FXUS63 KJKL 010551
AFDJKL
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON KY
1251 AM EST TUE DEC 1 2009
.SHORT TERM.../THE REST OF TONIGHT/
SPOTTER AND NWS EMPLOYEE REPORTS INDICATE PATCHY DENSE FOG IS
PERSISTING IN THE VALLEYS. IN ADDITION...WE HAD A SPOTTER REPORT OF
SOME ICING ON A COUPLE OF OBJECTS IN LEE COUNTY. 11-3.9 WV IMAGERY
CONTINUES TO INDICATE POSSIBLE DENSE FOG IN THE EASTERN RIVER VALLEYS...
SUCH AS THE KENTUCKY RIVER AND BIG SANDY RIVER BASINS. AT THE SAME TIME...
CWOP AND KY MESONET SITES INDICATE SEVERAL VALLEY LOCATIONS AT OR
BELOW FREEZING. WITH THIS IN MIND...HAVE UPDATED THE HWO AND GRIDS TO
INCLUDE PATCHY DENSE FOG AND FREEZING FOG OVERNIGHT. FOR NOW WE HAVE
HANDLED THIS WITH AN SPS...SINCE THE STRATOCU MOVING ACROSS THE AREA...
AND EXPANDING MAY TEND TO KEEP IT FROM GETTING TOO WIDESPREAD.
THE PREVIOUS SHORT TERM FORECAST DISCUSSION FOLLOWS...
/THE REST OF TONIGHT/
HIGH PRESSURE AT THE SFC AND ALOFT CONTINUES TO BUILD INTO THE
REGION IN THE WAKE OF AN UPPER LEVEL SHORTWAVE TROUGH. SKIES HAVE
CLEARED OUT IN MANY AREAS...WITH A FEW PATCHES OF STRATOCU TRAVERSING
THE AREA. VALLEY FOG APPEARS TO BE OVER THE EASTERN VALLEYS...ESPECIALLY
THE BIG SANDY REGION ATTM...AND LOZ HAS REPORTED SOME BR DURING THE
PAST FEW HOURS.
HAVE FRESHENED UP THE GRIDS FOR THE LATEST TRENDS TO ACCOUNT FOR THE
PATCHY STRATOCU AND TEMPS AT MANY MESONET SITES RUNNING A DEGREE OR
TWO BELOW THE PREVIOUS FORECAST. ALSO...BROUGHT IN FOG A LITTLE FASTER
THAN THE PREVIOUS FORECAST. WITH THE COLDER START OPTED TO LOWER MIN
T A FEW DEGREES IN SOME LOCATIONS BASED ON THE COLDER START. WE
JUST RECEIVED A SPOTTER REPORT OF DENSE FOG FROM HAZARD RECENTLY...SO
THIS TREND WILL HAVE TO BE MONITORED AND ANY POTENTIAL FOR FREEZING
FOG AS WELL. WE PLAN TO MAKE A COUPLE OF CALLS TO KSP POSTS SHORTLY
AND AT LEAST AN SPS FOR SOME PATCHY DENSE FOG OR AREAS OF DENSE FOG
MAY BE IN ORDER.
THE PREVIOUS SHORT TERM FORECAST DISCUSSION FOLLOWS...
/TONIGHT THROUGH TUESDAY/
PRECIPITATION IS COMING TO AN END ACROSS THE AREA THIS AFTERNOON WITH
NOTHING MORE THAN A FEW RENEGADE SHOWERS AND SOME PATCHY DRIZZLE TO
SPEAK OF. HOWEVER...SYSTEMS UPPER LEVEL TROUGH AXIS IS STILL OVER
CENTRAL PORTIONS OF THE COMMONWEALTH AND WILL NOT BE THROUGH THE AREA
FOR ANOTHER 6 HOURS OR SO. CONSEQUENTLY...LINGERING LOW CLOUD COVER
WILL BE THE MAIN FORECAST CHALLENGE FOR THE SHORT TERM PERIOD AND
WILL PLAY A MAJOR ROLE IN THE POTENTIAL OF OVERNIGHT FOG FORMATION.
THE NAM APPEARS TO HAVE THE BEST HANDLE ON ONGOING EVENTS...AND FCST
SOUNDINGS ALONG WITH TIME HEIGHT SECTIONS HOLD ON TO SOME LOW LEVEL
MOISTURE THROUGH AT LEAST THE FIRST SEVERAL HOURS OF THE FCST WINDOW.
SO DELAYED MOST SIGNIFICANT CLEARING ACROSS THE AREA UNTIL LATE THIS
EVENING. RAPID CLEARING LATE...COMBINED WITH SLACKENING WINDS AND
ADDED BOUNDARY LAYER MOISTURE FROM RECENT RAINFALL SHOULD SET THE
STAGE FOR SOME FOG FORMATION LATE TONIGHT OR POSSIBLY TOWARDS DAWN...
PARTICULARLY FOR OUR VALLEY LOCATIONS. THEREAFTER...SHORT WAVE
RIDGING AND SFC HIGH PRESSURE WILL PROVIDE DRY AND FAIR WEATHER.
THERE WAS GOOD AGREEMENT IN GUIDANCE...AND THEREFORE DID NOT STRAY
FAR FROM MOS TEMPS.
.LONG TERM.../TUESDAY NIGHT THROUGH MONDAY/
AT THE START OF THE PERIOD...CLOSED LOW THAT HAD BEEN PARKED OVER
THE SOUTHWEST CONUS WILL EJECT EASTWARD TO IN RESPONSE TO 110 KNOT
SUBTROPICAL JET. THIS EASTWARD EJECTION WILL BE IN RESPONSE TO RAMPED
UP 100-110 KNOT SUBTROPICAL JET CORE TRAVERSING THE SOUTH CONUS.
