE OF ZONAL
FLOW. BUT THE ECMWF CONTINUES TO TREND SLOWER AND WEAKER WITH
INITIAL SHORT WAVE TRACKING THROUGH THE CONUS OVER THE WEEKEND...
AND CONSEQUENTLY WITH RETURN OF MOISTURE LATE SATURDAY INTO SUNDAY.
TRIMMED TIMING OF POPS BACK SIGNIFICANTLY SATURDAY...FOCUSING
HIGHEST POPS IN A SATURDAY NIGHT...EARLY SUNDAY WINDOW. STILL CAN
NOT RULE OUT SOME MIXED PRECIPITATION CLOSER TO THE ONSET OF PRECIP
SATURDAY EVENING NORTH OF THE MOUNTAIN PARKWAY. BUT WITH THE OVERALL
SLOWER TREND IN EVOLUTION OF EVENTS...FELT THIS POTENTIAL WAS TOO
LOW TO MENTION IN THE FORECAST ATTM. THEREFORE KEPT THE BULK OF
PRECIPITATION AS RAIN FOR NOW. WILL READDRESS AS WE GET CLOSER TO
THE WEEKEND...AND MODELS HOPEFULLY CONGEAL ON A SOLUTION.
OTHERWISE...MORE SIGNIFICANT SHORT WAVE TROUGH MOVES INTO THE REGION
LATE MONDAY INTO TUESDAY. THERE CONTINUES TO BE SIGNIFICANT TIMING
ISSUES WITH THIS SECOND SYSTEM SO USED A BROAD BRUSH APPROACH FOR
THE LATTER PORTION OF THE FORECAST...GOING GENERALLY WITH CHANCE
POPS AND A SMALLER DIURNAL TREND TO TEMPS WITH ON AVERAGE MORE CLOUD
COVER THAN NOT.
&&
.AVIATION.../18Z TO 18Z/...UPDATED
WINDS ARE STILL INCREASING AND MIXING THE LOW LEVEL JET TO THE
SURFACE ACROSS EAST KY WITH POTENTIAL TO REACH 50+ KT GUSTS UNTIL
MID-AFTERNOON. WINDS WILL GRADUALLY SUBSIDE LATE TODAY AS THE SYSTEM
MOVES OFF TO THE NORTHEAST. LIGHT RAIN/SNOW SHOWERS ARE POSSIBLE THE
REST OF TODAY BUT MAINLY OVER THE NORTH PORTION. THREAT FOR LOW LEVEL
WIND SHEAR IS DECREASING AS LOW LEVELS ARE MIXED AND WINDS ALOFT WEAKEN
THROUGH THE DAY.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
HIGH WIND WARNING UNTIL 10 PM EST THIS EVENING FOR KYZ044-
050>052-058>060-068-069-079-080-083>088-104-106>120.
&&
$$
SHORT TERM...JP
LONG TERM....JP
AVIATION...GV
