Area Forecast Discussion
Issued by NWS Jackson, MS

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FXUS64 KJAN 222234
AFDJAN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON MS
434 PM CST MON DEC 22 2014

.DISCUSSION...
PERSISTENT ISENTROPIC ASCENT HAS KEPT A SOLID DECK OF LOW STRATUS
OVER THE CWA TODAY WITH VISIBILITIES REDUCED AT TIMES. NEVERTHELESS
STEADY WARM ADVECTION...STRONGER JUST ABOVE THE SURFACE THAN AT THE
SURFACE ITSELF...HAS ALLOWED TEMPS TO WARM INTO THE 60S ACROSS MOST
OF THE AREA. A FEW BREAKS IN THE CLOUDS ACROSS SOUTH MS AND CENTRAL
LA WERE ALLOWING TEMPS TO CRACK 70 IN FAR SOUTHERN AREAS. SCATTERED
SHOWERS ARE ONGOING ACROSS PART OF CENTRAL MISSISSIPPI...THOUGH
THUNDER ACTIVITY HAS REMAINED SOUTH AND EAST OF THE CWA THUS FAR.

HEADING INTO TONIGHT...IT IS UNLIKELY THE LOW CLOUDS WILL DEPART AS
WE REMAIN IN A VERY SIMILAR PATTERN TO LAST NIGHT. EVEN AREAS THAT
SEE BREAKS IN THE OVERCAST LATE THIS AFTERNOON INTO THE EVENING WILL
SEE A RETURN OF LOW CLOUDS LATER ON TONIGHT. ONCE AGAIN VISIBILITIES
MAY BE REDUCED AT TIMES...WITH POTENTIALLY EVEN SOME DENSE FOG
ESPECIALLY THE FARTHER SOUTH IN THE AREA. AS THE COLD FRONT
APPROACHES THE DELTA THIS EVENING...GUIDANCE CONTINUES TO INDICATE
NEW SHOWER DEVELOPMENT IN THE NORTHWEST MOVING EASTWARD THROUGH THE
NIGHT. OVERNIGHT ADDITIONAL SCATTERED SHOWER/TSTORM ACTIVITY IS
POSSIBLE FARTHER SOUTH. IT IS NOW LOOKING LIKE SURFACE-BASED INSTABILITY
WILL STRUGGLE TO MAKE IT NORTHWARD ACROSS THE ENTIRE CWA...THOUGH
ELEVATED THUNDER REMAINS A POSSIBILITY EVEN IN THE NORTH. OVER
CENTRAL AND SOUTH MS AND PART OF NORTHEAST LA THERE IS A LIMITED
THREAT FOR SEVERE WEATHER OVERNIGHT. WHILE EFFECTIVE BULK SHEAR WILL
REMAIN MORE THAN SUFFICIENT TO SUSTAIN CONVECTION...THERE WILL BE A
LACK OF SIGNIFICANT FORCING WHICH SHOULD KEEP ANY ACTIVITY RATHER
ISOLATED.

BY TUESDAY MORNING...THE FRONT WILL BE NEAR A TUPELO TO NATCHEZ LINE.
ALONG WITH A SURFACE LOW OVER EASTERN IA...ANOTHER LOW WILL BEGIN TO
TAKE SHAPE ALONG THE NW GULF COAST AND MOVE NORTHEASTWARD ALONG THE
FRONT DURING THE DAY. AREAS TO THE WEST OF THE FRONT WILL BE IN A
SOMEWHAT COOLER AIRMASS WITH TEMPS STRUGGLING TO REACH THE 60S
TOMORROW. MEANWHILE TO THE EAST IN THE WARM SECTOR...DEWPOINTS WILL
LIKELY REACH WELL INTO THE 60S WITH TEMPS APPROACHING 70 IN SOME
LOCATIONS. IN ASSOCIATION WITH THE SURFACE LOW AND INCREASING
DIVERGENCE ALOFT IN THE RIGHT ENTRANCE REGION OF AN UPPER JET
STREAK...SHOWERS AND THUNDERSTORMS WILL BECOME MORE WIDESPREAD THROUGH
THE DAY. GENERALLY WEST OF THE NATCHEZ TRACE...NO SEVERE WEATHER IS
EXPECTED AS MOST OF THAT AREA WILL BE BEHIND THE FRONT...THOUGH
ELEVATED INSTABILITY WILL STILL ALLOW FOR THUNDERSTORMS. FOR AREAS
ALONG AND EAST OF THE TRACE THERE IS A CONDITIONAL THREAT FOR SEVERE
WEATHER...CONTINGENT ON WHETHER CONVECTION EARLY IN THE DAY OR
POTENTIAL COASTAL CONVECTION WILL LIMIT INSTABILITY ACROSS THE AREA.
DURING THE AFTERNOON/EVENING TIME FRAME...THE SURFACE LOW WILL LIFT
NORTHEASTWARD ACROSS CENTRAL MISSISSIPPI. THIS WOULD BE THE MOST
LIKELY TIME FRAME FOR SEVERE WEATHER AS EFFECTIVE BULK SHEAR UP TO 50
KTS AND SBCAPES OF 500-1000 J/KG WILL BE SUFFICIENT FOR A FEW
SUPERCELLS. WE ARE CONTINUING TO HIGHLIGHT AREAS FARTHER SOUTH AND
EAST IN THE CWA FOR ANY SEVERE THREAT IN HWO/GRAPHICAL PRODUCTS.

