Area Forecast Discussion
Issued by NWS Shreveport, LA

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FXUS64 KSHV 041016

Area Forecast Discussion
National Weather Service Shreveport LA
416 AM CST Sun Dec 4 2016

...Moderate rainfall will take a break today but will make a
return tomorrow...

The cutoff ua low was noted across northwest Mexico early this
morning, which continues to promote sharp southwest flow aloft
across the Four-State Region and thus allowing for a persistent
fetch of mid-upper level Pacific moisture. As such, the 10Z
mosaic radar exhibited scattered showers and thunderstorms
extending from south and southeast TX and the nearby coast, east
northeast to across southern LA and portions of central LA.
Scattered light showers and light to moderate drizzle /and patchy
fog/ was more prevalent across central TX, east TX and portions
of north LA and southwest AR. This rather light precip across
portions of the Four-State Region is a result of an inverted sfc
trough shifting east of the FA as well as dry air entrainment in
the mid-upper levels, which is expected to continue further
throughout the day. This will lead to a lull in precip across
southeast OK and portions of east TX, north LA and southwest AR by
this aftn. However, central LA and points south will still
experience rainfall today as it coincides with the best moisture
axis, though much lighter than what was experienced yesterday with
amounts aoa 0.50 inches or so.

Tonight, the ua low is poised to translate east across Mexico
towards southwest TX and finally eject northeast across the FA
Monday evening/night, exiting the region early Tuesday morning.
Its sfc counterpart will promote sfc cyclogenesis whilst moving
northeast along the TX coast to across southeastern zones. The low
level jet will increase into the 30-40 kt range leading to best
PWATS no longer confined to the southern zones /ranging from
1.00-1.60 inches/. Embedded impulses within the flow aloft coupled
with increased large scale ascent as the system draws near and a
rather moist atmosphere will lead to the return of scattered to
widespread light to moderate showers with perhaps a few isolated
thunderstorms tomorrow. Heaviest rainfall is expected to fall
across portions of deep east TX east and northeast to across
north and central LA. The Weather Prediction Center shows anticipated
rainfall amounts of 0.25- 2.00 inches or so tonight through
Monday, with heaviest rainfall across central and southern zones.

Two questions still remain for Monday: is there a severe weather
threat and is there a need for a Flood Watch. In regards to the
severe weather threat, it will be dependent on how far north the
warm front will move.  Although the warm front is exhibited to move
across portions of central LA, the Storm Prediction seem to think
that the most unstable portions of the warm sector will struggle to
develop inland, hence a marginal and slight risk of severe storms
remains to the southeast of the FA. Nonetheless, will continue to
see how model solutions trend this possibility, as we can not
ignore progged curved low level hodographs, a veering vertical
wind profile with increasing winds aloft, 0-6 km bulk shear in
excess of 60 kts and meager mid-upper level instability, particularly
across the southeast zones. In reference to a Flood Watch,
rainfall totals for the event thus far has ranged from 1.00-5.00
inches, with highest totals noted across deep east TX and central
LA. Significant flooding issues have not been reported but am
sure that ponding of water along low-lying and poor drainage areas
do exist. Lack of calls about flooding issues suggests that the
soils are responding well to the rainfall and soaking it in, but
if we do indeed receive an additional 2.00+ inches across the
southern zones on Monday, where the heaviest rainfall has fallen
thus far, we may need to consider additional flood highlights.

Thereafter, a longwave trough moving east southeast from the Rockies
onto the Plains will send a slightly breezy cold front to impinge
on the region Wednesday evening, along with a chance for showers
to develop along the front. The main weather concern with this
front is still the significant CAA, as temps Thursday night/early
Friday morning will fall into the lower to middle 20s. This will
near Hard Freeze criteria and is something we will need to keep
an eye on. Speaking of temps, daytime highs will struggle to near
seasonal normals with 40s and 50s expected throughout the extended


SHV  52  46  51  45 /  50  70  90  50
MLU  54  47  55  49 /  70  70  90  60
DEQ  51  42  49  43 /  30  20  80  80
TXK  52  44  49  44 /  40  30  90  60
ELD  52  45  51  46 /  40  30  90  70
TYR  54  47  51  43 /  40  70  90  40
GGG  54  47  51  44 /  40  70  90  40
LFK  54  50  55  45 /  80  90  90  20




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