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fxus64 kjan 201038 aaa 
afdjan

Area forecast discussion...updated
National Weather Service Jackson MS
538 am CDT sun Oct 20 2019

Update...
updated for 12z aviation discussion

&&

Aviation...
12z taf discussion: variable flight categories will continue
through mid morning due to patchy fog and low clouds. By mid
morning, visibilities will improve with MVFR ceilings grdually
rising to VFR by afternoon. Isolated showers and thunderstorms will
be possible through much of the period for glh, gwo, gtr, Jan and
hks. MVFR/IFR ceilings will develop once again after midnight and
continue through the end of the period./Gg/



&&

Discussion...

Today and tonight:

Areas of fog have managed to form in the east during the evening
and overnight hours, but have been having trouble remaining as
higher clouds continue to move in from the west. These clouds and
some convection over la were resulting from a weak mid level
shortwave embedded in the southwest flow aloft. Do not expect the
fog to become much more than locally dense, mainly over the
southeast, as the system moving in from the west becomes
increasingly hostile to fog maintenance this morning.

As this weak shortwave moves across, low level warm advection
will work on the cap enough so for the scattered convection to
become deeper with some thunder during the afternoon, mainly in
the west. This wave will move quickly through by late afternoon
with attention turning west again to the larger scale system
approaching. The leading edge of the precipitation ahead of the
cold front will enter the far northwest portions prior to dawn
with the bulk of the precipitation moving through during the day
Monday. /Gg/

Monday through saturday:

A rapidly deepening low pressure system over the northern High
Plains will take on a negative tilt as it develops and moves east
toward the Great Lakes on Monday. At the surface, a strong cold
front trailing the low pressure system will sweep through our
region early Monday morning through Monday night, and bringing
with it a threat for severe weather. No changes have been made to
the overall threat areas in our forecast area, but the
westward/slower trend with regards to the cold front passage could
end up leading to a lower risk for daytime severe weather farther
east of the front in our area where the cap may not so easily be
eroded without lift or destabilization.

The various mesoscale guidance indicate an organized convective
system with severe weather potential approaching the arklamiss
Delta Region by early to mid Monday morning. Height falls in
advance of the front still look to be minimal, but strong moist
advection beneath a low level cap should help to increase
instability mid-morning to mid-afternoon. Even with minimal
instability in the morning hours, strong deep layer shear (35-50
kts of 0-6km shear) should maintain some potential for organized,
strong to severe thunderstorms near the cold front. The primary
hazards will be damaging wind gusts and a few possible tornadoes
where bowing segments can develop. Lapse rates look to be weak
enough that there is not much of a hail threat, but the deep layer
shear will support at least some supercell organization.
Therefore all modes of severe weather will be possible, especially
if any bowing segments develop along the line or isolated
supercells can develop ahead of the front.

Behind the front, a Continental airmass will bring cooler and
drier weather for Tuesday and Wednesday. Tuesday night looks like
an ideal setup for radiational cooling with a surface high over
the region and mostly clear skies, so nudged min temps closer to
MOS guidance values. Then the next system will begin to take shape
over the southern High Plains on Thursday. There is quite a bit
of disagreement among model solutions with development of a
shortwave trough or closed low Thursday night through the end of
the week, with the European model (ecmwf) and CMC solutions being the most
ambitious with closing an upper-level low pressure system over
deep Texas and slowly kicking that eastward. The operational GFS
lines up fairly well with the GFS ensemble mean with an open
trough. Therefore lower confidence remains with regards to timing
of next cold front and any precip chances. But if the system can
take its time to deepen and swing eastward, ample moisture from
the Gulf of Mexico could drive a heavy rain threat for the end of
the week. /Nf/ec/

&&

Preliminary point temps/pops...
Jackson 83 68 78 51 / 38 28 94 60
Meridian 81 67 80 53 / 9 11 91 76
Vicksburg 84 70 79 51 / 44 28 90 26
Hattiesburg 83 67 79 56 / 12 8 88 75
Natchez 84 70 78 52 / 41 21 91 34
Greenville 82 69 76 50 / 26 53 98 14
Greenwood 82 70 76 48 / 27 41 91 22

&&

Jan watches/warnings/advisories...
MS...none.
La...none.
Arkansas...none.

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