April 2024

[Cpv17]

Not sure why y’all were expecting much. The models and the WPC QPF forecast never had much of anything for our part of the state. Not sure where those high rain chances were coming from. I’ve never seen anything that would warrant such a high chance of rain.

Our local office is generally conservative with rain chances so if they put up 90% four days out, that usually means a decent soaking.

Unless it’s a bust, of course, and they start dialing it back.

91F today at the house.

I saw Channel 13’s future radar earlier and it had a pretty good soaking along the 59 corridor for Saturday night but it’s the only model I’ve seen so far that has a decent rain.

[Ptarmigan]

They seem to be adamant that Saturday night is going to be stormy.

[tireman4]

000
FXUS64 KHGX 191218
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
718 AM CDT Fri Apr 19 2024

...New AVIATION...

.SHORT TERM...
(Today through Saturday Night)
Issued at 323 AM CDT Fri Apr 19 2024

Active spring weather pattern expected on SAT:
Slight and Marginal Risk of Excessive Rainfall (levels 2 and 1 of 4)
Marginal Risk of Strong or Severe Storms (level 1 of 5)

Slightly drier/cooler air will be filtering into the northern half of
the CWA (mainly north of the I-10 corridor) through this afternoon as
the cold front slides into SE TX before stalling. South of this boun-
dary, warm/humid conditions will continue. The light WAA showers this
morning could give way to isolated activity along/near this line this
afternoon. Temperatures this afternoon will depend on the front, with
highs around 80 behind this front...to the mid and upper 80s ahead of
it. So please continue to be cautious if you are planning on any out-
door activities.

By tonight, the cold front will begin retreating north as the onshore
flow at the low/mid levels begins to strengthen in response to a weak
shortwave trough approaching from the west. This pattern will help to
increase PWs (to 1.8-2") through Sat afternoon/evening. Aloft, models
are indicating the development of a diffluent jet structure across N/
NE portions of the area. And so, these factors combined with the add-
ition of weak impulses aloft and the proximity of the semi-stationary
front, do favor the development of training storms as well as showers
and thunderstorms with locally heavy rainfall heading into Sat after-
noon. Guidance is continuing to favor locations north of the US-59/I-
69 corridor for the highest POPs...with areas from Brenham to Trinity
as where we could see the more significant rain totals. Activity will
persist/regenerate into Sat night across much of SE TX, so the threat
of flooding/heavy rains could be compounded. Current thinking has the
rain totals averaging from 1-3" north of US-59/I-69...from 0.25-1" to
the south. Locally higher amounts will be possible. 41

&&

.LONG TERM...
(Sunday through Thursday)
Issued at 323 AM CDT Fri Apr 19 2024

By Sunday morning, the aforementioned surface cold front will
approach the coast and depart offshore, with shower and
thunderstorm development ceasing as this occurs. As surface high
pressure moves into the area behind the boundary along with a
steady NE surface flow, we`ll see an influx of cooler and drier
air that should provide a few days of pleasant conditions heading
into the beginning of next week. Highs on Sunday are unlikely to
eclipse 70, with lingering cloud cover in the wake of the frontal
passage working to inhibit daytime heating while CAA provides a
persistent supply of cooler air. Overnight lows should dip into
the upper 40s/low 50s for most locations, with clearer skies
providing efficient radiative cooling. Pleasant conditions linger
into the start of next week with highs on Monday sitting in the
70s, lows dropping into the 50s, and surface dew points in the
upper 40s.

The eastward exit of surface high pressure on Tuesday will bring
about a return to an onshore flow regime, with southeast winds
increasing by mid-week with the development of a lee cyclone over SW
Colorado and the resultant tightening of the synoptic pressure
gradient. As such, we continue to anticipate steady increases in
both temperatures and moisture levels into the end of next week,
with highs returning to the upper 70s/low 80s on Tuesday and the mid
80s on Wednesday and Thursday. This will be accompanied by a rise in
surface dew points back towards 70. A few shortwaves embedded within
the prevailing midlevel flow will provide some nonzero but
nonetheless meager precipitation chances beginning on Wednesday.

