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Area Forecast Discussion (AFD)

Issued by Houston/Galveston, TX (HGX)

                            
000
FXUS64 KHGX 161851
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
151 PM CDT Sat Mar 16 2019

.AVIATION...
VFR. 9000-120000ft deck spreading northeast from the coastal
areas. Area of showers/light rain near PSX/BYY spreading up the
coast and may see some brief light rain at LBX/GLS 19-22z. Could
skirt SGR/HOU if the northern edge doesn't weaken. Northeasterly
flow 4-10kt through the period. Another chance of light rain or
showers Sunday probably out over the Gulf but could be close
enough to keep an eye on any impacts for GLS.
45

&&

.PREV DISCUSSION... /ISSUED 1038 AM CDT Sat Mar 16 2019/ 

UPDATE...

Forecast is generally on track, with mainly cosmetic tweaks to 
bring the first handful of hours in line with observations. 
The most substantial change was to pull PoPs in closer to the 
coast, and extending less inland today. Radar and water vapor 
imagery shows that the large majority of showers today are 
occurring over the waters and the immediate coastal areas. The WV 
imagery in particular suggests that this trend in the moist 
southwest flow aloft will continue, and possibly even push a bit 
more over the Gulf rather than over land up the coast. The 
pulling of PoPs is primarily a response to this. Unsure if any 
lightning will actually occur, but lightning detection networks 
and the GOES GLM have consistently shown activity over Corpus 
Christi's area, and so will conservatively hold Iso Thunder in 
place today.

PREV DISCUSSION /Issued 409 AM CDT Sat Mar 16 2019/...

DISCUSSION...
Weak impulses embedded in the sw flow aloft will continue to move
overhead and possibly trigger some additional sct showers closer
to the coast and offshore thru Sunday. Can't completely rule out 
an elevated tstm or two, but overall rain accumulations, if any, 
will be light over inland parts of the area. Precip chances should
trend downward Sun into next week with just some variable Pacific
cirrus streaming thru and mostly seasonable temps expected. Mid/upper
trof dipping sse thru the northern Plains and toward the Tennessee
Valley Tue-Thur will send its decaying surface frontal boundary 
into the region late Wed or Thurs, but with little noticeable 
impact. Onshore flow resumes and increases late in the work week 
allowing for a gradual increase of moisture levels in advance of 
the next storm system that'll be approaching from the west. 
Shra/tstm chances increases late Fri into the next weekend as it 
makes its way across the region. 47

AVIATION...
Not too many changes from the OVC/BKN VFR conditions currently over 
the region. The main forecast issues will be related to the deep SW 
upper flow pattern and the embedded shortwaves within it. Models do 
keep the scattered SHRAs/isolated TSRA activity mostly at the coast 
and coastal counties with the next disturbance this afternoon...and 
will likely word TAFs as such. However, given the trends yesterday, 
will advise the dayshift to keep close tabs on things for TAF sites 
further north. 41

MARINE... 
While decreased a bit, winds/seas over the coastal waters remain at 
SCEC/SCA criteria this morning. The slow downward trend is expected 
to continue today and we should see most of of these Caution/Advis- 
ory flags dropped by this afternoon...except for maybe the offshore 
waters (which could go through late this afternoon). Thereafter...a 
light/moderate NE flow to prevail for the remainder of the weekend. 
As the surface high shifts east, a more easterly flow will be deve- 
loping by the start of next week...persisting for much of the week.
A deep/persistent SW upper pattern will also help to keep scattered 
showers/isolated thunderstorms in place over the coastal waters the 
next several days. 41

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)      61  42  65  42  68 /   0   0   0   0   0 
Houston (IAH)              62  45  66  46  69 /  10  10   0   0   0 
Galveston (GLS)            59  50  63  54  65 /  20  10  10  10   0 

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...High Rip Current Risk until 6 PM CDT this evening for the 
     following zones: Brazoria Islands...Galveston Island and 
     Bolivar Peninsula...Matagorda Islands.

GM...SMALL CRAFT SHOULD EXERCISE CAUTION until 5 PM CDT this 
     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.

     SMALL CRAFT SHOULD EXERCISE CAUTION until 10 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.

&&

$$

Discussion...25
Aviation/Marine...45