FXUS63 KLMK 062339
AFDLMK
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
639 PM EST SUN DEC 6 2009
...UPDATED AVIATION DISCUSSION...
.SHORT TERM (TONIGHT AND MONDAY)...
A WEAK SFC LOW WILL MOVE FROM THE SOUTHERN PLAINS TO THE GREAT LAKES
TONIGHT UP THE SPINE OF AN INVERTED TROUGH ALREADY IN PLACE. THIS
LOW WILL THEN DRAG A WEAK FRONTAL BOUNDARY OVER THE AREA TOMORROW
AFTERNOON. THE PAST FEW MODEL RUNS HAVE REALLY DECREASED THE
MOISTURE WITH THIS SYSTEM AND SO HAVE LOWERED POPS TO 20% FOR LATE
TONIGHT AND TOMORROW MORNING. THINK THAT THERE/S STILL A SMALL
CHANCE FOR A RAIN/SNOW MIX CHANGING OVER TO ALL RAIN...BUT MOST
AREAS SHOULD STAY DRY THROUGH TOMORROW AFTERNOON. POPS MAY NEED TO
BE PULLED THIS EVENING IF THE SYSTEM COMPLETELY LOSES MOISTURE
BEFORE ARRIVAL. ANY PRECIP SHOULD CEASE AFTER 18Z TOMORROW WHEN THE
WEAK FRONTAL BOUNDARY PASSES THROUGH.
LOW TEMPS TONIGHT LOOK TO DROP INTO THE LOW 30S WITH A FEW UPPER
20S. HIGHS TOMORROW WILL BE HINDERED BY PLENTIFUL CLOUD COVER.
EXPECT TEMPS TO REACH THE LOWER 40S TOMORROW AFTERNOON.
.LONG TERM (MONDAY NIGHT - SUNDAY)...
HIGH PRESSURE WILL BE OVER THE NORTHERN APPALACHIANS AS FLOW ALOFT
BECOMES MORE SOUTHWESTERLY ON TUESDAY. BY 00Z WEDNESDAY EXPECT
CYCLOGENESIS OVER THE SOUTHERN PLAINS AS POTENT
SHORTWAVE...CURRENTLY OVER THE PACIFIC NORTHWEST STATES...ROTATES
OVER THE ROCKIES. MODELS ARE IN DECENT AGREEMENT ON THE STRENGTH OF
THIS SYSTEM AS IT CROSSES FROM OK TO MO AND THEN NEAR CHICAGO EARLY
WEDNESDAY MORNING. RUN TO RUN AGREEMENT IS ALSO INCREASING
CONFIDENCE IN A WET AND POSSIBLY STORMY SCENARIO. ALSO...ENSEMBLE
FORECASTS INDICATE A SIGNIFICANTLY BELOW-NORMAL LOW PRESSURE SYSTEM
MOVING ACROSS THE SAME REGION AS THE DETERMINISTIC FORECAST.
SOUNDINGS HAVE HIGH LOW LEVEL WIND SHEAR...BUT ALSO A STABLE LAYER
UP TO AROUND 850 MB...EVEN AS THE WARM FRONT ASSOCIATED WITH THIS
LOW BRINGS IN WARMER AND MORE MOIST SURFACE AIR. WINDS AT 850 RANGE
FROM 60-75 KNOTS DEPENDING ON THE MODEL. GIVEN THE STABLE LAYER HAVE
IT WILL BE DIFFICULT TO REALIZE A WIDESPREAD SEVERE WEATHER
OUTBREAK...BUT SHOULD ANY STORMS BECOME STRONG ENOUGH MAY SEE THE
WINDS ALOFT MIX DOWN TO THE SURFACE LATE TUESDAY NIGHT. AND EVEN
WITHOUT STORMS...EXPECT ENOUGH LOW-LEVEL MOMENTUM TRANSFER TO
PRODUCE A WINDY NIGHT.
