090
FXUS64 KJAN 050020 AAA
AFDJAN

Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
720 PM CDT Thu Jul 4 2024

...New AVIATION...

.DISCUSSION...
Issued at 240 PM CDT Thu Jul 4 2024

Tonight through Friday...

Ridge is expected to flatten through Friday. Longwave trough
analyzed this morning over the northern Plains is progged to swing
eastward across the Great Lakes. This will help drive a frontal
boundary southeastward into the Mid-South to Gulf Coast states
tonight & into Friday. Ongoing rain & storm chances should wind
down into the evening, which could alleviate concerns for any
upcoming outdoor activities. With clouds & deep tropical moisture
persisting, expect seasonably warm lows, some 5-7 deg F above
normal, in the mid-upper 70s. Another night of record warm lows
are possible at most climate sites along & north of the I-20
corridor. Rain chances will begin to encroach into the Hwy 82
corridor before daybreak Friday, into the I-20 corridor by mid-
morning Friday & areawide into Friday afternoon. With anomalously
high tropical moisture, near climatological maximum around 2.25
inches, there remains continued support that some of these
downpours could be heavy (i.e. HREF prob match mean (PMM) of 3" &
localized PMM of >3-4" maxima). For now, there isn`t enough
confidence to narrow down an area for HWO graphics but localized
flash flooding can`t be ruled out. Also with some northerly mean
bulk shear >10kts in the 0-2 to 0-3km layers, some strong to
isolated severe storms can`t be fully ruled out but not enough
confidence to add to the HWO. There are low probs in CSU machine
learning probs for marginally severe convection Friday.

Main concerns will be dangerous heat but that is much more
uncertain than previous days. With the boundary moving into the
Gulf Coast region, scattered to numerous rain & storms are
expected. Mixing will remain limited, keeping dewpoints in the
77-80 degree range. Convective initiation (CI) will be forced
early due to moist convergence along the boundary & moist
boundary layer. This will also keep cloud cover around longer &
initiate earlier. Highs will still remain seasonable in the low to
possibly mid 90s, with dangerous heat possible across the good
portion of the area. There are too many caveats to add any heat
headlines, but left the areawide "Elevated" in the HWO graphics
for dangerous heat as is. /DC/

Friday night into Saturday: As a front stalls across the area Friday
night, convection ongoing from the daytime may persist into the
early evening hours, especially over the southern half of the area,
then decrease overnight. The brief surge of drier air coming in from
the north will focus convective coverage on Saturday across the
southern half of the area, though much of it may actually remain
closer to the coast as hinted at by the most recent model runs.
Minor airmass relief is possible with the front, albeit with temps
still around climatological norms. Dewpoints may dip into the upper
60s over the northern half of the area, with temps mainly in the
lower 90s. Given this, heat indices could briefly peak near 105
across south MS, but there are currently no plans to advertise heat
stress concerns given the anticipated brevity of these readings, the
limited area impacted, and the relative improvement from recent days.

Sunday through next Thursday: An upper level pattern characterized
by longwave troughing over the central CONUS with southwesterly to
westerly upper flow over our area will persist into early next week.
With the trough remaining to the west, the surface front will
retreat northward allowing a moisture rich airmass to return across
the entire area on Sunday. This airmass will result in above average
rain chances each day through the remainder of the forecast period,
with timing primarily driven by instability and the diurnal cycle.
The good news is increased coverage of clouds and precip may spare
most areas from the prolific heat stress issues that have plagued
the region in recent weeks. Though dewpoints will recover into the
middle and upper 70s, temps will remain closer to seasonal averages
at most locations, resulting heat indices that are more marginal.

Guidance remains rather consistent on the future track of Hurricane
Beryl, with no direct impacts on our immediate area. However, it is
possible that remnant moisture from the system could serve to
enhance rain chances in the area around the middle of next week. The
extent to which that might be the case remains to be seen. /DL/

&&

.AVIATION...
(00Z TAFS)
Issued at 708 PM CDT Thu Jul 4 2024

A couple isolated TSRA will continue over cntrl MS through 01Z but
not affect TAF sites. VFR conditions and a light wind will prevail
through 09Z. After 09Z additional SHRA/TSRA wl be psbl in the
north ahead of a cold front that will drop into the area. This may
bring lower flight restrictions. Otherwise, isolated to scattered
of TSRA is expected during the aftn again Fri. /22/

&&

.PRELIMINARY POINT TEMPS/POPS...
Jackson       77  92  74  90 /  20  80  60  40
Meridian      75  94  73  92 /  20  80  60  50
Vicksburg     78  93  73  91 /  20  70  40  30
Hattiesburg   77  95  76  93 /  20  80  60  70
Natchez       77  93  74  90 /  10  70  60  50
Greenville    78  92  73  91 /  30  70  20  10
Greenwood     77  92  73  91 /  40  70  20  10

&&

.JAN WATCHES/WARNINGS/ADVISORIES...
MS...Excessive Heat Warning until 8 PM CDT this evening for MSZ018-
     019-025>030-032-034>037-040>043-047-048-053-054-059-060.

     Heat Advisory until 8 PM CDT this evening for MSZ031-033-038-039-
     044>046-049>052-055>058-061>066-072>074.

LA...Excessive Heat Warning until 8 PM CDT this evening for
     LAZ007>009-015-016-023>026.

AR...Excessive Heat Warning until 8 PM CDT this evening for ARZ074-
     075.

&&

$$

DC/DL/22