Areal Flood Warning 26, NWS Houston/Galveston, TX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
546 AM CDT Tue Jun 1 2021

.SHORT TERM [Today through Wednesday Night]...
Heavy rainfall overnight from Caldwell to College Station to
Crocket/Grapeland. Very heavy rainfall over Houston county with
rainfall estimates over 10" just east of Grapeland including 1 high
water rescue.

Band of storms continues to move through the area and should
continue to do so and have trended the forecast towards this with
the storms pushing down into the coastal counties by 10 am.
Rainfall rates this morning of 2-3"/hour are going to be possible
where storms train. The line should move and could split but will
also probably leave a boundary near the coast for the afternoon
hours in which storms could develop upon. In addition the pesky
cold front is going to move into the northern CWA this afternoon
and will probably become a focus for some garden variety storms
driven primarily by daytime heating and fortunately should
dissipate with the loss of heating but the coastal storms may not.

A potent shortwave is headed towards the area Wednesday and will
bring back 1.8-2.0" PW/a right rear quad up the upper jet and likely
a wave on the stationary front as a focus for more organized
rainfall. It may not arrive until the the late morning or more
likely afternoon/evening. After all of the rain recently and then
todays rains thinking that a Flash Flood watch will probably be in
the works for Wednesday as we head into the upcoming wet
period...see below.

Temperatures will be somewhat moderated by the expansive cloud cover
and rainfall the couple of days.

&&
.LONG TERM [Thursday through Tuesday]...

With the prevailing upper-level trough/low remaining to our
southwest, the period of unsettled weather will continue through the
end of the week and into the upcoming weekend. As the trough axis
ejects eastward and advances towards SE TX during the day on
Thursday, the synoptic pattern will become more favorable for the
development of locally heavy rainfall. At the surface, persistent
onshore flow will continue to make moisture plentifully available,
with global models indicating total PWs in the 1.75 to 2.0 in
range. The propagation of the upper low into Western TX by late
Thursday will place SE TX within the left rear quadrant of an
associated jet streak, which will enhance upper-level divergence.
As a series of shortwave troughs traverse the region beginning on
Thursday and persisting through the weekend, shower and
thunderstorm development will remain likely each day. Of the
latest deterministic solutions, the ECMWF remains the most
aggressive in its depiction of heavy rainfall on Saturday and
Sunday where jet dynamics/moisture availability look to be most
favorable. While the GFS is more bearish, its latest solution
nonetheless shows the entirety of SE TX receiving several inches
of rainfall.

WPC 7-Day QPF forecast amounts for SE TX remain in the 4-5" range.
Of course, these forecast values indicate areal average totals and
the occurrence of locally higher amounts is a distinct
possibility. As we draw closer to the weekend, the potential for
flooding will need to be monitored closely. Those planning any
travel/outdoor activities should continue to stay up to date with
the latest forecast information.

Generally overcast/broken cloud decks and precipitation should keep
daytime highs slightly below normal through the remainder of the
week and into the weekend, with forecast temperatures expected to
stay confined to the lower to mid 80s (normals for early June are 90
at IAH, 90 at CLL, and 87 at GLS). Overnight lows will remain near
normal, in the upper 60s to lower 70s.

Early indications are that the wet period may continue into next
week with the approach of another upper trough axis to our northwest
and continued onshore flow at the surface supplying widespread
moisture.

Cady

&&

.AVIATION [12Z TAF Issuance]...
VFR IAH southward to start off but that is short lived as band of
storms moves through the hub terminals with severely restricted
visibility in heavy rain/TSRA. Storms should stall out with a
possible split/break over the hubs by 15-17z and lingering into 20z
before storms reignite north and south.

45

&&

.MARINE...
Light to moderate onshore southeasterly flow should prevail
through the period. Increasing this weekend and with a longer
fetch to work with expect seas to build to 6 feet by Friday or
Saturday. SCEC/SCA conditions over the weekend look likely.

If storms this morning hold together they could move into the
coastal waters with strong gusty winds before noon then dissipate
with the greater threat of that near Matagorda bay.
45

.TROPICAL...
First day of Hurricane Season! All quiet so far.

&&

.PRELIMINARY POINT TEMPS/POPS...

College Station (CLL)  83  68  81  68  83 /  60  20  60  30  60
Houston (IAH)          85  72  84  72  83 /  60  60  60  40  70
Galveston (GLS)        83  76  84  78  82 /  30  50  40  40  60

&&

.HGX WATCHES/WARNINGS/ADVISORIES...

TX...None.
GM...None.

&&

SHORT TERM...45
LONG TERM...Cady

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