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fxus64 kshv 232046 

Area forecast discussion
National Weather Service Shreveport la
346 PM CDT Tue may 23 2017

precipitation continued to develop along and behind the front, as
it near deep East Texas and northwest la with a quick movement to
the southeast. Increasing instability provided by an upper level
jet streak coupled with plentiful low-upper level moisture, may
result in some of the storm activity to become strong to severe
particularly across deep East Texas. The main threats will be
large hail and damaging winds. A severe watch is in effect until
11 PM CDT.


Previous discussion... /issued 300 PM CDT Tue may 23 2017/

a broad upper air low across the northern plains late this aftn, was
progressing south-southeast thus resulting in the sharpening of
southwest flow aloft across the four-state region. Embedded in this
southwest flow aloft is a 90+ kt jet Max at 250 mb rounding the base
of this trough, and moving across the region which is allowing for
increasing ul diffluence. Looking at the sfc, a cold front has
impinged upon the forecast area and located along a kcdh, to a ktxk to a ktyr
line, with a movement to the southeast. Increased ul support
provided by the aforementioned jet streak, coupled with
frontogenetical forcing by the cold front and a rather moist
atmospheric profile /pwats of 1.20-1.60 inches/ has resulted in
isolated showers and thunderstorms, mainly along and behind the cold
front. The stratus deck has eroded but broken-overcast VFR ceilings remained,
further validating the moist atmosphere. Nonetheless, there have
been breaks in the cloud cover which have allowed temps to warm into
the 70s. As a result, some daytime destabilization/steepened lapse
rates has been realized which could aid in a few of the storms
nearing strong levels and producing small hail. The precip is
expected to not stick around for long, as model solutions displayed
precip exiting from west to east by tonight, as the ul jet streak
will be pushing east and hence ul support will be fleeting.

Overnight, skies are expected to scatter out and perhaps become
clear across most of the region, whilst relatively light west-
northwest sfc winds ensue. If this does indeed come into fruition,
this could set the stage for decent radiational cooling and promote
overnight temps to drop into the upper 40s across portions of
southeast OK, extreme northeast Texas and southwest Arkansas to lower to
upper 50s elsewhere. Tomorrow, as the upper air low commence to near the
middle/lower Mississippi Valley, the arklatex will be on the
backside of the disturbance and mid-upper level atmospheric drying
will occur. However, southwest Arkansas and northeast la will be the last
areas for the drier air to take effect, so a few lingering showers
nearing/brushing across the said areas can not be ruled out during
the day tomorrow. Otherwise, slight pressure rises tomorrow aftn
will result in a tightened pressure gradient, which will lead to
northwest sfc winds approaching lake Wind Advisory speeds. Due to
this close call, will elect to hold off on a lake Wind Advisory for
this forecast package and let the midnight shift make the call /and
see if models continue to show this trend/. Tomorrow night, wind
speeds will become light and at times variable a few hours after
sunset, whilst clearing skies take place. This will once again
result in excellent radiational cooling /and perhaps some patchy
fog/ leading to tomorrow night temps plummeting into the lower 40s
across the north to lower 50s elsewhere /or some 10-15 degrees below
norm/. We continue to undercut model guidance by a few degrees for
tomorrow night because guidance tends to trend towards climo and in
this case, it is not representative. On Thursday, srly sfc flow will
return to the region and the quick passage of upper air ridging on Friday
will result in temps rebounding into the upper 80s to lower 90s by
the end of the week into early weekend /some 5 or so degrees above

Thereafter, long term solutions hint at an upper air trough getting carved
out across the southern rockies by late weekend, resulting in flow
aloft veering from near zonal to the west-southwest across the four-
state region. The best ul dynamics will remain north of the region
closest to the center of the disturbance, but a sfc trough and the
impingement of another cold front will cause the generation of
showers and thunderstorms. Furthermore, the front is progged to
become quasi-stationary across the southern zones which will
maintain the unsettled wx into early next week. It is too early to
say with certainty whether or not a severe weather threat will exist
this weekend, but we will continue to monitor this plausibility.


Preliminary point temps/pops...
shv 54 73 52 85 / 60 10 0 0
mlu 56 73 50 83 / 70 10 10 0
deq 49 72 43 83 / 30 10 0 0
txk 52 72 49 83 / 50 10 0 0
eld 52 71 46 83 / 70 10 0 0
tyr 53 75 54 86 / 40 0 0 0
ggg 53 73 52 87 / 40 0 0 0
lfk 56 78 54 89 / 60 0 0 0


Shv watches/warnings/advisories...

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