FXUS63 KLMK 030818
AFDLMK
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
318 AM EST THU DEC 3 2009
.SHORT TERM (TODAY AND TONIGHT)...
AT 08Z THE LAST SMALL AREAS OF PRECIPITATION FROM WEDNESDAY/S STORM
SYSTEM WERE PULLING OUT OF THE LMK CWFA...WITH JUST A FEW PATCHES OF
DRIZZLE LEFT. RADARS UPSTREAM HAVE BEEN DRYING UP OVER THE PAST FEW
HOURS. A FEW SPRINKLES OR A PATCH OR TWO OF VERY LIGHT DRIZZLE WILL
BE POSSIBLE EARLY THIS MORNING...BUT FOR THE MOST PART IT LOOKS LIKE
OUR PRECIPITATION IS QUICKLY COMING TO AN END.
LOW LEVEL MOISTURE..GENERALLY AT AND BELOW 5000 FEET...LOOKS TO GET
TRAPPED UNDER AN INVERSION TODAY RESULTING IN CONTINUED WIDESPREAD
CLOUD COVER. THE CLOUDS SHOULD PARTIALLY BREAK UP TONIGHT AS DRIER
AIR MOVES IN ON THE NOSE OF HIGH PRESSURE COMING OUT OF THE PLAINS.
TEMPERATURES WILL BE CHILLY TODAY WITH HIGHS ONLY IN THE LOWER AND
MIDDLE 40S. HOWEVER WITH YESTERDAY/S LOW PRESSURE MOVING AWAY AND A
WEAKER PRESSURE GRADIENT THE WINDS WON/T BE AS STRONG AS THEY WERE
ON WEDNESDAY...WITH SPEEDS OUT OF THE WEST AROUND 10 MPH.
LOW TEMPERATURES TONIGHT WILL BE GREATLY DEPENDENT ON CLOUD
COVER...RIGHT NOW WILL GENERALLY GO WITH MIDDLE 20S WITH A GENTLE
WEST BREEZE.
.LONG TERM (FRIDAY - WEDNESDAY)...
TWO MAIN WEATHER SYSTEMS ARE OF CONCERN IN THE LONG TERM PERIOD.
OVERALL...00Z OPERATIONAL MODELS (GFS...ECMWF...GEM) ARE REASONABLY
SIMILAR THROUGHOUT PERIOD...LENDING SOME CONFIDENCE TO DAY TO DAY
EVOLUTION OF SYSTEMS.
THE FIRST SYSTEM COULD AFFECT OUR SERN FCST AREA LATE FRI NIGHT AND
SAT. MODELS ARE CONSISTENT IN SHOWING THAT A SRN STREAM SHORTWAVE
WILL ROTATE NEWD ON SRN FLANK OF MEAN 500 MB TROF AXIS. THE EXACT
PATH OF THIS SHORTWAVE WILL BE CRUCIAL TO SENSIBLE WEATHER DURING
THIS PERIOD. PRIMARY LOW-LEVEL JET WITH THIS SYSTEM WILL REMAIN SE
OF OUR FCST AREA. HOWEVER...MODELS SUGGEST SOME 850-700 MB
FRONTOGENETICAL FORCING OVER SERN KY...POSSIBLY INCLUDING A FEW OF
OUR SERN COUNTIES IN CNTRL KY. THERE IS ALSO WEAK 700-500 MB
FRONTOGENETICAL FORCING TO THE NW OF THIS AREA SUGGESTING A GOOD MID
DECK OF CLOUDS OVER MUCH OF CNTRL KY FRI NIGHT INTO SAT. FROM AN
UPPER-LEVEL JET PERSPECTIVE...A NICE SRN STREAM W TO E ORIENTED JET
AXIS IS SHOWN OVER THE GULF STATES WITH THE ENTRANCE REGION OF A NRN
STREAM JET OVER THE TN VALLEY. THIS WOULD ENHANCE UPPER-LEVEL
DIVERGENCE AND DEFORMATION OVER THE SRN APPALACHIANS INCLUDING ERN
TN AND INTO SERN KY. TEMPS SHOULD BE COLD ENOUGH FOR FROZEN PRECIP
DURING EVENT. BEST CHANCE OF SNOW WILL BE OVER SERN KY (EAST OF OUR
FCST AREA) WHERE SOME ACCUMULATION IS POSSIBLE. WILL INSERT A
SMALLER CHANCE OF SNOW FOR NOW OVER A TIER OF OUR SERN COUNTIES.
