Area Forecast Discussion
Issued by NWS Jackson, MS

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FXUS64 KJAN 231804
AFDJAN

Area Forecast Discussion
National Weather Service Jackson MS
1204 PM CST Fri Feb 23 2018

...SEVERE WEATHER EXPECTED ACROSS PORTIONS OF THE AREA SATURDAY
NIGHT INTO EARLY SUNDAY MORNING...

.UPDATE...
Updated for 18Z aviation discussion

&&

.AVIATION...
18Z TAF discussion:
An expansive area of showers with embedded thunderstorms will
continue to move north through the CWA this afternoon into this
evening. Showers will begin impacting HBG/JAN/HKS within the next
few hours with MEI and eventually GLH/GWO/GTR through the
afternoon into tonight. Expect MVFR ceilings with brief visibility
reductions with any of this activity. Ceilings will lower to IFR
across much of the area tonight with visibility reductions
possible at HBG. A few showers could linger overnight, but the
bulk of the rainfall will move out tonight. Winds will remain out
of the south/southeast through the forecast period and will
increase tomorrow morning, especially at GLH/GWO with gusts up to
20kts possible and increasing through tomorrow afternoon. /TW/

&&

.DISCUSSION...

The ArkLaMiss region remains entrenched beneath southwesterly flow
aloft as a stout shortwave trough digs across the Desert
Southwest and a subtropical ridge remains centered just off the
southeast coast. The best moisture quality is located over the
southern and western portions of the area this morning with a
relative min in PWATs over east central Mississippi. However, a
PWAT max located over Lake Pontchartrain will advect in to
southern Mississippi along with positive ThetaE advection. There
is already an area of ongoing convection associated with this
moisture max and latest hi-res guidance is in agreement that this
activity will spread north through the afternoon across much of
the area. While the thermodynamic environment is supportive of
severe weather, the shear profiles are weak and marginal.
Nonetheless, a few strong and perhaps an isolated severe
thunderstorm will be possible this afternoon. Additionally, these
storms will be capable of producing locally heavy rainfall so
isolated flash flooding concerns cannot be ruled out, especially
along and northwest of the Natchez Trace corridor and in the Delta
where the heaviest rain has fallen over the last few days. Will
continue to highlight this potential with the ongoing flooding
threat in the HWO/graphics. Made a few tweaks to PoPs and max
temps, but otherwise the ongoing forecast is still on track. /TW/

Prior discussion below:

Today and tonight...No real changes to the forecast. The boundary
remains just to the west of the CWA, where rain and a few
thunderstorms were training over the same areas. For now, it still
looks like the best flooding risk will remain over the Delta
region, where a few streams were out of their banks and standing
water remains on roadways. The models seemed to be a few hours
showers with the development of convection this afternoon.
Thinking showers will be isolated at best through early afternoon
and become more scattered in nature as the wave gets closer. The
best rain chances seem to be tonight. The models keep the boundary
west of the region, but agree a wave will move out of the gulf,
bringing rain and a few thunderstorms. With rain so close to
counties in the west that have standing water, left elevated risk
for flash flooding in the hwo. The grounds are saturated across
the entire area with lots of poor drainage area, so also kept the
limited flooding in for the rest of the area generally north of
20. It looks like the heavier rain won`t move in before Saturday.
Stuck with guidance for temps, above normal values in the lower
mid 80s should hold on through today, near record breaking again.

Saturday through Thursday night...Looks like a very active and wet
extended period in store for the ArkLaMiss. The strong ridge that
has been over the area will finally begin to break down on Saturday
as a strong short wave approaches the area. The big factor on
Saturday afternoon and evening will be the gusty southerly winds.
The strongest winds will be over the delta, where winds may approach
wind advisory criteria, with gusts to 40 mph possible. Isolated to
scattered showers and storms will be possible Saturday afternoon and
evening, but expect the bulk of the activity to occur Saturday
evening through early Sunday morning, as the short wave and
associated cold front move across the area. Expect a fast moving
QLCS to move across the area during this period, and with strong
pressure falls, 50-55kts of deep layer shear and good instability,
some of the storms will be strong to severe. The main risk for
severe looks like it will generally be along and north of the I-20
corridor, but there will be an enhanced risk for portions of the
delta. Will continue to highlight these areas in the HWO, and also
upgrade portions of the delta to an enhanced risk.

The boundary gets hung up over the area on Sunday, with another
short wave and associated surface low moving over the area Sunday
afternoon into Sunday night. There are significant differences
between the GFS/ECMWF on rainfall amounts and how far north the
precipitation develops across the area during this period. The ECMWF
is much further north and heavier, with around 1.0 to 1.5 inches of
rain Sunday and Sunday night, while the gfs is much lighter and
further south. The Canadian model is also towards the lighter side.
WPC guidance leans towards the heavier ECMWF, so will go with this
guidance for now. Due to the potential of more rain Saturday night
and Sunday, will continue to advertise a limited threat for Flooding
in the graphicast and HWO through the weekend.

We will finally get a break on Monday as cool high pressure builds
across the area, with high temperatures climbing to around 70
degrees. Overnight lows will fall into the 40s for much of the area
by Tuesday morning. Surface high pressure will continue to prevail
Monday night into Tuesday, but moisture will begin to increase once
again on Tuesday as the surface flow becomes more southerly. Another
round of showers and thunderstorms will move across the area Tuesday
afternoon through early Wednesday as another short wave moves across
the area. The active weather pattern will continue on Thursday as
another stronger short wave and associated cold front brings one
more round of storms. /15/

&&

.PRELIMINARY POINT TEMPS/POPS...
Jackson       81  66  82  56 /  65  58  45  88
Meridian      82  65  81  61 /  39  46  46  72
Vicksburg     81  66  84  54 /  71  48  46  75
Hattiesburg   81  66  83  65 /  59  46  37  55
Natchez       79  67  83  58 /  83  50  45  85
Greenville    76  65  80  51 /  60  75  67  92
Greenwood     80  66  81  53 /  54  72  64  79

&&

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

&&


$$

TW/07/15



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