Cady

&&

.AVIATION...
(12Z TAF Issuance)
Issued at 659 AM CDT Fri Apr 19 2024

Patchy fog has developed across much of SE TX this morning, with the
visibility at some (mainly inland) terminals down to 1/4 to 1/2 mile
at times. Elsewhere, visibilities are ranging from 4 to 6 miles with
MVFR/IFR ceilings. Conditions are expected to slowly improve by late
morning to early afternoon bringing VFR conditions back to most ter-
minals. However, sites along the coast and across our northern areas
could see lingering MVFR CIGS through the day. Deepening moisture at
the coast and the approach of a cold front, respectively, as the big
reasons. MVFR conditions should return across the area by this even-
ing and persist into the overnight hours. Did keep the mention of at
least VCSH for locations LBX northward during the late afternoon and
early evening hours. 41

&&

.MARINE...
Issued at 323 AM CDT Fri Apr 19 2024

Light to moderate onshore winds, along with the chances for patchy
fog development, will prevail through Saturday as a front remains
stalled to the north of the barrier islands. This boundary will
eventually push through the area on Saturday night, bringing with it
periods of showers and storms that will prevail until Sunday
morning. Moderate NE winds are expected behind the departing
boundary on Sunday, possibly requiring a Small Craft Advisory. Winds
will diminish on Monday with an onshore flow pattern returning on
Tuesday. Onshore winds will gradually increase through the middle of
next week.

Cady

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 80 67 78 53 / 10 20 70 90
Houston (IAH) 85 71 82 59 / 20 20 50 80
Galveston (GLS) 79 71 77 62 / 10 10 10 70

&&

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

$$

SHORT TERM...41
LONG TERM....Cady
AVIATION...41
MARINE...Cady

[DoctorMu]

The front is through CLL, at least for now, with slightly cooler air.

Hopefully, the s/w triggers heavy showers along the front Saturday night. I hope to keep the sprinkler use down.

A cooler, drier Sunday and Monday are on tap. Enjoy it while it lasts!

[jasons2k]

Jeff Lindner is seeing chances for heavy rain:

Heavy rain possible Saturday evening into early Sunday across the northern portions of SE TX.

Weak frontal boundary currently just north of Austin is sliding southward this morning with a warm and moist air mass in place across all of SE TX ahead of this feature. High resolution guidance continues the southward track of this boundary today to roughly along a line from Columbus to Tomball to Cleveland which is much further south than the global models have been suggesting. A weak disturbance is also approaching SE TX from the southwest currently similar to yesterday at this time, but the radar is mostly clear. Convection allowing models (CAMs) show some development near the frontal boundary late this afternoon and early evening from roughly Sealy to Tomball to Conroe. This may be some enhancement of the frontal boundary with an inland moving seabreeze. Anything that does develop looks to weaken and dissipate by 8-9pm.

Saturday:
Weak frontal boundary will attempt to lift northward early Saturday, but how much northward progress is questionable…effectively the boundary will be stalled/meandering somewhere between Houston and College Station during the day. CAMs show a robust disturbance moving out of MX tonight with a well defined thunderstorm complex developing over the Rio Grande plains, but this activity weakens as it moves eastward across SC TX. Can’t rule out a few showers Saturday morning with the front in the area and this disturbance approaching from the southwest.

Renewed influx of tropical air mass into the region will occur by early Saturday afternoon with PWS of 1.8-2.0 inches or near maximum levels for mid April moving into the area from the western Gulf of Mexico. Surface heating across the area when combined with the approach of a stronger upper level disturbance is setting the stage for thunderstorm development by mid to late afternoon. Short range guidance is not in great agreement on how activity will play out Saturday afternoon into the overnight period with several scenarios on the table. One scenario suggests storms begin to fire in the 3-5pm time frame from Austin County through NW Harris to Montgomery County and then slowly develop/move ENE. Another scenario is that a thunderstorm complex develops over central TX and moves into the region later in the evening. One or a combination of both of these potentials is plausible.

Heavy Rainfall:
Nearly all factors are in place for heavy rainfall late Saturday with copious moisture, a feed of tropical moisture off the Gulf, a slow moving low level boundary, and diffluent upper air winds aloft. The threat for cell training is certainly in place and this is where things could add up fast given the environment in play. Hard part of the forecast is where is the best potential for cell training and where is the southern cut-off of the heavy rainfall. There looks to be a strong rainfall gradient across the area with totals near the coast less than .50 of an inch and totals in the College Station to Livingston area of 1-3 inches. Higher isolated totals are almost certain and would not be surprised to see some locally 4-6 inches in places where storms anchor and training persists.

For the metro area think 1-2 inches north of I-10 is most likely, but will need to keep an eye on the southward extent of the potential heavy rains to the north and any trends that would suggest a slightly more southern extent to the heavy rainfall.

