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Area Forecast Discussion (AFD)

Issued by Houston/Galveston, TX (HGX)

FXUS64 KHGX 232041

Area Forecast Discussion
National Weather Service Houston/Galveston TX
341 PM CDT Sun Jun 23 2019


.SHORT TERM [Rest of Afternoon through Monday]... 
Scattered showers and thunderstorms this afternoon will tend to 
die off this evening with loss of daytime heating. Storms have 
been more clustered and intense ahead of a short wave trough 
lifting northeast across the area. At this time this slightly more
intense deeper convection...with some over 
northern parts of the forecast area and this trend should continue
as the short wave lifts northeast. 

Tonight all convective allowing models show a band of
thunderstorms moving from north to south across the area. NMM and
ARW WRF runs most aggressive in holding the line together...all 
the way to the coast. HRRR and especially TTU WRF tend to break up
the line as it progresses through the area. All 4 runs suggest 
squall line would be entering forecast area...up around 
Caldwell... Bryan and Madisonville around 06Z or 1 am...give or 
take...then reaching the coast toward daybreak. 12km NAM a little 
slower keeping storms in the area into daylight hours Monday 
morning. Some of these could be strong to severe...especially 
northern zones...with damaging winds the main threat. SPC has 
northern third of forecast area in slight risk...remainder just 
one level down in Marginal.

Monday...will likely see a break once the line of storms push
through with just some isolated showers and thunderstorms 
possible after line pushes off the coast. Also not expected to be
as hot as recent days. This afternoon we saw several sites exceed
heat index levels...and issued a heat advisory for southern half 
of forecast area. Don't expect that to be an issue tomorrow.

.LONG TERM [Monday Night through Sunday]...
We may have to keep an eye on things to the NW once again for Mon 
night as models are hinting at the possibility of another MCS 
developing over North Central TX overnight and moving it SSE 
toward our CWA through early Tue morning. However, there is not a 
lot of confidence with this as there still a lot of questions 
concerning how worked over the airmass will be (from Mon's 
activity). At any rate, there will be plenty of heating/some 
lingering moisture for perhaps widely scattered activity by Tue 

With a surface high pressure/upper ridge building into the region 
from the east by Tue, rain chances should be decreasing Weds/Thur. 
Any activity will likely be during the afternoon and isolated. By 
the end of the week, long-range guidance seems to be keeping with 
the idea of a slightly increased POPs as the Gulf opens up (via a 
weakness region between the main upper ridge). 41


.AVIATION [18Z TAF Issuance]...
Showers have developed as expected. Only a few lightning strikes 
so far. Am carrying at least VCSH all TAF sites away from coast 
this afternoon...with tempo for airports soon to see shower 
activity based on radar trends. Could see some lighting still as 
convection deepens. Should see convection die down this 
evening...then a line of storms...perhaps with gusty 
winds...should move from north to south across the area overnight.
For now am including a tempo for 4 hour window when chances are 
greatest...based on timing in HRRR and WRF runs and mention 30kt 
gusts to indicate wind potential. Should be able to narrow that 
down and be more specific on wind threat as we get closer. 


Elevated winds/seas will continue over the coastal waters tonight 
with slightly lower wind speeds across the bays. Models are still 
indicating the approach/passage of strong storms into SE TX 
overnight then reaching the Upper TX coastal waters by early Mon
morning. Winds/seas will be higher in and near these 

With high pressure building into the region from the east by Tue, 
we'll begin to see increasingly decreased winds/seas at that time. 
This weak surface high is expected to linger over the NW Gulf for
much of the week with generally light/moderate onshore winds 
prevailing over the marine waters. 41



College Station (CLL)  75  91  73  92  73 /  70  50  40  30  20 
Houston (IAH)          78  92  77  92  76 /  70  60  30  30  20 
Galveston (GLS)        82  87  80  90  80 /  60  70  30  30  20 



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

     Heat Advisory until 8 PM CDT this evening for the following 
     zones: Austin...Brazoria Islands...Chambers...Coastal 
     Brazoria...Coastal Galveston...Coastal Harris...Coastal 
     Jackson...Coastal Matagorda...Colorado...Fort 
     Bend...Galveston Island and Bolivar Peninsula...Inland 
     Brazoria...Inland Galveston...Inland Harris...Inland 
     Jackson...Inland Matagorda...Matagorda 
     Islands...Montgomery...Northern Liberty...Polk...San 
     Jacinto...Southern Liberty...Waller...Wharton.

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

     Small Craft Advisory until 10 AM CDT Monday 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.