Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 06/28/20
Area Forecast Discussion...UPDATED
National Weather Service Shreveport LA
928 PM CDT Sat Jun 27 2020
.UPDATE...
The diurnal cycle of shower and thunderstorm production and decay
and has just about finished up this evening with the rest of the
night expected to be dry, warm, and muggy. Modest and moist low
level southerly flow will promote broken lower cloud decks late
tonight through midday tomorrow, but fog potential is low.
However, there still may be some reduced visibilities through
early tomorrow due to the effects of the Saharan Dust layer
sprawling across the southeastern CONUS. Models suggests this dust
may not be quite as thick in our region tomorrow, but at least
some traces of it may stick around for a while. /50/
&&
.PREV DISCUSSION... /issued 645 PM CDT Sat Jun 27 2020/
AVIATION...
There are some isolated showers and storms generally slowly
advancing north along an outflow boundary which could affect (or
come in the vicinity) of SHV/MLU/ELD sites over the next few
hours. However, expect nearly all activity to diminish by mid to
late evening with the potential of significant impact at any of
these TAF sites relatively low. Otherwise, the Saharan Air Layer
over the region continues to bring visibilities down to 5 to 7
miles at the surface and the slant range visibilities will be
lowered quite a bit for aircraft on approach and passing through
the dust in the bottom 10 kft of the troposphere. This dust will
likely be around through at least the first half of tomorrow,
perhaps longer.
Late tonight, moist southerly flow should induce MVFR ceilings
over the most of the region and conditions will likely take until
the 15 to 17 UTC time window to start going back to VFR tomorrow
morning. South to south-southwest winds will be a little gusty at
times tomorrow, especially over eastern TX. Isolated to widely
scattered showers and storms will pop up in the afternoon hours,
but there is generally not enough confidence at any site to
include VCTS. /50/
PREV DISCUSSION... /issued 312 PM CDT Sat Jun 27 2020/
SHORT TERM.../Tonight though Sunday Night/
Despite the presence of the weak shear axis over the region,
convection has been quite isolated and primary confined to SE
OK/adjacent sections of SW AR near the decaying mid level theta-e
ridge. However, mosaic radar imagery indicates isolated convection
along a weak seabreeze pushing N into Deep E TX/Cntrl LA, but will
encounter a slightly drier air mass with PW`s still around 1.5-1.6
inches. With the isolated convection continuing to diminish across
the Nrn zones along the decaying mid level theta-e ridge, have
maintained slight chance pops through mid-evening for Deep E TX
and much of N LA closest to the residual shear axis, before this
elevated feature washes out overnight. Given the very moist bndry
lyr air mass in place with dewpoints unable to mix out of the mid
70s, temps will struggle to fall quickly overnight, and thus have
trended above the NBM once again and closer to the MOS guidance
given the recent trends in min temps. Low stratus will develop
once again by/after midnight which will help to hold temps up
especially once the low cigs set up. These cigs should lift and
possibly scatter out by late morning/early afternoon, although
elevated cigs will increase ahead of a shortwave trough over Srn
AZ this afternoon, which will gradually translate ENE into W TX
Sunday afternoon, with accompanying troughing farther ESE across
Nrn and Ern TX.
As has been the case the last couple of days, the NBM has been
a bit too aggressive with pops, with the 12z NAM/ECMWF with
agreement with some of the CAMs depicting drier solutions as they
maintain the persistent lower PW`s. In addition, the presence of
the Saharan dust in the atmosphere across the region should also
help to suppress sufficient cloud condensation nuclei needed for
organized cloud development despite the presence of large scale
forcing. Thus, have trended pops down to low chance areawide,
although MOS suggests even lower pops over much of the region.
Given the very warm start to the morning, temps should rebound
quickly into the lower 90s, with a tightening pressure gradient
contributing to the warm advection. Did maintain slight chance
pops Sunday night along/N of the I-30 corridor as the parent
shortwave trough lifts NE along the backside of the amplifying
upper ridge E of the MS Valley over the SE CONUS. Did trend min
temps Sunday night near or slightly above the NBM and closer to
persistence as of late with another round of low stratus
developing late.
15
LONG TERM.../Monday through Saturday/...
There is GFS/ECMWF/Canadian agreement that a mid-level ridge axis
will extend across the Mississippi Valley to the east of the area,
putting the local area in a southwesterly mid-level flow on Monday.
The low-level flow will remain southerly, advecting abundant low-
level moisture into the area from the Gulf of Mexico. With strong
instability in a weakly sheared environment and a weak mid-level
disturbance crossing the area, this will allow for scattered showers
and thunderstorms to develop Monday afternoon. Showers and storms
will quickly diminish Monday night as the wave slides east of the
area and with the loss of daytime heating.
On Tuesday, mid-level ridging will become the more dominant feature
across the Gulf of Mexico while locally diurnally driven widely
scattered showers and thunderstorms can be expected in the afternoon
to evening hours. Ridging building into Texas will keep portions of
East Texas dry with better chances eastward into southern Arkansas
and northern Louisiana. Wednesday into Thursday, an Omega Block will
develop with a closed low across the Northeast, a trough across the
Intermountain West, and the aforementioned ridge building into the
central U.S., just to our west. The block will allow for a similar
setup each day, between the ridge to our west and the upper low well
to our northeast. With our area in a southerly low-level, that will
leave us hot and humid with afternoon to early evening thunderstorms
expected each day. The best chances appear to be for the ArkLaMiss
with decreasing chances westward into southeastern Oklahoma, East
Texas and Deep East Texas.
The late week currently looks to be active with thunderstorms, but
there is some variance in rainfall amounts. By Friday, there is
model disagreement with the placement of an upper level low that
could develop across the Mississippi Valley. The ECMWF develops more
of a closed low to our east and if this is the case we could see
increasing chances of showers and thunderstorms with heavy rainfall
in the vicinity of this feature. The forecast is closest to the
GFS/Canadian models, however, which have the upper low north of the
area in the Missouri Valley and yet still a disturbed pattern with
afternoon thunderstorms each day.
For temperatures, the forecast is closest to the National Blend of
Models (NBM) with highs ranging from the upper 80s across
southeastern Oklahoma and southwestern Arkansas to the lower 90s
across East Texas, Deep East Texas, and northern Louisiana on Monday
and Tuesday. This hot and humid pattern will continue Wednesday
through Saturday with highs in the lower to mid 90s across the area.
Heat indices each day through this period will warm to near 100
degrees and may near Heat Advisory criteria of 105 degrees next
week, so we will need to monitor that in future forecast packages.
/04-Woodrum/
&&
.PRELIMINARY POINT TEMPS/POPS...
SHV 77 91 76 90 / 10 30 10 30
MLU 75 92 75 90 / 20 30 10 30
DEQ 74 90 73 88 / 10 30 20 30
TXK 76 90 75 87 / 10 20 20 30
ELD 75 92 73 89 / 20 20 10 30
TYR 76 90 76 89 / 10 30 10 20
GGG 76 92 76 90 / 10 20 10 30
LFK 77 92 76 90 / 10 30 10 30
&&
.SHV WATCHES/WARNINGS/ADVISORIES...
AR...None.
LA...None.
OK...None.
TX...None.
&&
$$
50/15/04