Hydro:
Heaviest rains on Saturday into early Sunday are expected north of HWY 105 which will impact the Trinity, east and west Forks of the San Jacinto River, Navasota, and middle Brazos basins. Currently, not expecting any significant flooding on any of these systems, but will at least need to keep an eye on the more flashy San Jacinto and Navasota basins and where any sustained corridor of heavy rainfall occurs.

Forecasted Rainfall (Today-Sunday):

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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

[don]

Things look pretty wet tomorrow evening/night especially north of I-10.

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[Cromagnum]

Yawn. When are all these boundaries ever gonna start coming south? Besides the one thunderstorm a couple weeks ago, it's been crickets.

[Ptarmigan]

As Yogi Berra says, "It ain't over till it's over."

[don]

It now looks like a MCS will be coming though tomorrow night.

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hrrr_ref_frzn_scus_26.png (167.27 KiB) Viewed 550 times

[DoctorMu]

The last time we had a heavy rain setup north of Hwy 1*5, the models missed out on an overperforming front...and the actual rain was I-10 and south.

We'll see.

[jasons2k]

Update from Jeff:

Heavy rainfall is likely over parts of SE TX this afternoon into the evening hours.

Weak surface boundary noted in surface observations this morning is stalled roughly along a line from Eagle Lake to Katy to Humble to Cleveland as noted by dewpoints in the mid and upper 60’s to the north of this line and low 70’s to the south. Additionally, winds to the north of this boundary are from the ENE/NE and ESE south of the boundary. With the approach of a trough out of the SW US by early afternoon, expect lift and convergence near this boundary to increase and the development of thunderstorms. There appears to be decent agreement that storms will develop along this boundary from Colorado County to southern Austin/Waller Counties into northwest Harris and Montgomery Counties as early as early afternoon but more likely mid to late afternoon. Additional activity possibly in the form of an organized thunderstorm complex may approach from central Texas this evening.

It is this initial development of thunderstorms that has the concerning heavy rainfall threat as these storms look to anchor near the low level boundary over the area, initially move slowly and potentially exhibit cell training for a period of time before eventually moving toward the east and weakening into the late evening hours.

Factors are in place for heavy rainfall including near maximum amounts of moisture for this time of year, sustained lift this afternoon and evening, a slow moving/quasi-stationary low level boundary, favorably aligned low level inflow off the Gulf of Mexico, and enhanced divergence aloft. The combination of these factors point toward a heavy rainfall event north of I-10 later today into tonight. It should be noted that there is going to be a strong rainfall gradient over the area with likely several inches of rainfall occurring to the north of I-10 and potentially very little rain near the coast. It is possible that locations into north and west Harris County (Katy, Cypress, Tomball, The Woodlands) see several inches of rain while areas over southeast Harris County (Clear Lake, Baytown, Pasadena) see very little rainfall.

Rainfall Amounts:
Widespread amounts of 2-4 inches is likely north of I-10 with isolated totals of 5-7 inches or higher. HREF guidance continues to show some fairly impressive isolated totals…and given the setup and moisture in place I would not discount the higher amounts. South of I-10 rainfall amounts will be less than an inch and locations near the coast may see no rain at all.

Additionally, rainfall rates of 2-3 inches per hour will be possible in the stronger storms and this will cause rapid onset flash flooding. This is certainly the setup where everything is fine and in 1-2 hours flash flooding is occurring with intense short duration rainfall rates. This will be especially true in any urban areas where primary street drainage systems can be quickly overwhelmed with such rainfall rates.

Hydro:
Depending on where exactly the corridor of heavy rainfall develops will determine which watersheds are most impacted. Current thinking is from the Trinity across the San Jacinto into the Brazos and San Bernard basins and would not rule out the creeks in NW Harris (Spring, Cypress, Little Cypress, Willow). Depending on totals and location, significant rises overnight will be possible on some of these basins.

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

[Cpv17]

Looks like Austin, Washington, Waller, Walker, and parts of Montgomery Counties are gonna get crushed later today.

[jasons2k]

The front is definitely north of me. I have a dew point of 72. Similar conditions a good ways to the NW too - I see 70+ dew point into College Station. There is a chance I'm going to be stuck with dark skies and hear lots of distant thunder to the northwest until the main MCS sweeps through later tonight.

Unless...if we can get those storms to pump out an outflow, and especially if that outflow runs parallel to the mean flow SW to NE, we could get storms slowly building to the SE, with the outflow pushing the 'front' south into the warm, unstable air.

A very busy setup this afternoon that will come down to 'nowcasting' watching the radar trends.

[jasons2k]

It's only 11:24am and I've already reached my forecast high of 81°F.

[Cpv17]

It's only 11:24am and I've already reached my forecast high of 81°F.

