April 2023

[tireman4]

00
FXUS64 KHGX 261037
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
537 AM CDT Wed Apr 26 2023

...New AVIATION...

.SHORT TERM...
(Today through Thursday Night)
Issued at 254 AM CDT Wed Apr 26 2023

Mostly cloudy, warm and humid conditions should prevail well into
the mid-late afternoon hours. Can`t rule out some isolated waa type
shra as we`ve seen from time-to-time overnight with the moist
profile in place under the capping inversion. By late afternoon,
fcst soundings show partial cap erosion across northern parts of the
CWA where we could see a few tstms emerge.

Attention turns to the northwest tonight where scattered discrete
cells near the surface low (and associated dryline, warm/cold
fronts) take on a more linear pattern as they track ese overnight
and closer to the region. Anticipate a line of storms to approach
the northern part of the CWA around or shortly after midnight, the
US59/I69 corridor 3-5am-ish, and mostly off the coast by early-mid
morning Thursday. (Of course, these things tend to swing through
faster this time of year should any significant cold pool develop
behind them...so that`s just a rough estimate). Highest instability
should be situated across the northern 1/3 of the CWA and that`s
where one would anticipate the better chances of severe storms &
concur with SPC`s outlook. Damaging winds & large hail should be the
primary threat. It`s also where we might see some localized heavy
rainfall as it`ll be closest to the better upper level diffluence
and threat of some slower moving, backbuilding cells. Wouldn`t be
surprised to see some localized 1-3" swaths. That said, it looks
progressive enough whereas flash flood threat should be localized
versus widespread. Heading into the late night and morning hours,
instability shouldn`t be quite as impressive and would expect less
intense storms. That`s not to say no strong (or even a few severe)
storms, but maybe a more prevalent 25-45mph gust type thing as the
storms pass across the remainder of the region.

Depending on mesoscale influences, the wind shift might get hung up
at the coast for a bit in the afternoon and possibly some iso
shra/tstm redevelopment, but looking for clearing skies from
northwest-southeast Thursday afternoon and evening. Mostly clear and
cooler Thurs night.

47

&&

.LONG TERM...
(Friday through Tuesday)
Issued at 254 AM CDT Wed Apr 26 2023

A strong shortwave over the Canadian Rockies will plunge
southeastward over the U.S. Intermountain West over the next few
days. By Friday, the trough is expected to dig southward over New
Mexico and become a more closed mid/upper level low. The
development of surface low pressure over West Texas is expected to
occur as the low enhances UL divergence and lift to its east. The
developing surface gradient over Texas will increase onshore flow
over our neck of the woods on Friday, bringing moist Gulf air into
southeast Texas. This will be measured by rising dew points. This
will be felt via rising humidity. With forecast temperatures in
the 80s, Friday is expected to be a warm and muggy day. By Friday
evening, the chance of showers and thunderstorms is expected to
increase over our northern and western counties as the next system
approaches. More on that system below!

The aforementioned UL low and surface low, along with the surface
low`s associated cold front, are expected to push eastward on
Saturday. There continues to be great model variance regarding the
forward speed of these features as well as uncertainty pertaining
to the exact track of the UL and LL lows. These variances create
a particularly challenging forecast this weekend. There has only
been a modest increase in the peak PoPs this weekend (25-45
percent). Perhaps the more meaningful change in this update is the
timing of the PoPs. NBM and GFS PoPs guidance suggest a more
progressively moving system. In this scenario, the bulk of the
shower and thunderstorm activity would occur on Saturday (maybe as
early as Friday night into Saturday morning) with most of the
rainfall moving out of our CWA by late Saturday night or early
Sunday morning at the latest. The ECMWF on the other hand suggest
an UL low that will take its time moving across Texas, keeping the
chance of showers/thunderstorms well into Sunday. To give some
weight to this scenario, our PoPs grids were populated with a
NBM/ECMWF blend which shows 20-30 PoPs lingering into Sunday
morning.

With such a robust UL system expected, we cannot rule out a few
strong to severe thunderstorms late in the day / evening on Friday
into this weekend. SPC has issued a Marginal Risk (Level 1 of 5)
of severe thunderstorms over our western counties on Friday. No
such risk has been issued for the weekend time frame at this time
due to the high uncertainty.

The outlook for early next week looks seasonably warm for the
beginning of May with low PoPs. However, if the weekend system
moves slower like the ECMWF suggests, then temps early next week
would likely to be cooler than currently predicted due to a more
prolonged period of northerly flow in the system`s wake.

Self

&&

.AVIATION...
(12Z TAF Issuance)
Issued at 537 AM CDT Wed Apr 26 2023

MVFR and a few embedded IFR ceilings will prevail this
morning...eventually lifting into VFR territory this afternoon. MVFR
stratus redevelopment by mid evening. Line of showers and
thunderstorms will be passing nnw-sse thru the region after 6z.
Strong winds/hail/lightning will be the primary storm threat. IFR
conditions can be expected along and just behind the storms. 47

&&

.MARINE...
Issued at 254 AM CDT Wed Apr 26 2023

Generally light to moderate southeasterly winds are expected
through this evening. Winds will become lighter overnight as a
front approaches. However, the front will also bring an increasing
chance of showers and thunderstorms. The chance of thunderstorms
is highest during the morning hours on Thursday. A few storms
could be strong. Locally higher winds and seas will be possible in
and near any thunderstorms. Winds could briefly become offshore
Thursday afternoon in the wake of the front. By Friday, increasing
onshore flow and seas will likely return. The forecast for the
weekend is uncertain. For now, we think there will be a chance of
showers and thunderstorms over the weekend as a disturbance moves
in from the west.

