SEPTEMBER 2018 - Very Wet Month Wrap Up

[Cpv17]

It now appears that the front next week will stall out to our north so it looks like rain chances will hang around through next week instead of clearing out.

[srainhoutx]

1-3” doesn’t seem like that much...

Considering that 3 inches have fallen in 90 minutes this afternoon near and just S and E of IAH, everything is going to be mesoscale driven and a lot of uncertainty even back to our West from the Rio Grande to San Antonio/Austin Area over the weekend. The combination of a dying EPAC tropical system, moisture pooling in the 2+ inch range and a stalled boundary with multiple upper air disturbances rolling along and S of that stalled boundary suggests an extreme amount of volatility in the sensible weather we may see.

[unome]

Time: 2018-09-20T18:25:00Z UTC
Event: TSTM WND DMG
Source: BROADCAST MEDIA
Remark: CARWASH ROOF BLOWN OVER ONTO CARS.

https://abc13.com/weather/conroe-car-wa ... m/4296261/

[unome]

Special Weather Statement
National Weather Service Houston/Galveston TX
502 PM CDT THU SEP 20 2018

TXZ195>199-210>213-202245-
Brazos TX-Washington TX-Grimes TX-Waller TX-Burleson TX-Colorado TX-
Inland Harris TX-Montgomery TX-Austin TX-
502 PM CDT THU SEP 20 2018

...SIGNIFICANT WEATHER ADVISORY FOR NORTHEASTERN COLORADO...AUSTIN...
SOUTHERN BURLESON...SOUTHERN GRIMES...WASHINGTON...SOUTHEASTERN
BRAZOS...SOUTHWESTERN MONTGOMERY...WALLER AND NORTHWESTERN HARRIS
COUNTIES UNTIL 545 PM CDT...

At 502 PM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from near Fayetteville to Willowbrook. Movement was
north at 45 mph.

Winds in excess of 40 mph will be possible with these storms.

Locations impacted include...
Conroe, Brenham, Katy, Tomball, Jersey Village, Navasota, Sealy,
Hempstead, Willis, Prairie View, Brookshire, Bellville, Pinehurst,
The Woodlands, Washington, Shelby, Hockley, Oak Ridge North, Waller
and Panorama Village.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

These storms may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

[jasons2k]

1-3” doesn’t seem like that much...

Considering that 3 inches have fallen in 90 minutes this afternoon near and just S and E of IAH, everything is going to be mesoscale driven and a lot of uncertainty even back to our West from the Rio Grande to San Antonio/Austin Area over the weekend. The combination of a dying EPAC tropical system, moisture pooling in the 2+ inch range and a stalled boundary with multiple upper air disturbances rolling along and S of that stalled boundary suggests an extreme amount of volatility in the sensible weather we may see.

Right - I was implying some folks are gonna get a lot more than that.

[Cpv17]

Models are performing very poorly with rainfall amounts. 1-3” is being conservative. I would expect most places to receive more than that.

[don]

The NWS mentioned in their discussion this afternoon that a Flash Flood watch may be required this weekend.

Area Forecast Discussion
National Weather Service Houston/Galveston TX
401 PM CDT Thu Sep 20 2018

.DISCUSSION...
Rain chances ramping up for the weekend and heavy rain threat.

This afternoon redevelopment over Harris county has lead to an
Urban and Small Stream advisory...and now Flash Flood Warning.
Scattered showers and thunderstorms developing mainly the central
and western areas of the CWA. These should taper down between 5
and 7 pm.

Tonight continued moistening up and will likely see a lull 7pm to
1am then showers start picking back up toward morning. As upper
s/w moves out of Hill Country into SETX expect showers and
thunderstorm coverage to increase Friday morning across much of
the area. A slow moving cold front will help to set the region up
for a wet weekend. Rain chances should again spike up Saturday
morning and threat of heavy rain increases. At this point the
models appear to struggle with timing of front and am strongly
leaning toward the forecast becoming mesoscale (rain-cooled
boundary) driven Saturday and Sunday. 850 front lagging well
northwest of the region with the surface boundary near the CWA.
Weak to moderate CAPE environment Saturday-Sunday gradually
lowering Sunday. Heavy rainfall threat Saturday through Sunday
looks high and couldn`t rule out the need for a Flash Flood Watch
Saturday/Sunday.

