December 2023

[sambucol]

Thank you. Any idea if it moves in really late in the day on Saturday? Maybe evening?

[tireman4]

000
FXUS64 KHGX 060855
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
255 AM CST Wed Dec 6 2023

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

.SHORT TERM...
(Today through Thursday Night)
Issued at 255 AM CST Wed Dec 6 2023

Surface high pressure centered around Arkansas today will make its
way toward the southeast portion of the country in the next couple
days. As it does so, we`ll see onshore winds resume across the area
tonight and Thursday. With the Gulf opening back up, we`ll see a
gradual upward climb of temps (esp at night) and cloud cover. Things
still too dry for precip Thursday, but late Thurs night PW`s will
climb back up to around 1.0" north to 1.5" south and some guidance
is suggesting the possibility of some iso-sct shra development as a
mid level shortwave passes through. Added some lowish POPs into the
fcst before sunrise Fri across southern parts of the CWA for this
potential. 47

&&

.LONG TERM...
(Friday through Tuesday)
Issued at 255 AM CST Wed Dec 6 2023

With surface low pressure deepening around the TX/OK panhandles on
Friday, moisture advection/WAA are enhanced leading to PW values
reaching the 1.2"-1.5" range (90th percentile: ~1.44") and 850mb
temperatures approaching the 99th percentile. The tightening
pressure gradient leads to fairly breezy southerly winds around 20
mph...and there`s even breezier winds to talk about coming up on
Saturday. Temperatures on Friday will be about 10°F above normal
with highs topping out in the mid to upper 70s. Rain chances also
gradually increase from south to north on Friday as moisture
increases out ahead of an approaching mid/upper level trough. With
moisture and subsequent cloud cover in place on Friday night
(along with breezy winds), I bumped up the low temperatures to the
mid to upper 60s...which is right around our normal high
temperature this time of year.

That`ll be a brief occurrence though as Saturday night will be 20+°F
colder thanks to a cold front that pushes through earlier in the
day. This front is pushed through by a surface low that develops
courtesy of the previously mentioned mid/upper level trough. The
GFS is trending slightly later in the day compared to yesterday`s
run, which places a little more confidence in an afternoon FROPA.
Also of note in today`s 00Z GFS run, the mid level trough is a
bit stronger and deeper compared to yesterday`s run and places it
closer to the solutions that the ECMWF/Canadian have been
consistent with. This is important to note because an afternoon
FROPA gives us a better opportunity to erode the subsidence
inversion layer aloft (cap) that will be in place due to an
extended period of southwesterly winds aloft at 850mb. We`ll be in
the warm sector ahead of the front, so we`ll have an axis of
instability and plenty of shear (LLJ overhead) to work with. As a
result, there is the potential for some storms ahead of and along
the frontal boundary to become strong to severe if they manage to
break through the cap. SPC still has part of Southeast TX
outlined in a 15% probability for severe weather on Saturday. The
best potential for these strong to severe storms will likely be
north of I-10 and east of I-45, where the LLJ is a bit stronger
to add to the speed shear. Additionally, with PW values near or
greater than the 90th percentile, locally heavy rainfall will also
be possible...but there are no flood concerns as this front will
be moving through rather quickly.

Ahead of the front, we`ll see temperatures top out in the mid to
upper 70s (can`t rule out some isolated locations reaching 80°F)
along and south of I-10 due to compressional heating. Behind the
front, the pressure gradient remains tight as strong surface high
pressure builds in. Breezy northwesterly winds around 20-25 mph
may prompt a Wind Advisory for parts of Southeast TX...so if you
have any outdoor holiday decorations that could be blown
over/away (e.g. inflatables), you should definitely ensure they
are tied down on Friday and Saturday night. Let`s not have Santa
take flight three weeks early! Strong CAA in the wake of the front
leads to a quick drop off in temperatures with lows ranging from
the upper 30 to mid 40s on Saturday night. High pressure slides
directly overhead on Sunday, so temperatures will only top out in
the mid to upper 50s underneath crisp and clear blue skies...a
great day to break out those Christmas sweaters! Sunday night will
be the coldest of the long term period with widespread lows in
the 30s and some locations in the Piney Woods/Brazos Valley seeing
a light freeze. That`s thanks to max radiational cooling (light
winds + clear skies) with surface high pressure remaining
overhead.

