Jeff Lindner, Harris County Meteorologist, has released another update on the approaching storm. Not much has changed since last night except that:
- A Flood Watch has been issued from 7:00 PM this evening until 7:00 AM Tuesday morning.
- Models point to the area from US59 to about 40 miles northwest of Lake Houston as the area of greatest risk for heavy rainfall.
- Isolated areas could reach higher than 7″ instead of up to 7″.
- Watersheds on the northern and northeast sides of the county are at greatest risk for flooding according to overnight modeling of different rain scenarios by Harris County Flood Control.
Here’s where things stand as of noon on Monday, 3/21/2022.
Severe Weather Risk from Tonight into Early Tuesday.
Gulf moisture quickly returned to the region overnight. Scattered light showers are moving quickly from south to north. An upper level storm system is approaching from West Texas with strong lift ahead of it. Conditions will favor strong to severe thunderstorms in our area by mid to late afternoon over the warm air mass.
The National Weather Service does not assign a mathematical probability to the definition of Enhanced Risk, but note that it is the mid-point (3) on a 5-point scale.
Tornados may form, especially in any supercells that may form in this area. The Brazos Valley area will see the highest tornado threat, according to Lindner. But the National Weather Service Storm Prediction Center extends the area of 10% risk to the entire north and northeast Houston area. Large hail and damaging winds will also be possible with these storms.
The SPC also gives a 30% chance of large hail and damaging winds to west, north and northeast Houston.
Severe Threat Gives Way to Heavy Rainfall Threat During Night
According to Lindner, the severe threat will gradually transition to a heavy rainfall threat during the night as the pre-frontal trough slows over the Houston area. Formation of a line or two of training thunderstorms will be possible. Models point toward the US 59 corridor northeast of Houston and about 40 miles to the northwest as the most likely area of cell training.
Lindner predicts rainfall amounts of 2-4 inches north of I-10 with isolated totals upwards of 6-7 inches. South of I-10, amounts of 1-2 inches look most likely. Given moisture levels, hourly rainfall rates of 2-3 inches per hour will be possible. Street flooding in urban areas is currently the greatest threat and the Tuesday morning commute may be impacted.
Runoff, River and Stream Report
While grounds are generally dry over the area, expected rainfall rates in short duration will generate rapid run-off. Rises on all creeks and bayous are expected tonight.
HCFCD modeled various contingency forecasts yesterday afternoon with different rainfall durations and amounts to see how area bayous and creeks would respond.
Most of the creeks and bayous will be able to handle 4-5 inches of rainfall in a 4-6 hour period or longer. Should parts of the area realize the higher isolated totals of 6-7 inches, there would likely be some concerns for channels reaching bankfull.
While uncertainty still exists on exactly where training lines will form, Lindner believes watersheds on the northern and northeastern sides of Harris County will be at greatest risk. He named:
- Cedar Bayou
- Luce Bayou
- East and West Forks of the San Jacinto River
- Cypress Creek
- Spring Creek
- Greens Bayou
- Halls Bayou
- Little Cypress Creek
- Willow Creek
These watersheds will likely see some of the higher rainfall amounts and responses.
To view real-time stream levels and inundation reports, visit the Harris County Flood Warning System and click on a gage near you. Stay home tonight. Don’t roam. Let your fingers do the slogging.
Posted by Bob Rehak at 12:30 PM on 3/21/22
1665 Days since Hurricane Harvey