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Helping Business Weather the Storm

National Weather Summary for Friday, July 20, 2018

by David Moran, on Jul 20, 2018 11:07:13 AM

A risk for widespread severe thunderstorms is likely from central Michigan southward into the Southeast on Friday. Some of this activity may produce excessive rainfall across the Ohio and Tennessee Valleys. Thunderstorms are expected from the western Ozarks into eastern Colorado ahead of a cold front. Scattered showers and thunderstorms are expected to develop during the afternoon across southern Arizona. There will be a risk for excessive rainfall across the coastal Carolinas as an area of low pressure moves across the region.

  • Severe Thunderstorms Expected Friday from Central Michigan into the Southeast
  • Excessive Rainfall across the Ohio and Tennessee Valleys on Friday
  • Thunderstorms Friday from the Western Ozarks into Eastern Colorado
  • Potential for Thunderstorms across Southern Arizona on Friday
  • Risk for Excessive Rainfall Friday for the Coastal Carolinas
  • Thunderstorm Potential from the Tennessee Valley into Coastal Georgia and Carolinas on Saturday
  • Risk for Thunderstorms Saturday across the Western High Plains
  • Excessive Rainfall for the Mid Atlantic and Northeast Saturday and Sunday
  • Thunderstorms Sunday for the Northern Plains
  • Potential for Thunderstorms from Northern Florida through South Carolina on Sunday

US Hazards Friday, July 20, 2018
US Hazards

Severe Thunderstorms Expected Friday from Central Michigan into the Southeast
Widespread severe thunderstorms are likely from central Michigan into portions of the Southeast on Friday. While marginally severe thunderstorms may develop this morning and into the early afternoon, conditions will become increasingly favorable for thunderstorms from the afternoon into the overnight hours. Strong instability and wind shear will be conducive for the development of thunderstorms capable of producing damaging winds and very large hail. A few tornadoes cannot be ruled out during the afternoon and evening. The greatest potential will likely be across west central Kentucky and Tennessee. 

Major Cities in Region: Memphis, TN, Evansville, IN, Indianapolis, IN, Nashville, TN, Louisville, KY, Cincinnati, OH, Detroit, MI, Toledo, OH, Columbus, OH, Cleveland, OH

Thunderstorm Risk for Friday, July 20, 2018
Thunderstorm Risk for Friday

Excessive Rainfall across the Ohio and Tennessee Valleys on Friday
In addition to the severe weather potential described above, there will be a risk for excessive rainfall. Widespread rainfall amounts in excess of an inch and locally higher amounts in excess of 2.00 inches are expected. This will allow for a risk for flooding. 

Major Cities in Region: Evansville, IN, Cincinnati, OH, Columbus, OH

Rainfall Accumulation for Friday, July 20, 2018
Rainfall Accumulation for Friday

Thunderstorms Friday from the Western Ozarks into Eastern Colorado
A cold front will slowly move southward across the Central Plains throughout the day. With strong instability ahead of the front, there will be the potential for thunderstorm development. Any thunderstorms that develop will have the potential to become severe. Damaging winds and large hail will be the primary hazards this afternoon and evening. Storm potential will be highest across the western High Plains, including western Kansas and eastern Colorado where upslope winds may allow for more widespread development. 

Major Cities in Region: Goodland, KS, Wichita, KS, Joplin, MO

Thunderstorm Risk for Friday, July 20, 2018
Thunderstorm Risk for Friday

Potential for Thunderstorms across Southern Arizona on Friday
Scattered showers and thunderstorms will likely develop across the region by mid to late afternoon. Damaging winds and large hail will be the primary hazards with the stronger storms. Activity should diminish after sunset.

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

Thunderstorm Risk for Friday, July 20, 2018
Thunderstorm Risk for Friday

Risk for Excessive Rainfall Friday for the Coastal Carolinas
A slow moving area of low pressure over southeast Georgia is producing scattered showers and thunderstorms across central and southeast South Carolina this morning. More significant development is expected during the afternoon with the increase in daytime heating. Rainfall totals of 1-2 inches with locally higher amounts in excess of 3 inches are expected. 

