#6692 Postby Tireman4 » Mon Jan 20, 2025 8:59 am
From HGX AFD
376
FXUS64 KHGX 201145
AFDHGX
Area Forecast Discussion
National Weather Service Houston/Galveston TX
545 AM CST Mon Jan 20 2025
...New AVIATION...
.SYNOPSIS...
Issued at 246 AM CST Mon Jan 20 2025
***SIGNIFICANT WINTER STORM TONIGHT INTO TUESDAY***
-Snow (and some sleet) is expected to impact much of
southeast Texas late tonight into Tuesday. Significant
disruptions to travel expected late tonight through midday
Wednesday.
-Heavy bands of snow will likely develop Tuesday morning.
-Uncertainty exists regarding the location of the bands.
However, recent data suggests that the I-10 corridor down to
the coast stands the best chance of being impacted by heavy
snow.
-Accumulations are expected to range from 3 to 5 inches
(locally higher) where heavy banding of snow develops.
Outside of the bands, accumulations range from as little as a
dusting to as much as about 2 inches.
-Widespread Hard Freeze likely Tuesday night into Wednesday
morning. Coldest temperatures likely to occur in areas that
receive the heaviest snowfall.
&&
.SHORT TERM...
(Today through Tuesday Night)
Issued at 246 AM CST Mon Jan 20 2025
GOES-East Water Vapor imagery show CONUS completely enveloped by a
long wave deep layer trough. On the western periphery of the
trough, a gradually amplifying shortwave is diving southward into
SW CONUS. This trough will quickly progress eastward today,
increasing large scale lift over southeast Texas by this afternoon
and into tonight. At the surface, a corridor of cold high pressure
systems stretches from the Canadian Prairies all the way down to
south-central CONUS, feeding arctic air into our region. The
southward advancing arctic air will enhance a baroclinic zone
over the western Gulf, which will eventually help induce the
development of an area of low pressure later this evening and into
tonight. All these features are moving into place to foment the
development of a winter storm that will impact much of the Gulf
Coast and Deep South this week.
The arctic chill will be immediately evident when you walk outside
this morning. As I type (currently 230AM), temperatures away from
the coast and outside of the urban heat island are in the 20s
while most observations in the city and at the coast are in the
low 30s. We`ll likely drop a few more degrees before sunrise.
Skies are clear over southeast Texas. But a quick glance of the
GOES-East RGB-Nighttime Microphysics imagery shows that mid-level
clouds are pushing northward from the Gulf which is a sign that
the clear skies will soon be no more.
Clouds should increase today from south to north. Afternoon highs
are expected to average in the low 40s today. This is somewhat
dependent on the timing of the approaching overcast. But overall,
today will be a nice albeit cold day. Light scattered
precipitation could develop as early as this evening (after 7PM).
It`s possible that precip (if any) this evening could be in the
form of plain liquid rain, especially for the southern half of the
CWA. But the more widespread precipitation is expected to hold
off until after midnight.
The 12AM to 6AM time frame on Tuesday is expected to feature
increasing coverage of snow and sleet showers. Areas south of
I-10 might start as more sleet while areas farther north favor
snow. But as the hours approach dawn, the situation is expected to
become increasingly dynamic, favoring the development of heavier
bands of precipitation. These dynamics will also tend to favor
snow over sleet. Therefore, we think the predominant precip type
will be snow as we head into Tuesday morning. However, areas near
the coast (especially our southern coast near Matagorda Bay) could
hang on to sleet as the dominant precip type for longer.
We are confident that heavy banding of snow (and some sleet) is
likely to develop Tuesday morning. We are less confident about the
location of specific snow bands. But if high resolution and global
models have their way, the best chance of heavy snowbands will be
from the I-10 corridor down to the coast. Areas that are NOT
impacted by one of these snowbands may get away with a dusting to
an inch or two of snow, which is still considered impactful here
in SE TX. But areas that do find themselves under one of these
snowbands are expected to receive 3-5 inches of snowfall, with
some potential for more. I`m sure many of you have seen social
media posts containing model guidance graphics showing up to 6-8
inches of snow. We don`t want to rule out totals that high,
especially given the potential convective nature of these bands.
But being near the Gulf, it can be difficult to get the snow to
QPF ratios we need to receive snowfall totals of that caliber. But
it`s worth mentioning again that even light accumulations of snow
result in significant impacts to travel in SE Texas.
Tuesday night and Wednesday morning temperatures are going to be
very difficult to predict. We are confident that widespread hard
freezing conditions (at or below 24F) are likely. But there is
potential for temperatures to drop well down into the teens in
areas that have a fresh but not melted snow pack. If the system
moves fast enough, then parts of the region could see the sun
return by the afternoon with temperatures possibly warming above
freezing. If this happens in a location where snow totals are
relatively light, then much of it could melt resulting in no
meaningful snowpack in time for nightfall. But locations that
receive heavier totals and/or little melting could find themselves
in the icebox Tuesday night since there will be more `intense`
radiational cooling in those areas. I wouldn`t be surprised if
less snowy areas end up being as "warm" as the mid 20s while
snowier locations dropped into the low teens. I also would not be
surprised if there wasn`t a lot of distance between those colder
and less cold locations. Wednesday morning`s temperature map will
be interesting. For now, we are going with widespread lows in the
mid/upper teens.
