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fxus64 kjan 232048 
afdjan

Area forecast discussion
National Weather Service Jackson MS
348 PM CDT sun Jul 23 2017

Discussion...
tonight through monday: latest rap analysis shows only subtle
westward movement to the upper- level low along the Louisiana
coast so far today. While the broad mid-level subtropical ridge is
somewhat evident across the deep south, it has broken down
considerably over the last day or so and become more centered back
to our west over the Desert Southwest/Four Corners region. This
has allowed for a downward trend in heat issues as a shortwave
trough swings through the Great Lakes region. Clouds and an early
start to showers and storms today have also helped to keep temps
cooler than previous days. The only heat stress issues remain
confined to the northwest Delta and western portions of the Hwy 82
corridor where a few sites have been close to or at the 105
degree heat index criteria, so will let the ongoing heat index
continue through the rest of the afternoon.

Numerous showers and storms are ongoing from glh to hbg in closer
proximity to the upper low and deep moisture axis. The greatest
coverage of storms will remain in this area with only scattered
coverage expected elsewhere through the rest of this afternoon with
activity driven by outflow boundary interactions. Poor lapse rates
and vertical totals will preclude a greater risk for mircobursts
with updrafts struggling to become deep and sustained, however
isolated flash flooding cannot be ruled out, especially with
slow/training storms. Storms should dissipate after sunset, however
a few isolated lingering showers will be possible through the
overnight. Low temps will be generally be in the low to mid 70s.

On Monday, the upper-level low that has been plaguing the area will
become an open wave and get picked up by the departing shortwave
trough lifting through the Great Lakes and into the northeast. This
will help to advect a deep moisture axis, characteristic of 2.25
inch pwats, across south central Mississippi and increase shower and
thunderstorm coverage. Weak 0-3km shear vectors will favor
slow/training storms and combined with the aforementioned pwats,
saturated forecast soundings and q-vector convergence will result in
the potential for a few instances of flash flooding, especially
along and south of the I-20 corridor and where heavy rain has fallen
the past few days. As such, went ahead and added a limited area for
flash flooding in the severe weather potential statement to account for this. Otherwise, cloud
cover and precip coverage will hold high temps to the mid to upper
80s. /Tw/

Tuesday through saturday: the weakness in the mid level ridge will
begin shifting east during this time frame allowing the ridge to
build back in by late week. As this occurs, a daily lessening of
convective activity and cloud cover will be seen as Max temperatures
start creeping back up. Heat stress will become a problem once
again by Wednesday as mid 90s heat and mid 70s dewpoints push heat
indices above 105. This looks to continue through Friday, but by
the weekend, troughiness looks to take shape over the eastern half
of the nation with the ridge breaking down somewhat over the area
as northwesterly flow back spread back into the region. A surface
cold front will be associated with the mid level troughiness and
drop through the forecast area Saturday afternoon. Some deep
layered shear will exist in the pre-frontal environment, but
lapse rates at present are feable./26/

&&

Aviation...
18z taf discussion:
IFR/MVFR stratus lingering through the morning has
lifted/scattered to VFR categories at most taf sites. A few sites
have briefly dropped to MVFR ceilings but the prevailing
conditions are expected to remain VFR through the rest of today.
Once again, scattered to numerous rain showers/thunderstorms and rain are expected with a
few areas already ongoing in the Delta and along the Hwy 84
corridor. Thunderstorms in the vicinity cannot be ruled out at any one location this
afternoon and early evening, but activity should dissipate by
24/3z. MVFR ceilings will once again be possible Monday morning at
all taf sites. /Tw/

&&

Preliminary point temps/pops...
Jackson 73 87 73 88 / 29 62 31 52
Meridian 73 89 73 86 / 20 60 34 57
Vicksburg 73 87 73 90 / 38 60 30 40
Hattiesburg 73 87 72 88 / 34 59 41 59
Natchez 73 86 73 89 / 41 58 30 37
Greenville 73 90 74 91 / 28 58 29 38
Greenwood 73 88 74 89 / 23 58 31 44

&&

Jan watches/warnings/advisories...
MS...heat advisory until 7 PM CDT this evening for msz018-019-025-026-
034.

La...none.
Arkansas...heat advisory until 7 PM CDT this evening for arz074-075.

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