Wind Chill Advisory 1, NWS Houston/Galveston, TX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
1143 PM CST Wed Feb 17 2021

.AVIATION [06Z TAF Issuance]...

IFR to LIFR conditions continue across the area with CIGs around
400 to 800ft and a breezy northerly wind around 10 to 15kts
(around 20 kts at GLS). The light freezing drizzle is coming in a
few hours ahead of schedule, so bumped up the timing of the -FZDZ
in the northern TAFs to generally between 9 and 11z, and also
added it into the HOU forecast for a few hours. The freezing
drizzle should transition to isolated light snow showers by
sunrise for IAH northward. Precipitation chances lower through the
mid morning and surface temperatures climb back above freezing by
noon. Ceiling may rise to around 1000-1500ft by the late
afternoon/early evening, but the IFR/MVFR conditions will persist
through the night.

There remains so intermittent communication/power issues at the
LBX ASOS sensor, so have added the AMD NOT SKED back into the TAF
for that site.

Fowler

&&

.PREV DISCUSSION /Issued 601 PM CST Wed Feb 17 2021/...

.SHORT TERM...(Tonight through Thursday Night)

Low pressure over the western Gulf has moved east and colder air
will funnel into SE TX in the wake of the low. Colder temperatures
will continue to surge back into SE TX tonight and only persistent
cloud cover will mitigate a stronger temperature fall. That said,
MinT values will likely bottom out in the mid 20's far NW to
around 30 over the south. Residual water on area roadways will
likely refreeze creating icy conditions on area highways/roads and
drivers should exercise extreme caution if venturing out tonight.
Ice that accumulated on trees and powerlines will not melt and
this could also create some trouble if branches should fall on
structures or take down power lines. Since the heavy icing that
occurred this morning has ended but the risk from residual icing
remains and additional light winter precip is expected later
tonight, feel a Winter Weather Advisory is more applicable than a
Winter Storm Warning in regards to discussing the ice hazard and
possible winter precip.

Most of the precipitation has exited the area but weak upper
level troughing remains over the state and a weak disturbance
embedded in the W-SW upper flow will bring additional
precipitation to the region later tonight into early Thursday.
Fcst soundings and thickness values support a mixture of light sleet
and snow changing to all light snow on Thursday morning. Moisture
levels look meager and fcst soundings show a lot of dry air in
the 850-700 mb layer so not expecting much more than a dusting.
That said, there is some fairly strong 850-700 mb frontogenetic
forcing from Columbus to Houston. Sometimes, the forcing is
strong to compensate for a lack of moisture so it's something
that bears watching. MaxT values won't warm much on Thursday and
will struggle to reach freezing at KCLL and probably only warm
into the upper 30's at KIAH and points southward. Could get a peak
of sun late Thursday afternoon as subsidence develops in the wake
of the morning short wave.

Skies will clear Thursday night and temperatures will once again
plunge to very cold values with mid teens likely by sunrise
generally north of a Brenham to Trinity line. Temperatures will
fall into the lower and mid 20's over the southern half of the
region. A Hard Freeze Watch will be in effect for Thu Night into
early Friday. SE TX will be looking at another 10-16 hours below
freezing and probably 8 to 10 hours below 25 degrees north of the
Brenham-Trinity line. Another Wind Chill Advisory or Warning may
also be required as Wind Chill values are expected to fall into
the single digits north and teens central. 43

.LONG TERM [Friday through next Wednesday]...

I'll start off with the bad news. Hard freeze conditions return on
Friday morning as surface high pressure settles into the South
Central CONUS and northerlies strengthen, with residents of the
northern counties expected to experience temperatures in the teens
once again as the sun rises while the Houston metro unlikely to
break 30 degrees overnight. As a result, we have issued a Hard
Freeze Watch for all non-coastal counties during this time.
Residents impacted by the current power outage situation should plan
to continue to take protective actions as the subfreezing
temperatures continue. Highs on Friday afternoon will reach the mid
30s to mid 40s, a slight increase over the previous day as a
relaxing surface pressure gradient moderates CAA.

The remainder of the long-term forecast period brings some better
news. One more night of subfreezing temperatures will arrive on
Friday evening, with lows once again dipping into the upper teens to
20s at most locations as clearing promotes more efficient nocturnal
cooling. However, by Saturday, an eastward shift of surface high
pressure will bring about a long-awaited return to an onshore flow
pattern which will gradually work to increase temperatures and dew
points through the weekend. Most locations finally see the 50s on
Saturday and subfreezing overnight lows finally cease. More
seasonable, but still below average temperatures return on Sunday as
continued WAA allows for highs in the upper 50s to low 60s.

A developing lee cyclone will push into the Great Lakes region as
troughing becomes dominant over the Central CONUS by early Monday,
and a surface cold front extending from this feature will approach
SE Texas. Fortunately, the passage of this feature looks to be
relatively uneventful. The main question continues to be the extend
to which scattered showers will accompany the approaching front.
Latest GFS & Canadian solutions indicate more ample moisture return
and as a result more precipitation as the front pushes through the
area by Monday afternoon. The EC remains drier with less
precipitation coverage. Have included slight chance PoPs for most
locations for the time being, but this will likely need adjusting
based on model consensus over the next couple of days.

Temperatures cool a bit with the fropa though am not currently
carrying any subfreezing overnight lows on Monday. Clearer and
gradually warming conditions look to persist through mid week with
highs on Wednesday breaking back into the 70s.

Cady

.MARINE...

Strong winds continue over the NW Gulf in response to a very tight
pressure gradient surrounding the departing coastal low. Sustained
winds have been around 25 knots with gusts near Gale force. Seas
have increased to 13 feet near buoy19 and marine conditions will
not change much overnight with only a gentle relaxation of the
gradient expected. Will maintain an SCA for the Gulf and bays
through 10z Friday and will continue the SCA for the Gulf waters
through 18z. A 1035 mb surface high will build into the southern
plains on Thursday and surge into South Texas Thursday night keep
the gradient tight. The surface high will drift over the west Gulf
on Friday with offshore winds relaxing. The high will move east
toward the Tennessee Valley on Saturday. This will allow for
onshore winds to return and persist through Sunday. Another cold
front will move across the coastal waters late Sunday night with
an offshore developing in the wake of the front. Offshore winds
will prevail on Monday as surface high pressure settles over East
Texas. 43

&&

.PRELIMINARY POINT TEMPS/POPS...

College Station (CLL)  34  26  32  16  34 /  20  10   0   0   0
Houston (IAH)          38  30  39  26  42 /  20  10   0   0   0
Galveston (GLS)        49  36  41  34  45 /  10  10   0   0   0

&&

.HGX WATCHES/WARNINGS/ADVISORIES...

TX...Winter Weather Advisory until noon CST Thursday for the
     following zones:
     Austin...Brazos...Burleson...Colorado...Grimes...Houston...Madison...Montgomery...Polk...San
     Jacinto...Trinity...Walker...Waller...Washington.

     Hard Freeze Watch from late Thursday night through Friday
     morning for the following zones:
     Austin...Brazos...Burleson...Colorado...Fort
     Bend...Grimes...Houston...Inland Harris...Inland
     Jackson...Madison...Montgomery...Northern
     Liberty...Polk...San
     Jacinto...Trinity...Walker...Waller...Washington...Wharton.

GM...Small Craft Advisory until 3 PM CST Thursday 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.

&&