Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 11/27/21

Area Forecast Discussion

National Weather Service Shreveport LA

 958 PM CST Fri Nov 26 2021

.SHORT TERM.../Tonight/

The evening satellite imagery indicates an extensive cirrus shield
across much of TX extending E into our region, although this
cirrus has thinned/remains thin generally along/N of the I-20
corridor from just W of the DFW Metroplex across E TX and N LA/SW
AR. As such, temps have fallen quickly with the setting sun given
the very dry air mass in place, with the 00Z KSHV raob depicting a
PW of only 0.16 inches. Temps have already neared forecast lows
across portions of N LA, with the last couple runs of the HRRR
trending colder with more of this area reaching/falling below
freezing tonight even with the cirrus shield in place. Have had to
lower min temps tonight over N LA and portions of SW AR/SE OK
given the current trends, although the cirrus should gradually
thicken back up late tonight and especially during the day
Saturday as the ample Pacific moisture continues to spread ENE
across TX into the region ahead of the closed low over NW Old MX,
which will shift NE into far W TX Saturday morning.

With temps already in the mid 30s across portions of N LA as of
03Z, have issued a Freeze Warning from Bossier Parish ESE to
Ouachita/Caldwell Parishes through 15Z Saturday as many of these
areas have yet to reach freezing so far this Fall season (and if
so, only very briefly). Have opted to leave Caddo Parish out of
the Warning for now as the Nrn half of the parish has already
observed freezing temps, and SHV itself has yet to fall to
freezing and should remain just above 32 degrees through the
overnight hours. However, KBAD as well as the Haughton areas have
fallen to 34-35 degrees already, and thus have erred on the side
of caution as Bossier City itself and the Srn sections of the
parish should see freezing temps.

Cigs should continue to thicken during the day Saturday as the
column begins to saturate from the top down especially during the
afternoon, as large scale forcing and isentropic ascent increases
ahead of the opening closed low as it traverses WCntrl and Cntrl
TX during the day. In fact, the column should moisten enough such
that areas of -RA should reach the ground across portions of E TX
by late afternoon. Thus, no changes were needed to pops attm,
although temps should gradually begin to fall in the afternoon
over E TX as evaporative cooling increases as the precipitation
moves into this area.

Zone update/Freeze Warning already out...grids will be available
shortly.

15

&&

.PREV DISCUSSION... /issued 545 PM CST Fri Nov 26 2021/

AVIATION...
VFR conditions will continue through the 27/00Z TAF period. An
extensive cirrus shield over E TX/N LA will begin to expand back
NE across extreme NE TX/SE OK/SW AR this evening, with cigs
expected to gradually lower by mid to late morning Saturday over E
TX as AC cigs develop ahead of areas of -RA that will develop
over Cntrl TX. As the air mass begins to saturate from the top
down, these AC cigs will spread E into SW AR/N LA after 18Z, with
the cigs over E TX lowering to 4-7kft as the areas of -RA move
in/reach the sfc. Have inserted prevailing -RA mention for the
TYR/LFK terminals at 22Z, and GGG at 23Z, with the -RA expected to
affect the remainder of the region Saturday evening. Thus, cigs
will eventually become MVFR during the evening over E TX, and
possibly TXK/SHV by 06Z Sunday. Lt S winds over E TX/SW AR, and
calm winds elsewhere tonight, will become SSW 5-8kts after 15Z.
/15/

&&

.PRELIMINARY POINT TEMPS/POPS...
SHV  33  61  46  61 /   0  30  60  10
MLU  31  61  45  61 /   0  10  60  20
DEQ  28  62  41  64 /   0  20  40   0
TXK  35  61  46  62 /   0  20  50  10
ELD  30  60  43  60 /   0  10  50  10
TYR  38  58  46  62 /   0  50  60  10
GGG  35  59  44  62 /   0  50  60  10
LFK  38  58  45  61 /   0  50  60  10

&&

.SHV WATCHES/WARNINGS/ADVISORIES...
AR...None.
LA...Freeze Warning until 9 AM CST Saturday for LAZ002-003-005-
     012>014-021.

OK...None.
TX...None.
&&

$$

15



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