Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 08/19/21
Area Forecast Discussion
National Weather Service Houston/Galveston TX
626 PM CDT Wed Aug 18 2021
.DISCUSSION...
00Z Aviation...Most convective activity has dissipated, but still
seeing a TSRA near SGR,a few SHRA near LBX and HOU and -SHRA at
IAH. Expect this activity to dissipate over the next couple of
hours. Think we will see scattered SHRA/TSRA near the coast early
Thu morning, expanding inland between 14-16Z and continuing most
of the day tomorrow.
Wood
&&
.PREV DISCUSSION... /ISSUED 354 PM CDT Wed Aug 18 2021/
SHORT TERM [Through Thursday Night]...
Numerous showers and thunderstorms will persist through the rest of
the afternoon. Latest AMDAR soundings indicate CAPE around 1500 J/kg
and a noticeable inverted-V layer beneath the LCL indicative of
strong downburst potential. This DCAPE signature was not apparent in
previous forecast soundings for areas as far south as Houston and
Galveston and only appeared in forecast soundings for northern
counties such as College Station. Therefore, expect strong and sub-
severe wind gusts with these passing showers and storms across our
entire CWA along with frequent lightning. With forecast soundings
and GOES-Satellite derived PWs hovering near 2.25 inches along with
weak low-level steering flow, and a weak disturbance aloft enhancing
low-level convergence, localized heavy rainfall amounts are also
possible with today`s activity. HGX radar and local gauges are
indicating rainfall rates of 2-3 inches per hour with some of the
strongest activity this afternoon. Fortunately this convection is
moving along at 10-15 mph, but any training storms or storms
repeatedly moving over the same area could lead to localized
flooding as was seen earlier in NE Harris County.
Activity will begin to subside this evening around sunset, but still
cannot rule out precip completely overnight as the aforementioned
upper-level disturbance pushes across our CWA. Isolated showers and
thunderstorms are expected overnight with a resurgence of convection
early tomorrow morning as coastal showers push onshore. Tomorrow
will be a competition between deep tropical moisture and upper-level
ridging building in from the west. Hi-res models have hinted that
upper-level ridging and drier air will mix in by early tomorrow
evening, squashing PoPs down to 20 or less by then.
Regarding temperatures, upper-level clouds and winds preventing the
low-levels from decoupling overnight will make overnight lows hover
near 80. By tomorrow, daytime highs will be a few degrees higher and
in the mid-90s as 850mb temps increase slightly.
KBL
LONG TERM (Friday through Wednesday)...
The fairly active diurnal pattern will persist into Fri...fueled
in part by a slug of elevated moisture (PWs progged near 2") and
daytime heating. This convection should decrease by Fri evening.
But, overall, rain chances are expected to decrease further this
weekend across SE TX as high pressure builds in from the east. A
combination of this deepening ridge and a slightly drier airmass
moving into the region (along with the time of year) could prod-
uce some very warm daytime temperatures starting on Sat and into
the start of next week. NBM/other MOS do hint at the possibility
of highs at/near 100F for portions of our CWA, but the aforemen-
tioned slightly drier air could help to mix out dewpoints during
the afternoon and keep heat index values from getting too crazy.
We`ll definitely have to keep an eye on things going forward for
the likelihood of a Heat Advisory for Sun/Mon next week. 41
MARINE...
Generally moderate/high SE winds and low seas will prevail through
the next couple of days. Seas (moreso than winds) should be on the
increase by Fri as Grace emerges off the western Yucatan Peninsula
and then restrengthens over the Bay of Campeche. Before its second
(and hopefully final) landfall on the eastern coast of Mexico, the
system could be strong enough to produce some elevated seas, minor
water run-up issues along our coast as well as increased risks for
rip currents for Fri and Sat (at least). Conditions should improve
by Sun as we return back to more light/moderate winds and seas for
the start of next week. 41
&&
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 77 94 77 96 76 / 20 20 0 20 10
Houston (IAH) 80 95 79 96 78 / 40 40 0 30 10
Galveston (GLS) 83 91 84 91 84 / 20 30 10 20 10
&&
.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...NONE.
&&
$$
Discussion...33