Area Forecast Discussion
Issued by NWS Jackson, MS

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FXUS64 KJAN 230252 AAA
AFDJAN

Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
852 PM CST Wed Feb 22 2017

...AT LEAST PATCHY DENSE FOG ANTICIPATED LATE TONIGHT...

.UPDATE...
Updated for evening discussion.

&&

.DISCUSSION...
Main concern through the remainder of tonight is dense fog
development. The previous forecast recognized the very good setup
for fog development tonight, such as favorable afternoon cross-
over temperatures indicative of a relatively moist boundary layer
and rather optimal radiational cooling conditions expected to
catalyze radiational fog growth. Earlier hi resolution model runs
backed up suggestions of widespread dense fog potential. However,
in the last few hours the latest hi res models have been quickly
backing off of widespread dense fog potential, although the
fundamental favorable setup remains pretty much in place. Current
interpretations of the model trends are that they are likely
backing off fog potential too much but the official forecast was
trended toward only patchy dense fog in western zones given some
mid layer clouds there may inhibit radiational cooling a bit. A
dense fog advisory was inherited from the previous shift and there
is certainly not enough evidence to drop it at this point, so will
let ride. HWO and forecast graphics will be updated to hit
potential of fog issues hardest roughly along and east of I-55.
Expect widespread lows ranging from 50 to 55 degrees, which is
coolish, but still well above average for the date. /BB/

Prior discussion below:

Tonight through Thursday:

Closed upper low continues to dive southeast into the Gulf of
Mexico this afternoon, while over our area shortwave ridging
continues to build in this afternoon. We have warmed nicely into
the upper 60s to low 70s, where some areas where clouds have been
more stubborn to clear, temperatures have only made the low to mid
60s. Overall expect a dry trend to continue into the evening and
through Thursday as shortwave ridging continues to be the main
weather maker in the area. Surface high over the western Atlantic
will begin to wedge into the area from the northeast tonight. PW`s
will be on the lower side tonight, closer to three quarters of an
inch. With the surface ridge wedging in from the northeast and
upper ridge axis directly over the area, winds should be pretty
light to near calm overnight. The crossover temperatures compared
to the low temperatures tonight will again be some 3-6 degrees or
so, as was the case yesterday. This is a carbon copy of the
favorable fog environment that was around yesterday. Hi-res
guidance is really the aggressive trend on low stratus and very
low visibilities near or less than a quarter mile. Thus, with the
environment similar to yesterday, drier air aloft and hi-res
guidance backing up that thinking, went ahead and issued a dense
fog advisory tonight, after midnight through 10AM tomorrow.

After the fog and stratus lift tomorrow, expect a dry and nice
afternoon Thursday as that surface ridge moves in to the east. We
will warm in the low levels around 5 degrees C around 850mb as
the surface ridge slowly builds east. With us being dry, we should
mix out well into the low 80s across the region. Only thing that
could be an issue for high temperatures Thursday is how long
clouds linger around, which could limit full insolation.
Regardless, this will be some 20 degrees above normal, and some
areas across the region could reach near or break record highs on
Thursday, with every site (GLH, GWO, TVR, JAN & HBG) except MEI.
As the surface low and frontal boundary develops across the
central Plains, the pressure gradient will increase across the
Delta, where winds could be somewhat gusty up to 15mph. Other than
that, expect a nice and very warm afternoon on Thursday. /DC/

Thursday night to Tuesday:

Before the start of the weekend, warm advection will dominate
Thursday into Friday. Temperatures on Friday are expected to reach
near daily record breaking across the CWA, with some areas
reaching as high as the mid to lower 80s.

A passing cold front associated with a low pressure system centered
in Midwest on Friday evening may bring a few showers into the Delta.
As of now, the only chance for isolated thunderstorms could occur
early Saturday morning in the central and southeast region of
Mississippi. The forecasted convection however looks shallow at this
time and could be very short lived. The window of opportunity for
anything severe seems unlikely. Looking at the forecasted SKEW-T
for this time frame shows that a capping inversion is the only
thing keeping the firing of convection before the front passes.

After the passing of the cold front Saturday, the region will return
to a more zonal flow before a weak cold front moves in from the
Plains Monday morning. Rain showers are expected to be widespread
across ArkLaMiss and end early Tuesday morning. /12/

&&

.AVIATION...
00Z TAF discussion:

Flight categories are expected to drop precipitously again tonight
at most (or all) sites, mainly after midnight, as the somewhat
moist boundary layer and light winds provide an optimal set up
for fog formation. Confidence in long-lasting sub-IFR conditions
is highest at GTR/CBM/NMM/MEI/PIB/HBG although even locations
further to the west should at least have temporary sub-IFR
conditions around daybreak. Expecting low clouds and fog to break
up relatively quickly in western zones tomorrow morning, but in
central and eastern MS flight cats may take until late morning to
entirely improve to VFR. Winds tonight will be light from the east
but should be more ubiquitously from the south by late tomorrow
morning. /BB/

&&

.PRELIMINARY POINT TEMPS/POPS...
Jackson       50  82  56  83 /   1   1   2   6
Meridian      52  81  55  82 /   1   1   3   5
Vicksburg     50  82  56  84 /   1   1   2  16
Hattiesburg   52  82  55  81 /   1   1   5   5
Natchez       52  81  57  80 /   1   1   2   8
Greenville    52  79  56  79 /   1   1   3  16
Greenwood     52  80  58  81 /   1   1   3  10

&&

.JAN WATCHES/WARNINGS/ADVISORIES...
MS...Dense Fog Advisory from midnight tonight to 10 AM CST Thursday
     for MSZ018-019-025>066-072>074.

LA...Dense Fog Advisory from midnight tonight to 10 AM CST Thursday
     for LAZ007>009-015-016-023>026.

AR...Dense Fog Advisory from midnight tonight to 10 AM CST Thursday
     for ARZ074-075.

&&

$$

12/DC/BB


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