Friday, April 20, 2018

Spring struggling against the lingering forces of winter

Despite being past Tax Day, with most foliage blooming or budding or growing, late winter still seems to want to keep popping its head up like an annoying rodent from Whack-a-Mole.


The past couple of weeks have been evidence, given that we had an 80-degree day a week ago, only to be followed up 3 days later by a record cool day in the mid 40s and several recent mornings with wind chill factors and patchy frost. A persistent pattern featuring an upper level trough over the eastern U.S. is to blame. It also is responsible for a relatively slow start to severe weather season this spring. What does the near-future hold?

Friday and Saturday

For now, we're back in "warm-up" mode after some frosty areas early this morning. April sun and wind that has shifted to the east, rather than north, means temperatures climbing towards 70 today. Saturday will see an increase in clouds, but wind that shifts further around towards the south. Pair it with a morning low that is about 10 degrees warmer, and we should make it to 70 without much trouble. That is still several degrees below our mid-April average though. There is a low chance of some afternoon sprinkles, but overall your Saturday looks to be pretty pleasant for outdoor activities and spring festivals!

Surface map for Friday evening. The low pressure in the Central Rockies will move slowly our direction, dragging the associated precipitation this way, but not before Saturday night. (NWS/WPC)

Saturday night into Sunday

This is when spring rains make their return as weak low pressure moves slowly out of the southern plains and scoots by to our south. Since it will be to our south, with little in the way of instability feeding into the area, I expect we'll see rain and very little thunder. That rain arrives Saturday night (chances increase during the evening) with the wettest period late overnight into Sunday morning. However, scattered showers stick around most of Sunday as the low moves slowly by. It may not be a washout, but you can just pretend that it is as timing any short dry spells will be difficult. Total rainfall will likely end up in the 1-2" range by Sunday night. Temperatures will be below average, as expected on a rainy day, but not too cold - lows in the mid 50s and highs in the lower to mid 60s.

Forecast precipitation amounts through Monday morning from the NWS Weather Prediction Center.

The Severe Weather Outlook for Sunday from the Storm Prediction Center shows that Memphis will be on the edge of a "general" risk of thunderstorms. No severe weather is expected, and in fact, there is a low chance of any thunder at all.

Early next week

As the low slowly shifts east across the southeast U.S. Monday, we'll see "wrap-around" showers off and on Monday, but it will be drier than Sunday. Temperatures will be very similar to Sunday though, so look for 60s in the afternoon. We should catch a bit of a break Tuesday. I don't expect a ton of sun, but rain chances should only be about 20% as the low weakens and departs the region. There is no strong high pressure center replacing it though, thus the lingering clouds mixing with a bit of sun. Temperatures will be a few degrees warmer, maybe pushing 70 again. The mid-week will see another front push through on Wednesday, bringing yet another chance of scattered showers and highs near 70.

By Monday morning, the rainy low pressure center will be well to our southeast, but still close enough to bring a chance of some showers to the area. (NWS/WPC)

Looking ahead

The longer-range shows a dry day Thursday and another front on Friday, but temperatures that reach 70 degrees both days. Fortunately, there are no cold air masses behind any of these, so there is no frost or really cold mornings in the crystal ball. If all goes to plan, we should see things clear up in time for the last weekend in April. Long-range climate models are split on May, but I am thinking that temperatures will be a bit below normal to start the month, then closer to normal by mid to late May. By late May, "near normal" means mid 80s, so don't be surprised if we warm up fairly quickly once we get into May!

The NOAA May outlook indicates slightly above average odds of above normal temperatures for the month, hinging fairly tightly to the American climate models. (NOAA/CPC)

On the other hand, the European ensemble models forecast for the next 6 weeks (46 days) is for below normal temperatures. We'll see which solution wind this battle! (WxBell)

As always, you can get the latest forecasts for the next 7 days, as well as current conditions, StormView Radar, and StormWatch+ severe weather alerts all via the MemphisWeather.net app. Find it at the links below and follow us on social for routine updates.

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

Friday, April 13, 2018

Update on tonight's severe storm threat

A strong spring cold front is moving towards the Mid-South, but it will take its sweet time, not arriving until Saturday afternoon. However, ahead of that, storms will form to our west later this afternoon and begin a slow march across Arkansas this evening. That is where the Storm Prediction Center has forecast the highest chance of severe weather, including large hail, damaging wind, and a few tornadoes.

Timing

As the storms move east overnight, they will encounter slightly more stable air, resulting in a general decrease in storm intensity, as well as organization into a squall line. The line will likely affect the metro between midnight and 4am, though a couple of high-resolution models favor a slightly earlier approach closer to 11pm. The good news for those who have evening plans, including the Friday Night Stripes event at the Liberty Bowl, is that the later time should allow those events to wrap up prior to the storm's arrival. However, there is a chance of showers this evening, so I'm not necessarily indicating it will be completely dry until the line hits.

The Memphis area is under an Enhanced Risk (level 3/5) of severe weather tonight, mainly after midnight. Damaging wind and very heavy rain are the primary threats.

Threats

While all modes of severe weather are possible to our west, where greater instability resides, as the line approaches, the primary threat shifts to the possibility of damaging wind. There is also an isolated tornado threat due to the magnitude of the wind with this system, but that threat drops off considerably as the line nears the Mississippi River. Finally, due to the copious amount of moisture in the atmosphere tonight and slow motion of the system, the storms and heavy rain that trails them could produce areas of flash flooding, particularly in the urban setting. Always be cautious of crossing water that covers a road in the dark. Rainfall totals by sunrise Saturday could be near 2-3" with up to an additional inch possible Saturday. A Flash Flood Watch is in effect through 1pm Saturday.

SPC-forecast probabilities of severe weather occurring within 25 miles: 5-10% chance of a tornado, 5% chance of large hail, and about a 45% chance of damaging wind. (SPC)

Prepare

Obviously with storms expected overnight, when many of you are already asleep, you need to have some way of getting warnings that will wake you up. NOAA Weather Radio works great and is recommended. We also highly recommend you check out StormWatch+ in the MemphisWeather.net mobile app. For about 1/3 of the cost of a weather radio, you get fully customizable, portable weather alerts that will wake you up only for the most severe storms. Visit app.memphisweather.net for more on the MWN mobile app, or simply activate StormWatch+ from the SW+ tab in your MWN app!

If you have plans to be out tonight, we recommend being where you have access to a safe place by about 11pm. Of course, we'll keep you updated on the latest timing and threats via our social media feeds, which you will find linked below.



Saturday

As for Saturday, because the system is moving so slowly, and the likelihood of a weak low pressure center forming and moving north along the front, there is a good chance of additional rain during the day. Models are somewhat split on the timing for Saturday, but my best educated guess says that lingering rain will occur into the morning, with a lull around mid-day, and then additional shower chances in the mid-to-late afternoon time period. In addition, the atmosphere is expected to destabilize again tomorrow afternoon, mainly east of Memphis, as the front finally moves through. Thus, a thunderstorm can't be completely ruled out, especially east of the city.

Areas east of the Mississippi River in the metro are under a Marginal Risk (level 1/5) of severe weather Saturday. The most likely location for any severe storms will be well to our south and east.. (SPC)
Dry and much cooler weather arrives on Sunday with clouds likely to linger as well. The dry trend looks to continue for most of next week with quickly moderating temperatures after Monday.

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 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