MAY 2020

[snowman65]

well certainly didn't see this coming today. hopefully this weekend won't be like this again

[DoctorMu]

Area Forecast Discussion
National Weather Service Houston/Galveston TX
630 PM CDT Thu May 14 2020

.AVIATION [00Z TAF Issuance]...

Heaviest remaining showers are north of UTS right now, but another
lighter patch between UTS and CXO will prompt an early VCSH there
before those fade off. Look for low MVFR again tonight, with some
potential for speckles of low IFR around the area, which may
impact some terminals. No explicitly IFR CIGs at this time, but I
do go to 010 at several sites given the uncertainty.

Late tonight, look for coastal showers again in the pre-dawn and
early morning hours, with gradual improvement to VFR around mid-
day. More uncertainty in coverage of precip tomorrow, but there
should at least be isolated showers and storms around the area, so
confidence is high enough for VCSH and VCTS to return.

&&

.PREV DISCUSSION /Issued 335 PM CDT Thu May 14 2020/...

.SHORT TERM...(Tonight Through Saturday Night)

Convection never really got going this afternoon and feel the
large MCS over the Gulf may have robbed the inflow. Could still
some widely scattered showers and thunderstorms with additional
heating later this afternoon but at this time coverage will be
less than what the CAMs suggested earlier today. A quiet night is
in store for the region but low level moisture will continue to
stream into the area beneath a capping inversion. CLouds will
return by late evening and the insulation provided by the clouds
will keep low temperatures on the warm side once again. Speed
convergence will allow for some weak showers to develop very late
tonight or early Friday. Weak upper level ridging amplifies into
the area on Friday with a weak disturbance rolling over the top of
the ridge. Not sure how it will play out so will maintain the
status quo and keep lowish PoPs in the forecast. High temperatures
look similar to today with values in the mid/upper 80`s. A fast
moving disturbance in advance of a potent upper low will bring an
increasing chance for showers and thunderstorms late Friday night.
43


.LONG TERM [Saturday Through Next Thursday]...

By Saturday, the upper-level low deepens as it pushes into Eastern
TX, slowing over the Arklatex region by the afternoon. GFS/ECMWF
have come into better agreement regarding the evolution and track of
this feature through the weekend over the past couple of runs, with
the GFS solution no longer pushing the low offshore and instead
following the ECMWF`s east/northeastward track towards the Ozark
Plateau. NAM solution remains slightly less progressive.
Nonetheless, confidence continues to increase in the likelihood of
heavy rain for portions of the area on Saturday and into early
Sunday.

Persistent onshore flow is expected to allow for a surge of low-
level moisture over the next 36-48 hours, with much of the area
expected to exceed 2.0 in of PWAT by Saturday afternoon.
Furthermore, forecast soundings continue to indicate a well-
saturated column by this time with the "skinny CAPE" profile
typically associated with heavy rainfall events apparent. As the
upper level low remains fairly stagnant through Saturday night and
into Sunday, widespread showers and thunderstorms are expected to
develop across most of the area with periods of localized heavy rain
likely. WPC continues to maintain a slight risk in its Day 3
Excessive Rainfall outlook for the entire CWA. While the QPF
forecast remains somewhat fluid, most areas appear progged to
receive widespread rain totals of 1-3" by Monday with isolated
totals of 4+". Still fairly early to pinpoint specific locations
where totals may be highest, as guidance continues to vary in its
depiction of any rainfall "bullseyes". However, we do expect a
general risk of flash flooding with these rains, so it would be
beneficial for individuals to review their flood safety plans in
advance of this event.

As the upper low departs on Monday, we experience a northerly wind
shift as a fairly amplified upper ridge builds in its wake and
surface high pressure builds into the central CONUS. This should be
short-lived, however, as onshore flow redevelops by early Wednesday
resulting in a renewed surge of Gulf moisture into SE Texas. Chances
for diurnally driven streamer showers increase by midweek as this
pattern looks to hold in place. Have continued to maintain 20-30%
PoPs as a result. A general warming trend looks to accompany this
pattern shift with temperatures projected to potentially eclipse
90 degrees by Thursday afternoon.

Cady


.MARINE...

Moderate onshore winds will persist through Sunday as low pressure
meanders across East Texas. An offshore flow is expected to develop
Sunday night as the weak surface low drifts east and eventually
southeast. A light and variable flow is expected Monday as the
pressure gradient goes flat. A weak N-NE flow will develop Monday
night into Tuesday as weak high pressure over the great Lakes
ridges into Texas. A persistent onshore flow will bring slightly
elevated water levels toward the coast through Saturday but water
levels are expected to remain below 3.0 feet. 43


.HYDROLOGY...

