FXUS64 KMEG 102331
AFDMEG
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEMPHIS TN
531 PM CST THU DEC 10 2009
.DISCUSSION...
UPDATED FOR 00Z AVIATION DISCUSSION.
&&
.PREV DISCUSSION... /ISSUED 352 PM CST THU DEC 10 2009/
DISCUSSION...
ARCTIC HIGH PRESSURE HAS BROUGHT THE COLDEST AIRMASS SO FAR THIS
YEAR TO THE MID SOUTH TODAY. THIS SYSTEM SHOULD MOVE DIRECTLY OVER
THE AREA TONIGHT AND ALLOW FOR EXCELLENT RADIATIONAL CONDITIONS
TO DEVELOP. MOSTLY CLEAR SKIES AND LIGHT WINDS WILL ALLOW
TEMPERATURES TO PLUMMET THIS EVENING WITH LOW TEMPERATURES
DROPPING INTO THE LOW AND MID TEENS OVER NORTHERN SECTIONS TO THE
LOWER 20S ACROSS SOUTHERN SECTIONS. HIGH CLOUDS MAY BEGIN TO
OVERSPREAD PORTIONS OF THE AREA LATE TONIGHT...BUT THIS SHOULD DO
LITTLE TO PREVENT THE VERY COLD TEMEPATURES. THIS HIGH PRESSURE
WILL REMAIN ENTRENCHED OVER THE REGION FOR THE REMAINDER OF THIS
WEEK WITH DRY WEATHER AND TEMPERATURES REMAINING SEVERAL DEGREES
BELOW NORMAL.
THE UPPER LEVEL PATTERN WILL BECOME INCREASINGLY SOUTHWESTERLY BY
THIS WEEKEND AS A LOW AMPLITUDE SHORTWAVE TRAVERSES ACROSS THE
SOUTHERN PLAINS AND TENNESSEE VALLEY. INCREASING ISENTROPIC
ASCENT IN ADVANCE OF THIS SHORTWAVE WILL OVERSPREAD THE MODIFYING
ARCTIC AIRMASS OVER THE REGION. LIGHT PRECIPITATION SHOULD DEVELOP
IN THE PRE-DAWN HOURS OF SATURDAY MORNING ACROSS PORTIONS OF
NORTHERN MISSISSIPPI AND SPREAD NORTHWARD ACROSS MUCH OF THE
REMAINDER OF THE MID SOUTH ON SATURDAY. TEMPERATURES ACROSS MUCH
OF THE REGION WILL LIKELY INITIALLY BE COLD ENOUGH NEAR THE
SURFACE SATURDAY MORNING ALONG AND SOUTH OF INTERSTATE 40 TO
SUPPORT A PERIOD OF WINTER WEATHER. WARM ADVECTION ABOVE A COLD
BOUNDARY LAYER ALONG WITH INITIAL EVAPORATIVE COOLING PROCESSES
SHOULD SUPPORT A MIX OF LIGHT RAIN...FREEZING RAIN...OR SLEET
SATURDAY MORNING ACROSS FAR NORTHERN MISSISSIPPI AND SOUTHERN
WEST TENNESSEE. ONLY EXPECTING MINOR ICE ACCUMULATIONS OVER THESE
LOCATIONS BEFORE WARM ADVECTION WARMS TEMPERATURES SUFFICIENTLY TO
CHANGE ALL MIXED PRECIPITATION TO RAIN BY LATE MORNING INTO EARLY
AFTERNOON.
FURTHER NORTH...ACROSS NORTHEAST ARKANSAS...THE MISSOURI
BOOTHEEL...AND NORTHWEST TENNESSEE...PRECIPITATION WILL LIKELY
HOLD OFF UNTIL EARLY SATURDAY AFTERNOON...BUT MAY FALL AS A MIX OF
RAIN...FREEZING RAIN...AND SLEET. THE CHANGEOVER TO RAIN OVER
THESE AREAS MAY TAKE UNTIL SATURDAY EVENING...BUT WITH ONLY LIGHT
PRECIPITATION EXPECTED...ONLY EXPECTING MINOR ICE ACCUMULATIONS
OVER THESE AREAS AS WELL AT THIS TIME. EVEN THOUGH THE WINTER WEATHER
PRECIPITATION SHOULD REMAIN LIGHT...IT ONLY TAKES MINOR ICE
ACCUMULATIONS TO RESULT IN HAZARDOUS DRIVING CONDITIONS. PLAN TO
HIGHLIGHT THIS WINTER WEATHER THREAT IN THE LATEST HWO.
LIGHT RAIN SHOULD CONTINUE AREAWIDE SATURDAY NIGHT WITH
TEMPERATURES REMAINING ABOVE FREEZING. THE RAIN SHOULD END BY
SUNDAY MORNING AS THE SHORTWAVE PULLS EAST. WEAK HIGH PRESSURE
WILL BUILD BRIEFLY ON SUNDAY WITH MAINLY DRY AND WARMER
TEMPERATURES. ANOTHER STORM SYSTEM WILL IMPACT THE AREA MONDAY AND
MONDAY NIGHT BRINGING ADDITIONAL RAIN CHANCES. A STRONG COLD FRONT
WILL MOVE THROUGH LATER MONDAY NIGHT INTO TUESDAY MORNING WITH
ANOTHER ARCTIC AIRMASS BUILDING SOUTH OVER THE AREA THROUGH THE
MIDDLE AND END OF NEXT WEEK. DRY AND MUCH COLDER AIRMASS EXPECTED
FOR THE EXTENDED FORECAST PERIOD. HAVE UNDERCUT GUIDANCE
TEMPERATURES IN THE EXTENDED...AND WILL LIKELY NEED TO CUT
TEMPERATURES EVEN FURTHER THAN CURRENTLY FORECAST. THIS WILL
CONTINUE TO BE MONITORED AND UPDATED AS WE MOVE CLOSER TO THE
FORECAST PERIOD.
JLH
&&
.AVIATION...
00Z TAF CYCLE
VFR CONDITIONS WILL PERSIST THROUGHOUT THE ENTIRE TAF CYCLE.
WINDS WILL BE NEAR CALM TONIGHT AND THEN BECOME EAST TO SOUTHEAST
AROUND 5 KNOTS BY LATE FRIDAY MORNING.
ARS
&&
.PRELIMINARY POINT TEMPS/POPS...
MEM 21 42 31 42 / 0 0 10 50
MKL 15 38 27 40 / 0 0 10 40
JBR 17 40 27 39 / 0 0 10 30
TUP 20 42 33 45 / 0 0 20 70
&&
.MEG WATCHES/WARNINGS/ADVISORIES...
AR...NONE.
MO...NONE.
MS...NONE.
TN...NONE.
&&
$$