Maybe that will add more fuel for some storms.

[DoctorMu]

There's a dryline or "wetline" about 10 miles north of here with DPs in the 50s by Hearne. When the 2nd front and disturbances arrive, there will be fuel for the fire.

[DoctorMu]

Area Forecast Discussion
National Weather Service Houston/Galveston TX
1249 PM CDT Sat Apr 20 2024

...New AVIATION...

.SHORT TERM...
(Today through Sunday Night)
Issued at 242 AM CDT Sat Apr 20 2024

A rather busy period is expected for SE TX today and tonight with the
approach/passage of a strong short wave from the west. The warm/humid
airmass already in place over the region will see an additional boost
of moisture from the Gulf this afternoon (as PWs increase to 1.7"-2")
with the development of a strong LLJ. Further aloft, models are cont-
inuing to indicate a broad diffluent jet structure along with a grad-
ually increasing shear pattern at the mid levels.

Although the primary weather concerns are for this evening on through
tonight with the arrival/passage of the associated cold front...there
is still a chance of isolated to scattered activity this morning into
this afternoon via embedded disturbances in the flow aloft. The high-
est POPs should be north and west of the US-59/I-69 corridor. As day-
time heating begins to peak, all the aforementioned factors will also
be coming together as well. This does point to increasing coverage as
well as the intensity of the developing showers/thunderstorms as this
next cold front begins to make its E/SE push through the CWA. Strong/
severe storms cannot be ruled out for this afternoon/evening. SPC has
a large part of SE TX in a Marginal Risk (level 1 of 5) for severe wx
starting later this afternoon. Strong winds and hail will be the main
threats.

As this widespread convection moves through the area, periods of mod-
erate to heavy rainfall will be possible. Models continue to indicate
that the best locations for training activity/higher rain totals will
be generally north of the I-10 corridor through tonight. WPC is main-
taining a Slight Risk (level 2 of 4) risk for excessive rainfall over
the northern half of the CWA...and a Marginal Risk (level 1 of 4) for
the rest of the area.

Rain chances will be ending (from west to east) by Sun morning as the
storm system pushes east of the area and helps to drag its associated
cold front front through. Cooler/drier air will be filtering into the
CWA through the day as N/NE winds develop. Clouds could take a little
more time to clear...but should clear out by tomorrow evening. 41

&&

.LONG TERM...
(Monday through Friday)
Issued at 242 AM CDT Sat Apr 20 2024

Mild and generally pleasant conditions will continue on Monday, with
morning temperatures sitting in the 40s/low 50s as surface high
pressure is centered just to our north. Afternoon highs will rise
into the lower 70s, but with dew points sitting in the 50 degree
range during the afternoon conditions should prove to be much more
pleasant than that of the preceding week. The aforementioned surface
high will begin to drift to the east by Tuesday, leading to the
reestablishment of an onshore flow regime and thus a gradual increase
in both temperatures and humidity through the end of the week. Highs
will reach the 80s once again by mid-week, while dew points will
break the 60 mark by Wednesday and approach 70 by Thursday. As this
pattern prevails, WAA and increasing low-level cloud cover will see
low temperatures again reaching the upper 60s for many areas by
Thursday.

As a midlevel trough swings into the Central Rockies on Thursday and
the associated lee cyclone at the surface deepens to around 990mb,
the resultant tight synoptic pressure gradient will produce gusty
conditions across SE TX to close out the week. Inland wind speeds on
Friday will reach around 20 mph with gusts in excess of 30 mph
possible at times. A weak surface boundary associated with this
feature will approach on Friday, but should stall to our north. This
could still produce some shower/storm activity across the far
northern zones, but as a whole rainfall chances will otherwise be
contained to isolated diurnally driven activity through the end of
the week.

Cady

[DoctorMu]

The dryline/front just blasted through. DP at 66°F and tanking. Brisk northerlies and heavy cloud. there's plenty of moisture aloft. I'm hoping for 2-3 inches of the liquid gold.

We've had only 0.83 inches of rain in April. I'd like to shut down the sprinklers and A/C for awhile.

[jasons2k]

The dryline/front just blasted through. DP at 66°F and tanking. Brisk northerlies and heavy cloud. there's plenty of moisture aloft. I'm hoping for 2-3 inches of the liquid gold.

We've had only 0.83 inches of rain in April. I'd like to shut down the sprinklers and A/C for awhile.

You can see it advancing on satellite. Things are about to go boom! between your place and mine.

[DoctorMu]

Spotty streamer showers are percolating upward with daytime heating.