Area Forecast Discussion
Issued by NWS Jackson, MS

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FXUS64 KJAN 031136 CCA
AFDJAN

AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE JACKSON MS
530 AM CST TUE MAR 3 2015

...WINTER STORM LOOKING MORE LIKELY FOR NORTHERN PORTIONS OF THE
DELTA REGION...

.DISCUSSION...

TODAY THROUGH THURSDAY...

THE FORECAST IS GENERALLY ON TRACK THROUGH TUESDAY NIGHT AS A STRONG
WARM ADVECTION PATTERN IS EXPECTED TO DEVELOP TODAY AND CONTINUE
THROUGH TONIGHT INTO WEDNESDAY. HAVE CONTINUED THE DENSE FOG ADVISORY
FOR THIS MORNING WITH IMPROVING CONDITIONS EXPECTED LATE THIS MORNING
INTO THE AFTERNOON. LARGE SCALE ASCENT AND INSTABILITY WILL BE
WEAK...BUT EXPECT ENOUGH HEATING OF THE MOIST AIRMASS TO GENERATE A
FEW SHOWERS THIS AFTERNOON. SOME FOG COULD REDEVELOP TONIGHT.

THE WELL-ADVERTISED STRONG COLD FRONT IS STILL EXPECTED TO PUSH INTO
NORTHWEST PORTIONS OF THE ARKLAMISS WEDNESDAY AFTERNOON AND "SLOWLY"
SAG SOUTHWARD ACROSS THE ARKLAMISS LATE WEDNESDAY AND WEDNESDAY
NIGHT. INCREASING MOISTURE CONVERGENCE ALONG THE FRONT COULD LEAD TO
DEEP CONVECTION AND SOME THUNDERSTORM POTENTIAL...BUT AGREE WITH SPC
THAT THIS ACTIVITY WILL QUICKLY GET UNDERCUT BY STABLE COLDER BL AND
WEAK LAPSE RATES WILL FURTHER LIMIT VIGOR OF THE STORMS. THE INTENSE
THERMAL GRADIENT ALONG THE BOUNDARY WILL SUPPORT A FEW STRONG WIND
GUSTS BUT NOT EXPECTING SEVERE WEATHER TO BE A BIG CONCERN WITH THIS
PATTERN.

AS FOR THE WINTER STORM WATCH AND POTENTIAL WINTRY WEATHER...THERE
ARE SOME CHANGES WITH FORECAST THINKING ON PRECIPITATION TYPE AND
TIMING. OVERALL THE THINKING IS THAT THERE WILL BE MORE FREEZING RAIN
AND LESS SLEET/SNOW...AND THAT IT WILL BE A FEW HOURS SLOWER THAN
PREVIOUSLY ANTICIPATED. THE GFS HAS BEEN CATCHING ON WITH THE SLOWER
FRONTAL SOLUTIONS OFFERED BY OTHER GUIDANCE IN RECENT DAYS AND IS NOW
IN FAIRLY GOOD AGREEMENT WITH THE ECMWF/CMC/SREF...BUT THERE ARE SOME
MODELS...PARTICULARLY THE UKMET/NAM SOLUTIONS THAT SUGGEST IT MAY
CONTINUE TO SLOW DOWN EVEN MORE. IN FACT THE 06Z GFS HAS SLOWED DOWN
SIGNIFICANTLY FROM THE 00Z RUN. GIVEN THE STRONG ANA-FRONTAL PRECIP
EVENT WITH STRONG RIDGING OVER THE SOUTHEAST CONUS...IT IS HARD TO
ARGUE WITH A SLOWER SCENARIO.

IN ADDITION...THE FORECAST THERMAL PROFILES HAVE CONTINUED TO GET
MORE SHALLOW WITH THE COLD LOW LEVEL AIR AND LESS SUPPORTIVE OF
REFREEZING/SLEET POTENTIAL. THIS IS NOT A GOOD TREND AS IT RAISES
THE CONCERN FOR ICE STORM CRITERIA BEING EXCEEDED IN THE WATCH AREA
AS A STRONGER BAND OF POST-FRONTAL PRECIPITATION DEVELOPS WED EVNG
INTO THE OVERNIGHT. RIGHT NOW IT APPEARS THAT UP TO HALF INCH OF
LIQUID PRECIP COULD FALL WITH SUB-FREEZING TEMPS IN THE WATCH
AREA...PARTICULARLY IN THE DELTA REGION WHERE NEAR-SFC CAA WILL BE
MAXIMIZED. THE MORE SHALLOW COLD ADVECTION SHOULD DEVELOPING LIMIT
SNOW PRODUCTION...AND TRIMMED BACK THE AMOUNTS A LITTLE IN THE GRIDS
AND RAISED ICE ACCUMULATION BASED ON LATEST TRENDS. HAVE ALSO
EXPANDED THE WATCH AREA TO INCLUDE EXTREME NE LA BASED ON THE
MODEL PREFERENCE FOR A MORE LONGITUDINAL GRADIENT ASSOCIATED WITH
THE DELTA REGION.

