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ms discuss

Office: JAN

FXUS64 KJAN 220919

Area Forecast Discussion
National Weather Service Jackson MS
419 AM CDT Fri Jun 22 2018


Today and Tonight: Early morning water vapor imagery/RAP analysis
showed the circulation around a nearly stacked low over southern
Illinois with a shortwave nearing the Ozarks that will continue to
swing around the base of the low today. Surface analysis had the
associated cold front dropping over the Missouri bootheel and
extending southwest across southwest Arkansas into northeast Texas.
The shortwave is expected to help initiate convection along the cold
front later this morning. Models agree that this activity will
spread east southeast into our northwest most zones shortly
thereafter eventually spreading to the Highway 84 corridor by late
afternoon. Our tropical airmass with greater than two inch PWATs got
dry slotted yesterday but a moist airmass remains over the region as
GOES total PW imagery suggests PWATs continue around 1.6 inches over
our CWA early this morning. Surface observations also had mid 70F
dew points over our CWA. Although the storms will get an early
start in our north they should encounter an environment with MLCAPEs
in excess of 2000j/k. Considering the flow around the low to our
north contributing to deep layer bulk shear around 40 kts, the
environment will support the potential for severe storms with
damaging wind and hail being the main threats. Locally heavy
rainfall will also be possible and a brief tornado or two cannot be
ruled out.

The nearly stack low will move northeast toward the Ohio River
Valley tonight and weaken stranding the cold front to stall across
our northern zones this evening before drifting back north toward
morning. Most of the convection over our CWA will dissipate this
evening with the loss of daytime heating but, convection will linger
in proximity of the frontal boundary through the night. There are at
least a couple models that suggest a complex of storms may develop
tonight and track along the stalled front, possibly dropping into
our CWA prior to sunrise. Wl maintain a MARGINAL area in our HWO
across the Highway 82 corridor to account for this threat.
Otherwise, temperatures will be held close to normal today due to
the convection and cloud cover but Saturday morning lows will be
warmer than normal again. /22/

This weekend: As a mid/upper trough pulls northeastward away from
the area, a surface front stalled across east AR into north MS will
retreat northward, with a surface ridge building in along the Gulf
Coast. This will begin to confine convection north of the region as
capping increases from the south. However, there remains the
potential for a complex of storms to brush the northern fringe of
the CWA into early Saturday as suggested by the 00Z Euro and some
CAM solutions, so chance POPs were maintained into that time period.
Otherwise, with fewer clouds/showers, temps will tick up again this
weekend, and given the remaining moist airmass, heat stress will
become more of a concern. We'll continue mention in the HWO for heat
indices approaching 105 over most of the CWA on Saturday, also now
including Sunday as well. It is possible a heat advisory may be
needed eventually for some portion of the area.

Monday through Thursday: The surface ridge will begin to retreat
eastward, resulting in an increase in diurnal convection as our
region moves to the periphery of said ridge. Outside of the rain,
generally warmer conditions are expected as mid/upper heights
increase over the area. With a rather humid airmass remaining in
place, heat stress could continue to be a concern. However, the
greater potential for clouds/rain will create uncertainty over daily
peak apparent temps. Eventually, we may need to highlight a heat
stress risk on one of more of these days in the HWO/graphics/NPW.


06Z TAF discussion:
IFR cigs were observed at MEI at 05Z with VFR conds observed
elsewhere. Satellite imagery suggests IFR cigs wl be psbl over
east MS the remainder of the night. Radars had a line of TSRA
north of HWY 82 that wl drift south through the night affecting
GTR by 0630Z and GLH-GWO after 07Z. The remainder of the TAF sites
wl see TSRA activity Friday. Away from TSRA activity VFR conds are
expected areawide after 14Z. /22/


Jackson       90  73  93  74 /  44  12   7   3
Meridian      91  73  94  74 /  50  15  10   3
Vicksburg     90  74  93  74 /  47  10   7   3
Hattiesburg   93  74  94  74 /  17   5   7   4
Natchez       91  74  92  74 /  17   5   8   3
Greenville    88  73  91  75 /  66  25  30   8
Greenwood     86  73  91  74 /  70  25  38  11