Weather Talk: Details on Monday’s rain chances
POSTED: Sunday, August 10, 2014 - 9:42pm
UPDATED: Monday, August 11, 2014 - 6:30am
TYLER, TX (KETK) — We are expecting scattered showers and thunderstorms around East Texas on Monday. Some of the storms could be strong, so you’ll want to be weather aware. Main threats with storms will be strong straight line winds, locally heavy rainfall, small hail, and frequent lightning.
A cold front will be pushing out of Oklahoma Sunday night into Monday morning. This front will be the trigger mechanism for the showers and storms to occur, mainly ahead and along the frontal boundary.
THE TRICKY PART OF THE FORECAST
The hardest part of this forecast is timing the rain and storms. The high resolutions models are indicating that the cold front is picking up steam fast and will be arriving to northern areas overnight and into Monday morning. Where this cold front sets up by daybreak is where we will focus our attention to the weather.
FORECAST MODELS…NOT SO GOOD
As I mentioned above, the high resolutions models are pushing the cold front into the area quickly on Monday with little to no precipitation with it until late in the afternoon for Deep East Texas.
Even our in-house KETK Futurecast model seems to struggle with the showers and storm threat on Monday. It wants to wait until late afternoon to produce rainfall, and mostly south of Tyler and Longview.
The model that I feel has a good handle on the situation (but still overdone) is the North American Mesoscale model (NAM). I will show you its results.
NAM wants to have cold front along Red River and stretching into north-central Texas and the Texas Panhandle. It will be a humid and muggy Monday morning for us. Rain chances look to be along the front as well. This means that northern counties along I-30 will have a chance at morning showers and t-storms.
By the early afternoon, the front will be moving slowly to the south toward East Texas. Notice how the front has pushed further south in west and central Texas. We will warm up to the low 90s by the early afternoon..indeed a hot and humid day once again. By this time, I believe showers and storms will be developing along the cold front due to surface heating, and the NAM reflects that with the blue and green colors.
If showers and storms are not ongoing in the early afternoon, they will definitely be occurring in the mid-to-late afternoon time frame. For Deep East Texas, you will likely see high temperatures in the middle and upper 90s before storms hit your area. It is during this time period (late morning through the evening) that storms will have the potential to be strong to severe with frequent lightning, gusty winds, and locally heavy rain.
Showers and storms continuing to push through Deep East Texas through the early evening hours. Storms should come to an end by the late evening.
*NERD ALERT* WEATHER EXPLAINER—WHY STRONG STORMS?
Our storms have potential to be strong to severe for two reasons. One, the approaching cold front provides a lifting mechanism for storms to develop. And these storms develop (reason #2) due to daytime heating. This daytime heating, in meteorological terms, is called CAPE (Convective Available Potential Energy). CAPE is a measure of instability in the atmosphere, the higher the number, the more unstable the atmosphere is. In the summer time, you don’t need a lot of CAPE to produce strong thunderstorms. Our number around East Texas on Monday is about 1,500 to 2,000—which is more than sufficient to support any storm that develops to become strong or severe.
If that last section confused you, don’t worry…there is more that you will understand below. I answer some basic questions that you are wondering.
FORECAST AND TIMING
1. Do KETK Meteorologists expect storms Monday? Yes.
2. What time should the storms take place? A few storms will be possible in the morning hours along the cold front. However, the best chance for showers and thunderstorms will be in the afternoon and evening hours as daytime heating will aid in storm development.
3. What can we expect with the storms? Storms will contain gusty winds, heavy rainfall at times, possible small hail, and lots of lightning.
The forecast is for highs to reach the low and middle 90s for northern and central counties, and the middle and upper 90s for Deep East Texas. Rain and storm chances will increase by the late morning/afternoon hours and continue through the evening hours. We expect most shower activity to be ending by late Monday evening (before midnight). Widespread severe weather is not expected.
Based on the data I have shown in this blog, here is a rough timeline for when the best chance of rain will take place.
We will keep you updated with the latest information. Stay weather aware on Monday.