Self
&&
.LONG TERM...
(Wednesday through Sunday)
Issued at 246 AM CST Mon Jan 20 2025
Temperatures on Wednesday morning will be tricky as it depends
entirely on where the bulk of the snow/ice falls, which looks to
be along and south of I-10. This would result in much colder
temperatures along the coast than further inland as most of the
area starts out in the mid to upper teens. Road conditions are
likely still going to be hazardous as temperatures likely won`t
reach above freezing for most locations on Tuesday afternoon. This
means that snow/ice are likely to remain in place and frozen
until temperatures finally rise above freezing on Wednesday
afternoon. It is recommended to stay off the roads until at least
noon on Wednesday, and be sure to check road conditions before
traveling and to travel with extreme caution. Surface high
pressure will be overhead on Wednesday leading to mostly cloudy
skies with high temperatures in the upper 30s to low 40s. This
will help to melt at least some of the snow/ice. However, if any
is leftover, it will refreeze on Wednesday night as low
temperatures fall into the low to mid 20s (likely necessitating a
Freeze Warning for a Hard Freeze).
Towards the end of the work week an upper level trough digs down
from the Four Corners region, which looks to bring another cold
front towards Southeast Texas. In spite of this, the general trend
into the weekend is a gradual warming trend as onshore flow quickly
returns late Friday/early Saturday. Still expecting freezing
temperatures on Thursday night with low temperatures in the mid to
upper 20s. That looks to be our last night in our below freezing
temperatures streak as low temperatures jump into the upper 30s/low
40s on Friday night and into the 50s over the weekend. Daytime
temperatures will see a similar climb with highs back in the 60s
over the weekend. That onshore flow does come with an increase in
shower/storm chances over the weekend as moisture converges ahead of
an approaching frontal boundary. There is quite a bit of uncertainty
on if this front will actually push through or not, but there is
good consensus on at least a rainy weekend.
Batiste
&&
.AVIATION...
(12Z TAF Issuance)
Issued at 545 AM CST Mon Jan 20 2025
The first 12 or so hours of these TAFs are great! VFR! Not even a
CIG until afternoon! Moderate NE winds! And then...we get the
mess. Conditions should degrade through the evening, with MVFR
CIGs arriving first as atmosphere moistens from top down. Around
06Zish, we`ll see first precip reaching the ground from SW to NE.
Type of precip at outset is...unknown. In general, the earlier it
starts and the closer to the coast you are, the more likely we
are to see a short bit of rain before transitioning to SN/PL.
Around 09Z, should see more prevailing precip, and likely to be
SN/PL, and a full transition to SHSN in the north. Though we could
see a full transition to snow all the way to Galveston,
confidence not quite high enough to put it explicitly in there
just yet, so will hold a mix through 12Z from HOU coastward. The
one high confidence factor? It will be windy! 15G25 is a good
ballpark to expect out of these NE winds.
In the extended at IAH, have the confidence to go fully to SHSN,
and though a faster system may see snow come to an end just before
18Z, will leave that for future cycles to handle.
&&
.MARINE...
Issued at 330 PM CST Sun Jan 19 2025
Strong northerly winds and enhanced seas will continue through the
rest of today. Winds decrease somewhat tonight while veering to the
northeast. By Monday, winds and seas will begin to increase once
again as the next storm system approaches. Gale conditions are
possible on Monday and especially Tuesday. A Gale Watch is in effect
late Monday night through Tuesday for the bays and Gulf waters. Low
water levels may be an issue as well. In addition to these hazards,
a mix of frozen precipitation is expected near the coast Monday
night into Tuesday afternoon.
Adams
&&
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 42 26 36 15 / 0 70 30 0
Houston (IAH) 41 27 34 18 / 0 80 80 0
Galveston (GLS) 44 31 36 29 / 0 70 90 10
&&
.HGX WATCHES/WARNINGS/ADVISORIES...
TX...Cold Weather Advisory until noon CST today for TXZ163-164-
176>179-195>200-210>214-226-227-235>238-300-313-335>338-
436>439.
Cold Weather Advisory from 9 PM this evening to 6 PM CST Tuesday
for TXZ163-164-176>179-195>200-210>214-226-227-235>238-300-
313-335>338-436>439.
Freeze Warning until 10 AM CST this morning for TXZ163-164-
176>179-195>198.
Winter Storm Warning from 6 PM this evening to 6 PM CST Tuesday
for TXZ163-164-176>179-195>200-210>214-226-227-235>238-300-
313-335>338-436>439.
Extreme Cold Watch from Tuesday evening through Wednesday
morning for TXZ163-164-176>179-195>200-210>214-226-227-
235>238-300-313-335>338-436>439.
GM...Small Craft Advisory from 9 AM this morning to midnight CST
tonight for GMZ330-335.
Gale Warning from midnight tonight to 6 PM CST Tuesday for
GMZ330-335-350-355-370-375.
Small Craft Advisory until midnight CST tonight for GMZ350-355-
370-375.
&&
$$
SHORT TERM...Adams
LONG TERM....Cady
AVIATION...Luchs
MARINE...Adams
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