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FXUS64 KJAN 250913
AFDJAN

Area Forecast Discussion
National Weather Service Jackson MS
413 AM CDT Sun Aug 25 2019

.DISCUSSION...
Today and tonight...

Our relatively wet pattern will continue today, and in fact, better
coverage of showers and storms should occur. PW values across the
area remain in excess of 2 inches, with around 2.25 inches being
sampled on the 00Z KLIX sounding. This tropical airmass will remain
across the area, which has contributed to continued showers and
isolated thunderstorms overnight across portions of the ArkLaMiss
along with a stalled frontal boundary. Models continue to show that
even more moisture will ooze its way into the region through the day
with PW values forecast to be around 2-2.5 inches across portions of
the area, especially the east and southeast part of the forecast
area. For some locations, this is in the 97th to 99th percentile.
The impetus for this influx of moisture is an area of low pressure
that is sitting across the northern Gulf of Mexico, just offshore of
Louisiana. Through the course of today, this low will slowly
progress to the north and east, eventually moving onshore across
southern Louisiana. As this occurs, additional showers and some
storms will move into the southern sections of the forecast area.

This low will trek to the north and east across southeast
Mississippi through the evening and overnight hours, increasing
potential for showers and storms in this location through pre-dawn
Monday morning. Because of this, the best rainfall QPF will be
generally along and east of the Natchez Trace Parkway, with the bulk
of it occurring most likely between midnight and 7am Monday.
Rainfall totals through Monday morning will be around 1.5 to 2.5
inches from roughly Bude to Columbus and locations south and east of
this line. With high atmospheric moisture, efficient rainfall should
occur and some locations may see heavier rainfall, especially if
rain/storms train over the same locations. This may lead to
localized flooding and will go ahead and advertise this limited risk
in the HWO/graphics for this area. This will coincide with at least
a portion of the Day 1 marginal and slight risks for excessive
rainfall from WPC. If rainfall totals increase or model guidance
suggests a slower moving low pressure system, future shifts may want
to consider a Flash Flood Watch for south/southeast/east Mississippi
for later tonight into early Monday but we will hold off for now.

Rain and storms expected today further north across the Highway 82
corridor will be less associated with this low pressure system and
more with a shortwave dropping south and this stalled boundary over
the region. Rainfall amounts in this corridor will range from half
of an inch in the Delta to two inches in the Golden Triangle(some of
which may also be influence from the incoming low later in the
night).

Clouds and rain today should hinder temperatures. Highs are
expected to reach into the 80s today across the area. /28/

Monday through early next weekend:

The perturbed & stormy pattern will remain in place around early
week before a drier, slightly cooler & near seasonable pattern will
move in mid-late week. At the start on Monday, a weak surface low
pressure & shortwave trough will be becoming phased into longwave
synoptic trough & cold front digging southeast out of the Plains.
This will only help bring a stronger low-level jet & influx of
tropical moisture (i.e. 2-2.5 inch PWs) across most of the area.
With a stationary front lingering across to the north, expect
increasing isentropic ascent & moisture transport & convergence to
combine with synoptic jet dynamics to favor widespread rain &
storms. Global & high resolution guidance continue to depict
tropical moisture laden air supportive of high rainfall totals. Some
gradual totals of 2-3 inches are indicated, possibly locally higher.
Will continue the threat for locally heavy rainfall & localized
flash flooding in the HWO & graphics into Monday afternoon. This
threat will likely be diurnally drive further north & more mesoscale
& surface feature driven further south closer to any surface low.
The Euro is a little more on the aggressive side on the surface
feature, while the other suite of consensus is a little less clear
on the details. Even saying that, the newer Euro has backed off on
QPF in the northeast, so resolving some of these mesoscale details
will be difficult. In the wake, we will be either in a zonal to
northwesterly synoptic flow, with a broad trough swinging off to our
north. This will lead to increased forcing & juxtaposition of
favorable parameter space (i.e. steeper lapse rates/vertical totals
into the mid-upper 20s & little better low-mid level bulk shear up
to ~20-25kts or so @ 0-3km & 0-6km) for some strong storms &
isolated severe storm potential by early-mid week (i.e. Tues.-Wed.).
Being on the eastern periphery of the ridge to the west will keep
any central Plains MCS of concern, but we may be just enough to the
east to remain out of the higher threat. For now, will keep mention
of severe out of the HWO, but may be needed as we get closer. Global
consensus has been consistent on the cold front around mid-late
week, with the GFS slightly slower. Regardless, surface high
pressure will build in the wake, with much drier air & pattern in
the wake & cooler than normal lows & near to slightly below normal
warmth. Global consensus continue to depict a broad & weak easterly
wave/surface trough drifting west across the eastern Gulf of Mexico
into early next weekend, with another front diving down, based on
the 00Z Euro.

Numerous rain & storms can be expected on Monday, with the highest
chances across the I-59 & Highway 45 corridor through midday Monday.
Expect these chances to build to the east-northeast into Tuesday.
Heat stress will remain hampered by this pattern, with some
potential west of the Mississippi River on Tuesday. For now, there
remain too much uncertainty on mesoscale storm details to outline
any heat potential. Highs will generally be below at the start of
the work week, due to widespread clouds & storms, before being near
or slightly below normal early-mid week or so. Below normal lows,
even into the low-mid 60s, are possible late week & into the
weekend. This cooler & drier pattern will be a nice reprieve from
the humid & stormy pattern early in the week. /DC/


&&

.AVIATION...
06Z TAF discussion:
SHRA continues across portions of the area this morning but should
gradually diminish through the night. With some brief
daybreak/early morning MVFR or lower stratus, VFR conditions
should resume by mid-morning. SHRA/TSRA looks to affect much of
the area today, most likely many TAF locations. However, opted to
return to VCTS for now before better timing can be pinpointed in
future forecasts. TSRA should be mostly confined to 17Z-01Z across
the area with some diminishing through the night. /28/

&&

.PRELIMINARY POINT TEMPS/POPS...
Jackson 87 72 87 73 / 80 69 63 16
Meridian 89 72 84 72 / 82 82 75 28
Vicksburg 88 73 89 75 / 64 49 42 11
Hattiesburg 88 72 85 73 / 82 82 75 19
Natchez 85 73 87 74 / 77 61 48 11
Greenville 88 72 89 74 / 74 50 26 10
Greenwood 87 72 86 74 / 81 59 44 14

&&

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

&&


$$

DC/28
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