FXUS64 KJAN 261117
AFDJAN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON MS
517 AM CST THU NOV 26 2009
.SHORT TERM...THANKSGIVING DAY THROUGH SATURDAY MORNING...FORECAST
CONCERN THIS PERIOD REVOLVES AROUND LOW TEMPERATURES FRIDAY MORNING
AND THE ASSOCIATED FREEZING CONDITIONS ANTICIPATED...AS WELL AS WIND
SPEEDS THIS AFTERNOON ACROSS AREA LAKES.
HIGH PRESSURE IS BUILDING INTO THE REGION IN WAKE OF A WEAK COLD
FRONT THAT PASSED THRU THE AREA OVERNIGHT. DRY NORTHWESTERLY FLOW
ALOFT WILL KEEP CLEAR SKIES IN THE FORECAST FOR THIS THANKSGIVING
DAY...AND CONTINUE INTO THE START OF THE WEEKEND. HIGH TEMPS FOR
TODAY WERE HANDLED WELL BY MAV GUIDANCE WITH LITTLE ADJUSTMENT
NEEDED...GENERALLY MID 50S AREA WIDE. NORTHWEST WINDS THIS AFTERNOON
WILL PICK ON THE LEADING EDGE OF THE HIGH PRESSURE. EXPECT 10 TO 15
MPH WINDS TO DEVELOP LATE MORNING AND CONTINUE THROUGH THE AFTERNOON.
CONSIDERED A LAKE WIND ADVISORY FOR THE AFTERNOON HOURS BUT
CONSIDERING SUSTAINED WINDS OF 20 MPH WILL BE TOUGH TO ATTAIN...EVEN
OVER THE WATER...WILL FORGO ISSUANCE. 15 TO 20 MPH WINDS THROUGH THE
AFTERNOON IS LIKELY.
A COLD FRIDAY MORNING IS IN STORE ACROSS THE ARKLAMISS...AND LOOKS
TO BE THE COLDEST OF THE YEAR SO FAR. MAV GUIDANCE HAS BEEN A LITTLE
WARM ON THE LOWS...ESPECIALLY EAST OF I-55 THE LAST COUPLE DAYS. FOR
FRIDAY MORNING...EXPECT LOW TEMPS NEAR 30 FOR MOST AREAS EAST OF
I-55 ALTHOUGH THE FARTHER WE GET INTO SOUTHERN MS THE TOUGHER IT
WILL BE TO GET TO 30. TEMPS CLOSER TO 31 OR 32 ARE EXPECTED IN THESE
AREAS. A TRICKY FORECAST ENSUES WEST OF I-55. TEMPS GENERALLY
EXPECTED TO APPROACH 32 EXCEPT NEAR AND SOUTH OF NATCHEZ...AS WELL
AS IN THE DELTA NORTH OF VICKSBURG WHERE LOW TEMPS AT OR ABOVE 33
ARE EXPECTED. AS A RESULT...THE COVERAGE OF FREEZING CONDITIONS AND
THE NEED FOR THE A FREEZE WARNING HAS BEEN PROBLEMATIC. ALONG AND
EAST OF I-55 NORTH OF HATTIESBURG I FEEL ITS A SLAM DUNK AND HAVE
ISSUED THESE AREAS ACCORDINGLY. ALONG A HATTIESBURG TO VICKSBURG TO
BASTROP LINE...IT APPEARS TEMPS NEAR OR JUST BELOW FREEZING ARE VERY
POSSIBLE AND INCLUDED THESE AREAS IN THE FREEZE WARNING AS WELL. THE
DURATION OF FREEZING CONDITIONS ALONG THIS LINE IS DEFINITELY IN
QUESTION...CALLING THE NEED FOR THE WARNING INTO QUESTION AS WELL.
HBG MAV GUIDANCE CAME IN WITH 32 FOR TONIGHTS LOW TEMP WITH A DEW
POINT OF 28...DEFINITELY POINTING TO EASIER ATTAINABILITY OF A
FREEZE. VICKSBURG CAME IN WITH 34 OVER 31 FOR 12Z TOMORROW WHICH IS
DEFINITELY ON THE MARGINAL SIDE OF THE NEED FOR A FREEZE WARNING. AS
A RESULT...THE NEED FOR A FREEZE WARNING FROM JEFFERSON DAVIS TO
MOREHOUSE WILL NEED TO BE MONITORED WITH FURTHER GUIDANCE AS IT IS
MARGINAL. FOR NOW...FEEL THE POSSIBILITY DEFINITELY EXISTS AND WILL
ISSUE THE WARNING ACCORDINGLY. THE REST OF FRIDAY WILL BE NICE ONCE
AGAIN WITH CLEAR SKIES AND HIGH TEMPS JUST BELOW SEASONAL NORMS.
