FXUS64 KMEG 111136 AAA
AFDMEG
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE MEMPHIS TN
536 AM CST FRI DEC 11 2009
.UPDATE...
UPDATED FOR 12Z AVIATION DISCUSSION.
&&
.PREV DISCUSSION... /ISSUED 410 AM CST FRI DEC 11 2009/
DISCUSSION...
THE SOUTHERN BRANCH OF THE UPPER JET WILL REMAIN ACTIVE THROUGH
THE WEEKEND...JUST AS ARCTIC AIR BEGINS TO MAKE ITS RETREAT.
THE MIDSOUTH WILL FIND ITSELF UNDER THE RIGHT ENTRANCE REGION OF A
180KT JET STREAK CENTERED OVER THE CAROLINAS. THIS WILL AID IN
ISENTROPIC LIFT OVER THE WESTERN PERIPHERY OF THE DEPARTING ARCTIC
HIGH PRESSURE. NAM PROGS SATURATION PRESSURE DEFICITS FALLING TO
LESS THAN 50 MB ALONG THE 295K SURFACE BY 12Z SATURDAY. THIS WILL
ROUGHLY CORRESPOND TO THE 800 TO 750 MB LAYER. MODERATE TO STRONG
ISENTROPIC UPGLIDE WILL ALSO OCCUR BELOW THIS LAYER...BUT WITH
INITIALLY SCARCE MOISTURE.
WEAK TO MODERATE WARM ADVECTION WILL LIKELY OCCUR LATE TONIGHT...BUT
MAY BE OFFSET BY EVAPORATIVE COOLING FROM PRECIPITATION ALOFT.
TOUGH CALL FOR SURFACE TEMPS...BUT BEST GUESS IS NEAR FREEZING
OVER NORTH MS AS THE SUBCLOUD LAYER SATURATES FROM SOUTH TO NORTH.
WILL CONTINUE A MENTION OF RAIN/SLEET MIX SATURDAY MORNING. BY MID
TO LATE MORNING... RAIN SHOULD PREDOMINATE ACROSS THE MIDSOUTH...
EXCEPT PERHAPS OVER NORTHERN WEST TN. NO SLEET ACCUMULATIONS ARE
EXPECTED WITH THIS EVENT.
SUNDAY WILL SEE A RETURN OF MOSTLY SUNNY SKIES AND MILD TEMPS...
UNDER LOW AMPLITUDE RIDGING ALOFT. EXPECT ANOTHER SOUTHERN BRANCH
SYSTEM ON MONDAY...BUT NO CONCERN AT THIS TIME WITH FREEZING OR
NEAR FREEZING SURFACE TEMPS. WHILE WARM ADVECTION IS EXPECTED
MONDAY... SIGNIFICANT CLOUD COVER AND RAIN SHOULD KEEP AFTERNOON
TEMPS FROM WARMING THE RATHER OPTIMISTIC MEX GUIDANCE HIGHS...WHICH
WERE AT THE HIGH END OF THE ENSEMBLE RANGE. DECIDED TO GO WITH THE
ENSEMBLE MEAN FOR FOR MAX TEMPS MONDAY.
WHILE MONDAY SEES RAIN AND MILD TEMPS ACROSS THE MIDSOUTH...AN
ALBERTA CLIPPER WILL DIVE SOUTHEAST INTO THE NORTHERN PLAINS AND
UPPER MIDWEST. THIS WILL OPEN THE DOOR FOR A 1045MB ARCTIC HIGH TO
PLUNGE SOUTH INTO THE PLAINS ON MONDAY...AND INTO THE MIDSOUTH EARLY
TUESDAY. PRESENT MODEL SOLUTIONS...WHICH ARE IN GOOD AGREEMENT...
BRING AND END TO THE PRECIP BEFORE THE ARCTIC AIR ARRIVAL...BUT THIS
WILL BEAR CLOSE WATCHING.
UNDER SUNNY SKIES...TUESDAY/S TEMPS WILL LIKELY BE 15 TO 20
DEGREES COLDER THAN THE CLOUDY AND RAINY MONDAY. MEX GUIDANCE
AGAIN APPEARS A BIT WARM AND HAVE UNDERCUT.
THE MID TO LATE PART OF NEXT WEEK APPEAR DRY...WITH SLOWLY
MODERATING TEMPS AFTER WEDNESDAY. THE VERY DRY ARCTIC AIRMASS
WILL ALLOW FOR COLD MORNINGS UNDER PRIME RADIATIONAL COOLING
CONDITIONS.
PWB
&&
.AVIATION...
12Z TAF CYCLE
VFR CONDITIONS WILL PERSIST THROUGH THE TAF CYCLE. HIGH CLOUDS
WILL INCREASE THROUGH THE DAY IN ADVANCE OF THE NEXT ROUND OF
PRECIPITATION ARRIVING SHORTLY AFTER 12/12Z. THERE COULD BE SOME
-FZRA OR -IP WITH THE INITIAL ONSET OF PRECIP NEAR 12Z...BUT
CONFIDENCE IS MUCH TOO LOW TO MENTION IN TAFS AT THIS POINT. WINDS
WILL BECOME EAST TO SOUTHEAST AT 5 TO 10 KNOTS BY LATE THIS
MORNING AND CONTINUE THROUGH TONIGHT.
BORGHOFF
&&
.PRELIMINARY POINT TEMPS/POPS...
MEM 45 29 45 40 / 0 10 80 60
MKL 43 27 43 40 / 0 10 70 60
JBR 39 27 40 36 / 0 10 50 50
TUP 44 31 44 42 / 0 20 100 80
&&
.MEG WATCHES/WARNINGS/ADVISORIES...
AR...NONE.
MO...NONE.
MS...NONE.
TN...NONE.
&&
$$
