Area Forecast Discussion
Issued by NWS Jackson, MS

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385
FXUS64 KJAN 200613 AAC
AFDJAN

Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
1213 AM CST Fri Jan 20 2017

...ACTIVE PERIOD OF WEATHER EXPECTED THROUGH THE WEEKEND...

.UPDATE...
Updated for 06Z aviation discussion.

&&

.AVIATION...

06Z TAF discussion:
Abundant low-level moisture has resulted in patches of dense fog and
scattered to broken low clouds across the forecast area tonight.
Expect these conditions to continue through Friday morning. Periods
of MVFR ceilings and no fog will be broken by IFR or LIFR ceilings
and visibility as low as 1/4 mile. By 15Z Friday, expect a period of
MVFR ceilings before low clouds scatter out by 21Z. There are
increasing chances for TSRA near the very end of the period, but
impacts are too uncertain at this time to include in TAFs. /NF/

&&

.DISCUSSION...
The mid/upper-level low responsible for our first round of severe
weather and flooding is currently located over the north Central
Plains with multiple embedded shortwaves, upper level divergence and
associated convection well to the east of our CWA now. In the wake of
the convection, temps have quickly dropped into the 50s with some
sites already in the low 50s, thus when combined with a very moist
boundary layer and weak to calm winds has already resulted in areas
of fog, mainly along and south of the I-20 corridor. For the
remainder of the overnight period, expecting this fog to expand with
widespread areas of fog across the entire CWA. While some patchy
dense fog has already been observed and cannot be ruled out at any
one location, confidence is currently not high enough in widespread
dense fog to warrant an advisory as visibilities have remained
variable with only brief drops below a half mile. Added an area wide
limited threat to the HWO to reflect this current thinking. However,
the trends will be closely monitored through the evening in the event
a dense fog advisory and/or HWO upgrade is needed later on. In terms
of overnight temps, current obs indicate that most area temps are
already cooler than guidance, therefore went on the lower end for min
temps. Most locations that have already bottomed out might not drop
much more through the evening and could even warm a degree or two as
more cloud cover moves in from the west. /TW/

Prior discussion below:

.Tonight and Friday...

Swath of light to moderate rain continues to track across the
ArkLaMiss region this afternoon. This will continue through the
remainder of the afternoon into the early evening before pushing
totally east of the region. This will come as the upper trough will
track northeast of the area and away from the ArkLaMiss. Given the
anomalous moisture in place over the region and the saturated
grounds, will continue with the limited risk for flooding through
the remainder of the afternoon. As the rain clears out later this
evening into tonight, there is good potential for patchy fog to
develop across the area. Some locations will likely see some dense
fog tonight but pinpointing exactly where is a little more
difficult.

Dry weather will occur tomorrow as we will be between today`s system
and the weather system set to move in from the southwest tomorrow
night. Partly sunny skies will help temperatures warm into the lower
to mid 70s. /28/

Friday night through Wednesday night...Another round of convection
will move north over the area Friday night with strong to severe
storms likely. This looks like it will be the first of a couple of
rounds of severe possible for the area this weekend. A surge of 1.3
to 1.5 inch PWATS will push into the southern portions of the area
Friday evening and push north across the area overnight. Initially
most of the storm look like they will be elevated with large hail the
primary concern. All of the models are in good agreement of -4 to -5
showalters, Vertical Totals of 29 to 30 and h700-h500 lapse rates of
at least 7.5 c/km, along with high sig hail values. These values are
very rare for this time of year, indicative of late February or
March. Some Significant hail looks possible, but will hold off on any
mention of this in the HWO for now. The storms may become more
surface based very early on Saturday as low level shear and moisture
increase. Expect an increased risk for damaging winds and tornadoes
generally along and south of the Hwy 84 corridor during this period.

The bulk of the first round of storms will shift east of the area
early on Saturday, but the GFS/NAM develop additional convection
Saturday afternoon/evening, and with steep mid level lapse rates the
large hail threat will continue. It really doesn`t look there will be
much of a break in the shower/thunderstorm activity Saturday night
as the upper low approaches the ArkLaMiss.

Showers and thunderstorms will once again be possible on Sunday as
the upper low passes over the area, and although the severe risk
looks limited, there will be some risk for large hail as mid level
lapse rates will range from 7.0-7.5 c/km. Showers will persist into
Sunday evening before ending overnight with lows falling into the
low/mid 40s.

High pressure will build in on Monday with cooler highs in the low
60s. The surface flow will swing back around to the southeast on
Tuesday with high temperatures climbing back into the mid/upper 60s
under partly cloudy skies. A cold front will swing across the area
on Wednesday which will bring another chance for showers to the
ArkLaMiss./15/

&&

.PRELIMINARY POINT TEMPS/POPS...
Jackson       75  58  74  54 /   8  68  49  65
Meridian      74  58  75  56 /   8  82  63  68
Vicksburg     74  57  74  53 /   9  62  46  64
Hattiesburg   75  61  76  57 /   8  90  69  67
Natchez       76  59  75  55 /   9  66  47  58
Greenville    70  56  72  52 /   8  48  40  70
Greenwood     73  57  74  52 /   8  55  43  67

&&

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

&&


$$

TW/NF/15



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