Area Forecast Discussion
Issued by NWS Jackson, MS

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FXUS64 KJAN 281157 AAA

Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
657 AM CDT Tue Mar 28 2017


Updated for 12Z aviation discussion


12Z TAF discussion:
Widespread MVFR conditions are at most TAF sites, except GLH.
There is some possibility some lower stratus could move in the
next couple of hours there. Some IFR lower ceilings and patchy fog
may also advect into PIB and HBG as well by 13Z. Any patchy fog
should lift by around 15-16Z or so. Widespread MVFR to IFR stratus
will linger through around 17-19Z before VFR conditions are
expected afterwards areawide at all TAF sites. Winds will mainly
be out of the south-southwest around 4-7kts, while near GLH may
shift from west-northwest due to the front near the area before
becoming more south-southeast in the afternoon. Some isolated
showers and VCTS are possible near GTR, CBM, HKS, JAN, NMM and JAN
around 19Z before conditions clear after 29/00Z. Some lower MVFR
visibilities and ceilings due to stratus/patchy are again expected
areawide between 29/05-08Z or so, while some IFR conditions due to
lower stratus are possible at HBG around the same time. /DC/


Today through tonight:

Surface analysis this morning shows the cold front draped across the
Highway 82 corridor down to the northeast Louisiana/southeast
Arkansas to south of Shreveport, Louisiana area. Water vapor imagery
shows the closed low spinning over northern Kentucky into the Ohio
Valley while all colder cloud tops are situated off to our east.
Most of the convection in our area has weakened with any stronger
more organized storms off to our east in central Alabama.  Overall
much quieter afternoon is in store today. This front will slowly
drift to the south, maybe only slightly towards the Highway 20
corridor, as upper trough/surface moves into the Appalachians and
forcing and shear axis pulls away. This will promote some shower and
thunderstorm activity mainly confined to the front just north of I-
20 early in the mid-morning. More will develop and spread south
through the afternoon. PWs will be near an inch to an inch and a
half, which will support more isolated to scattered convection. With
shear axis pulling away and shortwave ridging building in, this will
promote less potential for any organized convection. With decent
dewpoints and some lapse rates and weak instability, would not rule
out an isolated strong storm or two. However, most convection should
remain tame this afternoon. With boundary layer temperatures not
changing too much, except slightly cooler along and in the wake of
the front in the Delta, expect similar warm high temperatures to
yesterday, in the low-mid 80s, which some 10+ degrees above normal.

As the strong closed low/jet dives into the southern Rockies and
southern Plains into Texas late this afternoon to evening, the
shortwave ridging will be building east through the ArklaMiss. This
will help the cold front to slowly lift back to the north-northeast
as a warm front. Some increased moisture advection/isentropic lift
will help any chances of showers or very isolated convection/storms
to remain tied to that this evening. This will lift into the Highway
82 corridor late evening before lifting north of the area after
early Wednesday morning, around 3-4AM. Clouds should remain in the
area, with more low stratus moving back into the Pine Belt and I-20
corridor by daybreak. There is some weak isentropic subsidence which
could scatter out some cloud cover in the southwest before more
widespread clouds move back in by daybreak. With clouds still
lingering in the area, dewpoints holding up and and an increasing
pressure gradient/gusty winds from the developing low/cold front out
west, expect low temperatures to remain warm, a few degrees above
MOS, in the low-mid 60s. /DC/

Wednesday through Monday:

A potential severe weather event for the Wednesday night/Thursday
period will continue to be the main concern for the long term
portion of the forecast. Prior to the event, a strong and
progressive upper level ridge will move across the ArkLaMiss
bringing continued well above normal temperatures Wednesday, and a
few record highs are not out of the question.

A strong trough crossing the Southern Plains will approach the
ArkLaMiss late Wednesday night with significant height falls ( 12 hr
~ 5 to 10 dam) and widespread convective rainfall expected to reach
the Delta region before daybreak. Given steep mid level lapse rates
and strong deep layer shear, expect some storms to be severe with
all modes of severe weather possible. Global models show pretty good
agreement on this set-up and the severe threat is fairly clear for
the Wednesday night period.

However, the scenario will become more convoluted and messy Thursday
when a subtropical jet rounding the base of the trough leads to a
split upper jet pattern that will influence the mesoscale convective
evolution and subsequent severe threat outline.  This pattern
supports a coastal latitude mesoscale convective system that would
move well south of the I-20 corridor should it develop. Such a
system would disrupt low level flow and induce a meso-high over the
heart of the forecast area Thursday with any substantial severe
weather threat questionable to develop due to these stabilizing
effects. Over northern portions of the area, continued lift ahead of
the polar trough and adequate displacement away from a coastal MCS
would support additional severe storms over northwest/north central
portions of the forecast area. With all of that said, should the
potential MCS activity propagate more quickly eastward and allow low
level flow to redevelop early enough in the day, then
destabilization and the severe weather threat could increase for
most of Central and East MS.

The threat for storms/severe weather will end early Thursday night,
and another upper level ridge will progress across the region from
Friday through most of the weekend bringing more above normal
temperatures and generally dry weather. We should see the next
strong trough approach Sunday night bringing another chance for
severe weather as we go through early next week. Have held off on
mentioning this threat in the HWO/graphics with it being near the
end of the forecast period and given the threat is not squarely on
the ArkLaMiss, but it is likely we will be dealing with this system
in some capacity, including for both severe weather and heavy
rainfall, as we get closer in time. /EC/


Jackson       83  63  86  65 /  25   6   6  27
Meridian      83  62  85  63 /  26   6   5  10
Vicksburg     82  64  85  66 /  24   8   9  57
Hattiesburg   84  63  84  64 /  22   4   5  11
Natchez       84  65  84  67 /  23   7  10  54
Greenville    79  63  82  65 /  17  15   8  75
Greenwood     80  64  84  65 /  21  16   5  56





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