Locally heavy rain is expected on Saturday, possibly lingering
into Sunday. Depending on how quickly and where the rain falls
will determine the affect on area rivers. It is still too soon to
determine which watersheds will be affected by this rain event but
if 2 to 3 inches of rain can fall quickly, rapid response
watersheds would be the most likely to rise. Soils have become
increasingly saturated so any additional rainfall over the weekend
will run off quickly and allow a quick rise to area rivers. 43

&&

.PRELIMINARY POINT TEMPS/POPS...

College Station (CLL) 73 87 70 79 68 / 10 30 70 80 50
Houston (IAH) 74 87 74 82 70 / 10 50 50 80 60
Galveston (GLS) 75 84 76 81 73 / 20 40 30 70 60

&&

[Andrew]

well certainly didn't see this coming today. hopefully this weekend won't be like this again

Unfortunately, I feel like the threat will still be there this weekend for East Texas too. You may not see as much rain as places further west but grounds will be so saturated that anything will exaggerate the situation.

[davidiowx]

Flood Watches issued for Saturday..

Flood Watch
National Weather Service Houston/Galveston TX
514 AM CDT Fri May 15 2020

TXZ178-179-199-200-210>214-226-227-235>238-300-313-335>338-
436>438-151815-
/O.NEW.KHGX.FF.A.0001.200516T0900Z-200517T0000Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Austin-Brazoria Islands-Chambers-Coastal Brazoria-
Coastal Galveston-Coastal Harris-Coastal Jackson-
Coastal Matagorda-Colorado-Fort Bend-
Galveston Island and Bolivar Peninsula-Inland Brazoria-
Inland Galveston-Inland Harris-Inland Jackson-Inland Matagorda-
Matagorda Islands-Montgomery-Northern Liberty-Polk-San Jacinto-
Southern Liberty-Waller-Wharton-
Including the cities of Alvin, Anahuac, Angleton, Bay City,
Baytown, Bellville, Brookshire, Cleveland, Clute, Coldspring,
Columbus, Conroe, Corrigan, Dayton, Devers, Dickinson,
Eagle Lake, Edna, El Campo, First Colony, Freeport, Friendswood,
Galveston, Ganado, Hempstead, Houston, La Marque, Lake Jackson,
League City, Liberty, Livingston, Mission Bend, Missouri City,
Mont Belvieu, Old River-Winfree, Palacios, Pasadena, Pearland,
Pecan Grove, Prairie View, Rosenberg, Sealy, Shepherd, Stowell,
Sugar Land, Surfside Beach, Texas City, The Woodlands, Waller,
Weimar, Wharton, and Winnie
514 AM CDT Fri May 15 2020

...FLASH FLOOD WATCH IN EFFECT FROM LATE TONIGHT THROUGH SATURDAY
EVENING...

The National Weather Service in Houston/Galveston has issued a

* Flash Flood Watch for portions of south central Texas and
southeast Texas...including the following counties...in south
central Texas...Coastal Jackson and Inland Jackson. In
southeast Texas...Austin...Brazoria Islands...Chambers...
Coastal Brazoria...Coastal Galveston...Coastal Harris...
Coastal Matagorda...Colorado...Fort Bend...Galveston Island
and Bolivar Peninsula...Inland Brazoria...Inland Galveston...
Inland Harris...Inland Matagorda...Matagorda Islands...
Montgomery...Northern Liberty...Polk...San Jacinto...Southern
Liberty...Waller and Wharton.

* From late tonight through Saturday evening

* A slow moving upper level low pressure system meandering across
Texas will pull extremely moist air from the Gulf into Southeast
Texas Friday night into Saturday morning. As the system nears
Southeast Texas a line of showers and thunderstorms will develop
and spread eastward into the area early Saturday morning. This
line of storms will shift eastward across the region throughout
the day and be capable producing very heavy rainfall. Rainfall
rates of 3" per hour will be likely in the stronger storms and
these storms may train or successive storms may pass over the
same area. Rainfall totals of 2 to 4 inches should common across
the watch area. Isolated totals in excess of 6 inches will be
possible. The system should depart the region Saturday night
though rain chances will continue after it departs the threat of
any lingering heavy rain should diminish quickly Saturday
night.


* These storms with heavy rainfall will be capable of flooding
roadways quickly. Low water crossings may flood becoming
impassible and dangerous. Small creeks and bayous may rise
leading to minor flooding.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Flash Flood Watch means that conditions may develop that lead
to flash flooding. Flash flooding is a very dangerous situation.

You should monitor later forecasts and be prepared to take action
should Flash Flood Warnings be issued.

[Cpv17]

HRRR model is hinting at some pretty good storms firing up this afternoon in Harris County.

[Texaspirate11]

I'd BE happy with we see an inch of rain down by the bay.

[djmike]

Just started pouring again at my house in Beaumont. Storms firing up again all around the Golden triangle right now. Hopefully it’s something we can handle. Have a feeling by Sunday I will have had over a foot of rain. Right now just 3” shy and raining now.