The 850mb high pressure remains overhead going into early next week
leaving 850mb temperatures in the 5-9°C range, so expect highs to
remain in the low to mid 60s and lows generally in the 40s. Long
range NBM deterministic continues to keep the upper quartiles of max
temperatures well below the 70°F mark through midweek with a slight
downward trend. This is due to another mid/upper level trough moving
through the Four Corners region at the tail-end of the long term
period that may bring our next cold front some time after midweek.
Now of course...it`s too early to set that in stone so stay tuned
for tomorrow morning`s AFD and I`ll give y`all an update on model
trends for the next FROPA!

BONUS: I know that was a lot to read through...so I have a
special treat for those that read this far to make it worth it for
y`all! Skies will remain clear enough after sunset today
(Wednesday) to spot the International Space Station at 6:17pm CST.
It`s maximum height will be 86°, which means it`ll be directly
overhead! It`ll appear from the northwest horizon, be visible for
7 minutes, and disappear in the southeast horizon...so be sure to
head out there to catch a glimpse!

Batiste

&&

.AVIATION...
(12Z TAF Issuance)
Issued at 255 AM CST Wed Dec 6 2023

VFR for the next 30+ hours. 47

&&

.MARINE...
Issued at 255 AM CST Wed Dec 6 2023

Light to occasionally moderate northeasterly/easterly winds will
prevail into tonight, then become southeasterly on Thursday.
Onshore flow strengthens on Friday ahead of an approaching weather
system with wind speeds possibly reaching advisory threshold.
Rain chances begin to increase on Thursday night/Friday as well
due to building moisture, but the best chance of showers and
storms comes on Saturday afternoon as a strong cold front pushes
through the waters. In the wake of the front, northwesterly winds
will reach the 20-25 knot range with wind gusts approaching gale
force. As a result, seas will build to the 6-8 foot range on
Saturday night into Sunday morning. Mariners can expect a Small
Craft Advisory to be in effect during this time frame. On Sunday,
winds and seas gradually subside.

Batiste

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 67 44 70 59 / 0 0 0 10
Houston (IAH) 67 45 69 58 / 0 0 0 20
Galveston (GLS) 62 55 67 62 / 0 0 0 30

&&

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

$$

SHORT TERM...47
LONG TERM....Batiste
AVIATION...47
MARINE...Batiste

[JDsGN]

Thank you. Any idea if it moves in really late in the day on Saturday? Maybe evening?

Dialing in front timing this far out is gonna be pretty tough but most models seem to have it late evening almost into Sunday after midnight before its off the coast.

[Cpv17]

Massive difference right now between the GFS and Euro regarding precipitation.

[sambucol]

We are watching the weather closely and have a backup plan which is to all performances to Sunday. I think Sunday is clear from rain. But no decision has been made yet.

[Cpv17]

Ensembles are finally starting to look a lil bit better for some rain.

[tireman4]

000
FXUS64 KHGX 070912
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
312 AM CST Thu Dec 7 2023

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

.SHORT TERM...
(Today through Friday Night)
Issued at 312 AM CST Thu Dec 7 2023

A touch warmer today with the return of southerly winds. Variable
high cloudiness into early afternoon will lower and become overcast
from west-east during the afternoon and evening hours as low level
moisture gradually increases. Considering the thicker cloud cover
and steady sse winds, low temps tonight should be a good 15 degrees
higher than what we`re waking up to this morning. Guidance still
likes the idea of some weak shortwaves moving into the area from the
west late tonight and Fri. Assuming PW`s climb as forecast, we might
see some iso-sct shower development (better chances across the
southern half of the CWA)...eventually pushing off to the east late
Friday afternoon & evening with the departure of the upper
disturbance and higher PW axis. Hires models aren`t as bullish with
coverage as some of the global models. Overall, left POPs about
where they were advertised with earlier fcst packages. 47