OPERATIONAL MODELS WOULD SUGGEST THAT A CHANCE OF LIGHT SNOW OR AT
LEAST FLURRIES WOULD EXIST FARTHER WEST ACROSS PARTS OF S-CNTRL INTO
E-CNTRL KY. HOWEVER...00Z ENSEMBLES ARE SLIGHTLY FARTHER EAST WITH
PRECIP THAN OPERATIONAL MODELS. AGAIN...PATH OF SHORTWAVE WILL BE A
BIG DETERMINING FACTOR FOR THIS SYSTEM... ALTHOUGH MODELS HAVE BEEN
QUITE CONSISTENT FOR THE LAST FEW MODEL RUNS ON THE PATH OF THE
SYSTEM. FCST WILL BE REFINED AS LATER MODEL AND OBSERVATIONAL
GUIDANCE BECOMES AVAILABLE.
THIS SYSTEM WILL RACE NE OUT OF THE AREA BY SAT AFTERNOON AND
EVENING...LEAVING TRANQUIL WEATHER BEHIND. HIGH TEMPS SAT SHOULD
ONLY BE IN THE LOWER 30S OVER SERN FCST AREA WITH CLOUDS AND CHANCE
OF SNOW. ELSEWHERE...NOT MUCH BETTER...MAX TEMPS ONLY IN MID TO
UPPER 30S.
A SLIGHT MODERATION IN TEMPS OCCURS SUN AND MON WITH HIGHS GETTING
INTO THE 40S IN MOST AREAS. MODELS SUGGEST A WEAK SHORTWAVE PASSING
THROUGH AREA ON SUN NIGHT OR MON...BUT GIVEN UPPER-LEVEL JET
POSITION WITH THIS SYSTEM...ANY PRECIP SHOULD BE CONFINED TO THE
NORTH OF OUR FCST AREA (I.E. NORTH OF THE W TO E ORIENTED JET AXIS
ALOFT).
NEXT SIGNIFICANT WEATHER SYSTEM SHOULD AFFECT OUR AREA TUE AFTERNOON
INTO WED. THIS SYSTEM SHOULD HAVE ENOUGH WARM AIR WITH IT FOR A RAIN
EVENT OVER ENTIRE AREA...ALBEIT A CHILLY RAIN OVER NRN SECTIONS OF
OUR AREA. THIS LOOKS LIKE A DECENT RAIN EVENT AS SURFACE LOW
PRESSURE WORKS NEWD FROM THE SRN PLAINS/LOWER MS VALLEY INTO THE TN
AND LOWER OH VALLEYS. COLDER AIR FOLLOWS PASSAGE OF THE SYSTEM.
&&
.AVIATION (06Z TAF ISSUANCE)...
AS THE LOW PRESSURE SYSTEM THAT MOVED THROUGH THE AREA ON WEDNESDAY
PULLS OFF TO THE NORTHEAST WE WILL BE LEFT WITH SOME SCATTERED LIGHT
PRECIPITATION IN THE FIRST FEW HOURS OF THE TAF PERIOD...AND THEN
LOW CLOUDS FOR MUCH OF THE DAY THURSDAY. AS THE CLOUD SHIELD SLOWLY
SWEEPS THROUGH THE REGION MVFR CEILINGS CAN BE EXPECTED...WITH
OCCASIONAL FORAYS INTO HIGH-END IFR POSSIBLE EARLY THURSDAY MORNING.
THE CLOUDS LOOK TO LIFT A BIT THURSDAY AFTERNOON...AND THEN SCATTER
OUT THURSDAY EVENING.
WINDS WILL CONTINUE TO BE QUITE BRISK IN THE 10 TO 15 KNOT
RANGE...WITH HIGHER GUSTS...DURING THE OVERNIGHT HOURS BEFORE
SETTLING DOWN TO AROUND 10 KNOTS FOR THE DAY THURSDAY...AND CALMING
FURTHER THURSDAY EVENING AS SURFACE HIGH PRESSURE RIDGES IN. WIND
DIRECTION WILL BE CONSISTENTLY OUT OF THE WEST.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
KY...NONE.
IN...NONE.
&&
$$
SHORT TERM........13
LONG TERM.........TWF
AVIATION..........13