Major Cities in Region: Charleston, SC, Myrtle Beach, SC, Wilmington, NC

Rainfall Accumulation for Friday, July 20, 2018
Rainfall Accumulation for Friday

Thunderstorm Potential from the Tennessee Valley into Coastal Georgia and Carolinas on Saturday

Cooling temperatures and strengthening winds within the mid to upper levels of the atmosphere will overspread warm, moist air near the surface. Moderate instability and increasing wind shear will allow daily thunderstorm activity to become more widespread. Damaging winds and large hail will be the primary hazards, but an isolated tornado cannot be ruled out. The strongest storms will likely develop by mid to late afternoon before tracking southeastward.

Major Cities in Region: Birmingham, AL, Chattanooga, TN, Knoxville, TN, Atlanta, GA, Macon, GA, Charlotte, NC

SPC Convective Outlook for Saturday, June 21, 2018
SPC Convective Outlook for Saturday

Risk for Thunderstorms Saturday across the Western High Plains
An area of low pressure will move very slowly across eastern Montana throughout the day on Saturday. A cold front will extend southwestward into Wyoming. To the north, an area of low pressure will move into southern Canada. Ahead of this system, moderate instability will be present. Thunderstorms will be isolated as they develop during the afternoon and evening with damaging winds and large hail being the primary hazards with these storms. 

Major Cities in Region: Glendive, MT, Rapid City, SD

SPC Convective Outlook for Saturday, June 21, 2018
SPC Convective Outlook for Saturday

Excessive Rainfall for the Mid Atlantic and Northeast Saturday and Sunday
An area of low pressure off the East Coast will have the potential to produce a large area of moderate to heavy thunderstorm activity. Heavy precipitation may be underway Saturday morning from coastal North Carolina into southeast Virginia and the Delmarva peninsula. By late Saturday afternoon, the precipitation may extend into southern New Jersey and the New York City metro. The majority of the rainfall may hold off until Saturday night into Sunday. Rainfall amounts will range 1-2 inches with locally higher amounts in excess of 3 inches. 

Major Cities in Region: Washington, DC, Baltimore, MD, Philadelphia, PA, New York, NY, Albany, NY

Rainfall Accumulation for July 21-22, 2018
Rainfall Accumulation for Saturday and Sunday

Thunderstorms Sunday for the Northern Plains
A slow-moving area of low pressure will move into Nebraska and the Dakotas on Sunday. With moderate instability in place and an upper level disturbance providing forcing, thunderstorms will likely develop. Damaging winds will be the primary hazard with this activity. 

Major Cities in Region: Bismarck, ND, Pierre, SD, Fargo, ND

SPC Convective Outlook for Sunday, July 22, 2018
SPC Convective Outlook for Sunday

Potential for Thunderstorms from Northern Florida through South Carolina on Sunday
A weak area of low pressure will extend across the Southeast on Sunday. An upper level trough moving across the region will increase wind shear across the region. With this wind shear and instability in place, thunderstorms are expected to develop. Damaging winds and hail will be the primary hazards with these storms. 

Major Cities in Region: Columbus, GA, Tallahassee, FL, Macon, GA, Jacksonville, FL, Savannah, GA, Charleston, SC, Myrtle Beach, SC

SPC Convective Outlook for Sunday, July 22, 2018
SPC Convective Outlook for Sunday

A Look Ahead
Showers and thunderstorms are expected along the East Coast on Monday ahead of a cold front. This activity may continue into Tuesday. A cold front across the Northern Plains and Upper Midwest will be the focus for thunderstorm development on Tuesday. By Wednesday, thunderstorms will extend from the Great Lakes into the Central Plains. Showers may develop across the Northeast and Mid Atlantic on Thursday ahead of a cold front. 

Topics:Nowcast/Forecast

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