&&

.LONG TERM...
(Saturday through Wednesday)
Issued at 312 AM CST Thu Dec 7 2023

Going into Saturday, the surface low that subsequently develops from
a mid/upper trough sweeping through the Central CONUS will be moving
quickly to the NNE into the Great Lakes region as it rides along the
upper level wind pattern. Since the movement of this low is more
northerly than easterly, the associated cold front will take a bit
longer to push through. Think of it as the front gets caught in
traffic coming down I-45...I`m sure we all can relate. Model
consensus (including some high-res guidance) points toward a mid
to late afternoon FROPA for most. It`s too early to give a super
precise timeframe, but in general it`s looking like the front
begins to move into the Brazos Valley around 1-4pm and doesn`t
push offshore till around or after 9pm.

There remains "some" potential for strong to severe storms to
develop along and ahead of the frontal boundary given the
abundance of shear (0-6km shear greater than 60 kts) and an axis
of instability (MUCAPE 1200-1800 J/kg) within the warm sector of
the surface low...but there`s something that will likely hinder
our chances of seeing these stronger storms. With an 850mb high
off to our east providing southwesterly flow throughout most of
the week ahead of the approaching front, a fairly robust
subsidence inversion layer (cap) will be in place around
850-750mb. Check out some of the forecast soundings and you`ll see
it`s fairly sharp...so that`ll be tough for storms to overcome.
That`s not to say that storms can`t break the cap...but the odds
look to be more in favor of the cap holding. All that being said,
SPC has kept parts of Southeast TX in a marginal to slight risk
of severe weather on Saturday. Generally, areas along and east of
I-45 are in the slight risk...but the best chance of seeing
strong to severe storms will likely be in the Piney Woods
(northeast counties). Confidence in rainfall in general occuring
is fairly high though, and some locally heavy rain will be
possible as well along the front with PW values surging up to
1.4"-1.6" (90th percentile: ~1.44"). There are no concerns for
flooding.

With the cold front now moving through more in the mid to late
afternoon time frame, that allows more time for southwesterly
winds ahead of the front and compressional heating to get
temperatures into the mid to upper 70s on Saturday afternoon. Some
areas may even reach the 80°F mark...that`ll make the 12 hour
temperature difference that much more drastic. Behind the front,
strong CAA will prevail with northwesterly winds around 20-25 mph
and gusts of 30-35 mph. A Wind Advisory may be needed for parts of
Southeast TX Saturday evening into Sunday morning. So, if you
have any outdoor holiday decorations up (especially inflatables),
you`ll definitely want to make sure they are secured...it is the
season of giving but let`s not give accidental decoration
donations to your neighbors down the street. PW values drop sharply
behind the front reaching less than 0.2" by Saturday night, which
is near the climatological minimum. Gusty winds overnight will
keep temperatures from dropping as much as they could...but we`ll
still see a 30-40°F drop from Saturday afternoon with lows in the
upper 30s to low 40s.

Surface high pressure moves overhead on Sunday as daytime highs only
climb into the mid to upper 50s. With clear skies and light winds
overnight on Sunday, we have the perfect recipe for maximum
radiational cooling...so I nudged temperatures down a bit below
guidance. Expecting widespread low temperatures in the 30s with
parts of the Brazos Valley/Piney Woods experiencing a light
freeze. With a 850mb high remaining overhead into Tuesday, 850mb
temperatures remain around the 10th percentile. So, although high
temperatures will increase...they`ll only increase to the low to
mid 60s. Surface high pressure slides off to the east by Tuesday
leading to return flow increasing PW values back to 1.0"-1.3" off
the coast by Tuesday night. That leads to rain chances returning
generally south of I-10. Midweek looks rather...interesting to say
the least. Another mid/upper level trough moves from the NW CONUS
down towards the Four Corners on Tuesday. There is model
consensus on this becoming a cutoff upper level low that remains
in the SW CONUS past midweek. If you read last night`s AFD then
you`ll remember that there was talk of a potential midweek cold
front...well that would be postponed in this scenario if it
verifies. This is a good example of why we don`t set things in
stone a week out...each model run could (and likely will) show
something different at that range! The good news is that model
guidance has been very consistent on keeping temperatures
generally in the 60s for highs and the 40s for lows into next
week.

