Preview of NWS' New Version of Forecast
This preview is not operational and should not be used for support decisions.

Area Forecast Discussion (AFD)

Issued by Houston/Galveston, TX (HGX)

                            
000
FXUS64 KHGX 171228
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
628 AM CST Sun Feb 17 2019

.DISCUSSION [12Z TAF ISSUANCE]...

Areas of patchy fog is expected to dissipate as a cold front
continues to move across the forecast area this morning. VFR 
vis/cigs expected after around 15-18Z across most TAF sites, 
except KGLS and KLBX where MVFR cigs could prevail through around
22-00Z. N winds at 5 to 15 knots with occasional higher gusts 
will settle across the region today. Stronger gusty winds 
expected across KHOU, KSGR, KLBX and KGLS tonight as the local 
pressure gradient tightens.

&&

.PREV DISCUSSION... /ISSUED 444 AM CST Sun Feb 17 2019/ 

DISCUSSION...
Strange forecast this morning rather unexpected results...dry air
mixed in the lower levels to erode the fog near the coast but now
it is finally starting to return as winds have begun to relax
slightly with the approach of the front. At this point it looks
like a pre-frontal trough will push into the coastal area around
7 am with the cold front lagging back about 2 hours. Fog should
clear with the pre-frontal trough and will probably continue to
see the patchy light in the vicinity of the cold front as the next
speed max arrives from the west-southwest. Rainfall should be
light averaging less than 0.10" and probably a lot closer to
0.02". The dry air filters in late this morning from the northwest
to southeast and expect the lower clouds to lift and scatter out
by mid morning to noon time frame...but the moist southwesterly
flow aloft will probably continue to support cirrus and possibly
at times some mid clouds as well. So a little sunshine is the
offing this afternoon - and possibly even early Monday up north. 
Cooler and drier air will be here into Monday.

The front stalls (now well out into the Gulf) Monday and
isentropic upglide ramps up through the day Monday over SETX
leading to a rapid expansion of the clouds from the coast working 
inland as well as the high level clouds from the very persistent
southwesterly flow aloft. Rain chances start to increase Monday
night with the increasing ascent becoming well saturated Tuesday
morning. Widespread rain is likely Tuesday. In addition will very
likely see bands of heavier showers and elevated thunderstorms.
Impressive lapse rates aloft and wouldn't rule out some strong
thunderstorms and dare I say even a threat of small hail. Vigorous
upper s/w rotating out of the bottom of the upper trough produces
abundant diffluence/isentropic ascent and draws the front back up
into the nearshore waters or perhaps even the coastal counties
which yields a high confidence of rainfall and will have to watch
closely as this nears for any further changes give the subtle
nature of these southwest flow events. Tuesday night the s/w
departs and a weak Pacific front struggles to reinforce what
little cool air remains nudging the moisture rich boundary back 
out over the water. The upper flow tightens up and starts tapping
into the tropical moisture from south of Baja with the possibility
that late Wednesday through Thursday we could see another round of
storms. Stay tuned for changes.

Friday and Saturday are very low confidence other than to say a
chance of showers/thunderstorms/fog as the upper trough finally
moves east but timing this is probably a fools game at this point.

45

MARINE...
Patchy to dense sea fog is expected to continue across the bays 
and nearshore waters until a cold front moves over the Gulf water 
this morning. The local pressure gradient is forecast to tighten 
over the region as an upper level trough amplifies to the north 
and a surface low builds across the lower Texas coast. As a 
result, fresh to strong winds and building seas are expected. 
SCEC/SCA flags will be issued for the bays and Gulf waters for 
late tonight through Tuesday morning. Winds will become north 
northeast today and then gradually veer east late Monday night. 
Onshore wind flow returns Tuesday as the coastal low moves from 
the lower TX coast into the local waters increasing shower and 
thunderstorm activity. Thereafter, an upper level trough will move
across the region resulting in moderate to fresh north to 
northwest winds Tuesday night and Wednesday. Expect winds to 
fluctuate in direction during the rest of the week and into the 
weekend as well as periods of showers and thunderstorms due to 
another coastal low moving across the coastal waters Thursday and 
an upper level trough pushing into the region Friday. 24 

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)      60  44  59  47  51 /   0   0  10  50  70 
Houston (IAH)              66  47  62  50  58 /  50   0  10  70  80 
Galveston (GLS)            64  52  59  55  63 /  60  10  30  70  70 

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...Dense Fog Advisory until 8 AM CST this morning for the following 
     zones: Brazoria Islands...Chambers...Coastal Brazoria...
     Coastal Galveston...Coastal Harris...Coastal Jackson...
     Coastal Matagorda...Galveston Island and Bolivar 
     Peninsula...Inland Brazoria...Inland Galveston...Inland 
     Matagorda...Matagorda Islands...Southern Liberty.

     Dense Fog Advisory until 6 AM CST early this morning for the 
     following zones: Austin...Colorado...Fort Bend...Inland 
     Harris...Inland Jackson...Montgomery...Northern Liberty...
     Waller...Wharton.

GM...Dense Fog Advisory until 9 AM CST this morning 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...Galveston Bay...Matagorda Bay.

     Small Craft Advisory from midnight tonight to 6 AM CST Tuesday 
     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 this evening 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 Advisory from 10 PM this evening to 6 AM CST Tuesday 
     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.

     SMALL CRAFT SHOULD EXERCISE CAUTION from 4 PM CST this afternoon 
     through 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...45