868 ACUS48 KWNS 220820 SWOD48 SPC AC 220819 Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0319 AM CDT Thu Oct 22 2020 Valid 251200Z - 301200Z ...DISCUSSION... ...Sunday/Day 4 to Tuesday/Day 6... On Sunday, the medium-range models have west-southwesterly mid-level flow across most of the United States. A cold and dry air mass is forecast to be in place across much of the northern and central U.S. The moist sector should be confined to the Gulf Coast States where isolated thunderstorms could develop Sunday afternoon. Weak instability should limit a severe threat. On Monday, the models are forecasting a subtle shortwave trough to move northeastward from the mid Mississippi Valley into the Ohio and Tennessee Valleys. Thunderstorm development will be possible ahead of this feature Monday afternoon. However, instability is forecast to be weak on Monday suggesting a limited severe weather risk. On Tuesday, an upper-level low is forecast to move across the Desert Southwest. Southwest mid-level flow should be located across the southern and eastern states. In spite of a moist air mass across the Southeast, instability is forecast to remain weak during the day. Although some thunderstorm development could occur from the Arklatex into the central Gulf Coast States, any severe threat is expected to remain marginal. ...Wednesday/Day 7 and Thursday/Day 8... The medium-range models move an upper-level low across the southern High Plains on Wednesday and into the Red River Valley and Arklatex from Thursday into Thursday night. Thunderstorm development will be possible each day to the east of the upper-level low near the northwestern edge of the moist sector. Although instability is forecast to be weak ahead of the upper-level low, a marginal severe threat can not be ruled out each day. The risk for hail and strong gusty winds would be maximized in the Arklatex on Wednesday and in the Southeast on Thursday. However, predictability this far out in the forecast period remains quite low. ..Broyles.. 10/22/2020
