Saturday, January 23, 2021

Jan. 23 21

 Area Forecast Discussion

Issued by NWS Houston/Galveston, TX

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000
FXUS64 KHGX 232321
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
521 PM CST Sat Jan 23 2021

.AVIATION...
LIFR/IFR conditions will persist overnight and well into late Sun
morning across most of the region. A warm front will be making its
way inland overnight and bring periods of low cigs/-ra/dz/fg.
Southerly winds will increase Sun afternoon which should allow
cigs to possibly lift into MVFR for a while, but anticipate them
to fall once again after sunset. 47

&&

.PREV DISCUSSION... /ISSUED 347 PM CST Sat Jan 23 2021/
SHORT TERM [Through Sunday Night]...
It`s been yet another day of grey, gloomy, and foggy weather
across SE Texas, particularly near the coast where areas of dense
fog continue to persist in and around Galveston and Matagorda
Bays. The approach of a surface warm front towards the coast this
evening will prove favorable for a continuation of this pattern
throughout the day tomorrow. As the boundary exits the coastal
waters this evening, a shift to south-southeast winds in its wake
will allow for much more efficient moisture transport with dew
point values increasing by around 5 degrees by tomorrow afternoon.
The shift in wind direction will additionally provide a more
lengthy fetch which will enhance the development of sea fog
overnight and into tomorrow. We once again anticipate widespread
visibilities below one mile, particularly along the coast, on the
barrier islands, and in the bays and nearshore waters. Travelers,
whether by land or sea, should pay close attention to conditions
and exercise caution through the remainder of the weekend.
Continued overcast decks will furthermore inhibit nocturnal
radiative cooling, keeping lows at or above 60 for most of the
region.

Precipitation chances will be on the rise overnight and into
tomorrow as the surface warm front pushes inland, eventually
clearing the northern third of the area by the afternoon.
Scattered to isolated showers will develop along and behind the
boundary as it advances, aided by the ample low-level moisture in
place. While most locations can expect to see measurable rainfall,
accumulations are unlikely to be significant on Sunday. Highs will
be around 5-8 degrees warmer across the board with the arrival of
warm and moist air behind the front, with most locations
experiencing the low to mid 70s.

Cady

.LONG TERM [Monday Through Saturday]...
Pacific cold front should be approaching College Station around
6-9 AM with moist moderate southerly flow in place likely getting
a little gusty as the inversion breaks. At this point the guidance
is still bullish with the cap eroding over the far northern
counties and holding in across the south...A narrow wedge of 1000
CAPE trails down into the area and so have continued with the high
end POPs with TSRA prevailing mainly north of the I-10 corridor
(especially along and north of the Conroe area). Rainfall
accumulations should be relatively light with the fast progression
and mainly showers. Then by mid afternoon it should be out over
the Gulf with dry air replacing the persistent soup of the
previous days. This boundary hangs up in the NW Gulf only to
return as a warm front Tuesday night/Wednesday so you can guess
what that means...more FOG...but wait in this case the surface
warm front never quite reaches the nearshore waters so the fog
impacts for the bays may never arrive - possible further out
before the next cold front races through SETX Wednesday morning
with an abundance of clouds but likely lacking in rainfall. This
cold front has a decent ridge associated and should scour out the
area with gusty moderate northwest winds and much cooler
temperatures that persist Wednesday night through Friday morning.
The next upper trough deepening over CA/Baja should lead to return
flow - increasing warmth and moisture Friday afternoon into
Saturday. As would be expected the timing of the weekend system is
in question with a faster solution coming of the ECMWF bench and
a slower solution from the GFS. For now have split the difference
there with slight chance POPs.

45

.MARINE...
Reduced visibility due to marine fog will continue to be a
concern this evening as a surface warm front traverses the coastal
waters and southeasterly winds develop in its wake. Widespread
dense fog with visibility dropping to below 1 NM is expected to
persist into Sunday, and the Dense Fog Advisory has been extended
as a result. Scattered showers will accompany the passage of the
cold front. Onshore flow will increase by late Sunday and into
early Monday as a surface cold front approaches SE Texas. Caution
and/or advisory flags are likely to be needed as a result. As the
cold front approaches the coastal waters on Monday afternoon,
cooler and drier air will filter in in its wake which should put
an end to the past week`s prolonged sea fog episode.

Cady

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)      60  74  62  72  48 /  50  50  70  60   0
Houston (IAH)              61  74  65  75  52 /  50  40  40  60   0
Galveston (GLS)            60  69  64  69  57 /  50  20  20  40   0

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...Dense Fog Advisory until 6 PM CST Sunday for the following
     zones: Brazoria Islands...Galveston Island and Bolivar
     Peninsula.

GM...Dense Fog Advisory until noon CST 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...Galveston Bay...Matagorda Bay.

&&

$$

Discussion...99

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