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fxus64 kjan 200658 aac 
afdjan

Area forecast discussion...updated
National Weather Service Jackson MS
158 am CDT Thu Jun 20 2019

Update...

Updated for 06z aviation discussion.

&&

Aviation...

06z taf discussion:
a few lines of strong to severe thunderstorms continue to impact
portions of the region to start the period, with the potential for
gusty winds in excess of 50 kts with the strongest of storms.
Expect thunderstorms and rain activity to diminish by 12z, with impacts at taf sites
primarily being patchy br and areas of low stratus in the wake of
the storms. Expect VFR conditions to prevail after 14z Thursday. A
few rain showers or thunderstorms and rain may re-develop around the region after 18z, but
chances were too low include in the tafs at this time. /Nf/

&&

Discussion...

Rest of tonight:

Overall forecast is generally playing out on track, with a mesoscale convective system
diving down through southern Arkansas, in the west-northwest flow.
Strong shortwave trough is diving down across the arklatex,
leading to severe convection development propagating towards the
region. Severe thoughts are generally playing out on track, as
juxtaposition of strong mid-deep layer effective bulk shear & some
lingering instability (i.E. 35-45kts & 1500-3000 j/kg mlcape)
lead to a favorable parameter space for severe convection. Some
severe storms will continue to propagate to the east-southeast
through southeast Arkansas, northeast Louisiana and somewhat east
of the Mississippi River into the arklamiss Delta. The south &
eastward extent of these storms becomes more in question as it
moves into somewhat less destabilized & suppressed environment
from storms this morning & some mixing occurred into the
afternoon. Main adjustments were a collaborated Severe
Thunderstorm Watch over southeast Arkansas, northeast Louisiana &
northwest Delta through 4am. Main threats remain damaging wind
gusts & large hail. An isolated tornado or two can't be ruled out,
especially in any eastward bowing segments due to ~25kt 0-3km
shear vectors from west-northwest. No changes were needed to the
severe weather potential statement/graphics but eastward severe extent may become a question
mark into the night & might be less of a threat further east,
especially east of the I-55 corridor. /DC/

Prior discussion below:

Tonight and thursday: the outflow boundary from a decaying mesoscale convective system
moved across our County Warning Area earlier today and has scoured out our rain
chances with the exception of very low chances of a storm or two
this afternoon into the early evening over east Mississippi. Rain
chances will increase this evening though especially for the
northern half of our County Warning Area. Regional satellite imagery and radar
showed storms firing over the Southern Plains. A shortwave trough
will move over the plains and enhance develop of the storms that
are expected to form another mesoscale convective system as it approaches our County Warning Area. The
environment is expected to become more favorable for severe storm
development over our County Warning Area as the mesoscale convective system enters later this evening.
Considering the expected parameters, damaging wind gusts and hail
larger than quarter size will be the main threats but a tornado or
two cannot be ruled out. Brief heavy downpours will also accompany
the activity. Model timing and track of the convection still
differ but consensus suggests that an mesoscale convective system will move into the
northwestern portions of our County Warning Area by 10 PM and continue to spread
east across our County Warning Area through the night. There remains some question
as to how far south the severe threat will get before the
convection weakens but the threat for severe storms is expected to
end before sunrise Thursday. The shortwave will be east of
Mississippi Thursday but a moist airmass will be left over our
County Warning Area. A potential boundary left over from the mesoscale convective system along our
southern zones may become the focus for a strong storm or two
Thursday afternoon. In addition, dew points in the low to mid 70s
lingering over our southwest with temperatures in the lower 90s
will lead to heat index values near 105f Thursday afternoon. Wl
maintain mention of this in the severe weather potential statement. /22/

Thursday night through next week:

A few storms will likely linger into Thursday night as the
shortwave trough passes to the east and leaves behind a weak
surface boundary, but confidence is low on where these would focus
and just how much coverage there will be given the uncertainties
with convective evolution for Thursday and diminishing synoptic
scale support.

Showers and thunderstorms cannot be entirely ruled out for Friday,
especially if returning southerly flow can help any seabreeze
convection to spread northward. Then it looks like the next best
chance for more than a few isolated showers or storms will be next
Monday into Tuesday time frame as a low pressure system moving
eastward across the country brings some height falls and increases
convection at least to our north and west. For now it appears the
associated frontal boundary will stall out before dipping into our
forecast area, but we will continue to monitor the trends for this
early week setup.

Heat stress will continue to be a concern over mainly western/
southern portions of the arklamiss as dewpoints remain in the low to
mid 70s throughout the day while temperatures climb into the low 90s
resulting in heat index values in the 103 to 105 degree range. The
limited heat threat continues in the severe weather potential statement/graphics for heat indices
reaching 105, and we will continue to monitor for now the
possibility of heat advisory issuance. /Nf/ec/

&&

Preliminary point temps/pops...
Jackson 91 75 94 75 / 21 13 20 5
Meridian 90 75 96 76 / 28 24 23 8
Vicksburg 91 77 93 77 / 18 11 20 4
Hattiesburg 94 75 94 75 / 28 7 31 3
Natchez 91 75 93 76 / 19 8 24 3
Greenville 90 76 93 77 / 32 13 11 4
Greenwood 88 76 93 76 / 31 22 17 8

&&

Jan watches/warnings/advisories...
MS...none.
La...none.
Arkansas...none.

&&

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