Thursday, April 5, 2018

Second verse, same as the first: Another round of rain & storms, then Canadian cold

Another big front arrives Friday evening, resulting in yet another heavy rain threat and trailing Canadian air, but first we take a quick look back at Tuesday evening's Moderate Risk event that was(n't)...

Tuesday's storm reports overlaid on the early afternoon severe weather outlook. Blue indicators are severe wind or wind damage, green dots are large hail, and red dots are tornadoes (NOAA/SPC)

Recap of Tuesday's storm system

The image above shows the severe weather outlook issued early Tuesday afternoon with the storm reports received by the National Weather Service Tuesday and Tuesday night. Blue indicators are severe wind or wind damage, green dots are large hail, and red dots are tornadoes. From a big picture perspective, we were pretty fortunate. There were hundreds of reports, but basically none in the metro, outside of a hail reports in northwest MS. There was a confirmed EF-1 tornado in the southern Missouri Bootheel.

Overall, clusters of storms to our west and northwest produced mostly hail, then as they formed into a squall line, there was plenty of strong wind and wind damage to our east. This is not an unusual pattern - in which individual storms become a line as they move east. We are often in the transition area. In this case, we still had clusters of storms when the front hit the river, with the primary ones near the metro going by just to our north and south.

Radar loop from about 7pm Tuesday evening as storms split the metro.

See the total rainfall from the same time period below. Note the gap where the red arrows are lined up. Clusters of storms north (including the tornadic one) and a large area of storms in the Delta to our south. Meanwhile, we didn't get enough rain to wash the pollen off. That's the way it goes sometimes. I'd much prefer this to showing you photos of damage in the city and lives ruined.

24-hour rainfall from Tuesday 7am-Wednesday 7am. (NWS / WxBell)

One final image that I believe is poignant, given the events of the week here in Memphis:

Looking ahead - another round of rain and cold weather

Full April sunshine on Wednesday wasn't enough to overcome the cold air behind that system and highs remained in the low 50s. As high pressure moved overhead, we had ideal conditions for a very chilly morning this morning with lows in the 30s. Despite getting back into the lower 60s today, the next system looms, and it too will escort another blast of air more fit for winter than spring.

Showers arrive overnight tonight with rain increasing in coverage and intensity Friday. Have your rain gear on hand! A few thunderstorms are possible, though not severe. We'll top out near 60 Friday after a more mild night tonight on southerly wind. By late tomorrow afternoon into the early evening, another potent front moves through the region. Look for a slightly better chance of storms as it does, with a very low end risk of a severe storm. SPC places north MS in a Marginal Risk (level 1/5), mainly for a hail threat. Higher chances of severe storms will be well south and west of the metro where instability and strong upper level wind will be higher as the front plows into the region. Rainfall amounts with this storm system will likely end up in the 1-2" range.

The severe weather outlook for Friday, showing the most likely area for severe storms well south and west of the metro. (NOAA/SPC)

Behind the front, during the evening hours Friday, steady rain is likely and temperatures will plummet on very gusty north wind. Believe me, if you are out, you will know when the front hits! Wind picks up to include 30 mph gusts and temperatures fall quickly into the 40s. For a few days now, we have been watching carefully the timing of departing precipitation and arriving cold air. Yes, it is the end of the first week of April. Mother Nature doesn't care.

Fortunately, rain looks to move out overnight Friday night and temperatures look to stop falling when they get to the mid 30s. (Yes, mid THIRTIES.) So no wintry precipitation is expected in the metro. However, a light wintry mix is possible in northwest TN, the bootheel, and northern AR. Ridiculous, I know.


The weekend and beyond

For you early risers Saturday, wind chills will be in the 20s, temperatures in the 30s, but no frost is likely because of the gusty wind. Bundle up! Clouds depart during the day Saturday, but a cool wind makes it feel colder than the 50-degree high we will top out at. Another decent radiational cooling night is ahead Saturday night, meaning lows drop into the low to mid 30s Sunday morning. Picture this (Thursday) morning, but a few degrees colder. You'll want to protect outdoor vegetation that could be harmed by cold weather Saturday night.