ANOTHER SIGNIFICANT DIFFERENCE...THERE IS A TREND IN THE GUIDANCE
TO SLOW DOWN THE END OF THE PRECIPITATION THURSDAY MORNING MEANING
THERE MAY END UP BEING GREATER POTENTIAL FOR FREEZING RAIN IN SOUTH
CENTRAL AND SOUTHWEST MS AFTER DAYBREAK VS BEFORE DAYBREAK. WILL HAVE
TO KEEP A CLOSE EYE ON THAT TREND...BUT EXPECT ICING TO BE LIGHT
EITHER WAY SOUTH AND EAST OF THE CURRENT WATCH AREA AT THIS TIME.
/EC/

LONG TERM (THURSDAY NIGHT THROUGH MONDAY)...FOR THE END OF THE WEEK
INTO THE WEEKEND...THE PERSISTENTLY STRONG UPPER JET WILL BEGIN TO
DEAMPLIFY AND UPPER LEVEL FLOW WILL BECOME MORE ZONAL OVER THE AREA.
WITH THE JET STREAM REMAINING ATOP THE REGION...BELOW AVERAGE TEMPS
WILL STICK AROUND THROUGH MOST OF THE PERIOD AS SURFACE RIDGING
BECOMES ANCHORED FROM THE SOUTHERN PLAINS EASTWARD THROUGH THE MID
ATLANTIC. TEMPS WILL GRADUALLY INCREASE EACH DAY AS THIS AIR MASS
MODIFIES...POTENTIALLY GETTING A BUMP FROM AN INCURSION OF WARMER
GULF AIR WITH ANY COASTAL SYSTEM THAT SNEAKS FAR ENOUGH NORTH INTO
THE AREA.

THURSDAY NIGHT...TEMPERATURES IN THE TEENS LOOK TO BE A GOOD BET
ALONG THE HIGHWAY 82 CORRIDOR...WITH 20S ACROSS THE REMAINDER OF THE
AREA. WITH COLD ADVECTION CONTINUING OVERNIGHT WIND CHILLS WILL BE
EVEN LOWER...POTENTIALLY INTO THE SINGLE DIGITS AT TIMES ACROSS THE
DELTA. FRIDAY LOOKS TO BE ANOTHER FRIGID DAY ACROSS THE DELTA...WITH
TEMPS STRUGGLING TO GET OUT OF THE 30S ESPECIALLY IN ANY LOCATION
WITH NOTABLE WINTRY ACCUMULATIONS LEFTOVER FROM THE PREVIOUS DAY.

THOUGH PREVIOUSLY THE GFS HAD KEPT MOST OF THE AREA DRY AND THE EURO
HAD HINTED AT PRECIP CHANCES ACROSS THE SOUTH...NOW THERE IS BETTER
AGREEMENT IN A COASTAL LOW IN THE SUNDAY/MONDAY TIME PERIOD. FOR
NOW...WILL MAINTAIN CONSISTENCY WITH ISOLATED TO SCATTERED POPS
THROUGH THIS TIME FRAME UNTIL WE GET A BETTER HNDLE ON WHICH
PERIODS TO FAVOR HIGHER POPS. /DL/

&&

.AVIATION...WIDESPREAD LIFR RESTRICTIONS DUE TO LOW VSBYS/CIGS IN
FOG/STRATUS EARLY THIS MORNING SHOULD IMPROVE TO IFR CATEGORY AT
MOST LOCATIONS BY EARLY AFTERNOON AS STRONG WARM
ADVECTION AND DAYTIME HEATING HELP TO MIX THE BOUNDARY LAYER.
HOWEVER...EXPECT CIGS/VSBYS TO DETERIORATE OVERNIGHT WITH INCREASING
BOUNDARY LAYER MOISTURE AND LOSS OF INSOLATION. /EC/

&&

.PRELIMINARY POINT TEMPS/POPS...
JACKSON       74  62  76  27 /  40  35  68  92
MERIDIAN      77  61  76  31 /  28  29  59  90
VICKSBURG     75  63  76  26 /  40  37  80  95
HATTIESBURG   77  62  78  36 /  26  28  47  78
NATCHEZ       76  64  76  28 /  44  36  66  92
GREENVILLE    67  61  66  22 /  34  36  99  95
GREENWOOD     70  62  70  22 /  41  45  94  92

&&

.JAN WATCHES/WARNINGS/ADVISORIES...
MS...DENSE FOG ADVISORY UNTIL 9 AM CST THIS MORNING FOR MSZ018-019-
     025>066-072>074.

     WINTER STORM WATCH FROM WEDNESDAY EVENING THROUGH LATE WEDNESDAY
     NIGHT FOR MSZ018-019-025>030-034-035-040-041.

LA...DENSE FOG ADVISORY UNTIL 9 AM CST THIS MORNING FOR LAZ007>009-
     015-016-023>026.

     WINTER STORM WATCH FROM WEDNESDAY EVENING THROUGH LATE WEDNESDAY
     NIGHT FOR LAZ007>009-015.

AR...DENSE FOG ADVISORY UNTIL 9 AM CST THIS MORNING FOR ARZ074-075.

     WINTER STORM WATCH FROM WEDNESDAY EVENING THROUGH LATE WEDNESDAY
     NIGHT FOR ARZ074-075.

&&

$$

EC/DL








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