FXUS64 KJAN 272050
AFDJAN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON MS
249 PM CST FRI NOV 27 2009
.SHORT TERM...(TONIGHT THROUGH SUNDAY NIGHT)...
THE PRIMARY WEATHER CONCERN WILL BE OUR CHANCE OF SHOWERS WITH A
COLD FRONT FOR THE SUNDAY-SUNDAY NIGHT TIME RANGE. ALSO IF ANY
INSTABILITY WILL BE WITH THIS SYSTEM.
LATEST SATELLITE IMAGERY SHOWS AN UPPER RIDGE BUILDING TOWARD THE
REGION FROM THE SOUTHERN PLAINS AS WE REMAIN UNDER DRY NORTHWEST
FLOW ALOFT. A BLANKET OF MID TO MOSTLY HIGH CLOUDS WAS ASSOCIATED
WITH THE UPPER RIDGE. SOME OF THOSE HIGH CLOUDS WERE BEGINNING TO
ENTER THE SOUTHERN PORTION OF THE REGION.
FOR TONIGHT THROUGH SATURDAY NIGHT...SURFACE HIGH PRESSURE WILL MOVE
EAST OF THE REGION DURING THE PERIOD AS MID TO HIGH LEVEL CLOUDS MOVE
ACROSS THE REGION. NORTHWESTERLY FLOW ALOFT WILL GRADUALLY BECOME
WESTERLY AND EVENTUALLY SOUTHWESTERLY BY SATURDAY AS A WEAK SOUTHERN
STREAM S/WV CROSSES THE GULF COAST. THIS WILL HELP TO KEEP THE MID
TO HIGH LEVEL CLOUDS AROUND. LOOKING AT TEMPS FOR THE DRY PERIOD.
FOR TONIGHT WENT WITH MOS GUIDANCE WHICH BRINGS ONE MORE ROUND OF
FREEZING TEMPS FOR THE EASTERN COUNTIES. EVEN WITH THE HIGH CLOUDS
AROUND BELIEVE THAT IT SHOULD BE ABLE TO REACH IT WITH THE DRY
DEWPOINTS AROUND. FOR SATURDAY WITH RETURN FLOW AROUND AND 850 TEMPS
PUSHING TOWARD 10C...READINGS SHOULD REBOUND INTO THE LOWER TO UPPER
60S. THIS IS SUPPORTED BY AFTERNOON READINGS IN THE MID TO UPPER 60S
ACROSS THE ARKLATEX REGION...WHICH WILL COME TO OUR REGION ON
SATURDAY. WENT CLOSE TO MAV GUIDANCE. FOR SATURDAY NIGHT EXPECT
CLOUDS TO GRADUALLY INCREASE IN COVERAGE AHEAD OF THE APPROACHING
SYSTEM COMING FROM THE PLAINS. WE SHOULD BE ABLE TO REACH THE UPPER
30S IN THE EAST WITH 40S ELSEWHERE. WENT CLOSE TO THE COOLER MOS
GUIDANCE.
FOR SUNDAY INTO SUNDAY NIGHT. THE SREF...EUROPEAN...NAM...GFS AND UKMET
HAVE SLOWED THE RAIN TIMING WITH THE SUNDAY NIGHT-MONDAY FRONTAL
SYSTEM AND ASSOCIATED SHORT WAVE. MODELS STILL SHOW THAT THE INSTABILITY
WITH THIS SYSTEM WILL BE QUITE WEAK. IN THE ISENTROPIC DEPARTMENT
THERE WILL BE SOME PRETTY GOOD ISENTROPIC LIFT...SOME ISENTROPIC NET
OMEGA...SOME GOOD GENERAL INCREASING GENERAL OMEGA AHEAD AND BEHIND THE
FRONT. PRECIPITABLE WATER WILL INCREASE TO AROUND 1.5 INCHES. THIS
SHOULD PROVIDE SOME PRETTY GOOD RAIN COVERAGE FOR SUNDAY NIGHT. MOS
POPS LOOKED A LITTLE HIGH FOR SUNDAY...SO CUT BACK ON POPS FOR
SUNDAY. WENT CLOSE TO MOS HIGH POPS FOR SUNDAY NIGHT. AS FAR AS
TEMPS ARE CONCERN 850 TEMPS WILL BE IN THE 9-11C RANGE. SO TEMPS
WILL BE IN MIDDLE 60S TO LOWER 70S. WENT CLOSE TO MAV GUIDANCE. FOR
SUNDAY NIGHT TEMPS WILL CONTINUE TO MODERATE WITH LOWS FROM THE
LOWER TO MIDDLE 50S. WENT CLOSE TO MAV GUIDANCE AS THE GMOS GUIDANCE
LOOKED TOO COOL./17/
./PREVIOUS DISCUSSION...LONG TERM...MONDAY THRU THURSDAY...THE
FORECAST PROBLEM DURING THIS PERIOD IS THE EVOLUTION OF MID LEVEL
CUTOFF LOW OVER THE NRN BAJA OF CA AT 12Z SUNDAY AND THE
DISASSOCIATED MID LEVEL TROF PULLING AWAY OVER THE NRN PLAINS.
