Small Craft Advisory 17, NWS Houston/Galveston, TX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
1115 PM CST Mon Feb 15 2021

.AVIATION [06Z TAF Issuance]...

It is SKC across Southeast Texas, with two main exceptions: There
is a plume of lake effect cloud (and flurries?) off Lake
Livingston, and a plume of bay effect cloud (perhaps with some
contribution from added water from industrial plants on the ship
channel). The bay effect cloud is causing a ceiling at GLS, and
have MVFR conditions for them through the night. The Lake
Livingston plume is east of all terminals. Eventually, as winds
veer tomorrow, IAH could be in line, but suspect that the plume
will diminish rapidly as it loses its favorable fetch down Lake
Livingston. However, there has been a very minor lake effect plume
downwind of Lake Conroe, which is in line with IAH. It is non-
existent to minor in impact though, so I only tip my hat to it
with a FEW025 reference.

The last line at LBX and the extended at IAH hint at a much bigger
player that the 12Z TAFs will need to begin to grapple with across
the area: our next wintry weathermaker. This time, a coastal
trough will make its way up the Texas coast. And while it will
bring in some warmer air, it looks to create a freezing rain event
inland, gradually shifting to "merely" a cold rain from south to
north on Wednesday. But be cautious, as FZRA will make a push back
after the low begins to move off and gusty offshore winds return.

&&

.PREV DISCUSSION /Issued 532 PM CST Mon Feb 15 2021/...

.SHORT TERM [Tonight through Tuesday]...

...BITTERLY COLD TEMPERATURES EXPECTED TONIGHT AND INTO TUESDAY
MORNING...

Arctic high pressure will continue to settle across the region
tonight, with the core of the coldest air upon us. With 925mb
temperatures from -2 to -15 C over our area, dangerously cold
temperatures are expected tonight. Overnight lows will plummet
into the single digits across most of the region, and into the mid
to upper teens along the coast. Fortunately, pressure gradient
relaxes as the surface ridge settles in, leaving us with
relatively light winds through the night. However, dangerous wind
chill values are still expected, mainly early Tuesday morning.
Wind chills from the single digits to teens below are expected
north of I-10 and in the single digits above south of I-10. A Wind
Chill Warning and a Hard Freeze remain in effect until noon
Tuesday.

The good news is that no precipitation is expected, at least
through late Tuesday. Surface high pressure gradually moves east
throughout the day on Tuesday, shifting winds from the east, then
southeast by the afternoon. Temperatures will only make it into
the mid 20s to low 30s north of I-10 and into the mid 30s to low
40s along the coast. 05

.LONG TERM [Tuesday Night Through Monday]...

Another storm system will approach from the west on Tuesday night
and produce a round of precipitation beginning late Tuesday evening
and continuing through Wednesday night. The thermal profile favors
rain and freezing rain for most of this event, so it is critical as
to where surface freezing temperatures will be present around
midnight Wednesday. Thinking that coastal areas will see some
warming due to modification of the cold airmass and the freezing
rain threat will begin a little south of I-10 for western areas,
with Houston right on the southern edge of the threat. During the
day on Wednesday, temperatures will warm some and the freezing rain
threat will lift northward, but remain for far northern areas. Some
additional light sleet and freezing rain are possible across the
same area as the storm system is exiting off to the east late
Wednesday night. Ice accumulations are likely to range from a little
less than a tenth of an inch for south central areas to around a
quarter of an inch across northern areas. Note, a half inch is
possible around Crockett and Trinity.

Behind this storm system, cold air will surge south again with an
inland hard freeze expected Friday morning. Min temperatures will
likely be back in the teens across NW areas with mid 20s across
central and inland areas. By Friday afternoon, with abundant
sunshine, the entire area should warm above freezing; however,
northern areas will only reach the mid to upper 30s. A more
significant warmup begins on Saturday and continues the rest of the
weekend.

Wood

.MARINE...
Although winds have subsided some, small craft advisory
conditions will continue most of tonight. Bitterly cold
temperatures will persist with temperatures below freezing and
wind chills below zero at times into Tuesday morning. A coastal
trough will develop along the middle Texas coast during the day on
Tuesday, allowing for a slight warm up, but bring another round
of unsettled marine conditions into Thursday until it passes.
Another front will push off the coast in its wake with moderate to
strong northwesterly winds, cold temperatures and elevated seas.

Wood

&&

.PRELIMINARY POINT TEMPS/POPS...

College Station (CLL)  20  -1  26  21  33 /   0  80  90  20  10
Houston (IAH)          24   8  31  27  41 /   0  60  80  30  10
Galveston (GLS)        29  14  42  38  54 /   0  80  90  30  10

&&

.HGX WATCHES/WARNINGS/ADVISORIES...

TX...Hard Freeze Warning until noon CST Tuesday for the following
     zones: Austin...Brazoria
     Islands...Brazos...Burleson...Chambers...Coastal
     Brazoria...Coastal Galveston...Coastal Harris...Coastal
     Jackson...Coastal Matagorda...Colorado...Fort
     Bend...Galveston Island and Bolivar
     Peninsula...Grimes...Houston...Inland Brazoria...Inland
     Galveston...Inland Harris...Inland Jackson...Inland
     Matagorda...Madison...Matagorda
     Islands...Montgomery...Northern Liberty...Polk...San
     Jacinto...Southern
     Liberty...Trinity...Walker...Waller...Washington...Wharton.

     Wind Chill Warning until noon CST Tuesday for the following
     zones: Austin...Brazoria
     Islands...Brazos...Burleson...Chambers...Coastal
     Brazoria...Coastal Galveston...Coastal Harris...Coastal
     Jackson...Coastal Matagorda...Colorado...Fort
     Bend...Galveston Island and Bolivar
     Peninsula...Grimes...Houston...Inland Brazoria...Inland
     Galveston...Inland Harris...Inland Jackson...Inland
     Matagorda...Madison...Matagorda
     Islands...Montgomery...Northern Liberty...Polk...San
     Jacinto...Southern
     Liberty...Trinity...Walker...Waller...Washington...Wharton.

     Winter Storm Warning from midnight Tuesday night to 6 AM CST
     Thursday for the following zones:
     Austin...Brazos...Burleson...Coastal
     Harris...Colorado...Fort Bend...Grimes...Houston...Inland
     Harris...Madison...Montgomery...Northern
     Liberty...Polk...San Jacinto...Southern
     Liberty...Trinity...Walker...Waller...Washington...Wharton.

GM...Low Water Advisory until 9 AM CST Tuesday for the following
     zones: Galveston Bay...Matagorda Bay.

     Small Craft Advisory until 3 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...Galveston Bay...Matagorda
     Bay...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.

&&

SHORT TERM...05
LONG TERM...Wood
AVIATION...Luchs
MARINE...Wood