757
FXUS64 KJAN 191742
AFDJAN

Area Forecast Discussion
National Weather Service Jackson MS
1242 PM CDT Thu Oct 19 2017

.UPDATE...
Updated for 18Z aviation discussion

&&

.AVIATION...
18Z TAF discussion:
VFR conditions will prevail at all TAF sites through the period.
Patchy fog with brief reductions cannot be ruled out at any one
location from 20/10z through 20/13z, however confidence in
coverage and intensity isn`t high enough to warrant dropping
visibilities below VFR with this issuance. /TW/

&&

.DISCUSSION...
Expect height rises today as a ridge axis moves through the
ArkLaMiss. These height rises coupled with anomalous H850 temps in
the 90th percentile will lead to warm afternoon highs in the low
80s. Only change was to increase max temps by a degree or two.
Otherwise, sunny skies will persist with a very dry airmass (PWATs
of 0.33" on the 12z JAN sounding) in place across much of the
region. Some high clouds could filter in later this afternoon and
into the early evening hours in the southwest, but overall
coverage isn`t expected to be enough to impact daytime max temps.
/TW/

Prior discussion below:

Today through Tonight:

Another quiet weather day is expected across the ArkLaMiss region.
Water vapor satellite imagery early this morning shows a large area
of dry air over the Southeast U.S. associated with a ridge of high
pressure anchored over the Gulf Coast region. Expect some
amplification of the upper-air pattern through tonight as a southern
stream jet streak slides over the US/Mexico border and a deeper
northern stream shortwave moves onshore the West Coast. Mid-level
height rises over our region should push high temperatures up
another 3 to 5 degrees today, with most locations reaching into the
low 80s. Some increasing high clouds and the return of southeasterly
surface winds by tonight should keep low temperatures a few degrees
above normal. /NF/

Friday into the middle of next week:

Rain (and some storms) still look to return this weekend into
early next week as a series of disturbances (and associated cold
fronts) impact our region. However, the devil is in the details
and discrepancies between model solution are making it difficult
to have great confidence in those details.

The gist of the situation is an initial big disturbance dropping
into an evolving central states trough will push a cold front toward
(possibly well into) our forecast area by Sunday. This
disturbance will likely briefly cut-off from the northern stream
flow before getting kicked off to the east and northeast late
Monday or Tuesday. During this "stall" time the front should stall
a bit as well with some potential for a deeper area of low
pressure to develop along the boundary over the Lower Mississippi
Valley before heading quickly east sometime Monday or Monday
Night. In its wake should come a secondary cold front likely
packing the chilliest temps of the fall season thus far.

There is good potential enough moisture/lift/instability
ingredients will come together over portions of the Southern
Plains on Saturday and Saturday night to erupt some severe severe
storms along the initial incoming cold front. In this area SPC
already has a large area of central Oklahoma into north-central
Texas under an "Enhanced" risk of severe weather. There still is
some chance a portion of the volatile ingredients in this area
will shift east and south toward the Lower Mississippi Valley
later Sunday through early Monday to bring some powerful storms to
portions of our forecast area. However, at this juncture, we are
continuing to refrain from mentioning anything in the HWO or
graphics because of large uncertainty with how the complicated
interaction of disturbances and fronts will evolve this far east.
But even in the worst case the parameter space capable of
supporting severe weather should not be as potent as what is
expected to come together Saturday in the mentioned "Enhanced"
risk area. So, for now, we will continued to closely monitor the
situation for the Sunday through early Monday time frame, but we at
least have confidence a fairly widespread coverage of showers and
thunderstorms is in the cards. Expect chances of showers and
thunderstorms to ramp up pretty quickly in advance of the front
Saturday afternoon through Sunday morning with only higher clouds
increasing on Friday.

Even more uncertainty exists with regard to when precipitation
will ultimately exit. General model consensus suggests the
deepening low in pulling away from the vicinity should at least
have enough upper support from the lagging upper low to keep some
shower chances going through Monday night in many areas, and it
can`t be ruled out some showers may continue into next Tuesday in
at least northern areas.

Confidence is higher for temperatures with above normal warmth
expected through the weekend in advance of initial cold fropa,
with temperatures quickly trending to at least a little below
normal behind the front. But, as mentioned earlier, the chilliest
air will likely wait until after a reinforcing cold front pushes
through the region around next Tuesday. /BB/

&&

.PRELIMINARY POINT TEMPS/POPS...
Jackson       83  53  82  64 /   0   0   1   2
Meridian      81  51  80  60 /   0   0   1   2
Vicksburg     82  53  82  63 /   0   0   2  10
Hattiesburg   82  54  82  63 /   0   0   4   2
Natchez       82  56  82  65 /   0   0   5  10
Greenville    81  52  81  60 /   0   0   1  11
Greenwood     81  51  81  61 /   0   0   1   3

&&

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

&&


$$

TW/NF/BB

NWS JAN Office Area Forecast Discussion