Area Forecast Discussion
Issued by NWS Jackson, MS

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FXUS64 KJAN 240432 AAA

Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
1132 PM CDT Mon Oct 23 2017

Updated for 06Z aviation discussion


06Z TAF discussion:
VFR conditions canditions can be expected through the period. A
dry cold front will track across the forecast area overnight. In
the wake of the front expect winds of 15-18knots with gusts of
20-28 knots during the day Tuesday. Expect the winds to taper off
by 00-01z./17/


A reinforcing cold front, currently located over southeast
Oklahoma and northwest Arkansas, will continue to propagate
towards the ArkLaMiss tonight. Ahead of this front, regional obs
indicate that boundary layer decoupling has occurred at most
locations in the presence of large dewpoint depressions resulting
in efficient radiational cooling with numerous sites already in
the low to mid 50s. The aforementioned front is progged to be
knocking on our northwest doorstep by 6z and pushing out of the
Jackson metro by daybreak before clearing the southeast portion of
the CWA by mid morning. Even drier air will filter in behind this
front with dewpoints falling well into the 30s. The going forecast
remains on track for the rest of tonight and the only changes were
to update the hourly temps and lower the overnight min temps just
a tad. /TW/

Prior discussion below:

Tonight through Tuesday: Overall a much drier & cooler night is
in store as much drier PW air will be present over the region. By
this evening, expect the previously mentioned longwave trough to
have absorbed & phased with the closed upper low in the upper
Great Lakes. This will help the strong surface low to occlude over
the Great Lakes & deep troughing & vorticity advection to amplify
the longwave trough. As the strong surface low occludes, it will
help drive down the strong cold front tonight. Expect the cold
front to be moving down into the Delta late tonight between 10PM
to 1AM & through most of the area by around 4- 6AM. This will help
turn winds more northwesterly & drive down much drier air into
the region. Dewpoints will being to to fall into the 30s by early
morning Tuesday. Due to some winds around, expect lows to fall to
near normal, into the mid-upper 40s or so, especially across the
northern areas.

Expect cooler & drier air to continue to filter in on Tuesday,
bringing much drier air & lower dewpoints into the area. As the
trough amplifies & cold front pushes PWs less than an half an inch &
low level dry air into the area, expect dewpoints to fall into the
low-mid 30% range. In addition, as strong surface ridging (~1026-
1028mb surface high) builds into western Texas, our area will be
under strong pressure gradient across the entire ArkLaMiss region
(~3mb pressure gradient). This will lead to gusty sustained winds,
beginning in the mid-morning & continuing into the afternoon. These
winds could gust as high as 30-35mph, mainly along and west of the I-
55 corridor but especially into the ArkLaMiss Delta. Continued the
limited risk for gusty winds in the HWO/graphics as we could
potentially reach a little higher with such strong pressure gradient
& associated winds & extremely favorable mixing environment. We also
should warm efficiently due to dry ground & low dewpoints, but still
some 5-8 degrees below normals into the upper 60s-low 70s.

In addition, increasing fire danger will be possible across the
western area due to such strong sustained winds & near critical
relative humidity values approaching the 25-30% range. Due to some
recent rainfall over southern areas & strongest sustained winds
being confined to the Delta, kept only a limited risk for the fire
danger in the HWO/graphics for west of the I-55 corridor. Also some
of the recent soil moisture & rainfall & dry Delta soils should
limit the potential & not as much into the timber land further east.

Tuesday night through Sunday: Surface high pressure, centered
over TX, will continue to build into the area at the beginning of
the period. Though the atmosphere will want to decouple due to the
better radiation in the drier air, the surface pressure gradient
looks to remain at least tight enough to keep winds up Tuesday
night keeping temps from falling to their lowest potential and
inhibiting any frost development. Some frost does look possible by
Thursday morning as high pressure center moves over southeast
MS/southwest AL with surface temps dropping down into the mid 30s
over the southeast. Flow around the high will bring southwesterly
winds to the rest of the area resulting in warmer mins.

Another strong cold front/upper level system will move through the
area Friday into Friday night. Not much time for moisture recovery
ahead of this system, thus only expecting a few showers with the
frontal passage. The bigger story will be the cool/dry airmass that
will build in Saturday. A strong cooling potential will exist by
Saturday night as the pressure gradient relaxes. Dewpoints in the
teens late in the day will allow for rapid decoupling and strong
radiative heat loss during the evening. Freezing temperatures look
possible by early Sunday morning over at least north-central
portions with mid 30s and widespread frost elsewhere./26/


Jackson       48  71  39  65 /   0   0   0   1
Meridian      48  69  39  64 /   0   0   0   1
Vicksburg     48  71  40  66 /   0   0   0   1
Hattiesburg   49  69  41  65 /   0   0   0   1
Natchez       48  70  40  65 /   0   0   0   0
Greenville    48  69  39  66 /   0   0   0   0
Greenwood     46  69  38  64 /   0   0   0   1




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