Batiste

&&

.AVIATION...
(12Z TAF Issuance)
Issued at 312 AM CST Thu Dec 7 2023

VFR today and into overnight hours. As high pres departs further
eastward, llvl flow will transition to a more sly direction and
bring a gradual return of increased moisture levels. Look for 3-5kft
ceilings to make their way in from the west later this afternoon and
into the I-45 terminals 0-3z. From there, expect them eventually to
fall into MVFR territory after about 9z...and maybe even some higher
end IFR around CLL around sunrise Friday. 47

&&

.MARINE...
Issued at 312 AM CST Thu Dec 7 2023

Onshore flow returns later this morning and begins to strengthen
going into tonight and Friday as the next weather system
approaches. Winds may reach the caution threshold as early as
tonight and will be fairly close to the advisory threshold Friday
afternoon into Friday night. As a result of the strengthened
onshore flow, the risk of rip currents will also be elevated on
Friday. A strong cold front will push through the waters late
Saturday with moderate to strong northwesterly winds in its wake.
Mariners can expect at least a Small Craft Advisory to be in
effect from Saturday evening into Sunday morning. Wind gusts to
gale force will be possible in the Gulf waters. Due to the
elevated offshore flow, low water levels will be possible in the
bays during low tide on Sunday morning. Wave heights also
increase due to the strong offshore flow and peak in the 7-9 foot
range on Saturday night/Sunday morning. Winds and seas gradually
subside on Sunday with onshore flow returning by Monday afternoon.

Batiste

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 71 61 76 67 / 0 10 10 10
Houston (IAH) 70 59 76 68 / 0 20 30 10
Galveston (GLS) 67 63 71 67 / 0 10 30 10

&&

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

$$

SHORT TERM...47
LONG TERM....Batiste
AVIATION...47
MARINE...Batiste

[DoctorMu]

A light freeze Monday night around CLL, but chances of rain and severe weather look pretty weak now. NWS lost their confidence.

The FROPA is more likely to generate showers near Houston Saturday evening.

[MontgomeryCoWx]

I like what I see from the AI modeling and extended GFS and Euro. Siberian air looking to come to our side with some amplification happening.

We will be seasonal until Christmas time with periods of slightly brlow. After that could be fun.

[Stratton20]

AI modeling? Saw Cosgrove mentioned about Christmas- new years week getting interesting, mentioned AI modeling as well, wonder how useful that will be with forecasts, must be something new because ive never heard of that until today

[MontgomeryCoWx]

AI modeling? Saw Cosgrove mentioned about Christmas- new years week getting interesting, mentioned AI modeling as well, wonder how useful that will be with forecasts, must be something new because ive never heard of that until today

It’s relatively new. Been in production a while but being used more frequently the last couple of quarters, especially the last quarter for Nat Gas traders

[jasons2k]

Defining those terms is a slippery slope. Machine Learning is a subcomponent of AI and the models have been incorporating machine learning for decades now. The way the models were built in the first place isn’t very different from machine learning. Conceptually it’s the same - you get a set of initial conditions, run a set of possible outcomes, choose the most accurate outcomes verified against the control (the actual weather verification), rinse and repeat to improve the outcome. We’ve been essentially doing that since 1956 with every model update but now it’s accelerating like an exponential curve with today’s computing power.

Interestingly, AI is now advancing at a much faster rate than Moore’s law. It’s exciting and scary all at once.