Monday the cold front retreats northward through Tuesday morning
then a stronger push of cold/dry air shoves the front south into
SETX Wednesday or Thursday. Rain chances remain high with the
presence of PW 2.1-2.3 which is well above normal and with a
persistent boundary and weak lift during this Tuesday through
Thursday period.

https://forecast.weather.gov/product.ph ... glossary=1

[srainhoutx]

2 inches in 45 minutes in my backyard.

[Katdaddy]

Light showers moving across SE TX this morning as the wet and humid weather pattern continues through the weekend and into next week. Locally heavy rains will be possible each day with the tropical environment in place.

[Cromagnum]

It now appears that the front next week will stall out to our north so it looks like rain chances will hang around through next week instead of clearing out.

That sucks. So more hot and wet.

[snowman65]

It now appears that the front next week will stall out to our north so it looks like rain chances will hang around through next week instead of clearing out.

That sucks. So more hot and wet.

We should be getting the updated outlook for Oct saying above average temps for our region now. You know it changes daily. Those of us that have lived here for any length of time knows that the firt real front or 2 don't make it all the way down. That's just life in S.E. Texas.

[tireman4]

Not so fast...still next week on this..models lose cooler/cold air within 3-5 days of the front passing. Happens all the time. Just be patient.....

FDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
931 AM CDT Fri Sep 21 2018

.DISCUSSION...

Seeing scattered showers this morning as a weak mid level
disturbance moves across SE Texas. The elevated showers
associated with this feature are moving to the northeast with the
mid-level flow, and then there are some isolated showers across
southeast areas that are moving northwest with the low-level flow,
with the latter being driven by some limited heating. I am
expecting a fairly convectively active afternoon with some
additional heating due to low convective temps and ample moisture
in place. Localized amounts of 1 to 3 inches could occur this
afternoon where showers/storms move repeated over the same
area(s). Updated the forecast to account for current conditions
and to adjust pops slightly using a consensus of high resolution
models for the rest of today and tonight. Expect max temps to
reach the upper 80s across most locations, but could remain in the
mid 80s across NW areas due to the expectation of more persistent
cloud cover. 33

&&

[Cromagnum]

It now appears that the front next week will stall out to our north so it looks like rain chances will hang around through next week instead of clearing out.

That sucks. So more hot and wet.

We should be getting the updated outlook for Oct saying above average temps for our region now. You know it changes daily. Those of us that have lived here for any length of time knows that the firt real front or 2 don't make it all the way down. That's just life in S.E. Texas.

I know. We usually don't get comfortable weather (anymore) until November. I can't remember the last time we had Fall, maybe in the 90s.

[Cpv17]

The front still may pass through, but it looks like it may be delayed by a couple days. It keeps getting pushed back and that’s not a good sign.

[unome]

radar loop http://tempest.aos.wisc.edu/radar/sp3comphtml5.html

• Excessive Rainfall Discussion
  NWS Weather Prediction Center College Park MD
  1223 PM EDT Fri Sep 21 2018
  
  Day 1
  Valid 1622Z Fri Sep 21 2018 - 12Z Sat Sep 22 2018
  
  ...THERE IS A HIGH RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF THE SOUTHERN PLAINS...
  
  ...Significant and locally life-threatening flash flood event underway across portions of northern TX and southern OK...
  
  16z Update: Decision was made to upgrade to a HIGH risk of excessive rainfall across portions of northern TX into southern OK. Given recent radar trends, observations thus far suggesting very efficient tropical rainfall processes at play, and 12z HREF/HRRR guidance...pockets of 6-10" of rain appear likely across the HIGH risk area today into tonight. The highest threat is focused along and south of the nearly stationary west to east convective line stretching across southern OK as of 16z. Expect convection to continue to develop into this boundary from the south as the low over west TX slowly pushes east. Convection will eventually expand southward into north TX ahead of this low... with slow moving/training likely here as well as we head through the day into tonight. See the latest MPD for the most up to date information. -Chenard