ALTHOUGH SUBTLE DIFFERENCES DO EXIST...GFS...GFS ENSEMBLE AND ECMWF
ARE ALL IN REASONABLE GOOD AGREEMENT DURING THIS TIME PERIOD.
DISASSOCIATED MID LEVEL TROF PULLING AWAY FROM THE CUTOFF LOW WILL
CONTINUE TO TRANSITION EAST...DEEPENING AS IT DOES SO. THIS FEATURE
WILL DRAG A FRONT INTO THE AREA BY SUNDAY NIGHT/MONDAY. UNTIL IT DOES
SO...PERSISTENT SWLY FLOW WILL SLOWLY MOISTEN THE ATMOSPHERE IN
STEADILY INCREASING DEEP LAYER WARM AIR ADVECTION. BEST ISENTROPIC
LIFT LOOKS TO GET GOING JUST ALONG AND BEHIND THE FRONT AS IT ENTERS
THE AREA MOVING INTO MONDAY MORNING. WHILE OVERALL OMEGA INCREASES
DURING THIS TIME FRAME...MAGNITUDES AND LACK OF INSTABILITY SUGGEST
ADIABATIC MOTIONS WILL DOMINATE WITH A LACK OF DEEP CONVECTION. HAVE
REMOVED THUNDER WORDING PREVIOUSLY IN THE FORECAST.
PRECIP WANES DURING LATE MONDAY NIGHT/TUESDAY MORNING AS FRONT
STALLS ALONG THE COAST...WINDS VEER AND ISENTROPIC LIFT SHUTS DOWN.
THIS IS SHORT-LIVED...HOWEVER AS BACKING WINDS DURING THE AFTERNOON
ALLOW BOUNDARY TO LIFT RAPIDLY BACK NORTH IN RESPONSE TO THE
APPROACHING COLD CORE LOW MOVING OUT OF TX BY THIS TIME. A SURFACE
LOW LOOKS TO DEVELOP OVER THE NRN GULF IN INCREASING WAR
ADVECTION/ISENTROPIC LIFT WHICH WILL GIVE THE AREA ANOTHER SHOT AS
SOME SHOWERY ACTIVITY TUESDAY NIGHT ESPECIALLY SOUTH. SHOWERS WILL
ONCE AGAIN BE POSSIBLE WEDNESDAY AS THE COLD CORE LOW ACTUALLY MOVES
ACROSS THE CWA. /GRG/
&&
.AVIATION...VFR CONDITIONS WILL CONTINUE THROUGH THE PERIOD OVER
MUCH OF THE AREA AS HIGH PRESSURE PREVAILS OVER THE AREA. PATCHY FOG
WILL BE POSSIBLE FOR MEI/HBG WHICH MAY BRING OCCASIONAL MVFR
CONDITIONS EARLY ON SATURDAY. SKIES WILL REMAIN CLEAR AND THE WINDS
WILL BE LIGHT OUT OF THE WEST THIS AFTERNOON SWINGING AROUND TO THE
SOUTH ON SATURDAY./15/
&&
.PRELIMINARY POINT TEMPS/POPS...
JACKSON 37 65 44 70 / 0 0 3 14
MERIDIAN 31 66 38 70 / 0 0 0 13
VICKSBURG 40 66 45 71 / 0 1 8 16
HATTIESBURG 33 67 44 71 / 0 0 0 12
NATCHEZ 41 66 46 71 / 0 2 8 15
GREENVILLE 41 64 45 66 / 0 2 6 24
GREENWOOD 38 66 42 67 / 0 0 3 20
&&
.JAN WATCHES/WARNINGS/ADVISORIES...
MS...NONE.
LA...NONE.
AR...NONE.
&&
$$
17/15
