December 2023

General Weather Discussions and Analysis
Cromagnum
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Got down to about 34 here, but saw some frost on the west side of roofs.
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tireman4
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000
FXUS64 KHGX 111132
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
532 AM CST Mon Dec 11 2023

...New AVIATION...

.SHORT TERM...
(Today through Tuesday Night)
Issued at 316 AM CST Mon Dec 11 2023

High pressure will begin a slow movement east during the day today,
with surface to 850mb winds becoming southerly to southwesterly in
nature. This will lead to a rebound in temperatures today, with
highs warming into the 60s area wide. Winds will be calm out of the
southeast.

Tonight`s low temperatures will be a bit warmer than last nights
with lows dropping into the upper 30s to 40s inland and into the 50s
along the coast.

The warming trend will progress Tuesday as southwesterly flow
continues. Highs will be in the 60s with some locations in the
southern counties and along the coast reaching into the low 70s. A
slight increase in cloud cover will occur over the southern coastal
counties as a result of onshore flow and moisture convergence. Lows
on Tuesday night will be in the 40s generally north of I-10.
Increased cloud cover further south will limit radiational cooling
and keep lows slightly warmer with temperatures in the 50s.

Adams

&&

.LONG TERM...
(Wednesday through Sunday)
Issued at 316 AM CST Mon Dec 11 2023

Moisture will be streaming around periphery of an expansive broad
high pressure area encompassing much of the eastern US and
northern Gulf coast (stretching into east Tx). So, with the
exception of maybe some iso-sct shra along the coast/offshore and
our far western zones...much of the region will remain dry into
Thursday night. For those of you that live along the immediate
coast, you might want to view the blurb about potential high tide
levels in the marine discussion below.

The next western upper trof will make its way into the the Desert
Southwest Wednesday and eventually into West Texas early Friday.
With an amplifying ridge on its backside, guidance is then digging
the base of the trof southeast and overhead on Saturday then on into
the Gulf. The combination of increasing moisture, large scale
lift, and its associated frontal boundary should provide some
fairly good rain chances (and maybe an elevated tstm or two) across
the region Fri-Sat. The associated front itself looks to pass
through late Friday night, but trailing wrap- around light rain
might not fully exit til early Sunday morning. Rain totals with
this system might be in the 1-2" range for many locations. 47

&&

.AVIATION...
(12Z TAF Issuance)
Issued at 525 AM CST Mon Dec 11 2023

VFR conditions prevailing through the period with clear skies and
light winds continuing. Winds will become south-southeasterly
during the afternoon hours.

&&

.MARINE...
Issued at 316 AM CST Mon Dec 11 2023

As surface high pressure moves off to the east today, look for
light onshore winds to resume. A long fetch of moderate east winds
is then forecast to set up across the Gulf for the remainder of
the work week. Look for increasing east winds in the 15-25kt
range...highest in the Gulf. Caution flags might be needed
offshore as early as Tuesday afternoon, but advisories are a good
bet thereafter and for the remainder of the week as seas
eventually build into the 7-12ft range.

This set-up is also favorable for above normal tide levels across
the Upper Texas coast and bays. Astronomical levels at high tide
are inching close to 2ft MLLW. Add an additional 1.5-2ft on top
of that in addition to wave action...I wouldn`t be surprised if we
see some minor coastal flooding at the more prone spots (Bolivar,
parts of Galveston Island, Blue Water Highway, Surfside, etc) as
we get into the Thurs-Fri timeframe. Too early for any specifics,
but worth watching trends. High risk of rip currents looks like a
good bet along area beaches with the elevated surf on the way too.

An upper level storm system and associated cold front is forecast
to move into the region Friday and Friday night. Showers and
isolated thunderstorms are expected ahead of the front during the
day Friday, followed by the frontal passage late Friday night and
some trailing light rain tapering off late Saturday. 47

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 63 40 67 46 / 0 0 0 0
Houston (IAH) 62 43 67 46 / 0 0 0 0
Galveston (GLS) 62 55 65 55 / 0 0 0 0

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...Freeze Warning until 9 AM CST this morning for TXZ197-199-
210>212.

GM...None.
&&

$$

SHORT TERM...Adams
LONG TERM....47
AVIATION...Adams
MARINE...47
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DoctorMu
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31°F this morning. That should tamp down the insects for awhile.
user:null
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This morning's low at IAH was 33°F — the freeze-free streak continues.
Cpv17
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user:null wrote: Mon Dec 11, 2023 1:57 pm This morning's low at IAH was 33°F — the freeze-free streak continues.
I’m sure you’re happy about that.
Cpv17
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The WPC has slightly increased our rain totals in their latest update.
user:null
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Cpv17 wrote: Mon Dec 11, 2023 2:06 pmI’m sure you’re happy about that.
Freeze-free IAH is a chance to break a record ... in a good way.

