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Updated: Weather Talk: Storms Thursday, very warm and stormy Friday

Updated: Weather Talk: Storms Thursday, very warm and stormy Friday
MGN Online
Weather Talk

POSTED: Thursday, March 27, 2014 - 9:59am

UPDATED: Thursday, March 27, 2014 - 10:05am

THURSDAY AM UPDATE:

Good morning. We have a very mild and breezy morning.

The SPC has removed East Texas from a Slight Risk today—however; we'll still keep a close watch for the chance of a few strong storms today.

This morning, there is a lot of low-level cloud cover in our area along with light rain in our northern counties and mist area-wide. The 7AM run of the RPM Model shows some cloud breaks by the early afternoon. With the cloud breaks, we could see some showers and storms develop as well.

The ingredients needed for severe weather are: moisture, wind shear, lifting mechanism, and instability.

We have the moisture in place over our area. Dew points this morning are in the middle to upper 50s. Saturation has also taken place at 5,000 feet.

Wind shear is present. Here at the surface, it is breezy with south/southeast winds between 5-20 mph. Wind speeds are also increasing with height—at 5,000 feet winds are at 45-60 mph. This tells us that if storms do occur, we will likely see strong winds.

We do have a lifting mechanism in place, and that is the dryline located between Lubbock and Abilene. As this line moves eastward, this could trigger some area showers and storms by this afternoon. But, the limiting factor right now is the cloud cover we have in East Texas. If clouds break, the potential for storms to develop will increase. Otherwise, we will remain cloudy.

Looking ahead to Friday, it previously looked like showers would be scattered in nature as the cold front approached the area. New model data now suggests that strong storms are possible on Friday ahead of the cold front.

The setup for this is that another upper-level disturbance will swing through during the late morning and afternoon. As this happens, there will be an increase in upward vertical motion over our area, priming the atmosphere for some strong storms by the mid-afternoon. Here is the NAM output of the vorticity at 18,000 feet.

With this, showers and storms will be likely as the shortwave moves over our region. Here is the NAM at 4PM & RPM output at 6PM tomorrow afternoon.

The CAPE severe weather parameter is very high over our area (> 3,000 joules per kilogram), and additional parameters are not as strong. This could potentially not allow storms to remain sustained once they start.

Because of the new model data, the SPC has upgraded their Slight Risk for Friday to include all of East Texas.

We’ll continue to keep you updated.

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Wednesday Update:

We started off this week with cooler temperatures, but Wednesday is our “day of transition” as clouds will begin to increase over the area. We’ll have storms on Thursday—some of them could be strong to severe at times. In this post, I’ll walk you through the rain chances and when our likely time to see the severe storms could be.

THE SETUP

For Wednesday, an upper-level disturbance will move through our area. This forcing mechanism is weak, so it will provide scattered showers and an isolated thunderstorm Wednesday afternoon and evening. The map below shows wind speeds at 18,000 feet at 7PM Wednesday evening. Wind speeds over East Texas at that height are between 50-70 miles per hour—which is a very slow flow of air aloft.

At the surface Wednesday evening, a warm front will be advancing toward our area. Warmer air will begin to move in, and it will be felt by tomorrow morning. Our dew points today have been in the 30s and 40s—and those numbers will be in the middle to upper 50s and near 60s as we move to Thursday.

The two main threats with the strong storms for Thursday will be damaging wind and hail. The winds will be very strong in the low/middle levels of the atmosphere. Below is the wind speeds at 18,000 feet showing wind speeds increasing to almost 70-75 miles per hour.

At 5,000 feet, the wind speeds are moving very fast as well. By 10AM Thursday, wind speeds will be projected at 45-70 mph. This will prime the atmosphere with rich Gulf moisture.

