Area Forecast Discussion
Issued by NWS Jackson, MS

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000
FXUS64 KJAN 220339 AAA
AFDJAN

Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
939 PM CST Sat Jan 21 2017

...SEVERE STORMS EXPECTED THIS EVENING...

.UPDATE...
Updated for evening discussion.

&&

.DISCUSSION...
Local weather service radars are lit up this evening with severe
storms from the Delta region across central Mississippi and over
southeast Mississippi. Surface analysis had a 996mb low near Bastrop
Louisiana with the associated warm front extending east just north of
Interstate 20. Water vapor imagery/RAP analysis showed the nose of a
110kt jet streak over southwest helping to enhance the convection.
Have increased pops earlier across the area to reflect the latest
radar trends. The convection will continue lifting northeast across
the CWA this evening with the severe potential ending from the
southwest. Until then, large hail, damaging winds and a few tornadoes
will be possible with the storms. /22/

Prior discussion below:

Tonight through Sunday...Mid afternoon surface analysis had a
stalled boundary just south of Highway 84 and a 994mb low near the
Texas panhandle. Mid afternoon water vapor imagery/RAP analysis had a
closed low spinning over the Texas/Oklahoma panhandles. Our CWA was
located upstream from the low in an increasingly diffluent flow
region with increasing waa ahead of the approaching low pressure
system. This will result in the stalled boundary lifting north this
evening across our CWA and becoming the focus for severe storms. The
favored quad of >100knot upper level jet will move into our area this
evening. The approaching cold core low will steepen mid level lapse
rates to 7-8C/km leading to vertical totals in the lower 30s. This
combined with 20-30 knots of 0-1 km bulk shear and 60-70 knots 0-6 km
bulk shear will promote very robust rotating updraft with all modes
of severe weather possible. The best parameters for large hail is
expected over the western half of our CWA while the greatest
potential for tornadic development is expected across the southern
half of our CWA. In addition, there will exist the threat for
damaging winds and locally heavy downpours areawide. Due to
antecedent conditions our southern zones may have the greatest chance
of experiencing minor runoff issues. The severe convection looks to
lift northeast of our CWA by 3am however, the cold core low will
track across north MS through Sunday and prolong rain chances into
the evening. /22/

Sunday night through Tuesday: Showers will linger, especially over
the northeast portion of the area, into Sunday evening as the mid
level low lingers across North AL pushing into the southern
Appalachians. A cooler but seasonable airmass will move into the
area as surface flow veers around to northwesterly behind the
departing surface cyclone. Cooler conditions will continue into
Monday, but as a ridge axis shifts across the area Monday night,
return flow will bring a quick warm up on Tuesday ahead of a weaker
storm system approaching the region. High temps are expected to
return to the 70s across the southwest part of the area.

Tuesday night through next Saturday: A relatively weak cold front
will pass across the area Tuesday night into Wednesday. Negligible
upper forcing will accompany this system and upper flow trajectories
will be close to parallel to the surface front. In addition, it
appears the warmth/moisture surge ahead of this front will be
insufficient to produce the instability needed for storms. Still,
scattered showers will be possible especially over the southeastern
half of the area. A surface high will build over the region
beginning Thursday, bringing dry conditions through the remainder of
the week with temps returning closer to seasonal norms. /DL/

&&

.AVIATION...
00Z TAF discussion:
VFR conditions were still being observed at 01Z but regional radars
were showing an increase in convection south and west of the area.
Flight conditions will deteriorate during the next several hours as
numerous TSRAs move across the area. Severe storms are expected with
hail greater than golfball size...winds in excess of 50kts and
tornadoes possible. TSRA/SHRA activity wl continue Sunday although no
severe storms are expected. Cigs wl likely remain MVFR/IFR Sunday as
an upper level low moves across north MS. /22/

&&

.PRELIMINARY POINT TEMPS/POPS...
Jackson       57  66  45  58 /  85  48  30   3
Meridian      58  66  45  57 /  73  64  34   6
Vicksburg     57  64  44  59 /  85  28  18   2
Hattiesburg   60  68  47  61 /  85  41  13   2
Natchez       57  65  44  62 /  85  20  11   1
Greenville    55  62  42  55 /  86  56  30   2
Greenwood     56  64  43  55 /  85  67  47   5

&&

.JAN WATCHES/WARNINGS/ADVISORIES...
MS...None.
LA...None.
AR...None.

&&

$$

DL/22



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