FXUS63 KJKL 010312 AAB
AFDJKL
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE JACKSON KY
1012 PM EST MON NOV 30 2009
.SHORT TERM.../THE REST OF TONIGHT/...UPDATED
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
CNTRL 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 WARMUP 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.../00Z TO 24Z/
LINGERING PRECIPITATION HAS EXITED INTO VA AS AN UPPER LEVEL TROUGH
SHIFTS EAST OF THE REGION. UPPER LEVEL AND ASSOCIATED SFC HIGH PRESSURE
WILL QUICKLY BUILD INTO THE AREA TONIGHT. THIS WILL LEAD TO CLEARING
SKIES BETWEEN 0Z AND 6Z...THOUGH SOME PATCHES OF THE STRATOCU WILL
TRANSIT THE REGION DURING THIS PERIOD. NEAR THE WV AND VA BORDERS A
FEW PATCHES OF STRATOCU SHOULD LINGER AS LATE AS 8Z...BUT THESE
CLOUDS WILL AVERAGE IN THE 3K TO 5K FT RANGE...FOR GENERALLY VFR
CONDITIONS. ONCE SKIES CLEAR...THERE IS A POSSIBILITY OF SOME MVFR FOG
IN THE VALLEYS WITH WET GROUND FROM RECENT PRECIPITATION IN PLACE.
AT THIS POINT...CONFIDENCE IN ANY VIS REDUCTIONS BELOW 5SM IS NOT
THAT HIGH WITH DRIER AIR WORKING IN AT THE SFC...SO ONLY BROUGHT SME
AND LOZ DOWN TO 6SM. ONLY SOME THIN HIGH CLOUDS ARE EXPECTED AFTER
12Z...SO VFR WILL PREVAIL FOR MOST OF...IF NOT THE ENTIRE PERIOD AT
THE TAF SITES. WINDS ARE EXPECTED TO BE LIGHT.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
SHORT TERM...RAY/JP
LONG TERM....SCHOETTMER
AVIATION...JP