[Cpv17]

I think today could pose a bigger flood risk for some people rather than tomorrow. Tomorrow all I’m seeing on the models is a quick moving squall line that’ll give us about an inch or two of rain and that’s it.

[djmike]

I think today could pose a bigger flood risk for some people rather than tomorrow. Tomorrow all I’m seeing on the models is a quick moving squall line that’ll give us about an inch or two of rain and that’s it.

Yup. Looking at the training storms over us in Beaumont right now concerns me. The squall lines are usually not the problems. Its these that meander and sit on top of us that cause the big problems. 10” yesterday here in Beaumont. We dont need this again today.

[jasons2k]

This is from Jeff Lindner. I wonder what impacts this may have on tomorrow's setup:

Short range guidance continues to show the development of slow moving thunderstorms this afternoon over portions of SE TX. This appears to be in conjunction with the approach of weak disturbances aloft, a westward moving outflow boundary from SW LA, and daytime heating. Storm motions today will be on the slow side…generally less than 10mph. Air mass will be very capable of producing very heavy to excessive rainfall rates this afternoon especially with slow cell motions. Rainfall rates of 1-3 inches per hour will be possible. It will be possible that certain areas could see a lot of rainfall and other locations nearby none in this sort of pattern.

Street flooding will be the main threat this afternoon.

Will need to monitor radar trends closely.

[snowman65]

looking forward to our annual flood filled season in S.E. TX....the new normal....

[sau27]

Looking at some of the meso models + radar + satellite I am seeing what amounts to an absolute mess of boundaries. We have a boundary moving west from LA, one moving south from an MCS in Oklahoma, the sea breeze, any local boundaries from storms this afternoon, and the squall line coming tonight. Given that it sometimes only takes one little boundary to induce a huge dump of rain this is going to be interesting.

[DoctorMu]

Looking at some of the meso models + radar + satellite I am seeing what amounts to an absolute mess of boundaries. We have a boundary moving west from LA, one moving south from an MCS in Oklahoma, the sea breeze, any local boundaries from storms this afternoon, and the squall line coming tonight. Given that it sometimes only takes one little boundary to induce a huge dump of rain this is going to be interesting.

A patchwork of feast or famine. It won't take much - the air is mega juicy today. Just a few degrees from 90°F. There's nothing on the radar now near here, but things could really light up about 3 pm.

The boundary near Beaumont is slowly retrograding west.

[don]

Slow moving storms are starting to enter the city... And almost everyone in Southeast Texas is in a Flash Flood watch for tomorrow.

[Cromagnum]

One of these strong cells formed 1 mile north of my house and kept trucking. Cannot catch a damned break.

[Andrew]

Getting heavy rain at my house now. What's interesting is mesoscale models are indicating storms may not be as strong as initially anticipated across a lot of the region. It may be a combination of the worked-over atmosphere from today and a faster-moving system. Unfortunately, some locations across SE Texas (Beaumont in particular) have already received a lot of rain so any more will not soak in at all. As always, we will have to monitor trends overnight and keep an eye on any development that occurs ahead of the main line.

[don]

My street is flooded now rainfall rates are very heavy,sometimes its not about the amount of rain but how fast it falls.

[jasons2k]

Getting heavy rain at my house now. What's interesting is mesoscale models are indicating storms may not be as strong as initially anticipated across a lot of the region. It may be a combination of the worked-over atmosphere from today and a faster-moving system. Unfortunately, some locations across SE Texas (Beaumont in particular) have already received a lot of rain so any more will not soak in at all. As always, we will have to monitor trends overnight and keep an eye on any development that occurs ahead of the main line.

I had a feeling today's storms were going to throw a bit of a wrench into things.

I got a heavy downpour, but it didn't last long. Got a quick .41" but I need more than that.

[davidiowx]

Getting heavy rain at my house now. What's interesting is mesoscale models are indicating storms may not be as strong as initially anticipated across a lot of the region. It may be a combination of the worked-over atmosphere from today and a faster-moving system. Unfortunately, some locations across SE Texas (Beaumont in particular) have already received a lot of rain so any more will not soak in at all. As always, we will have to monitor trends overnight and keep an eye on any development that occurs ahead of the main line.

I had a feeling today's storms were going to throw a bit of a wrench into things.

I got a heavy downpour, but it didn't last long. Got a quick .41" but I need more than that.

Yep, had the same thoughts as well as this boundary was heading towards our area. Work over the atmosphere and later tonight into early tomorrow would be much weaker than anticipated. Time will tell. I guess it will depend on how long this current storm lingers around. Maybe it moves out of the area quicker than it took to get here. Models have really been very poor about all of this.

[don]

I wouldn't sleep on tomorrow folks, the disturbance tomorrow seems to be pretty vigorous with the amount of moisture available it wouldn't take much to cause flash flooding, hopefully the mcs moves quickly through the area as some of the models show.