Funnel Cloud in Texas, July 27, 2020

Area Forecast Discussion
National Weather Service Houston/Galveston TX
1249 PM CDT Mon Jul 27 2020

.AVIATION [18Z TAF Issuance]...

This morning's IFR CIGs scattered out through the past few hours
leaving CIGs of around 3000 feet across the area. The main concern
through this evening will be the scattered TSRA that develop
across the area. They will be slow moving, so if a storm forms
over a terminal, it will likely remain there through the
afternoon. The storms will initially form along the coast, impacting
LBX and GLS, then expand in coverage north up through CXO by mid
afternoon. UTS and CLL may be far enough north to not see any
precipitation. The thunderstorms will mainly bring gusty winds and
heavy rainfall bringing visibilities to less than a mile. Shower
activity will then diminish in the evening and overnight hours.
Overnight MVFR to IFR CIGS redevelop across the area that will
again scatter out in the mid morning hours of tomorrow. Lingering
moisture will again set up for additional scattered showers and
thunderstorms tomorrow afternoon.

Fowler

&&

.PREV DISCUSSION /Issued 544 AM CDT Mon Jul 27 2020/...

.SHORT TERM [Tonight Through Tuesday Afternoon]...

Another pretty active day is anticipated today for Southeast TX. An
upper cutoff low located over western LA and eastern TX will dip a
little more southwest today with a speed max (50-60KT) positioned
over the local area late this morning and afternoon. The low will
continue to progress southwestward positioning itself over Southeast
TX overnight and over the Middle Texas Coast Tuesday. Along the
surface, models indicate ample moisture persisting across the region
today and Tuesday. GOES 16 TPW this morning indicated PWs of around
2.1 along the northern areas of the CWA, increasing to around 2.4
inches along the southern areas and Gulf waters. The moisture along
with the upper low and speed max will likely ramp up convection late
this morning and afternoon with storms possibly still firing up
through early tonight.

Even though the Doppler radar was not showing much activity out in
the Gulf overnight as previously expected, slow moving isolated to
scattered showers are moving into the Chambers, Matagorda and
Jackson counties from time to time. Showers and thunderstorms are
expected to build over the local waters and move into the coastal
locations this morning and as diurnal heating kicks up in the late
morning and afternoon, it will combine with the upper low, speed max
and moisture to produce scattered to numerous showers and
thunderstorms across the CWA. Strong showers and thunderstorms will
be capable of producing frequent lightning, gusty winds and reduced
visibility. Heavy rain could lead to minor flooding issues,
particularly with slow moving showers and thunderstorms in locations
that have been receiving good amounts of rainfall these past few
days. Activity is expected to dissipate in the evening, but the
environment could still be favorable for isolated activity
developing through early tonight.

Fairly calm weather is expected overnight with a few showers and
possible isolated thunderstorms developing once again over the Gulf
waters and occasionally moving into the southern counties through
Tuesday morning. Areas of patchy fog could also develop overnight
into early Tuesday morning; keep an eye out on that if you plan to
do and early morning commute. A similar weather pattern is to be
expected Tuesday, with showers and thunderstorms to occur most
likely along the Gulf waters and the southern portions of the CWA,
and ramping up northward across the rest of Southeast TX in the late
morning and afternoon hours.

High temperatures today will range generally be in the low 90s along
areas west of I-45 and in the upper 80s to low 90s along areas south
of I-45. Lows will once again be in the upper 70s. Highs will be
similar Tuesday, possible a degree or two higher along areas west of
I-45 and north of I-10. Southerly winds will be at 5 to 10 MPH today
and Tuesday. 24

.LONG TERM [Tuesday Night Through Monday]...
By Tuesday evening the upper low over LA today will have drifted
southwest through coastal SETX and be over the Brownsville area.
This will help to set the stage for one more good chance of
rainfall with deep southerly flow aloft (relatively moist) along
with weak LLJ arcing up into SETX and convective temperatures that
should be easily reached at 83-84 degrees. So an early start to
storms in the coastal waters spreading inland in the morning and
then probably active along the I-69 corridor early in the
afternoon expanding inland (like a more typical seabreeze pattern)
quickly in the afternoon as some drier air aloft arrives. Then
with loss of heating expect a quick demise of the storms early in
the evening. Upper level ridging holds sway Thursday with just
some spotty showers and thunderstorms in the late
morning/afternoon hours and hotter especially in the northwest
counties. Friday will probably be another hot one across the
region but if the upper level trough dropping south through the
Plains ends up being faster like the 00z GFS implies then will be
looking for the potential for storms in the
afternoon/evening...leaning more toward the ECMWF for now with a
slower progression and increased thunderstorm chances Saturday
and Sunday. This is going to get more scrutiny as we go through
the week but a cold front (weak) this time of year with
northwesterly flow aloft and 2500+ CAPE certainly appears to be a
good setup for at least one good round of storms. Monday the front
could be washing out over the region or well north of the area so
will keep rain chances low for now and trend temperatures back
toward climo.

As for the Tropics...Hanna raining herself out over Mexico.
Tropical wave over Central Atlantic near 45W is racing westward.
Looking at satellite imagery abundant Saharan dust is surrounding
the system and extending well out ahead of it. GFS/ECWMF are slow
to develop (dust?) still chug it up into the Puerto Rico/Haiti
area by Thursday afternoon...ECMWF still further west over the
northern Caribbean and a little faster...GFS 06z slower and
further east on the Atlantic side of the islands...GFS 00z much
faster and much further northeast. Given these three tracks and
the trends still worried that the ECMWF or a split between the 06z
GFS/ECMWF is on the right track...enough so that it will be worth
paying attention to on Thursday as to which course it has given
that the ocean heat content being so high over the Northern
Caribbean.
45

.MARINE...

Seas across the offshore waters have yet to drop further this
morning. Bouy 42019 is still reporting seas of around 7 feet,
therefore, the Small Craft Advisory will continue through 7 AM CDT
this morning and may be extended if seas do not improve. High Risk
of Rip Currents is in effect for the beaches for today; if you plan
to go for a swim today it is recommended to swim near a lifeguard.
Winds and seas will continue to subside today and are expected to be
below SCEC criteria by tonight. Periods of showers and thunderstorms
are anticipated for the bays and Gulf waters through mid week with
low chance of rain continuing into the upcoming weekend. 24

&&

.PRELIMINARY POINT TEMPS/POPS...

College Station (CLL)  75  94  76  93  77 /  30  40  10  40  10
Houston (IAH)          76  91  77  92  78 /  40  70  20  60  10
Galveston (GLS)        80  89  81  89  82 /  40  60  30  60  10

&&

.HGX WATCHES/WARNINGS/ADVISORIES...

TX...High Rip Current Risk until 7 PM CDT this evening for the
     following zones: Brazoria Islands...Galveston Island and
     Bolivar Peninsula...Matagorda Islands.

GM...SMALL CRAFT SHOULD EXERCISE CAUTION until 7 PM CDT this evening
     for the following zones: Waters from Freeport to Matagorda
     Ship Channel TX from 20 to 60 NM...Waters from High Island
     to Freeport TX from 20 to 60 NM.

&&

SHORT TERM...24
LONG TERM...45
AVIATION...Fowler
MARINE...24