Area Forecast Discussion
Issued by NWS Jackson, MS

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FXUS64 KJAN 272138

Area Forecast Discussion
National Weather Service Jackson MS
438 PM CDT Thu Apr 27 2017


Tonight and Friday:

Surface high pressure will continue to prevail across the area
tonight. Skies will begin clear, but expect and increase in
stratus development very early on Friday. Lows will fall into the
upper 50s and lows 60s across the area.

Moisture will increase across the region Friday afternoon with PWATS
climbing to around 1.3-1.5 inches. Although there will be a fairly
strong cap Friday afternoon, a couple of isolated showers or
thunderstorms are possible. The main concern will be the tightening
surface gradient resulting in gusty winds friday afternoon. Expect
sustained winds in the upper teens to near 20 mph likely. Will issue
a limited graphic for gusty winds and also discuss this in the HWO.
Expect a very warm day with highs climbing into the mid/upper

Friday night through the middle of next week:

The main active weather will be off to our north and northwest
through Saturday as a big storm system digs into the Southern
Plains. Off to the east and southeast of the deepening associated
surface low our region will be in a regime of increasingly moist
and strong low level southerly flow, originating from a warmer-
than-normal western Gulf of Mexico. Subtle lift from minor
shortwaves emanating out of the larger trough to our west could
combine with the increasing moisture and instability to produce a
few showers and storms but precipitation through early Saturday
should generally be spotty at best. A wind advisory may be
necessary for Saturday as we get closer in time as tightening
pressure gradients spur south to southeast winds a few thousand
feet above the surface up to 50 kts.

Model consensus agrees that the main active time period for our
forecast area will be later Saturday night through Sunday evening,
with of course the weather starting in western zones and finally
clearing to the east out of the eastern Mississippi. Some
uncertainty exists as to the specifics of timing for certain
localities, but in general the timing uncertainties are not large.
The pseudo-stalled nature of the system to our west over the next
few days will lead to an enhanced flooding threat out that
direction but the whole system will be turning more progressive as
it passes through the Lower Mississippi Valley. One would think
this would greatly reduce the flooding risk for our region, but in
this case the heavy rain squeezed from thunderstorms late this
weekend could be truly torrential owing to high moisture transport
working on an environment containing very anomalous moisture
amounts (2+ inch precipitable water values). Due to this threat of
extremely heavy rains in a short period of time we have upped the
flooding risk in the HWO and graphics to elevated and will watch
the situation closely going forward.

But of course the heavy rain with this system will not be the only
threat we face since many parameters (dealing with wind shear and
instability) suggestive of severe weather potential should come
together. No modes of severe weather can be ruled out at this
juncture but it does look like the meridional nature of the
system and its attendant wind shear does not look to have the best
correlation with widespread severe weather around this region in
the spring. Also, usually when the flooding risk associated with
slower moving squall lines goes up the associated severe weather
threat tends to go down.

So, at this point we are starting to focus more on the extremely
heavy rain threat with this system since the ground is at least
somewhat saturated (primed) in quite a few areas of the region.
That certainly does not mean the severe weather threat is marginal
and we will continue to watch that aspect of the forecast closely
as well.

By Monday the big system and its rain and storms should be getting
to the east of the region with at least a day or two of quieter
and somewhat cooler weather anticipated. However, model consensus
still suggests another potent disturbance moving through Southern
Plains and arriving on our doorstep by the middle of next week,
bringing more locally heavy rain and thunderstorm threats. We will
focus more on that system once we get clear of this weekend`s
weather maker. /BB/

.AVIATION... 18Z TAF discussion:
A mix of VFR/MVFR ceilings prevail across TAF sites early this
afternoon. Expect the low clouds to continue to erode with all
sites becoming VFR over the next hour or so. VFR conditions will
continue through approx 09-10z when stratus will redevelop early
on Friday./15/


Jackson       63  88  71  88 /   3  17   6  27
Meridian      61  87  70  88 /   3  20   7  20
Vicksburg     61  87  72  89 /   3  16   8  29
Hattiesburg   65  87  70  87 /   9  27   8  28
Natchez       64  88  72  87 /   4  17   9  35
Greenville    59  85  72  88 /   3  22  14  34
Greenwood     59  85  71  88 /   3  16  10  23





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