Area Forecast Discussion
Issued by NWS Jackson, MS

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FXUS64 KJAN 250920
AFDJAN

Area Forecast Discussion
National Weather Service Jackson MS
420 AM CDT Tue Apr 25 2017

...Severe Storms Expected Wednesday Night...

.DISCUSSION...Today and Tonight: Both the ridge axis and surface
high will shift east of the forecast area over the next 24 hours.
With a storm system beginning to take shape and strengthen across
the nation`s mid-section during this time, flow aloft will become
more west to southwesterly through the period. Surface winds will
become southerly and be on the increase as the surface pressure
gradient begins to tighten across the CWA. This increased
southerly flow through the atmosphere will result in moistening,
and thus warming, conditions across the forecast area today and
tonight.

Skies will remain mostly sunny this afternoon, despite some high
clouds beginning to stream in from the west.  Winds will again be
southerly, and increase to between 10-15 mph with some higher gusts
possible.  The aforementioned tighter pressure gradient will be most
felt over the Delta.  Here, southerly winds will become sustained
between 15-20 mph, with a few gusts between 25-30 mph possible
during the afternoon hours.  Otherwise, highs will warm into the low
and middle 80s this afternoon.

The weather will remain quiet through the overnight hours.
Increasing deep moisture will result in increasing clouds across
mainly the western half of the forecast area through early Wednesday
morning.  Lows will be a good bit warmer as they range from the
middle 50s to the middle 60s. /19/

Wednesday through Monday: A deepening northern stream upper level
trough over the southern Plains Wednesday will track northeast
across the mid Mississippi River valley Wednesday night while
supporting a surface low that will send a cold front across our CWA
Wednesday night. WAA wl increase significantly over our region
Wednesday ahead of the approaching cold front. This will result in a
breezy south wind across much of our CWA with the strongest winds
northwest of a Winnsboro Louisiana to Grenada Mississippi line where
a Wind Advisory will likely be needed from afternoon into the
evening. Anomalous moisture is expected to pool ahead of the cold
front with surface dew points in the upper 60s and PWATs in excess
of an inch and a half inch. Models still show a decent cap over our
CWA until late afternoon in the west just ahead of the cold front. A
squall line is expected to develop along and just ahead the cold
front and move into our western most zones before evening. The
initial environment over our western zones will feature mid level
lapse rates >7.5c/km, MLCAPEs near 2000j/k, deep layer shear of 50-
55kts and 0-3km Helicity 200-300m2/s2. These conditions are expected
to become less favorable over eastern Mississippi toward morning. As
the squall line progresses across our CWA, severe storms capable of
damaging wind gusts, quarter sized hail and a tornado or two will be
possible. Considering the PWATs, locally heavy downpours will
accompany the strongest storms as well. The GFS is a little faster
but consensus places the line near I-55 by midnight and southeast of
I-59 by 6AM. A weak surface high but much drier airmass will move
over our CWA Thursday in the wake of the front but a second
shortwave and associated surface low will move over the southern
Plains and help the cold front move back north as a warm front
Thursday night. Our CWA wl be back in the warm sector Friday with
rain chances mainly across our north near the front. The longwave
pattern still looks to amplify sharply during the weekend with a
591dam high developing just off the coast of the southeast states
while a closed low drops over the southern Plains Saturday.
Strengthening WAA ahead of this system looks produce breezy to windy
conditions across our CWA again by Saturday afternoon. Model
consensus has sped up the timing of this system and are in better
agreement with the potential for severe thunderstorms over our CWA
Saturday night into Sunday. In addition to severe storms, models
suggest potential for heavy rainfall over a large portion of our
area as well. This system is expected to shift east of our area
Sunday night with dry weather on Monday. /22/

&&

.AVIATION...
06Z TAF discussion:
VFR flight categories will prevail at TAF sites over the next 24
hours. Light to calm winds and clear skies overnight could lead to
some patchy ground fog at a few sites towards day break. This
could bring a brief reduction to visibilities between 10-13Z, but
these will quickly rebound after sunrise this morning. Winds
later this morning will increase from the south between 5-10
knots, with 10-15 knots and some higher gust possible along and
west of the Mississippi River. /19/

&&

.PRELIMINARY POINT TEMPS/POPS...
Jackson       83  60  85  58 /   0   1   5  78
Meridian      83  56  85  63 /   0   0   3  76
Vicksburg     83  63  84  56 /   0   1  13  79
Hattiesburg   84  58  86  64 /   0   0   5  76
Natchez       81  63  83  56 /   0   1  10  78
Greenville    81  64  81  54 /   0   2  25  82
Greenwood     82  61  82  56 /   0   1  10  80

&&

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

&&


$$

19/22



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