Monday, April 6, 2015

Late week storms bring another chance of severe weather

Many of you were able to get out and enjoy a cooler Easter weekend despite cloudy skies and sprinkles on Sunday, but those waiting for the next period of warm temperatures and thunderstorms, you’re wish is soon to be granted! Indeed, spring weather is quickly returning to the Mid-South and this may include a chance of strong thunderstorms before week’s end as well.


The first ‘phase’ in setting up this week’s weather already moved through this morning, as scattered showers and a few thunderstorms developed and moved across the metro around daybreak this morning, in advance of a warm front lifting north through the region. While these storms were not severe, some areas did receive a quarter inch or so of rainfall, and perhaps a few of you got a slightly early wake-up call thanks to thunder! That system has exited to the northeast, leaving behind mostly cloudy skies and warming temperatures.


Before getting to the potential strong thunderstorms later this week, in the interim, the weather pattern over the Mid-South should be relatively quiet. The main story for Tuesday and Wednesday will be the return of above-average temperatures, as highs reach the lower 80s. The Mid-South will be increasingly situated in a “warm sector” atmosphere, which means higher moisture levels, instability, and breezy south winds to accompany those warm temperatures. During this period, it appears rain chances should be relatively low. However, with the amount of moisture and unstable air present, and a few weak upper-level disturbances moving nearby in the upper-level wind flow, a few showers or a stray storm can't be ruled out. The threat for organized storms should stay north and west of the metro through at least Thursday afternoon.

NAM forecast of temperatures at 4 pm on Wednesday, April 8. Highs in the lower 80s are expected both Tuesday and Wednesday in the metro, with only slight shower and thunderstorm chances.

Thursday - severe weather possible

On Thursday afternoon, things will begin to change, as a strong low pressure system moves northeast out of the Plains states into the Upper Midwest, with a cold front trailing the low and approaching the western border of Arkansas near lunchtime. Thunderstorms should develop and organize along and ahead of the front within the established unstable airmass and move toward the Mid-South region by Thursday evening and night. There remains some uncertainty on the exact timing of when the metro might be affected by the strongest storms, as models continue to show a bit of disagreement on the speed of the front.  Nevertheless, thunderstorms should become likely by some point Thursday night.

Precipitation forecast from the GFS model between 7 pm Thursday and 1 am Friday, indicating likely widespread showers and thunderstorms nearby/in the metro area. Heavy rainfall amounts (1" or greater) possible. Graphic courtesy WxBell.
GFS model forecast of CAPE, which is a measure of instability, for Thursday evening.
Values of 1000-2000 in the metro support the potential for strong thunderstorms. Graphic courtesy WxBell.

Severe weather risk

With a decent amount of instability in place, aided by relatively strong winds aloft, thunderstorms that move into the region may be strong to severe in nature. Currently, the Storm Prediction Center  (SPC) has the entire metro in a 15% risk area for severe weather (equivalent to a Slight Risk, category 2 out of 5) on its Day 4 outlook issued earlier this morning. Damaging wind is likely to be the primary hazard, but hail and some tornado risk cannot be discounted yet either. Early indications from the SPC show the highest tornado risk might be north of the metro, toward Missouri and Illinois, closer to the primary low pressure center (30% region in graphic below). Thunderstorms are also likely to contain a large amount of rainfall, so a risk of localized flash flooding may exist as well.

Severe weather risk outline valid for Thursday, April 9 via Storm Prediction Center.
The metro area is within the 15%/Slight Risk (Category 2) area.

Friday into the weekend

It appears the front should push through the region with relative ease by early Friday, which would mean drying conditions and slightly cooler temperatures into the early part of the weekend. However, that might be short lived as another active pattern looks to develop by next Sunday, which may persist into much of next week. We’ll be looking closer into those possibilities in the days ahead and after Thursday’s event passes!

Of course, you’ll want to stay with MWN via our social media channels listed below in the upcoming days as we’ll have more updates on severe weather chances as the event draws closer. Now is also a good time to download the MWN mobile app and add StormWatch+ within the app for instant watches and warnings during severe weather. These push notification-based alerts will only sound for the location(s) that are of interest to you and for the alert types that you select, at the times you want them. MWN is the only LOCAL source of weather information that provides this life-saving service. Links are provided below for more information or to download.

Kevin Terry
MWN Meteorologist Intern

Erik Proseus
MWN Meteorologist

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