Area Forecast Discussion
Issued by NWS Jackson, MS

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696
FXUS64 KJAN 201017 AAA
AFDJAN

Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
517 AM CDT Fri Oct 20 2017

.UPDATE...
Updated for 12Z aviation discussion

&&

.AVIATION...
12Z TAF discussion:
VFR conditions are expected to continue through the next 24 hours
as clouds increase ahead of our next system for this weekend.There
may be some very brief shallow patchy fog in some locations which
will lift by around 13z. Otherwise, winds will be out of the
southeast at around 5-10kts today and around 5 knots tonight./17/


&&

.DISCUSSION...
Today and Tonight...Latest rap and satellite imagery showed a
strong layered ridge subsidence across the Lower Mississippi Valley.
The nearest showers and thunderstorms were ahead of a shortwave
coming out of the Southern Plains.  On the surface high pressure was
centered over East Tennessee with light surface flow over the region
under some high thin clouds. Predawn temperatures were mainly in the
50s with some patchy shallow fog.

For today with cross over temps expect the patchy shallow fog along
and east of the Mississippi River to lift by 13z. Areas west of the
Mississippi River where thick high clouds ahead of the shortwave may
limit patchy shallow fog development coming from the southwest.
Otherwise anomalous low level temperatures and subsidence will help
to push temps five to eight degrees above normal into the lower to
middle 80s for today. Dewpoints in the 50s will bring minimum
humidity around 35 percent under light winds, which will add to the
recent dry conditions for fine fuels such as grasses and leaves.
Scattered thick high clouds will come into the region under
southwest flow as the layered ridge axis moves over Georgia.

For tonight high clouds will increase in coverage across the region
from the southwest. With some inflow across the region lows will be
a little milder with readings in the middle 50s to the middle
60s./17/

Saturday through next Thursday...High pressure aloft and at the
surface will gradually relinquish their grip on the forecast area
through the course of the upcoming weekend.  This is in response to
a trough that`ll deepen as it swings east into and through the
nation`s mid-section Saturday into Sunday.  This trough will
eventually become a cutoff low as it pivots across the forecast area
Monday into Monday night.

At the surface, this will cause a cold front to approach the
forecast area from the west early Sunday morning.  As the front
shifts into and through the forecast area during the course of the
day Sunday, and the upper trough becomes a cutoff low, another
surface low is progged to develop along the southern extent of this
front, and lift northeast through the CWA Sunday evening into Monday
morning.  As both the surface low and front lift out through the day
Monday, rain chances exit the forecast area as well.

Persistent northwest flow aloft and at the surface set up through
mid-week, will result in another bout of cooler drier air advecting
into the forecast area through Wednesday.  Flow becomes more
westerly by the end of the forecast period on Thursday, resulting in
warm and moistening conditions heading into late next week. However,
before we get to the cool down at the beginning of the new work
week, the ongoing warming trend will continue into the upcoming
weekend as moisture subtly feeds back into the CWA.

With the increased warm advection ahead of the front on Saturday, in
addition to daytime heating, rain chances on Saturday look to be
best of locales west of the Mississippi River Saturday afternoon.
These chances will lessen into Saturday night as heating is lost.
The best chance for showers and storms through the period will be
Sunday into Sunday night as the developing surface low and front
shift east into and through the forecast area.  Again, rain chances
gradually come to an end during the course of the afternoon Monday
as both features pull out to the northeast.

Confidence in the potential for severe storms remains quite low at
the moment.  Some deep wind shear will be present over the CWA along
with some adequate instability.  However, the biggest question
regarding where this combination of ingredients will be best over
the forecast area, if at all, depends on where and when exactly the
surface low develops and lifts northeast through the CWA.  Models
this morning don`t have the greatest handle on these exacts either.
So with that said, I`ll leave the HWO clear on this morning`s
package. However, I can`t rule out that before all is said and done,
and at a minimum, a "Marginal" risk for an isolated severe storm
could be needed for a portion of the CWA sometime this weekend.  If
anything, this front will bring some needed and appreciated rainfall
to the forecast area. /19/

&&

.PRELIMINARY POINT TEMPS/POPS...
Jackson       84  62  85  67 /   0   4  25  20
Meridian      83  59  84  65 /   0   1   9  12
Vicksburg     84  63  85  68 /   0   6  49  33
Hattiesburg   82  62  83  67 /   0   2  24  21
Natchez       83  66  84  68 /   0   8  51  33
Greenville    82  61  83  67 /   0   9  29  41
Greenwood     82  60  83  67 /   0   5  17  26

&&

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

&&


$$

17



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