Area Forecast Discussion
Issued by NWS Jackson, MS

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FXUS64 KJAN 291031
AFDJAN

Area Forecast Discussion
National Weather Service Jackson MS
531 AM CDT Wed Mar 29 2017

...SIGNIFICANT SEVERE WEATHER POSSIBLE TONIGHT AND THURSDAY...

.DISCUSSION...

Tonight through Thursday night,

Concerns are increasing for the possibility of significant severe
weather, including strong tornadoes and large hail, for late
tonight and Thursday over western/northern portions of the
ArkLaMiss. The scenario being portrayed by most guidance is for
two rounds of potential severe weather. The first would take place
late tonight and continue into the early morning for locations
mainly along/west of the MS River, and the next round would
develop by Thursday afternoon east of the MS River with the
greatest threat over North Central MS.

An impressive upper low crossing the Southern Plains will
approach the ArkLaMiss tonight. Height falls associated with a
pre-frontal trough and outflow from early convective complex
combined with ML CAPE near 2000 j/kg will support vigorous
thunderstorm development west of the ArkLaMiss later today.
Strong deep layer shear will support a mix of linear/cellular
development, but CAM guidance displays different degrees of
organization and especially timing. Confidence is quite low on ETA
tonight for the first round of storms. Indications are for
slightly quicker arrival than previously anticipated and reflect
this in the HWO/graphics, but once again, confidence is on the low
side. Given the degree of instability/shear in the environment
over the Delta region tonight (vertical totals > 30 and effective
STP values > 2) and the potential for supercells, will ramp up
wording for this area late tonight. It looks like initial
supercell mode would graduate to a more organize linear mode as
storms move east of the MS River toward daybreak with storms
weakening as they move away from better support/lift.

As described in the past couple of days, the scenario will become
more complex Thursday when the upper level jet structure/height
falls into the northern GOM support a coastal latitude mesoscale
convective system that would move well south of the I-20 corridor.
Such a system would initially disrupt low level flow and induce a
meso-high over the heart of the forecast area Thursday, but recent
guidance trends suggest this disruption will be more temporary and
not as impactful to the severe weather threat in the ArkLaMiss
Thursday. It looks more likely that storms will develop ahead of
the cold front by Thursday afternoon in the upper Delta region and
shift east and develop southward over central/eastern MS going
into the late afternoon/evening. With the environment still very
unstable, expect additional significant severe threats to
continue, and perhaps be even greater roughly along the Hwy 82
corridor and points north. SPC has included a moderate risk for
severe weather in this area with the concern for strong tornadoes
greater. The threat for severe weather farther south is a little
more conditional, but much of the CAM guidance shows impressive
destabilization and lift with storm redevelopment even in the
immediate wake of the earlier convection, which reveals how
impressive the setup is for the region. Expect severe storms to
continue into the early evening at least over eastern MS. /EC/

Friday through next Tuesday,

A quiet period of weather is expected across the forecast area
Friday into Saturday as high pressure builds into and through the
region. With no appreciable airmass change expected over the
forecast area behind Thursday night`s frontal passage, warm
conditions will persist as highs both Friday and Saturday
afternoon range from the middle 70s to middle 80s. Some slightly
drier air will advect into the region, which will translate to
lows temperatures both Friday and Saturday night generally in the
50s.

Another 24 hour period of active weather looks possible over the
forecast area late Sunday afternoon into Monday.  Another closed low
will swing east southeast from the Four Corners region into the
Southern Plains Sunday, and then northeast from the Southern Plains
into the Mid-South region Sunday night through Monday.  As this
closed low`s attendant surface low deepens and lifts northeast from
the Southern Plains towards the Mid-Mississippi River Valley, it`ll
send a couple of potent spokes of energy through the region during
the late Sunday afternoon through Monday evening period.

While this is still 5 and 6 days out, models are in pretty good
agreement that at least one round of severe weather, along with some
potential for heavy rain, will be possible with this system late
Sunday afternoon into Monday morning.  Models also hint at perhaps a
second round of severe storms being possible Monday afternoon, but
confidence in this is currently low. However, with confidence
currently being best with the potential for severe storms late
Sunday afternoon into Monday morning, a "Slight Risk" for severe
storms will be added to the HWO for this timeframe.  This potential
currently looks best for my counties/parishes along and west of the
Mississippi River. Please continue to monitor later forecasts and
outlooks concerning this severe weather potential late Sunday
afternoon into Monday.

Clouds and rain chances gradually exit the region overnight Monday
and through the day Tuesday.  High pressure will again build into
the region Tuesday.  Other than some slightly drier air over the
CWA, high Tuesday will still range from the middle 70s to lower 80s
and lows Tuesday night will fall into the middle 50s. /19/

&&

.AVIATION...
06Z TAF discussion:
Return flow stratus event is underway early this morning with
MVFR/IFR ceilings developing and expected to impact
HKS/JAN/GTR/MEI/HBG for a few hours around daybreak, and IFR/LIFR
fog is possible at HBG. Expect stratus/fog to mix out quickly with
VFR conditions returning quickly during the mid/late morning and
lasting into Wednesday evening. /EC/

&&

.PRELIMINARY POINT TEMPS/POPS...
Jackson       87  66  79  54 /   4  43  72  42
Meridian      86  65  80  55 /   3  13  57  59
Vicksburg     85  66  79  53 /  10  70  62  21
Hattiesburg   86  66  77  56 /   4  18  69  46
Natchez       84  67  78  56 /  16  67  59  18
Greenville    83  65  77  52 /   6  76  62  17
Greenwood     87  66  79  53 /   3  51  72  36

&&

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

&&

$$


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