SPC 0830Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0144 AM CST Mon Nov 16 2020 Valid 181200Z - 191200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorms are not expected on Wednesday or Wednesday night. ...Synopsis... A somewhat amplified but progressive mid/upper-level pattern will exist over the CONUS on Wednesday. The period will begin with an amplified upper ridge oriented from the Upper Midwest to the south-central states. Upper-level troughs will flank either side of the ridge, oriented near the Pacific and Atlantic coasts. As the Pacific trough shifts east, the upper ridge will deamplify as it migrates eastward across the eastern U.S., and overall upper flow pattern will become quasi-zonal. Strong surface high pressure east of the Mississippi River will maintain dry and stable conditions with little thunderstorm activity expected. A weak surface lee trough will develop over the central and southern Plains after 00z, resulting in modest Gulf return flow across Texas and perhaps into Oklahoma, though instability will be too meager and moisture too shallow to support any thunderstorm activity in this weak WAA regime. Isolated thunderstorms are possible near the Pacific Northwest coast from WA/OR into northeast CA ahead of a weak front moving onshore early in the period. Cold temperatures aloft will result in steep lapse rates and weak, albeit sufficient instability supporting sporadic lightning flashes. As the upper trough weakens and shifts east with time, thunderstorm activity should diminish into the evening/overnight hours. Weak instability and modest shear will preclude severe thunderstorm concerns. ..Leitman.. 11/16/2020
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