Area Forecast Discussion
Issued by NWS Jackson, MS

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FXUS64 KJAN 180836
AFDJAN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON MS
336 AM CDT THU SEP 18 2014

.SHORT TERM...THERE WILL EXIST A COUPLE FORECAST CHALLENGES FOR
TODAY INTO THIS EVE. FIRST WILL BE WITH TEMPS AND WHAT EFFECTS OF
THE HIGH CLOUDS WILL PLAY ON POSSIBLY KEEPING THEM LOWER THAN
FORECAST. THE OTHER CHALLENGE WILL BE WITH CONVECTION AN HOW MUCH
COVERAGE WILL EXIST. ITS A LOW CONFIDENCE FORECAST AS A
RESULT...MAINLY BECAUSE FORECAST GUID HAS DIFFERENCES. THE GLOBAL
MODELS ARE MORE BEARISH ON PRECIP CHANCES TODAY WHILE A HANDFUL OF
THE HI-RES CONVECTIVE ALLOWING MODELS SHOW MUCH MORE IN THE WAY OF
STORMS. ITS TOUGH WHEN MOS GUID IS OFFERING 10-20% AND OTHER RAW
OUTPUT MAKES YOU THINK MORE LIKE 50-60%. ADDITIONALLY...ITS HARD TO
NOT ACCOUNT FOR THE LATEST TRENDS WHICH HAVE SUPPORTED THE SITUATION
WHERE PRECIP HAS BEEN HARDER TO COME BY. OVERALL...THERE WILL BE A
WEAK SFC BOUNDARY ACROSS THE NE PART OF THE CWA WHICH SHOULD HELP
PROVIDE SOME FOCUS...BUT THEN AGAIN...FLOW IN THE LOWER 2-3KM IS
QUITE WEAK AND ANY LOW LEVEL CONVERGENCE WILL BE VERY MARGINAL.
THERE WILL BE A DECENT S/WV MOVING SE AND THIS FEATURE IS ALREADY
KICKING OFF STORMS TO OUR NW. BASED ON ALL THIS...HAVE INCREASED
POPS SOME WITH THE BEST CHANCES IN THE NORTH.

BASED OFF CERTAIN THERMO PARAMETERS ALONG WITH INCREASED DEEP LAYER
FLOW...A STRONG STORM OR TWO CANNOT BE RULED OUT OVER THE NW HALF
LATER TODAY. COOLER MID LEVEL TEMPS (ASSOCIATED WITH THE APPROACHING
S/WV) WILL OFFER STEEPER LAPSE RATES THAN WHAT OUR AREA HAS SEEN
RECENTLY. ADDITIONALLY...SFC MOISTURE (DEWPTS) WILL LIKELY HOLD A
BIT HIGHER ACROSS PARTS OF THE W/NW WHICH WILL SUPPORT HIGHER
INSTABILITY NEAR 2500 J/KG OF SBCAPE.

AS FOR TEMPS TODAY...HAVE GONE WITH 87-90 DEGREES WITH A DOWNWARD
TWEAK OVER PARTS OF THE NORTH. IF CLOUD COVER LIMITS INSOLATION
MORE...THEN READINGS COULD FALL SHORT OF THOSE VALUES BY 3-5
DEGREES.

ANY CONVECTIVE ACTIVITY SHOULD DISSIPATE BY 9-10 PM THIS EVE. AN
OVERALL MUCH DRIER ATMS THROUGH A DEEP LAYER WILL PUSH INTO THE CWA
IN THE WAKE OF THE S/WV. THIS WILL SUPPORT NEAR ZERO POPS FRI-FRI
NGT WITH MOSTLY CLEAR SKIES AS WELL. /CME/

.LONG TERM...SATURDAY THROUGH NEXT WEDNESDAY

ABOVE NORMAL TEMPERATURES AND MOSTLY DRY FOR THE WEEKEND WITH A COOL
DOWN TOWARD NORMAL READINGS LATE MONDAY INTO MID WEEK AS A COOL AND
SLIGHTLY MOISTURE STARVED FRONT SLIDES THROUGH THE REGION.