SATURDAY MORNING WILL BE WARMER THAN FRI AS RETURN FLOW GRADUALLY
SETS UP ACROSS THE CWA. NEAR FREEZING TEMPS WILL STILL BE POSSIBLE
ACROSS FAR EASTERN ZONES...GENERALLY IN LINE WITH MAV GUIDANCE. /BK/
.LONG TERM...SATURDAY THRU WEDNESDAY...GFS AND ECMWF TEND TO AGREE
EARLY IN THE PERIOD WITH A SPLIT FLOW REGIME TAKING SHAPE ACROSS THE
CONUS. SIGNIFICANT MID LEVEL PIECE OF ENERGY BREAKS OFF IN TROF
MOVING THRU THE WESTERN STATES AND DEEPENS INTO A CUT OFF LOW OVER
NRN MEXICO WHILE NRN STREAM TROF PULLS AWAY ACROSS THE NRN TIER OF
STATES. THIS NRN STREAM TROF WILL ALLOW A RATHER SHALLOW SURFACE
FRONT TO SLIDE THRU THE AREA SUNDAY NIGHT AND MONDAY. STRONG WARM
ADVECTION SETS UP IN ADVANCE AND WITH THE PASSAGE OF THE FRONT
MAINLY BELOW 600 MB. INSTABILITY LOOKS VERY LIMITED (MUCAPES BLO 300
J/KG)...BUT WITH STRENGTH OF THE FORCING BELIEVE SOME THUNDER WILL
BE SEEN.
ISENTROPIC LIFT LOOKS TO WANE MONDAY NIGHT AS S/W RIDGING
TEMPORARILY BUILD INTO THE AREA. MODELS DIVERGE FROM HERE ON HOW SRN
STREAM SYSTEM PROGRESSES THRU THE AREA. ECMWF AS WELL AS MAJORITY OF
GFS ENSEMBLE MEMBERS HAVE THE MID LEVEL CUT OFF LOW OPEN UP AND
BEGIN PHASING WITH SECONDARY MID LEVEL WAVE DIVING RAPIDLY SOUTH OUT
OF CANADA...WHILE THE OPERATIONAL GFS STILL WANTS TO MAINTAIN THE
LOW AS CUT OFF. ACTUALLY...LOOKING AT THE NEW 06Z RUN...THE
OPERATIONAL GFS IS BEGINNING TO COME INTO MORE ALIGNMENT WITH THE
REST OF THE ENSEMBLE AND ECMWF. REGARDLESS OF THE EXACT SCENARIO OF
THE LIFTING OUT LOW...DEEP ISENTROPIC LIFT WILL GET UNDERWAY ONCE
AGAIN TUESDAY AS THE LOW/OPEN TROF MOVE ACROSS THE AREA. GFS MODEL
SOUNDINGS SHOWING SOME POSSIBILITY OF SOME CONVECTIVE SNOW SHOWERS
OVER THE NRN CWA WEDNESDAY AS THE COLD CORE MOVES THRU. WONT MENTION
IN THE FORECAST YET...BUT WILL HAVE TO WATCH FUTURE MODEL RUNS FOR
CONSISTENCY./GRG/
&&
.AVIATION...VFR CONDS XPCTD THRU THE PERIOD AS HIGH PRES BUILDS ONTO
THE REGION. GUSTY NORTHWEST WINDS WILL DEVELOP THIS AFTERNOON AS THE
PRES GRADIENT TIGHTENS ON THE LEADING EDGE OF THE HIGH. WINDS WILL
TAPER OFF NEAR SUNDOWN WITH LIGHT WINDS XPCTD OVERNIGHT. COLD TEMPS
CAN BE XPCTD TOMORROW MORNING...WITH FREEZING CONDITIONS XPCTD EAST
OF I-55...AS WELL AS ALONG A HBG TO BASTROP LINE. /BK/
&&
.PRELIMINARY POINT TEMPS/POPS...
JACKSON 56 31 59 37 / 0 0 0 0
MERIDIAN 57 30 60 32 / 0 0 0 0
VICKSBURG 59 32 60 39 / 0 0 0 0
HATTIESBURG 60 31 61 35 / 0 0 0 0
NATCHEZ 56 32 61 40 / 0 0 0 3
GREENVILLE 56 33 59 41 / 0 0 0 0
GREENWOOD 56 32 58 38 / 0 0 0 0
&&
.JAN WATCHES/WARNINGS/ADVISORIES...
MS...FREEZE WARNING FROM 4 AM TO 8 AM CST FRIDAY FOR MSZ026>033-
036>040-042>059-061>066-072>074.
LA...FREEZE WARNING FROM 4 AM TO 8 AM CST FRIDAY FOR LAZ007>009-015-
016-023-025.
AR...NONE.
&&
$$
BK/GARRETT