FOR RAINFALL...EXPECT OVERRUNNING TO START BRINGING IN RAINS LATE
TUESDAY AFTERNOON. THEN AS THE WARM FRONT IS IN THE AREA LATE
EVENING WILL SEE MORE INDIVIDUAL CELLS DEVELOP. THUS WILL CONTINUE
CATEGORICAL POPS FOR TUESDAY NIGHT. RAINFALL TOTALS FROM THE
ENSEMBLE MEMBERS RANGE FROM A QUARTER OF AN INCH TO ONE AND A HALF
INCHES...SO WILL GO ROUGHLY IN BETWEEN FOR QPF.
WEDNESDAY WILL BE WINDY AS THE LOW CONTINUES STRENGTHENING OVER THE
CENTRAL GREAT LAKES AND CANADIAN HIGH PRESSURE BUILDS IN FROM THE
WEST. MAY ALSO SEE SOME LIGHT RAIN ON THE BACK SIDE OF THE FRONT
BEFORE WE DRY OUT WITH THE HIGH BUILDING IN. MAY HAVE A TRANSITION
TO LIGHT SNOW/FREEZING RAIN OVER OUR NORTHEAST CWA IN THE
EVENING...BUT NOT EXPECTING MUCH IN THE WAY OF ACCUMULATION.
FLOW ALOFT WILL BECOME ZONAL BEHIND THIS SYSTEM...AND GENERALLY
REMAIN THAT WAY THROUGH THE REST OF THE PERIOD. THURSDAY WILL SEE
MODERATE BREEZES AS THE PRESSURE GRADIENT WEAKENS AND THEN BY EARLY
FRIDAY THE HIGH CENTER WILL BE CLOSE TO THE REGION. WITH THE WIND
EXPECT THURSDAY MORNING TO FEEL THE COLDEST OF THE PERIOD...WITH
WIND CHILL READINGS POSSIBLY GETTING INTO THE SINGLE DIGITS.
FRIDAY MORNING'S LOWS SHOULD BE SIMILAR TO THURSDAY...BUT WINDS
SHOULD BE LIGHT. HIGH CLOUDS MAY MOVE IN WITH AN UPPER LEVEL SYSTEM
OVERNIGHT...AND THAT WOULD PREVENT TEMPERATURES FROM DROPPING TOO
FAR. SOUNDINGS ALSO INDICATE PLENTY OF MOISTURE IN THE SNOW-GROWTH
ZONE THROUGH THE DAY FRIDAY...BUT DRY LOW LEVELS SHOULD DISSIPATE
ANY PRECIP UNTIL PERHAPS LATE IN THE DAY/EVENING OVER THE NORTHERN
CWA.
THE NEXT WEEKEND LOOKS DRIER THAN IN PREVIOUS FORECASTS DESPITE A
SERIES OF UPPER LEVEL DISTURBANCES MOVING ACROSS THE CWA WITHIN THE
ZONAL FLOW. GIVEN THE FAST MOVING NATURE OF THE FLOW AND DIFFICULTY
IN PREDICTING THESE SMALLER DISTURBANCES OUT TO DAY 6-7...WILL LOWER
RAIN CHANCES TO SLIGHT FOR SATURDAY AND NOT MENTIONABLE SUNDAY AND
KEEP TEMPERATURES FAIRLY CONSTANT GIVEN THE NEAR-STEADY LOW LEVEL
THICKNESSES.
&&
.AVIATION (00Z TAF ISSUANCE)...
CIGS WILL LOWER TONIGHT BUT REMAIN VFR AS A WEAKENING UPR LEVEL TROF
AND FRONTAL SYS APPROACHES FROM THE WEST. CIGS WILL REACH MVFR
LEVELS AFTER SUNRISE MON AS WINDS INCREASE A BIT AND SHIFT TO SW.
SOME VERY LIGHT PRECIP...IN THE FORM OF RAIN OR SNOW...COULD
APPROACH BWG IN THE PREDAWN HRS MON AND AROUND SUNRISE AT SDF AND
LEX...HOWEVER AT THIS TIME...PRECIP LOOKS TO BE TOO SPARSE AND
LIKELY WILL NOT AFFECT VSBY...TO INCLUDE IN THESE TAFS.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
KY...NONE.
IN...NONE.
&&
$$
SHORT TERM........AML
LONG TERM.........RJS
AVIATION..........DK/11