Contrast that with the past atrocious August — had the city hit 110°F+, that would have been a bad record to break. And considered that parts of Golden Triangle and Acadiana actually hit that 110°F+ mark, it's quite clear that (much of) Houston could easily have gotten to that point — so remaining "only 109°F and lower" was pretty much a "lucky near miss" in that regard.
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jasons2k
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Pretty sure it was 31-32 here. I don’t have my weather station setup yet. My neighbor has a Tempest station and I don’t think it’s very accurate. The precip. measurements are off, sometimes by a lot. He showed a low of 37 but there is plenty of evidence of a light freeze. The placement isn’t bad - it’s out in the open, so I think it’s the gauge.

The walk with the dogs was amazing.
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sambucol
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We had frost on the roof and ground in Baytown this morning around 7:30.
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tireman4
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000
FXUS64 KHGX 112002
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
202 PM CST Mon Dec 11 2023

...New SHORT TERM, LONG TERM, MARINE...

.SHORT TERM...
(This evening through Tuesday Night)
Issued at 202 PM CST Mon Dec 11 2023

Tranquil and cool conditions are expected tonight with mostly clear
skies over the inland portions and partly cloudy skies near the
coasts. The lows overnight into early Tuesday morning will be in the
low to mid 30s over the Piney Woods region, the upper 30s to low 40s
for areas north of I-10, the low to mid 40s for areas south of I-10,
and the upper 40s to low 50s along the coasts.

On Tuesday, benign conditions will prevail. Skies will gradually
turn from mostly clear to partly cloudy starting from the west and
expanding east during the afternoon as low level moisture begins to
move back into the region. Temperatures will be warmer with highs in
the mid to upper 60s over areas north of I-10 and the mid 60s to low
70s over areas south of I-10. The lows Tuesday night into early
Wednesday morning will be in the upper 30s to mid 40s along the
Brazos Valley and Piney Woods region, the upper 40s to low 50s for
areas along and south of I-10, and the low to mid 50s along the
coasts.

&&

.LONG TERM...
(Wednesday through next Sunday)
Issued at 202 PM CST Mon Dec 11 2023

And now for the messy part of the forecast - the weather that is,
not the forecaster. I mean...I`ll grant that it`s possible that
the forecaster is also a mess, but unlike that one X-Files
episode, whether or not that`s true is entirely irrelevant to how
the weather will turn out. Which, we`ve established, is messy.

Wednesday morning, like through the short term, we find ourselves
on the southwestern fringe of a broad, strong, eastern US high
pressure center. Beyond that, however, we start getting changes.
We`re continuing to see a weak shortwave stroll over the Gulf. In
past days, despite its disorganization, it looked like it would
spin up a weak surface trough to follow. That appears to have
largely disappeared from the guidance. But no worries! (I don`t
think you were worried) Instead we look for a surface trough
coming in from the east, farther south in the Gulf. This will keep
the pressure gradient tight and promote increased cloud cover,
compressing the diurnal temperature range (through both cooler
days and warmer nights). However, there`s higher confidence that
rain chances will be restricted to the Gulf waters off Matagorda
Bay...for Wednesday, anyway.

Another big piece of this mess is an upper trough closing off over
the Southwest US, and though Wednesday morning that looks to be
happening near Vegas, it does not stay near Vegas. It will spend
the second half of the week traversing Arizona, New Mexico, and
finally Texas. How quickly it does that will be key to when rain
potential pushes its way into the area from the west. Like most
closed lows in this position, that is a fairly uncertain thing at
this point. For the time being, I`m rolling with something
pretty close to the NBM consensus, which seems reasonable at this
point. That would mean some lead shortwave/ejected vorticity
looks to drag some PoPs up towards the Matagorda Bay area from the
Gulf on Thursday, but mostly leave the rest of the area dry.
Then, around Thursday night, the first rain chances make their way
in from the west as the upper low approaches.

Then we get to another big question - how exactly does this upper
low cross the state? If it`s fairly progressive, we get something
pretty typical with low pressure spinning up to our north and
heading northeastward as the low gets drawn back into the northern
stream and we see a cold front pass through. But an idea that`s
gaining steam is that a strongly building ridge upstream over the
western US deforms the flow, and sends the upper low instead
diving through Southeast Texas to the Gulf. In this scenario, we
get something that looks like a weird NW flow/surface
trough/proto-low hybrid...thing...that brings a solid round of
rain and some isolated thunderstorms as it trucks through,
eventually forming a more coherent surface low over the NW Gulf
that may continue some lingering spurts of wraparound light
showers through Saturday and into early Sunday.

