000
FXUS64 KJAN 210523 AAC
AFDJAN

Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
1223 AM CDT Sat Oct 21 2017

.UPDATE...
Updated for 06Z aviation discussion

&&

.AVIATION...
06Z TAF discussion:
VFR flight categories will prevail at all TAF sites tonight, and
throughout the day Saturday.  An isolated shower can`t be ruled out
across southern and western portions of the region later this
afternoon, i.e. KHBG and KGLH.  Of course, this will result in a
brief degradation of visibilities and/or ceilings if observed within
a particular site`s respected aerodrome.  Much of this activity will
quickly dissipate around sunset this evening.  Winds will be a tad
breezy today as they blow from the southeast around 10 knots,
gusting at times to around 17 knots. These will subside to between
5-10 knots during the evening hours. /19/

&&

.DISCUSSION...
Considerable high cloudiness is overspreading the area this
evening, though there are still plentiful patches of mostly clear
sky. In fact, some of the clear areas have been large enough to
allow a few spots to cool off a bit quicker than originally
anticipated, mainly in the Delta. Still, expecting additional
cooling in those areas to be tempered as clouds continue to
increase overnight. Due to that, some areas mainly in the
south/west part of the CWA may already be at or near tonight`s low
temp. Regional radar has been detecting a few high-above-the-
surface echoes across LA this evening, but with the 00Z KJAN
sounding sampling considerable dryness in the mid and lower
portions of the atmosphere, measurable rain will be difficult to
come by overnight. No notable changes were made to rain chances,
but hourly temperature curves were adjusted based on current
trends. Updated forecast products have already been transmitted.
/DL/

Prior discussion below:

Tonight through Saturday:

The primary focus will be centered beyond the near term forecast as
a major shortwave trough and associated cold front advance toward
the Lower Mississippi Valley later this weekend. For now, a dry
airmass is keeping the weather quiet for the ArkLaMiss, and expect
rain-free weather to continue through tonight. As we approach
daybreak Saturday, low level winds will begin to veer to a more
southerly direction with the approaching trough, and increasing
moisture transport/convergence should support shower development,
especially over western/southern portions of the forecast area, but
rainfall amounts should be light. Have continued to show increasing
cloud/rain chances for Saturday, but temperatures may still climb
into the mid 80s before clouds thicken up. /EC/

Sunday through next week:

An upper low pressure system is expected to cutoff from a digging
trough in the mid-Mississippi Valley region on Sunday. As this low
pressure passes over the area, a cold front will accompany this
passage as well. As the models come into a bit better agreement on
the timing and evolution of this system, it appears the system and
rainfall should completely exit the region by Monday night. There
may be a couple rounds of rainfall between Sunday and Monday as
cyclogenesis occurs and the low begins to lift northeast Monday.
During all of this, the severe potential remains rather low. CAPE
values are decent and low-level moisture will be abundant but poor
lapse rates and the evolution of the cyclogenesis over the area
will limit severe storms. This system however has plenty of
moisture flowing into it from the Gulf. PWs ahead of the front
will be near 2" on Sunday. Storm total rain amounts with this
system could be as high as 4" in some places, with widespread 2"
likely. Our area has been quite dry lately though and part of the
area is under a D1 drought. With the abundant moisture available,
convective rain rates could be high within the strongest storms.
This being said, where rain rates are high enough, some limited
flash flooding will be possible. This has been added to the HWO
and the threat will continue to be monitored.

After the cutoff low exits to the northeast on Tuesday, the upper
trough digs deeper into the region and brings a reinforcing cold
front through the area. A much drier airmass is expected behind
this front. PWs will likely drop below 0.5" and dewpoints will
drop into the 30s. Height falls will be significant going into
Wednesday morning and will bring the coldest temperatures of the
season so far. Lows Wednesday morning may dip into the upper 30s
in some places. High temps will mostly be in the 70s next week
with Wednesday topping out in the mid 60s. /10/

&&

.PRELIMINARY POINT TEMPS/POPS...
Jackson       68  79  60  72 /  16  83  74  39
Meridian      65  80  64  74 /   4  66  75  55
Vicksburg     68  78  58  72 /  22  87  74  33
Hattiesburg   68  79  64  74 /   7  79  70  38
Natchez       69  78  57  71 /  27  86  69  27
Greenville    67  77  57  71 /  30  86  69  37
Greenwood     68  78  58  71 /  10  79  77  49

&&

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

&&


$$

19

NWS JAN Office Area Forecast Discussion