Fortunately, a rebound is in order next week and the crystal ball says this weekend should be the last really cold blast of the season. We're looking at 70s by mid-week and continued warming further out.



Erik Proseus
MWN Meteorologist

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MWN is a NOAA Weather Ready Nation Ambassador Meteorologist Erik Proseus is an NWA Digital Seal Holder

Monday, April 2, 2018

Severe weather threat materializing for Tuesday

A warm front has been moving north across the metro today, putting the region back into warmer, more muggy air that has remained south of us today. The warm front is lifting north as low pressure moves east across the Missouri Valley from Kansas towards the southern Great Lakes region by tomorrow evening. Meanwhile, a potent front sweeps towards the region on Tuesday.

Surface map from the National Weather Service valid overnight tonight shows the warm front just to our north with strong low pressure over Kansas.
On Tuesday, the Mid-South will be firmly entrenched in the warm sector of the approaching system, resulting in a windy day with southerly gusts of 30-40 mph and eventually partly sunny skies. (A Wind Advisory is in effect for counties east of the Mississippi River on Tuesday.) The appearance of the sun will boost instability indices, meaning the air will be more unstable, similar to turning the heat up on a tea kettle (or a pot of water on the stove, for those that don't drink hot tea!).


As the front approaches by late afternoon, thunderstorms will develop to our west and gain strength as they move into an airmass marked by temperatures in the mid 70s and dewpoints in the lower to mid 60s. A watch box appears likely. As the storms band together into a squall line, they will race across the Memphis area during the early evening, also likely prompting severe weather warnings.

The high-resolution NAM model from Monday morning projects a line of strong storms across the heart of the metro between 7-8pm Tuesday. (WxBell)

The bottom line:

What: Squall line of strong to severe storms, moving quickly east
When: 5-10pm CDT, Tuesday (likely moving across the city in the 6-8pm timeframe)
Threats (highest to lowest):

  1. Damaging wind of 60+ mph (moderate-high threat)
  2. Hail up to 1", or quarter size (moderate threat)
  3. Isolated tornado embedded within the squall line (low threat)
  4. Heavy downpours that could lead to ponding of water (low threat)

The follow graphic summarizes the event, as of 3:30pm Monday:

Behind the front, wind will shift to the northwest and remain gusty, quickly ushering in much cooler air. Temperatures will fall to near 60 degrees immediately when the line hits and then through the 50s during the late evening and 40s overnight as skies clear. Wednesday morning lows will be in the lower 40s with wind chills in the 30s! Despite sunshine, highs only top out in the 50s Wednesday with a reduced north wind. Thursday morning lows will be in the 30s and could result in widespread frost, particularly outside the city.

Be prepared!

Tuesday early evening brings a decent potential for severe storms. Know where you will be during the times of concern and what your action plan will be if warnings are issued. Keep in touch with your favorite local weather sources throughout the day for any updates. And finally, have multiple ways to receive these warnings. We strongly recommend StormWatch+ Alerts in the MemphisWeather.net mobile app, available through a one-time in-app purchase, to provide you pinpoint warnings for your specific location.

In addition, gusty wind throughout the day will require that you secure any loose outdoor objects in order to avoid losing them! Finally, don't be surprised by temperatures that are about 35 degrees colder Wednesday morning than they are on Tuesday afternoon!

Erik Proseus
MWN Meteorologist

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Follow MWN on Facebook and Twitter for routine updates and the latest info!
Complete MWN Forecast: MemphisWeather.net on the mobile web or via the MWN mobile app
Download our iPhone or Android apps, featuring StormWatch+ severe weather alerts!
MWN is a NOAA Weather Ready Nation Ambassador Meteorologist Erik Proseus is an NWA Digital Seal Holder