Area Forecast Discussion
Issued by NWS Jackson, MS

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FXUS64 KJAN 260945
AFDJAN

Area Forecast Discussion
National Weather Service Jackson MS
445 AM CDT Wed Apr 26 2017

...SEVERE STORMS EXPECTED TONIGHT...

.DISCUSSION...Today and Tonight: Early morning water vapor
imagery showed the circulation around a potent shortwave over
northeast New Mexico that will track east today and deepen a
surface low over east Texas before tracking northeast tonight
across the mid Mississippi river valley. The deepening surface low
and increasing WAA ahead of the approaching system will result in
windy conditions across our western zones and breezy conditions
across the remainder of our CWA. A Wind Advisory is in effect from
later this morning into early evening, generally northwest of a
Natchez to Grenada Line where occasional southerly wind gusts to
45 mph are expected. These gusty southerly winds will help
contribute to a deep moisture increase ahead of the approaching
cold front that will move into our northwest most zones early this
evening. Confidence has increased that a squall line will develop
along and ahead of the cold front today. Model soundings still
indicate a stout cap over our CWA that should limit convection
until the squall line arrives at our northwest most zones around 5
pm by model consensus. Overall, environmental parameters over our
western zones at the time the squall line arrives hasn`t changed
much from previous runs. Anomalous moisture with surface dew
points in the upper 60s and PWATs in excess of an inch and a half
inch will pool ahead of the cold front. Steep mid level lapse
rates >7.5c/km, MLCAPEs near 2000j/k, deep layer shear of 50-55kts
and 0-1km helicity 200-300 m2/s2 will contribute to severe storm
development capable of damaging wind gusts, large hail and
tornadoes. SPC has outlooked our southeast Arkansas counties and a
portion of our northeast Louisiana Parishes in a Moderate Risk
with an Enhanced Risk east to the I-55 corridor. A Slight Risk
remains over east Mississippi as the line is expected to slowly
weaken the later into the night and farther east into Mississippi
it pushes. Considering the PWATs, locally heavy downpours will
accompany the strongest storms as well but, the progressive nature
of the line should limit duration. Model consensus moves the line
southeast of our CWA before sunrise with cooler and drier air
back across our CWA in the wake of the cold front. /22/

Thursday through Tuesday Night: Rain should be clear of the
forecast area by sunrise on Thursday, with clearing skies and
lighter winds expected throughout the day. Temperatures will
quickly rebound to around 10 degrees above normal for Friday as
southerly winds return. Parts of the area could reach 90 degrees,
which combined with humidity could lead to heat index values
approaching 95 degrees. Capping should keep convection from
developing on Friday, but a few isolated showers or storms can`t
be ruled out with daytime heating. Saturday will see a
continuation of hot and humid weather, increasing southerly winds,
and a low end chance for showers or storms across the area as the
next upper-level low pressure system swings from New Mexico
toward the Panhandle of Texas. Tightening pressure and height
gradients ahead of this system could see near wind advisory
conditions develop across portions of the ArkLaMiss region.

The main period of concern with this approaching weather system will
be late Saturday night through the day on Sunday. Model guidance is
in fairly decent agreement on an organized line of thunderstorms
approaching southeast Arkansas and northeast Louisiana by around
sunrise on Sunday and reaching the eastern edge of Mississippi by
Sunday evening. Modest amounts of instability and deep layer shear
will support at least a Slight Risk for severe thunderstorms during
the day on Sunday. Moisture will also be concentrated ahead of the
line of storms, and forecast PWAT values approaching 2 inches would
place the system near the climatological maximum for this time of
year. Therefore we will also continue to highlight a limited risk of
flash flooding during the day on Sunday due to the potential for
heavy rainfall. Quieter weather is expected for the early part of
next week, though rain chances look to increase ahead of another
possible low pressure system by midweek. /NF/

&&

.AVIATION...
06Z TAF discussion: VFR conditions will continue through 09Z.
After 09Z MVFR to IFR category ceilings are expected mainly along
and west of the I-55 corridor. Cigs will improve to VFR by 16Z.
Strong gusty south winds will develop Wed with sustained speeds
around 15-23kts and gusts to around 25-33kts into the evening. A
squall line is expected to move in vcty of GLH around 23Z and
continue across the area overnight. /22/

&&

.PRELIMINARY POINT TEMPS/POPS...
Jackson       85  56  79  63 /   6  84   2   5
Meridian      85  59  81  62 /   2  79  11   7
Vicksburg     84  55  78  61 /  16  90   2   5
Hattiesburg   86  62  84  64 /   3  67  10   7
Natchez       84  55  79  62 /  10  86   2   5
Greenville    81  55  75  60 /  47  90   2   5
Greenwood     84  55  75  60 /   7  90   3   5

&&

.JAN WATCHES/WARNINGS/ADVISORIES...
MS...Wind Advisory from 11 AM this morning to 9 PM CDT this evening
     for MSZ018-019-025-034-035-040-041.

LA...Wind Advisory from 11 AM this morning to 9 PM CDT this evening
     for LAZ007>009-015-016-023>026.

AR...Wind Advisory from 11 AM this morning to 9 PM CDT this evening
     for ARZ074-075.

&&

$$

NF/22


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