FXUS64 KMEG 120243
AFDMEG
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEMPHIS TN
843 PM CST FRI DEC 11 2009
.DISCUSSION...
CLOUDS ARE STARTING TO INCREASE ACROSS THE WESTERN HALF OF THE
FORECAST AREA THIS EVENING WHILE SKIES REMAIN CLEAR OVER EASTERN
SECTIONS. TEMPERATURES ARE RANGING FROM THE MID 20S TO UPPER 30S.
CLOUDS SHOULD CONTINUE TO INCREASE OVERNIGHT ACROSS THE ENTIRE
FORECAST AREA. WILL NEED TO SEND UPDATE TO REMOVE SOME EVENING
WORDING BUT NO MAJOR CHANGES ARE PLANNED AT THIS TIME.
ARS
&&
.PREV DISCUSSION... /ISSUED 559 PM CST FRI DEC 11 2009/
DISCUSSION... /ISSUED 336 PM CST FRI DEC 11 2009/
MODIFIED ARCTIC HIGH PRESSURE REMAINS ENTRENCHED OVER THE MID
SOUTH THIS AFTERNOON AS NOTED BY TEMPERATURES IN THE MID 30S TO
LOWER 40S AND DEWPOINTS MAINLY IN THE SINGLE DIGITS. THIS WILL
LIKELY SET THE STAGE FOR A PERIOD OF LIGHT WINTER WEATHER ON
SATURDAY.
A LOW AMPLITUDE SHORTWAVE OVER THE SOUTHWESTERN U.S. THIS
AFTERNOON WILL MOVE QUICKLY INTO THE MID MISSISSIPPI VALLEY ON
SATURDAY AS THE SUBTROPICAL JET STREAM REMAINS ACTIVE. THIS SHOULD
ADVECT INCREASING MOISTURE AND PROMOTE STRENGTHENING ISENTROPIC
ACSENT OVER THE FORECAST AREA ON SATURDAY. AS THIS MOISTURE AND
LIFT OVERRIDE THE RETREATING MODIFIED ARCTIC AIRMASS EXPECT
PRECIPITATION TO BEGIN AS A MIX OF LIGHT RAIN...SLEET...AND
POSSIBLY FREEZING RAIN OVER FAR NORTHERN MISSISSIPPI...EASTERN
ARKANSAS...AND SOUTHERN PORTIONS OF WEST TENNESSEE ON SATURDAY
MORNING AND AREAS FURTHER NORTH BY EARLY SATURDAY AFTERNOON.
EVAPORATIVE COOLING PROCESSES SHOULD SUPPORT THIS WINTERY MIX
INITIALLY AS MOISTURE ALOFT FALLS INTO A COLD AND VERY DRY
AIRMASS NEAR THE SURFACE. EXPECT ONLY A COUPLE HOUR PERIOD FOR
WINTER WEATHER POTENTIAL BEFORE WARM ADVECTION ERODES AWAY THE
RESIDUAL ARCTIC AIRMASS AND TEMPERATURES WARM SUFFICIENTLY TO
RESULT IN A CHANGE OVER TO ALL RAIN. THIS SHOULD OCCUR AROUND OR
BEFORE NOON ALONG THE INTERSTATE 40 CORRIDOR AND BY MID AFTERNOON
ACROSS NORTHERN PORTIONS OF THE MID SOUTH. SINCE PRECIPITATION
SHOULD REMAIN LIGHT...NOT EXPECTING MUCH IN THE WAY OF MAJOR
TRAVEL PROBLEMS OR ACCUMULATIONS. BUT A FEW ICY SPOTS...ESPECIALLY
ON ELEVATED ROAD SURFACES...COULD DEVELOP DURING THIS PERIOD.
AGAIN...ANY ICY SPOTS ON ELEVATED ROAD SURFACES SHOULD BE BRIEF IN
DURATION AND DO NOT PLAN TO ISSUE ANY HEADLINES AT THIS TIME.
LATER SHIFTS CAN ACCESS THE EVOLUTION OF THIS SYSTEM AND PROVIDE
UPDATES AS NEEDED. WILL LIKELY HIGHLIGHT THE LIGHT WINTER WEATHER
POTENTIAL IN AN SPS AND THE LATEST HWO.
RAIN SHOULD CONTINUE THROUGH SATURDAY NIGHT AREAWIDE AS THE
SHORTWAVE PULLS THROUGH THE AREA. PRECIP TYPE SHOULD BE ALL RAIN
SATURDAY NIGHT WITH TEMPERATURES REMAINING SEVERAL DEGREES ABOVE
FREEZING. ALL RAIN SHOULD COME TO AN END BY SUNDAY MORNING AS THE
SYSTEM MOVES EAST AND WEAK HIGH PRESSURE BUILDS OVER THE AREA.
ANOTHER SHORTWAVE WILL APPROACH FROM THE WEST ON MONDAY WITH
ISENTROPIC LIFT INCREASING AND RAIN ONCE AGAIN DEVELOPING OVER THE
REGION FROM SOUTHWEST TO NORTHEAST. PRECIP TYPE SHOULD NOT BE AN
ISSUE THIS TIME AROUND AS TEMPERATURES CONTINUE TO WARM FURTHER.
RAIN SHOULD COME TO AN ABRUPT END ON TUESDAY AS ANOTHER ARCTIC
COLD FRONT MOVES THROUGH THE AREA. EXPECT FALLING TEMPERATURES AND
STRONG GUSTY NORTHWEST WINDS BEHIND THE FRONT ON TUESDAY AFTERNOON
AND TUESDAY NIGHT. DRY AND COLD WEATHER WILL FOLLOW FOR THE MIDDLE
TO END OF NEXT WEEK AS ARCTIC HIGH PRESSURE SETTLES OVER THE MID SOUTH.
JLH
AVIATION...
00Z TAF CYCLE (12/00Z-13/00Z)
VFR CONDITIONS WILL CONTINUE OVERNIGHT. RAIN WILL SPREAD ACROSS
THE REGION FROM THE SOUTHWEST AFTER 12/12Z SATURDAY AS A WARM
FRONT MOVES TOWARD THE AREA. FLYING CONDITIONS WILL DETERIORATE
DURING THE DAY SATURDAY WITH CONDITIONS FIRST BECOMING MVFR...THEN
IFR. MAY EVENTUALLY SEE DEVELOPMENT OF LIFR CONDITIONS BUT
CONFIDENCE TO0 LOW TO MENTION ATTM. WILL NOT BE SURPRISED TO SEE
SOME -PL AT THE INITIAL ONSET OF THE PRECIPITATION...BUT CONFIDENCE
REMAINS TOO LOW TO MENTION IN THE TAFS.
JCL
&&
.AVIATION...
&&
.PRELIMINARY POINT TEMPS/POPS...
MEM 32 41 40 56 / 10 90 80 10
MKL 27 40 40 53 / 10 90 80 10
JBR 28 39 38 50 / 10 80 60 10
TUP 31 43 43 58 / 10 100 90 30
&&
.MEG WATCHES/WARNINGS/ADVISORIES...
AR...NONE.
MO...NONE.
MS...NONE.
TN...NONE.
&&
$$