AS THE SURFACE LOW ADVANCES NORTHEASTWARD...THE HEAVIER CONVECTION
WILL SHIFT EAST OF THE AREA BY 6Z...THOUGH LINGERING LIGHTER SHOWERS
MAY CONTINUE FOR MUCH OF THE NIGHT. IN FACT...AS THE UPPER TROUGH
AXIS LINGERS TO OUR WEST AND A STRENGTHENING UPPER JET REMAINS
OVERHEAD...MUCH OF THE MID AND PARTICULARLY LOW LEVELS OF THE
ATMOSPHERE WILL REMAIN MOIST. BUFR SOUNDINGS SUGGEST PERSISTENT
CLOUDS AND DRIZZLE/LIGHT RAIN THROUGH MUCH OF THE DAY CHRISTMAS EVE...
WHICH WOULD NOT BE SURPRISING IN THE CAA REGIME BEHIND THE FRONT.
TEMPS WERE TRENDED TOWARD RAW MODEL GUIDANCE THROUGH MUCH OF THE
SHORT TERM PERIOD AS ADVECTIVE PROCESSES WILL BE THE PREDOMINANT
INFLUENCE.

THE UPPER TROUGH AXIS WILL FINALLY SHIFT ACROSS THE FORECAST AREA
EARLY CHRISTMAS DAY...ALLOWING FOR THE SUN TO RETURN AND HOPEFULLY
PROVIDING CLEARING SKIES AS SANTA TRAVERSES THE ARKLAMISS. THE UPPER
PATTERN WILL REMAIN PROGRESSIVE HOWEVER...AND OUR NEXT SYSTEM WILL
ALREADY BE TAKING SHAPE OVER THE WEST THURSDAY INTO FRIDAY. RAIN
CHANCES RETURN FRIDAY NIGHT INTO THE WEEKEND AS A FRONT SLOWLY
MIGRATES ACROSS THE REGION. THERE CONTINUE TO BE NOTABLE
DISCREPANCIES BETWEEN THE GFS AND EURO SOLUTIONS FOR THIS SYSTEM...
WITH THE EURO BRINGING A POTENT MID/UPPER WAVE AND ASSOCIATED SURFACE
LOW ACROSS THE AREA LATE SATURDAY INTO SUNDAY WHILE THE GFS DEPICTS A
LESS AMPLIFIED SCENARIO AND A DRIER FORECAST. WILL MAINTAIN CHANCE
POPS IN THIS PERIOD...THOUGH THESE WOULD NEED TO BE INCREASED IN THE
FUTURE IF THE EURO SOLUTION PANS OUT. SURFACE HIGH PRESSURE BUILDS
BACK IN BRINGING A RETURN TO DRY CONDITIONS BY NEXT MONDAY. /DL/

&&

.AVIATION...IFR CEILINGS AND/OR VISIBILITIES CONTINUE AT TAF SITES
THIS AFTERNOON AS A RESULT OF LOW STRATUS AND/OR PATCHY FOG. IFR
CEILINGS ARE EXPECTED TO CONTINUE THROUGH THE EVENING HOURS WITH
MOST SITES BECOMING LIFR AFTER 06-07Z. INCREASING CHANCES FOR
THUNDERSTORMS TOWARDS THE END OF THE PERIOD WILL ALSO BRING A
DEGRADATION IN FLIGHT CATEGORIES WHEN OBSERVED ON STATION. THE WINDS
WILL REMAIN OUT OF THE SOUTH AT 6-10KTS BECOMING NORTHERLY AT
GWO/GLH LATE IN THE PERIOD./15/

&&

.PRELIMINARY POINT TEMPS/POPS...
JACKSON       59  67  45  50 /  35  86  76  22
MERIDIAN      61  68  51  53 /  46  99  91  27
VICKSBURG     58  64  42  50 /  26  83  66  21
HATTIESBURG   64  70  52  55 /  44  99  74  19
NATCHEZ       60  66  43  50 /  23  86  57  18
GREENVILLE    53  57  42  48 /  44  71  80  27
GREENWOOD     55  62  44  48 /  52  75  88  31

&&

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

$$

DL/15




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