The final setup factor for our strong storm possibility tomorrow is a dryline setting up in West-Central Texas. A dryline is a separation of airmasses—hot/dry air to the west & warm/moist air to the east—while remaining very tropical. Dryline can be determined by air temperature, wind speed, and dew point. Below is the dew points for Texas by Thursday at 1PM. Note that East Texas’s dew points are in the 60s (very moist), and just to the West of DFW/Metroplex, dew points sharply drop into the 40s/50s (dry air). The dryline can aid in storm development.

FORECAST DETAILS

WEDNESDAY NIGHT/THURSDAY AM

As of 1PM earlier this afternoon, there were scattered showers across East Texas. Some were heavy at times, but this activity is quickly moving to the east/northeast. There has been some sunshine but overall an overcast day.

Today has been breezy—making this morning rather cold—with south/southeast winds between 5-15 mph. The breeze will remain in place through the overnight.

This evening, there will be a few area showers across the area with everybody under cloudy skies. Temperatures this evening will be in the 50s and 60s by early evening.

By daybreak Thursday, our dew points will be reaching the 50s to near 60. This will make tomorrow morning feel a lot warmer thanks to the increase in moisture. Tomorrow morning will also be breezy. Below is the NAM output of temperatures and dew points at 1AM and 7AM Thursday morning.

THURSDAY

As mentioned in “The Setup” section, we will remain breezy on Thursday at the surface and at 5,000 feet. Temperatures will quickly climb into the 60s by midday and in the upper 60s and low 70s by afternoon.

Here is the GFS and NAM guidance of 1PM temperatures. Notice how warm and breezy it is.

Also, take note that it will be very muggy at 1PM Thursday as well.

Storms look to initiate between late morning and early afternoon. The GFS and NAM both have storms firing up by lunchtime.

These models are not properly exemplifying the heavy rainfall/strong storm potential for Thursday afternoon. Our threat of storms will be based on instability in the atmosphere.

Mesoscale forecast models are hinting at the atmosphere not being fully capped off—meaning that storms that form have the potential to last and become strong to severe. Here is the NAM forecast of the mixed layer CAPE (Convective Available Potential Energy)—which takes into account instability throughout the column of air and not just at the surface. Note that at 4PM the atmosphere is unstable—showing contoured regions of 1,500-2,000 joules per kilogram of CAPE—meaning the chance for strong storms.

With this instability, the RPM model is showing strong storms by the afternoon.

If the showers and storm activity occurs during the late morning, it will likely not be as severe due to not enough time to provide heating to the atmosphere. So, the biggest factor for tomorrow’s storms is what happens in the morning hours. If convection is limited/none and there is instability, it will make the afternoon storms strong to severe.

Because of this threat, the Storm Prediction Center has our Northern counties under a Slight Risk of strong to severe storms. However, KETK Meteorologists would encourage all of East Texas will need to keep a close watch to the weather conditions on Thursday.

THURSDAY NIGHT

We’ll have lingering scattered showers and storms ending by late evening. The severe weather potential weakens as we approach evening on Thursday. Overnight, temperatures will remain mild. Areas of fog will be likely due to the rainfall received during the day Thursday. By Friday morning, temperatures will be in the 60s area wide. A few of our northern counties could see the upper 50s.

FRIDAY

By Friday, we will be tracking a cold front moving into our area by evening and overnight.

Friday will be a very warm day. Temperatures will be in the upper 70s by lunchtime and highs will top out in the 80s! The last time official high temperatures above 80° were reached—Tyler: November 17, 2013 (85°); Longview: December 4, 2013 (80°); and, Lufkin: March 21, 2014 (81°).

As far as rain for Friday, showers and storms will be widely scattered in nature. A strong storm is possible on Friday, but the majority of the severe weather threat will be to the northeast of our area.

Our weather story on Friday will be the arrival of the cold front. Here is the GFS/NAM at 1AM & 7AM Saturday morning as the cooler is moving into our area.

The weekend will be looking fabulous—cooler and dry. Highs will be will be in the 70s with overnight lows in the 40s.

We’ll keep you updated with the latest forecast details at our KETK Weather Page.

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