Now, this second idea had always kind of existed in the guidance
envelope, but I had mostly discounted it as an outlier. But, a
couple things have me thinking differently today: the first is
that while an outlier, not all outliers are equal. It`s not that
unusual for numerical guidance to whiff on how far south these
types of closed lows tend to dig. So while it may not have been
popular in earlier guidance for this scenario to occur, it was
still in line with a more common failure mode of the guidance. And
second, more models are starting to hop on board with this idea.
Even the Euro, which had been steadfast in the prior scenario,
shows this happening now; albeit later and to our east. It`s
turned enough of the tide that the resultant NBM fields more
closely indicate this occurring. Given the broad uncertainty here,
again it seems most responsible to follow the lead of the
consensus here. Fortunately for me, while a lot of the
meteorological differences between models here are nuanced and
interesting, the ultimate forecast isn`t *that* different - more
clouds, small diurnal temperature ranges, and unsettled weather
through the late week.

Now, there is one more thing that does concern me a bit. Having
the upper low truck straight through our CWA rather than swing a
cold front through probably does maximize lift on Friday when that
trucking happens. This does tend to concentrate rainfall more, and
the QPF forecast reflects that with light rainfall amounts
Thursday and on the weekend, focusing the heaviest rains on
Friday. This is as high as 2-4 inches for the day where the
highest amounts near the coast are. This had me focus a little
more on heavy rainfall potential than I did yesterday. And, while
concentrating the rainfall more in one day is more worrisome on
the flooding potential front, there are still a couple big things
going in our favor: because of the fairly mild week, we look to
only have minimal instability built up. This should limit
convective updrafts, and keep high end rain rates out of the
picture. The rates are usually the killer for us! Secondly,
ensemble mean precipitable water values in both NAEFS and EPS are
not climatologically extreme, below the 90th percentile for both
cases. So, while it`s still something to keep an eye out for - and
indeed, WPC has reasonably introduced a marginal risk for
excessive rainfall for the area on Friday - my freakout level is
still relatively low. Basically right in line with having a
marginal risk.


&&

.AVIATION...
(18Z TAF Issuance)
Issued at 1109 AM CST Mon Dec 11 2023

VFR conditions with light SE winds today and tonight. Models are
hinting at a shallow llvl cloud layer developing late tonight into
Tue morning...added FEW010-020 for the time being, but may end up
having MVFR cigs for a few hours. Cigs, if any, are expected to
scatter out and lift shortly after sunrise. Winds will turn E at
5-10 KTS Tues.

24

&&

.MARINE...
Issued at 202 PM CST Mon Dec 11 2023

Enjoy the relatively quiescent conditions on the waters while we
have them - for now, high pressure moving by sets us up for light
onshore flow and low seas. However, that high will set up shop and
the pressure gradient will tighten, giving us a persistent and
long easterly fetch for the next several days. This will build
seas and increase water levels at high tide above expected
astronomical tides, which are already relatively high.

By midweek, we should expect the need for some sort of small craft
advisory as winds and seas look to be near and sometimes exceed
the advisory threshold. Late in the week as the upper level low
moves in, conditions should deteriorate further, and offshore
seas could reach as high as 10-12 feet. At the shore, we will also
be on the lookout for minor coastal flooding depending on how we
see a combination of the higher astronomical tides, increased
water levels from easterly winds, and wave runup from higher seas.

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 38 67 45 64 / 0 0 0 0
Houston (IAH) 41 66 46 63 / 0 0 0 0
Galveston (GLS) 53 65 55 63 / 0 0 0 0

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...None.
&&

$$

SHORT TERM...Cotto (24)
LONG TERM....Luchs
AVIATION...Cotto (24)
MARINE...Luchs
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Ptarmigan
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Nice to see cooler weather. It should of been on a weekend. ;)
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DoctorMu
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Our local KBTX mets are backing off the heavy rain progs for Friday. It will probably rain, but we're expecting less - we'll see.
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DoctorMu
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0z GFS shifts the rain east, but Ensembles are sticking to their solution for now.
Cpv17
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The WPC cut back on rain totals by a pretty good bit in their latest update. Only shows about 1 to 1.5” now. Seems to be happening with just about every rain event now. The closer it gets, it almost disappears.
Stratton20
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I can feel another bust coming, wouldn’t be surprised lol
Cpv17
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Yeah it’s not looking good for rain now. Figures.
Stratton20
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Yeah models are trending further north with the low, taking the heavier rains with it, im not believing a model anymore until i see it actually happening, such a sick joke lol
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Ptarmigan
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Stratton20 wrote: Tue Dec 12, 2023 11:30 am I can feel another bust coming, wouldn’t be surprised lol
The bust can go either way.
kyzsl51
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Thats ok rainy days make me feel sad lol...we are in drought I get it.
Cpv17
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kyzsl51 wrote: Tue Dec 12, 2023 10:00 pm Thats ok rainy days make me feel sad lol...we are in drought I get it.
Rainy days make me hyped! Unless it’s a light rain, then it’s kinda just meh.
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