MEANWHILE...THE POLAR JET BEGINS TO CARVE OUT ANOTHER TROUGH OVER
THE NORTHERN PLAINS...DRAGGING A TRULY POLAR AIRMASS WITH IT. GFS
HAS BACKED AWAY FROM STRONGER PHASING BETWEEN POLAR AND SUBTROPICAL
JETS AND AS A RESULT SURFACE LOW DEVELOPS OVER THE WEST GULF COAST
AND MOVES TOWARD THE CWA WITH OVERRUNNING PRECIPITATION BEGINNING
EARLY WEDNESDAY FROM SOUTHWEST TO NORTHEAST. HAVE GONE CATEGORICAL
POPS ON WEDNESDAY...EXCEPT IN THE SOUTHEAST WHERE STRONG DOWNSLOPE
COMPONENT WITH LOW TO OUR SOUTHWEST WILL KEEP THINGS A LITTLE DRIER.
SURFACE LOW IS PROGGED TO TRAVERSE THE AREA WEDNESDAY NIGHT...AS
MODELS HAVE COME INTO MUCH BETTER AGREEMENT ON THE TRACK. THIS DRAGS
THE POWERFUL COLD FRONT THROUGH THE AREA WITH STRONG CAA ON THE BACK
SIDE AND A LATE CHANGEOVER TO A RAIN SNOW MIX LATE ON WEDNESDAY
NIGHT. EXPECT NO ACCUMULATION WITH THIS CHANGE OVER AS GROUND WILL
STILL BE QUITE WARM. STILL WILL BE OPTIMISTIC THAT THERE COULD BE A
SLIGHT DIURNAL WARM UP ON THURSDAY...HOWEVER WILL MOST LIKELY SEE
NEAR STEADY OR FALLING TEMPERATURES.
BY THURSDAY NIGHT...CONTINUED STRONG COLD AIR ADVECTION SHOULD ALLOW
FOR A CHANGE OVER TO ALL SNOW. A LACK OF DEEP MOISTURE AT THIS POINT
WILL KEEP THINGS LIMITED TO VERY LIGHT SNOW AND MOST LIKELY JUST
FLURRIES. AS A RESULT...AM NOT GOING WITH ANY ACCUMULATION OTHER
THAN JUST A DUSTING ON THE RIDGETOPS FROM THURSDAY NIGHT THROUGH
SUNDAY MORNING. THE HIGHEST RIDGES NEAR THE VIRGINIA BORDER COULD
SEE AN INCH OR SO BY THE TIME THE EVENT ENDS. 12Z EURO DID COME IN
WITH MORE QPF THROUGH THE WEEKEND AND WITH UPSLOPE FLOW AND STEEP
LAPSE RATES FROM HIGHLY AMPLIFIED H5 TROUGH...COULD SEE SOME LARGER
SNOWFALL TOTALS ON RIDGES. WILL KEEP AN EYE ON THIS IN CASE HIGHER
POPS/SNOW TOTALS ARE WARRANTED. FOR NOW WILL HANG ON TO 20 POPS FOR
MOST OF THE WEEKEND.
RELIED MORE ON RAW MODEL TEMPERATURES AFTER THE FRONTAL PASSAGE...AS
THESE USUALLY WORK BETTER FOR STRONG SYNOPTIC SYSTEMS. THIS RESULTS
IN HIGHS AND LOWS MAINLY BELOW GUIDANCE FROM WEDNESDAY NIGHT ON.
COULD END UP WITH A SIZABLE RIDGE AND VALLEY SPLIT ON TUESDAY NIGHT
...ESPECIALLY IN THE EASTERN VALLEYS WERE SKY COVER IS DELAYED.
UPPER TWENTIES IN THE COLDEST VALLEYS WITH UPPER 30S ON THE RIDGES
SEEMS REASONABLE. WARM AIR ADVECTION AHEAD OF THE LOW ON WEDNESDAY
COULD JUMP THE MERCURY UP TO THE LOWER 50S BEFORE FROPA...HOWEVER
THIS IS STILL BELOW GUIDANCE IN THE LOW TO MID 50S.
&&
.AVIATION.../06Z TO 06Z/...UPDATED
AN AREA OF BKN STRATOCU WITH BASES ABOUT 4K MSL WILL CONTINUE TO
MOVE EAST AND SHOULD MOVE OUT OF EASTERN KENTUCKY BETWEEN 8 AND 9Z.
SOME PATCHES OF DENSE FOG HAVE ALREADY FORMED. THE FOG WOULD HAVE
BEEN MORE WIDESPREAD IF IT HAD NOT BEEN FOR THE STRATOCU DECK. WITH
THE DECK MOVING OUT...EXPECT THE FOG TO GET MORE DENSE WITH SOME
VLIFR CONDITIONS...MAINLY IN THE TYPICAL RIVER VALLEYS. EXPECT THE
LOZ AND SME TO BE MVFR AND JACKSON TO STAY VFR. THERE MAY BE SOME
TEMPO MVFR AT JKL AS THE FOG LIFTS OUT OF THE VALLEYS...HOWEVER WILL
NOT INCLUDE IT IN THE TAF. AFTER 13Z...IT WILL STAY VFR UNTIL AROUND
14 TO 15Z ON WEDNESDAY AS THE NEXT FRONT MOVES INTO THE AREA.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
SHORT TERM...RAY/JP
LONG TERM....SCHOETTMER
AVIATION...JJ