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 80 64 77 55 / 30 80 30 0
Houston (IAH) 81 67 80 59 / 20 60 60 0
Galveston (GLS) 78 70 79 67 / 10 60 70 10

&&

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

&&

$$

[don]

We need to watch this Friday/Saturday for a potential localized heavy rain event as a MCS moves in and a coastal trough/ low develops.There is still some disagreement on where the heaviest rains setup as some models have the heaviest rain in South Texas instead.But something to keep an eye on.(12Z GFS)

[Stratton20]

Yep been noticing the euro and Gfs both have been hinting at that for a few days now, guess we will see how the mesoscale models handle this

[tireman4]

.AVIATION...
(18Z TAF Issuance)
Issued at 1226 PM CDT Wed Apr 26 2023

Cigs continue to lift towards VFR levels, which should continue
for the remainder of the afternoon as SE winds prevail at around
10 knots. Conditions will deteriorate this evening ahead of the
approach of a cold front, with cigs dropping to low end MVFR to
IFR levels after 00Z. A line of thunderstorms associated with a
cold front will move through the area overnight, reaching CLL
around 03Z, IAH around 07Z, and GLS around 10Z. Strong wind gusts
and periods of locally heavy rain are expected to occur with these
storms, which could result in some brief periods of very low
visibility. Showers will linger into mid-morning as the front
moves offshore, with conditions clearing out by late morning/early
afternoon and remaining within VFR thresholds through the
remainder of the day and into Friday.

Cady

[DoctorMu]

Potential bow echo MCS tonight around here tonight. Not sure how long it will hold together.

[DoctorMu]

NAM and HRRR are definite maybes.

[Cromagnum]

Probably nothing for Houston proper today. Looks to be well north. Maybe this weekend?

[don]

Most areas should see showers and storms tonight,but the storms will be weakening by the time they reach the I-10 corridor. So no real concerns for severe weather for the southern half of the area.Could be some brief heavy rain though.

[Cpv17]

Hail from that Waco supercell is insane.

[don]

Yep it looks like grapefruit size hail or larger!

[Stratton20]

Im now under a tornado watch, lovely

[jasons2k]

New watch…

[jasons2k]

URGENT - IMMEDIATE BROADCAST REQUESTED
Tornado Watch Number 170
NWS Storm Prediction Center Norman OK
705 PM CDT Wed Apr 26 2023

The NWS Storm Prediction Center has issued a

* Tornado Watch for portions of
West-central Louisiana
Central to east Texas

* Effective this Wednesday night and Thursday morning from 705 PM
until 100 AM CDT.

* Primary threats include...
A few tornadoes possible
Scattered large hail and isolated very large hail events to 2.5
inches in diameter likely
Scattered damaging winds likely with isolated significant gusts
to 80 mph possible

SUMMARY...Intense supercells across central Texas will spread
east-southeast and likely consolidate into a cluster with embedded
bowing segments into southeast Texas, yielding a mix of large hail,
damaging winds, and a few tornadoes. A leading supercell over
west-central Louisiana may continue east-southeast along the
instability gradient with a primary threat of large hail.

The tornado watch area is approximately along and 45 statute miles
north and south of a line from 35 miles west southwest of Austin TX
to 15 miles north northeast of Alexandria LA. For a complete
depiction of the watch see the associated watch outline update
(WOUS64 KWNS WOU0).

PRECAUTIONARY/PREPAREDNESS ACTIONS...

REMEMBER...A Tornado Watch means conditions are favorable for
tornadoes and severe thunderstorms in and close to the watch
area. Persons in these areas should be on the lookout for
threatening weather conditions and listen for later statements
and possible warnings.

[Cromagnum]

Insane hail from Waco.

[DoctorMu]

There's definitely shear up there. Plenty of juice now.

Things should stabilize a bit as the sun sets, but don't count these cells out.

[DoctorMu]

There goes the outflow. The cells will congeal into the MCS mess. Lightning, straight line winds, and heavy rain possible. Spin up tornado less likely. Flooding is the biggest threat tonight.

[jasons2k]

There goes the outflow. The cells will congeal into the MCS mess. Lightning, straight line winds, and heavy rain possible. Spin up tornado less likely. Flooding is the biggest threat tonight.

You have a good shot. The cap is starting to erode. The story further south will be how much the outflow outruns the storms. If the cold pool aloft can keep up with the outflow we have the potential for a decent rain with the storms later tonight.

[DoctorMu]

There goes the outflow. The cells will congeal into the MCS mess. Lightning, straight line winds, and heavy rain possible. Spin up tornado less likely. Flooding is the biggest threat tonight.

You have a good shot. The cap is starting to erode. The story further south will be how much the outflow outruns the storms. If the cold pool aloft can keep up with the outflow we have the potential for a decent rain with the storms later tonight.

The MCS is definitely ripping and sagging south.

https://www.star.nesdis.noaa.gov/GOES/s ... &length=24

[Stratton20]

Seeing lots of flash flood warnings with these cells just to our north

[Stratton20]

really heavy rain here with some lightning, nothing severe though