Area Forecast Discussion
Issued by NWS Shreveport, LA

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022
FXUS64 KSHV 212052
AFDSHV

Area Forecast Discussion
National Weather Service Shreveport LA
352 PM CDT Mon May 21 2018

.SHORT TERM.../Tonight through Tuesday Night/
Despite the presence of the weak shear axis overhead and the moist
air mass in place (characteristic of PW`s of 1.5-1.8"),
convection has been widely sct at best this afternoon, mainly
confined to portions of Deep E TX where better onshore flow was
observer earlier, and also across portions of SE OK/SW AR, near a
residual MCV drifting near/just W of MEZ. It appears as if the
mixing of some slightly drier air discussed this morning over
portions of N LA/extreme Srn AR (as noted on the CH 9 and 10 water
vapor imagery) has resulted in lower instability than previously
expected, as MLCapes currently range around 1000 J/Kg over much of
NE TX SE into N LA. However, outflow bndrys from the existing
convection over Deep E TX may still yield isolated to widely sct
convection over the current rain-free areas late this afternoon
through this evening in VC of the shear axis, before diminishing
later this evening with the loss of heating. Thus, have left in
low chance pops this evening for E TX/Wrn LA/SW AR, although this
may be a stretch before the convection diminishes. Did retain
slight chance pops overnight in VC of the shear axis, as the short
term progs suggest that additional redevelopment may occur late.
But otherwise, areas of AC/cirrus will linger overnight as was the
case this morning, and can`t rule out patchy FG over areas that
receive rain, similar to what was observed early this morning
across portions of the region. However, the extent and low
confidence of this precludes mention in the forecast attm.

This shear axis will linger over much of the region Tuesday,
although it may pivot more NE to SW during the day as the primary
shortwave energy currently over Srn MN/Nrn IA shifts E into the
Upper Midwest tonight and into the OH Valley Tuesday. Should see
sct convection develop once again mainly during the afternoon
areawide given the strong heating, adequate moisture, and remnant
outflow bndrys in place, thus have blanketed mid chance pops
areawide but lower the guidance is suggested, which is in the
likely category. Given the lack of areal coverage this afternoon,
am not totally convinced greater coverage will be seen Tuesday.
Have also raised temps 2-3 degrees above guidance given the strong
insolation that should develop once most of the AC/cirrus is
eroded with heating/mixing. Did maintain slight chance pops
Tuesday evening for any lingering isolated convection, although
any should again diminish with the loss of heating.

15

.LONG TERM.../Wednesday through Monday/
Unseasonally early summer pattern characterized by a broad upper
ridging that will persist across the mid south with mean long wave
troffing across Rockies. Diurnally driven widely scattered to
possible scattered convection closer to the MS River Valley to
persist, lgt winds at least outside of convection, and daytime
highs either side of 90 and overnight lows either side of 70 to
continue. A deeper upper low over the southern rockies to amplify
ridging over southern plains towards the wknd, which by itself
will serve to ramp up temps, especially in East TX, with most pops
further east. What the models remain in poor agreement on, is the
tropical upper low trying to redevelop over the gulf. Depending
on this low, and where and when it may approach the coastline,
could add greatly to potential rainfall amounts during, and after,
the Memorial Holiday Weekend. For now the ECMWF is the much more
aggressive model with regards to this feature. /07/

&&

.PREV DISCUSSION... /issued 1201 PM CDT Mon May 21 2018/

AVIATION...
Cigs have become mostly vfr across area with isold brief mvfr
cigs possible. Scattered convection across se TX advecting nwd
and nearing the klfk terminal. Storms this aftn may contain brief
but stg wind gusts. With mstr axis splitting the cwa, terminals
most likely to be affected will be klfk, kshv, and possibly ktxk
and keld later this aftn, but should diminish with setting sun.
Winds to remain mostly lgt and vrbl thru period. Lack of southerly
flow and presence of mid/upper cloud decks will both make fog
development, and low cloud advection, too uncertain for any
mention in fcst attm. /07/

&&

.PRELIMINARY POINT TEMPS/POPS...
SHV  71  87  70  90 /  30  40  20  30
MLU  70  90  70  90 /  20  40  20  30
DEQ  67  86  67  87 /  20  40  20  40
TXK  69  86  68  87 /  20  40  20  30
ELD  69  87  68  89 /  30  40  20  30
TYR  70  87  70  87 /  20  40  20  30
GGG  70  86  69  89 /  30  40  20  30
LFK  68  88  68  89 /  30  40  20  30

&&

.SHV WATCHES/WARNINGS/ADVISORIES...
AR...None.
LA...None.
OK...None.
TX...None.
&&

$$

15/07



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