Area Forecast Discussion
Issued by NWS Jackson, MS

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FXUS64 KJAN 260539 AAA
AFDJAN

Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
1239 AM CDT Wed Jul 26 2017

.UPDATE...
Updated for 06Z aviation discussion

&&

.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/

&&

.DISCUSSION...
All convection has diminished now and clouds are disappearing as
well. The latest hi-res models don`t really show any regeneration
of convection overnight and with the clearing skies, it is highly
unlikely any precip will pop up before sunrise tomorrow.
Therefore, pops have been adjusted accordingly. Conditions will
remain warm and muggy tonight, as is the climatological norm. /10/

Prior discussion below:

Tonight and Wednesday:

An MCV is currently being observed on radar spinning east across
the Pine Belt region of Southeast Mississippi this afternoon. This
disturbance, along with other ingredients factored into the
recipe, was responsible for yet another round of torrential rains
which brought widespread flooding across portions of South Central
and Southeast Mississippi today. Unfortunately, this occurred
almost directly over some locations which experienced torrential
rains and flash flooding on Monday. Fortunately, activity is
gradually subsiding across these areas as the MCV continues its
eastward trek into Southwest Alabama. This trend is expected to
continue through the remainder of this afternoon and into this
evening.

Across the remainder of the CWA, the overall troughing across the
region, coupled with afternoon heating and a warm moist and unstable
airmass, is resulting in scattered storms developing across the
region.   This activity is essentially diurnally driven, and will
begin to dissipate across the CWA after sunset and daytime heating
begins to wane.  Overnight, while an isolated shower or storm can`t
be ruled out, primarily across the eastern half of the CWA, things
will remain quiet as lows fall into the low and middle 70s.

Currently, a much more subdued forecast is shaping up for Wednesday.
As strong high pressure aloft begins to build back into the Lower
Mississippi River Valley, the better rain chances will be shunted to
the far eastern half of the CWA as the trough is finally pushed out
of the region.  However, this will result in increasing heat across
the forecast area as highs are expected to top out in the low and
middle 90s areawide.  This, in addition to dew points in the 70s,
will cause afternoon peak heat indices to climb up around the
century mark across much of the area. /19/

Wednesday night through next Tuesday morning:

The pattern will begin hot and humid with increasing heat stress
before a cold front brings increasing rain & storm chances &
drier air in the wake, which will lower temperatures and reduce
the heat stress issues by this weekend.

Overall a hot and humid pattern is in store Thursday as strong &
anomalous upper ridge will continue to amplify & the center of the
593-595DM 500mb upper ridge axis will continue to pivot east-
southeast towards the ArkLaTex. As the cold front stalled to our
northeast over the Appalachians propagates east along the
Appalachians to the Atlantic seaboard, heights will gradually
build into our western portions & help us dry out. Isentropic
subsidence and PWs gradually falling to around an inch and a half
or so will help suppress convection. With increasingly anomalous
low-mid level heights & low level boundary layer temperatures
(~20-21 deg C @ 850 mb) this will support efficient warming easily
into the mid 90s. Some locales in the Delta could reach into the
mid-upper 90s around the 96-97 degree range in the ArkLaMiss Delta
but there is potential areas in the east could still reach around
the 95 degree mark. This in addition to some decent soil moisture
from previous rainfall the past week & drier air, heat indices
should peak around the 105 degree mark, especially in the Delta
where they could get around the 105-107 degree range. Expanded the
graphic further east to mainly along and northwest of the Natchez
Trace corridor. There is some potential we could mix out
dewpoints somewhat into the lower 70s to maybe upper 60s, due the
drier low level air, which could limit the eastward extent of the
heat stress issues. But with recent rainfall & more saturated
soils, decided to expand the HWO/graphic for limited heat further
east. We will have to monitor for potential for heat advisory
potential as we get closer. Heat stress & heat related illnesses
will be possible. Make sure to drink plenty of water & stay cool!
Warm and muggy & above normal lows are expected into the overnight
hours, with some locales, especially in the ArkLaMiss Delta,
getting near the top 5 warmest low temperatures.

Overall a pattern change will be in store as the ridge weakens
its grip on us by Friday & into the weekend & builds back to the
west. Aloft a strong shortwave and surface low/cold front will be
propagating southeast from Canada through the Great Lakes and
into the northeast & potentially the northern Appalachians. This
helps an increasing stronger 300mb jet to strengthen and trough to
amplify to our northeast. This cold front will move down towards
our area by late Friday & Saturday. Moisture will quickly be on
the increase to around 2-2.25+ inch PWs (90-97th+ percentile) and
345-350K 850mb Theta E ahead of the front. More convection will be
in store beginning in the Highway 82 corridor by early Friday
morning before more widespread convection is possible areawide by
Friday afternoon. Heavy rainfall & locally heavy downpours are
possible but due to weak lapse rates/flow, not expecting much in
the way of more stronger, organized convection. Expect the rain &
storm chances to linger overnight into Saturday. Models are
faster to push the cold front through by around Saturday,
especially the GFS which is more amplified, but the Euro/Canadian
kept a slower push of drier air into the area. Kept scattered
convection chances around Saturday. Much drier air is progged to
filter in by later Saturday & through the late weekend. This will
help PWs fall to only around or less than an inch (<10th
percentile) & with dewpoints falling into the mid 60s, this will
help temperatures fall a few degrees below average, with highs
only reaching the mid-upper 80s and lows in the upper 60s. This
will bring much needed relief from recent heat.

By next week, the pattern becomes a little more uncertain on
bringing back in convection from the south-east as the pattern
becomes less amplified & a potential disturbance moves towards our
area from the east. Kept some PoPs chances in the Highway 45
corridor Monday & along & east of I-55 Tuesday as moisture will
only be on a slow increase. /DC/

&&

.PRELIMINARY POINT TEMPS/POPS...
Jackson       73  95  74  92 /   5   9  10  39
Meridian      75  96  74  93 /  11  17   8  32
Vicksburg     72  96  74  92 /   3   5  11  38
Hattiesburg   75  95  73  93 /  12  19   5  19
Natchez       72  94  73  92 /   3   6   7  24
Greenville    74  96  76  91 /   3   4  17  55
Greenwood     74  95  75  90 /   3   5  16  57

&&

.JAN WATCHES/WARNINGS/ADVISORIES...
MS...None.
LA...None.
AR...None.

&&


$$

BB/10/19/DC



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