Extreme Temperatures, Heavy Rain/Snow, Severe Weather

Wet Weather and High Humidity Are Coming

You know that dry weather we’ve had for much of the Spring and Summer? How about those warm days with low humidity? Well, both will be a distant memory by this time next week.

A weather pattern that is both typical and atypical of summer at the same time is going to settle into the nation over the next several days. The typical part is that we’ll have a ridge of high pressure off the East Coast, and another one in the Southwest. The ridge off the East Coast will result in heat and humidity up and down the coastline for the next several days. The ridge in the Southwest will bring very hot conditions to the Southwest and especially the Southern Plains, where record highs are expected over the next several days. The Atypical part is across the Midwest. Normally, in between the two ridges of high pressure you’d have a trough of low pressure, but in this case, we actually have a closed upper-level low pressure system. While these are common in the fall, winter, and spring, they usually don’t occur much in the summer. This will bring cooler than normal conditions into the Midwest for the next few days.

500wh.conus

What is this, April? The upper-level pattern features ridges of high pressure in the Southwest and off the East Coast, and an upper-level low pressure system in the Great Lakes. Image provided by Pivotal Weather.

With high pressure anchored off the East Coast, a warm and humid pattern will set up for much of next week (and possibly longer). Notice that we said “warm”, and not “hot”. While temperatures will still be a little above normal this weekend into much of next week, highs will only be in the 80s to lower 90s for most of the Eastern US. While the temperatures won’t be that bad, humidity levels will. With high pressure anchored off the East Coast, a southerly flow will help moisture stream northward from the tropics right up the East Coast this weekend and into much of next week. Dewpoints will be in the upper 60s and 70s across the region, so even though temperatures may not be hot, it will feel oppressive across much of the region.

GFS Pressure Lev East Coast USA Precipitable Water

Moisture will stream northward from the tropics into much of the East Coast over the next several days. Loop provided by WeatherModels.com

 

With a warm and humid airmass in place for much of the week, it won’t take much for showers and thunderstorms to develop each day. With plenty of available moisture, some of these storms will end up producing very heavy rainfall. While the map above is a forecast that shows widespread coverage of heavy rain, in many cases, the storms will be very localized. Some locations could get hit by slow-moving thunderstorms over and over, while other spots a few miles away get little to no rainfall. Across the Mid-Atlantic States, where heavy rain led to flooding during the Spring, similar conditions are possible again for the next week. Across the Northeast, things are a little different.

GFSMA_prec_precacc_204

That’s a lot of rain from the Carolinas northward over the next week or so. Image provided by College of DuPage.

 

Here in New England, and in New York too, much of the Spring and early summer has been very dry. Localized thunderstorms have brought heavy rain to a few spots, especially earlier this week, but overall, rainfall has been well below normal across the area. Some relief will come this weekend. A weak low pressure system will move across the region late Saturday into Sunday as an upper-level low pressure system moves into the Midwest. The surface low will bring heavy rain and some gusty winds to parts of Southern New England and southeastern New York. The heaviest rain is expected late Saturday night into early Sunday morning, so neither day should be a complete washout. Once that system moves by, a warm and humid airmass will settle in, with a daily chance for showers and thunderstorms this week. Again, some places could get drenched, and some might get missed completely. Some could see off-and-on showers and storms for 6 hours, some could get a shower that lasts 6 minutes. Basically, it’ll be like living in Florida for a week, without having to worry about looking outside and finding an alligator in your swimming pool.

20180717_Northeast_trd

It’s been very dry across New England and New York for a few months now, with drought conditions developing. Image provided by the National Drought Monitor.

 

Think warm and humid conditions with a daily chance of thunderstorms isn’t fun? It could be worse. Normally, it’s hot across Texas and the Southwest during the summer. This week though, the ridge of high pressure that is currently setting up across the Southern Plains and Southwest will bring in temperatures that are well above normal. In fact, record highs are expected for the next several days across much of Texas, as temperatures soar past 100 across much of the state, with some locations possibly exceeding 110 degrees. Unlike when the models were forecasting those temperatures here a few weeks ago, this time it’s going to happen. The heat won’t be confined to the Lone Star State either, with triple-digit highs also expected from parts of the Lower Mississippi Valley into the Southern Plains as well as parts of Colorado and New Mexico. There won’t be much, if any, relief at night either, as low temperatures will stay in the 70s, with many locations, especially urban areas like the Dallas-Fort Worth Metroplex likely not dropping below 80 degrees for low temperatures.

ndfd_record_high_tx_2

Friday looks to be the hottest day across the Southern Plains and Texas, with many record highs expected to be broken. Image provided by WeatherModels.com

 

As we head into next week, the heat will ease a bit across Texas and the Southern Plains, but the core of the intense heat will shift westward into the Desert Southwest. High temperatures will top 110 degrees across much of the area for the first half of next week, with the usual hot spots such as Lake Havasu City, Arizona; Laughlin, Nevada; and Death Valley, California likely exceed 120 degrees during some of the afternoons. Highs will also top 100 across much of interior California once again. Anyone wanna place a bet as to whether Death Valley reaches 125? Better yet, will they have a night where the temperature doesn’t drop below 100 (it’s happened before)?

fema04_swody2

A severe weather outbreak is possible on Friday across the Ohio and Tennessee Valleys. Image provided by the Storm Prediction Center.

Meanwhile, an upper-level low pressure area will settle into the Midwest. With the clash in airmasses along a cold front, showers and thunderstorms will develop. Some of these storms will become strong to severe on Friday, especially across the Ohio and Tennessee Valleys. The main threats with any storms that develop will be strong winds, large hail, and torrential rainfall that could trigger flash flooding. Some tornadoes are also possible. The storms may start during the morning closer to the Great Lakes, with the afternoon and evening seeing the most widespread activity across the region. While activity should weaken at night, the threat of severe weather will continue across southern and eastern parts of the region.

NAM-WRF 3-km null Simulated Radar

Strong to severe thunderstorms are expected across the Midwest on Friday. Loop provided by WeatherModels.com

 

As these storms crossed the Midwest today, they produced wind gusts to 90 mph and more than 30 tornadoes across Iowa. The town of Marhsalltown was devastated by a tornado earlier today. How bad was it? We’ll end this post with the Storm Report from the National Weather Service Office in Des Moines with the description of what happened in Marshalltown:

 

REPORTS OF CATASTROPHIC DAMAGE, INCLUDING 
VEHICLES MISSING, VEHICLES OVERTURNED, TOPS
OF BUILDINGS GONE, TREES DOWN, POWER LINES,
GAS LINES, ETC...
Standard

One thought on “Wet Weather and High Humidity Are Coming

  1. Pingback: Weekly Outlook: July 23-29, 2018 | Storm HQ

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