Area Forecast Discussion
Issued by NWS Jackson, MS

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000
FXUS64 KJAN 230339 AAA
AFDJAN

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE JACKSON MS
939 PM CST MON DEC 22 2014

.UPDATE...
EVENING SFC ANALYSIS INDICATES WARM FRONT GRADUALLY LIFTING TO THE
NE INTO THE AREA. MOISTURE ADVECTION/ISENTROPIC ASCENT AHEAD OF THE
S/WV OVER SC TX IS AIDING IN WIDESPREAD CLOUDINESS THAT HAS COVERED
THE AREA TODAY. DUE TO INCREASING WAA/MOISTURE ADVECTION TONIGHT...AREAS
OF FOG...SOME POSSIBLY DENSE...ARE POSSIBLE ESPECIALLY IN AREAS THAT
THE PRESSURE GRADIENT CAN LIGHTEN UP IN THE E/SE. LEFT AREAS OF FOG
ACROSS THE REGION TONIGHT AFTER 06Z BUT DUE TO GOOD LOW LEVEL
MIXING...EXPECTING DENSE FOG POTENTIAL TO NOT BE WIDESPREAD.

THE SEVERE POTENTIAL REMAINS IN THE FAR SE OF THE AREA IN PROXIMITY
TO THE MARINE BOUNDARY WHERE HIGHER DEWPOINTS/BETTER ASCENT RESIDE.
00Z UPPER AIR ANALYSIS INDICATES DEEP NEUTRAL TILT H5 UPPER TROUGH
OVER THE CENTRAL CONUS WITH NEAR 100KT H3 JET...INCREASING DIVERGENT
FLOW FROM THE RIGHT ENTRANCE REGION WILL INCREASE OVERNIGHT. 00Z
REGIONAL SOUNDINGS INDICATE AROUND 1 INCH PWATS IN THE I-20 CORRIDOR
WHILE NEAR 1.4 INCHES NEAR THE COAST...WHERE IN THE 00Z KLIX SOUNDING
SUFFICIENT SFC BASED INSTABILITY/SHEAR/HODOGRAPHS EXISTS. SOME OF THE
CURRENT ACTIVITY IN THE DELTA COULD LINGER TONIGHT DUE TO ISENTROPIC
ASCENT. STORMS IN THE N HAVE SHOWN SOME ROTATION BUT ARE TOO FAR N OF
THE SFC WARM FRONT AND WILL REMAIN ELEVATED. HOWEVER...THE HRRR
CONTINUES TO HIGHLIGHT MORE OF THE ACTIVITY IN THE E/SE TONIGHT AFTER
MIDNIGHT DUE TO MORE SFC BASED INSTABILITY AND 0-3KM BULK SHEAR
AROUND 40-50KTS. NOT EXPECTING THE MOISTURE TO MAKE MUCH FURTHER THAN
E/SE MS TONIGHT. UPDATES ALREADY SENT OUT TO GRAPHICS/HWO TO REFLECT
THIS THINKING. ADJUSTED HOURLY TEMP/DEWPOINT CURVES TO CURRENT
TRENDS. REST OF THE FORECAST IS ON TRACK. /DC/

&&

.AVIATION...LOW CLOUDS AND FOG WILL BE THE RULE THROUGH THE PERIOD
WITH LIFR/IFR CONDITIONS PREVAILING. SCATTERED SHOWERS AND
THUNDERSTORMS WILL ALSO BE THROWN INTO THE MIX BY 23/18Z...ESPECIALLY
OVER GTR/MEI AND HBG. CONDITIONS SHOULD BEGIN IMPROVING FROM THE WEST
AFTER 24/00Z. /26/

&&

.PREV DISCUSSION... /ISSUED 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/

&&

.PRELIMINARY POINT TEMPS/POPS...
JACKSON       59  67  45  50 /  39  86  76  22
MERIDIAN      61  68  51  53 /  46  99  91  27
VICKSBURG     58  64  42  50 /  28  83  66  21
HATTIESBURG   64  70  52  55 /  47  99  74  19
NATCHEZ       60  66  43  50 /  23  86  57  18
GREENVILLE    53  57  42  48 /  34  71  80  27
GREENWOOD     55  62  44  48 /  41  75  88  31

&&

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

$$

DC/26/DL





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