OVERALL, LONG TERM MODELS IN GOOD AGREEMENT SHOWING SHORT LIVED
RIDGING SATURDAY GIVING WAY TO MORE ROBUST TROUGHING DIVING OUT OF
THE GREAT LAKES SUNDAY INTO MONDAY ACROSS THE EASTERN CONUS. EXPECT
A DRY SATURDAY AS RESIDUAL DRIER AIRMASS /PWATS 1.2"/ AND SURFACE
HIGH PRESSURE/H5 RIDGE SUPPRESS ACTIVITY. HOWEVER, BY SUNDAY, A
RIBBON OF 1.5-1.6" PWATS WILL PIVOT INTO NW/W AREAS AHEAD OF A FRONT
AIDED BY STRONGER NW FLOW AS EASTERN CONUS TROUGH AMPLIFIES SOUTH IN
CONJUNCTION WITH STRONG SURFACE HIGH IN CENTRAL PLAINS. THIS
ENVIRONMENT COULD SUPPORT A FEW WEAKLY INSTABILITY INDUCED SHOWERS.

THE NEW EC IS MORE BULLISH (AND MORE IN LINE WITH GFS) THEN PREVIOUS
RUN ON STRONGER SOUTHWARD FRONTAL MOMENTUM THROUGH REGION LATE
MONDAY INTO TUESDAY MORNING. AS FRONT MOVES THROUGH MONDAY, MOISTURE
LOOKS TO BE LACKING AND WEAK LOW-LVL CONVERGENCE WILL ALSO BE IN
PLAY. YET, FEEL SHOWERS AND A RUMBLE OF THUNDER WILL HAVE A CHANCE
TO DEVELOP AS BOUNDARY MOVES THROUGH. BEST CONCENTRATION OF RAIN
WITH CURRENT THINKING OF TIMING WILL BE ALONG AND SOUTH OF I-20
WHERE INSTABILITY WILL BE GREATER MONDAY AFTN. AT LEAST LOWER 50F
DEWPOINTS LOOK TO INFILTRATE THROUGH MOST OF REGION BY MIDDAY
TUESDAY ALONG WITH SOME CAA IN THE 925/850MB LAYERS. THESE
COMPONENTS WILL ALLOW FOR TEMPERATURES TO FALL BACK TOWARDS NORMALS
IN THE UPPER 50S/LOW 60S AND HIGHS IN THE MID 80S TUESDAY WITH
SLIGHT MODERATION WEDNESDAY AS FRONT MAY WAFFLE BACK NORTH ALONG FAR
SOUTH AREAS. /ALLEN/

&&

.AVIATION...EXPECT VFR CONDITIONS TO PREVAIL FOR NEARLY ALL OF THE
FORECAST. THE EXCEPTIONS WILL BE IF ANY SITE IS IMPACTED BY
CONVECTION. AT THIS TIME...CONFIDENCE IS TOO LOW TO MENTION PRECIP
AT ALL SITES. HOWEVER...ENOUGH CONFIDENCE EXISTS TO INCLUDE A VCTS
FOR GLH/GWO. /CME/

&&

.PRELIMINARY POINT TEMPS/POPS...
JACKSON       90  66  91  66 /  20  20   2   1
MERIDIAN      90  64  90  64 /  11  12   4   1
VICKSBURG     90  64  91  65 /  23  19   2   1
HATTIESBURG   92  67  92  67 /  22  29   4   4
NATCHEZ       88  66  89  66 /  28  27   3   3
GREENVILLE    88  66  89  66 /  30   5   1   3
GREENWOOD     88  64  90  65 /  30   6   1   3

&&

.JAN WATCHES/WARNINGS/ADVISORIES...
MS...NONE.
LA...NONE.
AR...NONE.
&&

$$

CME/ALLEN/





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