Next Storm Summary to be posted at 4 PM CDT https://www.wpc.ncep.noaa.gov/discussions/nfdscc5.html

[tireman4]

HGX Update

[unome]

https://www.wpc.ncep.noaa.gov/metwatch/ ... 73&yr=2018

• Mesoscale Precipitation Discussion 0873
  NWS Weather Prediction Center College Park MD
  153 PM EDT Fri Sep 21 2018
  
  Areas affected... Central/Northern TX... Central/Southern OK
  
  Concerning... Heavy rainfall... Flash flooding likely
  
  Valid 211753Z - 212353Z
  
  Summary...Dangerous flash flooding will become likely as a result of very heavy showers and thunderstorms persisting through the afternoon hours, with rainfall rates of as much as 3 inches/hr.
  
  Discussion...The latest GOES-16 satellite imagery shows a well-defined mid-level closed low center across west TX which is advancing very slowly off to the east. This energy is interacting with an extremely moist and at least moderately unstable airmass pooled up across the southern Plains and particularly up against a rather strong baroclinic zone. In fact, the latest surface analysis depicts a cold front dropping slowly south down toward the lower MS Valley but extending back to just north of the Red River over southern OK and then southwest down into west TX where there is a well-defined area of low pressure.
  
  PWATs out ahead of the low center are highly tropical in nature with values of 2.0 to 2.25 inches as per the latest Blended-TPW product and also GPS-derived data sets. Meanwhile, a rather strong instability gradient is in place along the front, with MUCAPE values as high as 2000 j/kg pooled up near the Red River. The combination of both will lead to extremely heavy rainfall rates that will be as much as 3 inches/hr within the stronger convective cores.
  
  On the larger scale, there is excellent large scale forcing, with right-entrance region jet dynamics in place, robust isentropic ascent along and north of the front, and persistent deep layer southerly flow which is maintaining the transport of very favorable thermodynamics.
  
  Given these ingredients, all signs continue to point to a longer duration and high impact flash flood event across especially areas of southern OK and northern TX. Already as much as 9 inches of rain has been reported over Pontotoc county, OK in the vicinity of Fittstown.
  
  Over the next several hours, there will be a tendency for more convection to begin focusing just south of the Red River over northern TX, but expect very heavy rains to continue over southern OK where dangerous flash flooding is already occurring. The latest 12Z HREF model consensus and recent HRRR guidance favors as much as an additional 4 to 6+ inches of rain through late afternoon.
  
  Expect life-threatening and dangerous flash flooding to occur this afternoon across southern OK. Areas of northern TX will also become increasingly susceptible and should be closely monitored for excessive rainfall as well going through the mid to late afternoon hours.
  
  Orrison
  
  ATTN...WFO...EWX...FWD...LUB...OUN...SHV...SJT...TSA...
  
  ATTN...RFC...ABRFC...LMRFC...WGRFC...

https://twitter.com/NWSWGRFC
https://www.weather.gov/wgrfc/

[Cpv17]

This is one soggy forecast for the next couple weeks if I’ve seen one.

[unome]

kinda sparkly



http://en.blitzortung.org/live_lightning_maps.php
http://en.blitzortung.org/live_lightnin ... php?map=30
http://en.blitzortung.org/live_lightnin ... php?map=31

[srainhoutx]

Stick to the ensembles when trying to figure out when our first Fall Cold Front arrives in the longer range. The operational global models are just background noise to the forecaster beyond 3 to 5 days. Temperatures across portions of Alberta in Western Canada were in the single digit Fahrenheit this morning. Follow the temperatures across our source Regions in Canada next week. Those ground truths upstream offer some hints as to how cold the air building to our N and NW may be as it spills S into the Plains. Anytime I see such a robust full latitude trough extending from the Canadian Prairies into the Southern Plains it raises an eyebrow in Fall and Winter. Remember it will be modified as it far too soon for massive snow cover across the Plains. The deterministic guidance always struggles with cooler/dense air in the day 5+ range. We witness that every year. Whether that front arrives on the 27/28th or 29/30th really doesn't make that much difference when attempting to analyze what our sensible weather may bring late next week...