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Area Forecast Discussion (AFD)

Issued by Houston/Galveston, TX (HGX)

FXUS64 KHGX 160127

Area Forecast Discussion
National Weather Service Houston/Galveston TX
827 PM CDT Sat Jun 15 2019

Winds increasing tonight with developing LLJ and should see an
increase in coverage of showers toward morning. SCA conditions
should be developing late this evening/overnight. Seas of 4 to 6
feet and winds near 20 knots at times. 

Additional concern is for the strong rip currents to 
continue...Galveston Beach patrol had 8 rip current rescues today 
and with the further building of the seas and stronger winds will 
need to continue to advertise the strong rips in the Beach hazards


.AVIATION [00Z TAF Issuance]...

Isolated showers near the coast on the northern edge of the deeper
moisture surge moving in from the Gulf. Overnight expect mostly
VFR conditions with some patchy MVFR ceilings probably over the
southern terminals. Showers should start to increase in coverage
around 12z in the Gulf and spreading gradually inland with much of
the southeastern 1/2 of the area dotted by showers by 15z.
Guidance is a very mixed bag with placement and intensity. Trended
the forecast toward the drier NAM/TTWRF solutions with the higher
rain chances holding off til 15-21z time frame with isolated
thunderstorms. After 18z could see more thunderstorms develop but
drier air may start to wedge in from the southwest shunting storms
into the central and eastern area. VSCH most sites between 15-18z
then a mix of VCTS or VCSH into the mid afternoon hours inland.
May have a better handle on the placement with the 00z package and
will hopefully be able to distinguish between something
propagating in from the northwest/north with a cold pool or if
this will be more of just a WAA pattern setup with a weak s/w.


Trinity near Riverside may finally be near a long flat crest 
around 134 feet (minor) dropping very slowly Wednesday or Thursday
if the upstream sites don't get too much rainfall from Sunday's
system over NCTX/ARKLATEX. Moss Bluff still in (minor) flood and
given the upstream inflow into Lake Livingston will likely remain
in flood through the coming week but probably on very minor


.PREV DISCUSSION /Issued 324 PM CDT Sat Jun 15 2019/...

.SHORT TERM [Tonight Through Sunday Night]... 
Once lower 90s were achieved this afternoon, ordinary thunderstorms 
developed and traveled north-northeast this afternoon. Most of this 
activity will remain benign but there could be an isolated 
northeastern forecast area thunderstorm cell that could become 
strong and put down 30 mph wind gusts and small hail along it's 
northern trek. Background onshore winds will remain in the 15 to 25 
mph range through the early evening.

A warm, breezy and humid early Sunday morning with increasing 
probabilities for early day developing convection. A strengthening 
low level jet in response to lowering heights from a shortwave 
trough passage will increase slight morning chances to high 
end/likely chances by early afternoon. A possible MCS feature over 
the Red River Valley could spit out outflow boundaries that would be 
entering our northern CWA during peak heating...or a more-structured 
storm cluster could be cold pool-driven and track more southeast. 
Either way, the northern half of the forecast area has a better than 
not chance of experiencing late morning through late afternoon rain 
and thunderstorm activity. If convection remains organized enough 
then clustering storms could impact Houston metro and move south of 
the I-10 corridor by late afternoon. More mid-day overcast and 
precipitation will regulate tomorrow's warmth to the upper 80s to 
lower 90s. 31

Showers and thunderstorms may be ongoing Sunday evening as an 
outflow sags south across the CWA. Some of the stronger storms
could produce strong damaging winds. Any residual activity will 
be ending during the evening. Isolated to scattered showers will 
be possible for the remainder of the night as SE TX lies on the 
east side of an upper level trough over the southern plains. 
Showers and thunderstorms will again be possible on Monday as the 
the region will remain east of the upper level trough axis and PW 
values remain near 2.00 inches. High temperatures should warm into
the lower 90's and convective temps will only be in the upper 
80's. The upper level trough will begin to move east Monday night
but this feature will still be close enough to generate some
showers especially over the eastern half of the CWA. Weak capping
will begin to develop on Tuesday as upper level ridging over the
Gulf expands. That said, daytime should remain sufficient to 
break the cap by afternoon with scattered showers and isolated
thunderstorms possible. Upper level ridging looks stronger on
Wednesday and the ridge will probably remain the dominant weather
feature through next Friday. 850 mb temperatures warm as well so 
am expecting a warm up with surface temperatures in the middle 
90's over the second half of next week. Subsidence from the 
expanding ridge will likely keeps things on the dry side as well.

Moderate to occasionally strong onshore winds will create minor 
coastal run-up during times of high tide and enhance rip current 
strength. Gulf Advisory conditions with Bay Cautions through 
tomorrow morning. A Beach Hazard Statement will cover both the minor 
coastal run up and rip current issues along Galveston Island and the 
Bolivar Peninsula. A Rip Current Statement is in effect for points 
down coast of San Luis Pass. The onshore pressure gradient will 
weaken enough to lower flags going into late Monday or early 
Tuesday. This weekend's 4 to 6 foot seas will fall to between 3 to 4 
feet by Tuesday afternoon. Re-tightening of the onshore pressure 
gradient Thursday will pick southerlies back up to Advisory levels 
by that afternoon. 31



College Station (CLL)  76  91  74  89  74 /  10  50  30  50  10 
Houston (IAH)          77  91  77  90  77 /  10  50  40  50  20 
Galveston (GLS)        82  88  79  87  81 /  20  40  40  50  20 



TX...High Rip Current Risk through Monday morning for the following 
     zones: Brazoria Islands...Galveston Island and Bolivar 
     Peninsula...Matagorda Islands.

GM...SMALL CRAFT SHOULD EXERCISE CAUTION through Sunday afternoon for 
     the following zones: Galveston Bay...Matagorda Bay.

     Small Craft Advisory until 10 AM CDT Sunday for the following 
     zones: Coastal waters from Freeport to Matagorda Ship 
     Channel TX out 20 NM...Coastal waters from High Island to 
     Freeport TX out 20 NM...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.

     SMALL CRAFT SHOULD EXERCISE CAUTION from Sunday morning through 
     Sunday afternoon for the following zones: Coastal waters 
     from Freeport to Matagorda Ship Channel TX out 20 
     NM...Coastal waters from High Island to Freeport TX out 20 
     NM...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.