[jasons2k]

I almost forgot why I stopped by. Here is an update from Jeff:

Strong cold front will move across the area Saturday afternoon and evening.

Southerly flow overnight has helped to begin the return of moisture to the region and with that the low clouds, drizzle, and light rain this morning. This activity should continue through mid morning with scattered showers evolving into the early afternoon hours mainly south of I-10 as a weak disturbance moves overhead in the southwest flow aloft.

An upper level storm system currently over the Rockies will eject into the plains with surface low pressure forming in New Mexico later today and moving toward the Great Lakes by Sunday. This surface low will sweep a strong cold front across Texas on Saturday. While moisture profiles will be plentiful ahead of this front, 850mb winds turn southwest and a strong aping inversion develops tonight over the area and will linger into Saturday. With abundant low clouds in place on Saturday only modest heating into the upper 70’s is expected, and this will likely fall short of enough heating to break through the capping inversion and generally prevent much in the way of active weather. Lift along with incoming front should be enough to get a line of showers and thunderstorms going with the greatest and most intense activity to the northeast of Houston around Lake Livingston and likely just a think line of showers around Matagorda Bay where capping will be greatest. While SPC has parts of the area outlooked for a severe risk on Saturday, think the severe threat will be more into Louisiana and the ARKLATX area.

Bigger news is the sharp drop in temperatures with the front and onset of strong northerly winds Saturday evening. Front will arrive across the Brazos Valley in the early to mid afternoon and clear the coast by early to mid evening. Temperatures in the 70’s will fall into the 50’s behind the front and then into the 40’s by Sunday morning with gusty northerly winds of 15-25mph and gust up to 35-40mph Saturday night. Compared to today and Saturday…Saturday night and Sunday will feel like winter.

Temperatures will only warm into the 50’s on Sunday even with mostly clear skies.

Next item is low temperatures on Monday AM…current guidance suggests a light freeze for areas along and north of US 59 away from the urban areas. With clear skies, light winds, and low dewpoints will have to watch how temperature guidance trends over the next 24-48 hours as low 30’s down toward the US 59 corridor and south of there in the usual cold spots is looking at least possible.

Jeff Lindner
Director Hydrologic Operations Division/Meteorologist
Harris County Flood Control District
9900 Northwest Freeway | Houston, Texas 77092
346-286-4000 (main) | 346-286-4165 (direct) | 281-924-2091 (cell)
jeff.lindner@hcfcd.org | Twitter: @jefflindner1

[MontgomeryCoWx]

Yep, I’m expected to freeze Monday morning. First freeze comes one day before the average first day.

[Cpv17]

Yep, I’m expected to freeze Monday morning. First freeze comes one day before the average first day.

I don’t think we’ll hit freezing here. I’m expecting about 35-36 for my area. Weimar is usually about 2-4 degrees colder than my location.

[Pas_Bon]

No freezing temps forecast for League City/Galveston County, but consistently seeing mid/upper 30's for Sunday night. I'll take it.

[jasons2k]

I think it’s still too early to pin down Monday’s freeze line. It could be further south than currently forecast, hence Jeff’s comments about monitoring the trends over the next couple of days. FWIW I’m preparing for the worst and have mentally prepared that Sunday evening I’ll be bundling-up and moving things into the garage. I’m currently forecast at 34 and that’s too close to comfort knowing how many times they drop the lows at the last minute, sometimes even after the 4pm package goes out. I’d prefer not to be unprepared for an 11pm freeze warning again.

[Stratton20]

Hope the weather next week / especially thursday isnt bad, im graduating from Texas A&M with a degree in environmental studies! I joined this group right as i began my first year at A&M, amazing how fast time goes by

[jasons2k]

Tomorrow is looking iffy on the rain. Not surprised.

[Cpv17]

Tomorrow is looking iffy on the rain. Not surprised.

You might get a quarter or half inch up there. Doubt I’ll get anything down here though. I’m expecting a big fat goose egg, so even if I can a tenth of an inch I’ll consider it a win.