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Helping Business Weather the Storm

National Weather Summary for Monday, August 20, 2018

by David Moran, on Aug 20, 2018 11:16:38 AM

Thunderstorms are forecast to develop across the Central Mississippi Valley on Monday ahead of a cold front. There will be a risk for excessive rainfall from the Midwest into the Mississippi River Valley as an area of low pressure moves northeastward. An upper level system will aid in the development of thunderstorms across southern Virginia and North Carolina. Upslope flow will allow for a risk of thunderstorms across the Northern Rockies.

  • Thunderstorms for the Central Mississippi Valley Monday
  • Excessive Rainfall Monday for the Midwest and Mississippi Valley
  • Potential for Thunderstorms across Southern Virginia and North Carolina Monday
  • Risk for Thunderstorms Monday across the Northern Rockies
  • Thunderstorm Potential for the Appalachians and Mid Atlantic on Tuesday
  • Excessive Rainfall Tuesday for the Appalachians and Mid Atlantic
  • Potential for Thunderstorms  across the Southern High Plains Tuesday
  • Potential for Excessive Rainfall Tuesday for Arizona
  • Thunderstorms for the Southern High Plains Wednesday

US Hazards Monday, August 20, 2018
US Hazards

Thunderstorms for the Central Mississippi Valley Monday
An area of low pressure over southern Iowa will slowly move to the northeast with a cold front extending southward. An upper level low is forecast to provide additional support for the development of thunderstorms. By the afternoon and evening, with instability building and forcing from the cold front, thunderstorms are expected to develop. Strong winds will be the primary hazard with these storms, but hail and an isolated tornado cannot be ruled out.

Major Cities in Region: Memphis, TN, Paducah, KY

Thunderstorm Risk for Monday, August 20, 2018
Thunderstorm Risk for Monday

Excessive Rainfall Monday for the Midwest and Mississippi Valley
As the area of low pressure described above continues to move northeastward, heavy rain is expected across the Midwest and into the Mississippi Valley. Rainfall amounts of 1-2 inches with locally higher amounts in excess of 3 inches are expected. 

Major Cities in Region: Des Moines, IA, Cedar Rapids, IA, Chicago, IL, Grand Rapids, MI

Rainfall Accumulation for Monday, August 20, 2018
Rainfall Accumulation for Monday

Potential for Thunderstorms across Southern Virginia and North Carolina Monday
Widespread thunderstorm activity is expected to continue throughout the region on Monday. With a jet streak passing over the region into the afternoon, additional strong to severe thunderstorm development is expected. Strong wind gusts and large hail will be the primary hazards along with frequent lightning and heavy rainfall. 

Major Cities in Region: Asheville, NC, Charlotte, NC, Raleigh, NC, Wilmington, NC

Thunderstorm Risk for Monday, August 20, 2018
Thunderstorm Risk for Monday

Risk for Thunderstorms Monday across the Northern Rockies
Upslope flow and moisture at the surface will allow for the development of thunderstorms during the afternoon and early evening. Upper level support will be in place due to an upper level trough moving across the region. Strong winds and large hail will be the primary hazards with any storms that develop. 

Major Cities in Region: Butte, MT, Bozeman, MT

Thunderstorm Risk for Monday, August 20, 2018
Thunderstorm Risk for Monday

Thunderstorm Potential for the Appalachians and Mid Atlantic on Tuesday
The area of low pressure over the Midwest is expected to continue intensifying as it tracks northeastward with the cold front extending to the south. An upper level system is forecast to pass over the region, providing upper level support for thunderstorm development. With daytime heating and available moisture at the surface, along with the advancing area of low pressure and cold front, strong to severe thunderstorms are expected. Strong winds and large hail will be the primary hazards with these storms. 

Major Cities in Region: Pittsburgh, PA, Buffalo, NY, Richmond, VA, Washington, DC, Baltimore, MD

SPC Convective Outlook for Tuesday, August 21, 2018
SPC Convective Outlook for Tuesday

Excessive Rainfall Tuesday for the Appalachians and Mid Atlantic
In addition to the thunderstorm risk described above, there will be a risk for excessive rainfall. Rainfall amounts will range 1.50-2.00 inches with locally higher amounts in excess of 3.00 inches expected. 

Major Cities in Region: Columbus, OH, Pittsburgh, PA, Washington, DC, Baltimore, MD

Rainfall Accumulation for Tuesday, August 21, 2018
Rainfall Accumulation for Tuesday

Potential for Thunderstorms across the Southern High Plains Tuesday
Plentiful low level moisture is expected to be in place across the Southern High Plains on Tuesday. With upslope flow providing lift, isolated strong to severe thunderstorms may develop during the afternoon and evening. Strong winds and large hail will be the primary hazards, along with frequent lightning and heavy rainfall. 

Major Cities in Region: Colorado Springs, CO, Trinidad, CO, Lamar, CO, Dumas, TX, Guymon, OK

SPC Convective Outlook for Tuesday, August 21, 2018
SPC Convective Outlook for Tuesday

Potential for Excessive Rainfall Tuesday for Arizona
An upper level trough is forecast to dig into the Southwest, causing the area of low pressure over Nevada to shift slightly southward. With the trough and area of low pressure, increased moisture will lead to scattered showers and thunderstorms across Arizona. Rainfall accumulations will range 0.50-0.75 inch with locally higher amounts in excess of 1.25 inches.

Major Cities in Region: Flagstaff, AZ, Phoenix, AZ, Tucson, AZ

Rainfall Accumulation for Tuesday, August 21, 2018
Rainfall Accumulation for Tuesday

Thunderstorms for the Southern High Plains Wednesday
Upslope flow is forecast to continue to persist with moisture remaining in place at the surface on Wednesday. Upper level winds will be sufficient to support the development of strong to severe thunderstorms. By the afternoon and evening, isolated thunderstorms are forecast with strong winds and large hail the primary hazards.

Major Cities in Region: Trinidad, CO, Lamar, CO, Dumas, TX, Guymon, OK

SPC Convective Outlook for Wednesday, August 22, 2018
SPC Convective Outlook for Wednesday

A Look Ahead
A developing area of low pressure will bring a potential for showers and thunderstorms to portions of the Northern Plains on Thursday. This activity will move into the Upper Midwest and Great Lakes on Friday. By Saturday, a few thunderstorms may develop across portions of the Upper Midwest ahead of a cold front. Additional activity will be possible on Sunday.

Topics:Nowcast/Forecast

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