Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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FXUS64 KHGX 190912
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
412 AM CDT Tue Mar 19 2024

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

.SYNOPSIS...
Issued at 412 AM CDT Tue Mar 19 2024

A fairly typical springtime week ahead for Southeast Texas.
Seasonable temperatures and mixed stretches of fair weather and
showers/storms. Here`s a quick summary of the days to come:
- Expect temperatures pretty near seasonal averages for the next
  several days. Today will be a bit on the cooler side of that
  average, and we`ll gradually warm up to being just a bit warmer
  by the weekend.
- The first window for showers and storms runs from Wednesday
  night through Thursday night. A marginal risk of severe
  thunderstorms (threat level 1 of 5) is in place around Matagorda
  Bay Wednesday, which expands to include all of Southeast Texas
  on Thursday. There is also a marginal risk of excessive rainfall
  (threat level 1 of 4) from the Houston metro coastward on
  Thursday.
- Window number two for showers and storms comes early next week,
  generally centered around Monday. There is high confidence in
  this broad idea of early week rain and storms, but the fine
  details currently have too much uncertainty to say anything more
  specific with much confidence.

&&

.SHORT TERM...
(Today through Wednesday Night)
Issued at 412 AM CDT Tue Mar 19 2024

Dry cool weather will prevail today and tonight, even as the surface
high over the region begins moving east. Light NE winds this morning
will be slowly transitioning to the E and then SE this afternoon and
evening. And so, with mostly to partly sunny skies, temperature this
afternoon should top out in the mid and upper 60s. Lows should range
from the upper 40s across the northern CWA...to the lower to mid 50s
elsewhere tonight.

The main forecast problem(s) are going to be with the pattern aloft,
with the pesky closed low that has been lingering in/around the Four
Corners region the last few days. This resultant W/SW flow aloft has
kept a steady stream of mid/high clouds in place over SE TX (as well
as some weak embedded disturbances at times). This system is progged
to finally begin moving east on Weds while weakening a bit. And when
combined with the return low-level moisture, rain chances should re-
turn to the area as well. We`ll likely start seeing some isolated to
widely scattered activity move up from the W/SW by tomorrow evening,
then becoming more widespread by tomorrow night. The latest from SPC
has our southwestern FA in a Marginal Risk (level 1 of 5) for severe
weather initially for tomorrow night (Day 2)...then for all of SE TX
for Thurs (Day 3). More details below.

&&

.LONG TERM...
(Thursday through Monday)
Issued at 412 AM CDT Tue Mar 19 2024

Let`s start off the long with some fun, huh? Thursday opens up
with the end of zonal flow aloft, and we are pretty likely to see
some showers, perhaps with some embedded thunderstorms, as early
as the morning as a shortwave trough zips overhead, helping to
spur the development of a weak coastal low.

The main fun is likely to hold off until later into the day and
Thursday night, however, as a more potent upper trough makes its
way in from the west, resulting in height falls aloft and
deepening of a surface low. Both the NAEFS and Euro ensemble means
are pretty moist, progging Thursday`s precipitable water values
around the 90th percentile (roughly correlating to over 1.25
inches inland, exceeding 1.5 inches at the coast). The EPS is a
bit drier, hanging out just under the 90th percentile, while the
NAEFS mean is a little bit higher. Either way, ample moisture is
in place. Height falls and daytime heating will help build some
instability, though it appears we may have a fairly sharp gradient
through the area. The NBM distribution shows that probabilities
of SBCAPE in excess of 500 J/Kg Thursday afternoon change pretty
rapidly to the west of Houston - practically nil right along I-45,
but increasing above 50 percent before you`re even west of the
west Beltway. While there are some questions for the east, it`s
pretty high confidence for some Thursday thunderstorms, and
potentially some strong to severe storms as well.

Just how much potential do you ask? Well, at the moment, there`s
a *lot* of uncertainty for what the top end for thunderstorm
potential is on Thursday thanks to numerous open questions. Will
morning clouds and rain sap instability to keep storm development
down in the afternoon? Will any storms that do initiate die off
as they cross the instability gradient? Or do they become
organized enough to hold insulate themselves from the poorer
environment, carrying all the way through our area? Given how high
PoPs are, I`ve got to think the messiness of the day from the jump
will cap high end potential somewhat. SPC`s Day 3 marginal risk
seems appropriate, and if we do end up getting a cleaner
environment overall, there may be a need for a little more
alertness, particularly west of the Houston metro.

Fair weather prevails Friday with northwest flow in place from the
ground through the middle layers in the wake of the exiting
trough. Though there will technically be some amount of cold
advection occurring here, I would expect temperatures to reach or
even exceed Thursday`s highs as clouds scatter out for the
afternoon. Weak ridging keeps the fair weather in place through
the weekend, and we can generally expect highs in the 70s each
day. Friday and even Saturday night should be cooler (and by
cooler, I only mean near seasonal averages) but onshore flow
returns late Saturday into Sunday, and as usual, our overnight
temperature floor goes up with the humidity into next week.

Our next round of more unsettled weather looks to be Monday into
Tuesday. It`s a pretty classic case of big upper trough digs into
the Plains, inducing lee cyclogenesis that swings through the
Panhandles and ejects northeastward towards the Great Lakes.
For whatever its worth, ensemble data suggests that moisture will
be high, but seasonably so (below the 90th percentile), and the
probability of getting back over an admittedly arbitrary 500 J/KG
SBCAPE threshold is already around/over 50 percent, so showers and
thunderstorms of some sort seem like a safe bet. Beyond that,
however, there`s just not enough signal in the guidance to
say anything more specific that that with a lot of confidence
right now.


&&

.AVIATION...
(06Z TAF Issuance)
Issued at 1139 PM CDT Mon Mar 18 2024

Benign weather conditions as high pressure remains over the
region and slightly moves east. Light north winds will gradually
shift to the east in the morning, then to the south/southeast in
the afternoon and evening. Overall, VFR conditions are expected
through the period.

JM

&&

.MARINE...
Issued at 412 AM CDT Tue Mar 19 2024

Winds are gradually diminishing, with seas slowly subsiding as
well very early this morning. Much of the area has already fallen
below the threshold for caution flags, but a smattering of
caution-level winds and even occasional gust around 20 knots are
being seen. Along with this, seas have only come down to 6 feet at
Freeport Buoy so far. Though conditions will continue to improve
through the morning, small craft will still want to exercise
caution beyond 20 NM out while winds and seas are still somewhat
elevated. Deeper into the afternoon though, winds will diminish
more shifting more easterly. Onshore flow will fully return by
Wednesday. This will lead us to the late week development of a
coastal low, which will boost winds and seas, as well as bring us
our next round of showers and storms.

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)  66  51  67  58 /   0   0  10  40
Houston (IAH)  68  54  70  60 /   0   0   0  50
Galveston (GLS)  62  57  68  63 /   0   0   0  40

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...Small Craft Should Exercise Caution until 11 AM CDT this morning
     for GMZ370-375.

&&

$$

SHORT TERM...41
LONG TERM....Luchs
AVIATION...JM
MARINE...Luchs


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