Area Forecast Discussion
Issued by NWS Jackson, MS

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FXUS64 KJAN 260942
AFDJAN

Area Forecast Discussion
National Weather Service Jackson MS
442 AM CDT Wed Jul 26 2017

.DISCUSSION...

Today through tonight:

The eastern extent of the vast expansive upper level ridge axis
(heat dome) will be building firmly into the region today and
clearing out the very wet regime that has been in place over
portions of the area over the past few days. We still may get a
few isolated showers and thunderstorms from midday through early
evening over mainly eastern MS, but locations in south central and
southeastern MS that have received recent deluges will have a
chance to dry out.

Hot temperatures have been trying to infiltrate into the northern
through western corners of the forecast area over the past few
days and the hotter regime will come all the way in starting
today. Usually in summer around here quick regime changes do not
happen because of relatively subtle features involved, but in this
case quite a few spots in southern through southeastern portions
of the area will notice a big spike in temperatures. Maximum
temperatures will generally be in the low to mid 90s but high
relative humidities will push the heat index much higher than the
actual temp. The hottest absolute temperatures should be in the
far northwest where upper 90s are possible, although in these
spots increased moisture mixing will keep heat indices from
getting way out of hand. But all in all expect heat indices
peaking up near 105 degrees in widespread fashion and perhaps
slightly higher across the Arklamiss Delta where a heat advisory
was hoisted that will go through tomorrow. This heat advisory may
eventually need to be expanded but our graphics will cover some
heat stress potential in all areas starting today.

Tonight, expect generally quiet conditions after early evening
isolated showers and storms in eastern zones diminish after
sunset. Skies will be mostly clear to partly cloudy with lows in
the balmy and humid low to mid 70s. /BB/


Thursday through next Tuesday:

This period will start off with continuing heat stress on
Thursday and into Friday before a front sweeps through the region
bringing with it rain/storm chances for late in the week into the
early weekend. This rare late July front will also bring a relief
from the heat for the upcoming weekend and early parts of next
week.

There is good confidence in warm temperatures and and humid
conditions combining to result in dangerous conditions during the
day on Thursday. The ArkLaMiss will be on the eastern extent of
the broad, stagnant upper ridge centered over the SW US, resulting
in anomalously high low to mid levels heights. By Thursday, 850mb
temps will have surpassed 20C areawide. This typically results in
high temperatures in the mid to upper 90`s this time of year.
Although some mixing will occur as day progresses, expect
dewpoints to range from 71-75 during during the warmest hours of
the day. This will result in heat indices in the range of 107-103
with the highest values occuring in the Delta. A heat advisory
has been issued for the areas where confidence in eclipsing the
105 heat index mark is best. However, this area may have to be
expanded at a later time.

By Friday, upper level heights will begin to decrease over the
area in response to a deep upper level low in Eastern Canada and
troughing over the eastern seaboard. A slow moving cold front
stretching from SE Canada through the Southern Plains will begin
to approach the region from the north as another cutoff low forms
near the Great Lakes, helping push the front towards the ArkLaMiss
on Friday and Saturday. There is still quite a bit of temporal
differences within model solutions with the GFS and the NAM
projecting quicker solutions than the Euro. SPC is advertising a
marginal risk for severe thunderstorms for our region on Friday
to account for strong to severe storms along the front. Decided
to not advertise that risk locally just yet due to the lack of
confidence in the timing of the front since the GFS has started to
come more in line with the Euro, estimating a nocturnal frontal
passage. However, to account for this slower fropa, the limited
heat threat was expanded for Friday.

The front will linger through the southern portions of the region
on Saturday, increasing chances of shower and thunderstorms
before exiting the region completely by Sunday morning. Cooler,
drier air will exist behind the front, providing relief from hot
temperatures. The ArkLaMiss will remain between steep ridging in
the west and troughing in the east, resulting in NW flow aloft
from late in the weekend through early next week. This pattern
will make for a difficult forecast as it weakens by mid week with
rain and storm chances beginning to increase again by Tuesday and
Wednesday.

&&

.AVIATION...
06Z TAF discussion:

A few showers late tonight cannot be entirely ruled out around
PIB/HBG/MEI/NMM but generally anticipate mostly clear to partly
cloudy skies overnight through tomorrow with some patchy daybreak
MVFR flight cats possible around the region due mainly to fog/mist.
Any temporary IFR condition potential at daybreak will likely be
limited to GLH/GWO/HBG/PIB where rainfall from yesterday has lead
to very moist ground. Otherwise, expect very light winds tonight
and northwest through west winds tomorrow remaining mainly less
than 10 mph. /BB/

&&

.PRELIMINARY POINT TEMPS/POPS...
Jackson       94  73  95  74 /  13   8   4   3
Meridian      94  74  96  74 /  21  15  14   4
Vicksburg     94  73  96  74 /   8   3   2   4
Hattiesburg   93  74  95  74 /  24  13  16   4
Natchez       92  72  94  73 /   9   3   4   3
Greenville    94  75  96  76 /   6   3   2  16
Greenwood     94  74  95  75 /   9   6   2  15

&&

.JAN WATCHES/WARNINGS/ADVISORIES...
MS...Heat Advisory from 11 AM this morning to 7 PM CDT Thursday for
     MSZ018-019-025>027-034>036-040>042-047.

LA...Heat Advisory from 11 AM this morning to 7 PM CDT Thursday for
     LAZ007>009-015-016-023>025.

AR...Heat Advisory from 11 AM this morning to 7 PM CDT Thursday for
     ARZ074-075.


&&


$$

JPM3/BB



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