Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0359 AM CST Mon Dec 28 2020 Valid 311200Z - 051200Z ...DISCUSSION... ...Thursday/Day 4 and Friday/Day 5... An upper-level low is forecast to move northeastward across the southern Plains on Thursday as an associated cold front advances eastward into the lower Mississippi Valley. Moisture advection appears likely to continue ahead of the front across the central Gulf Coast states where surface dewpoints should be in the 60s F. Thunderstorms may develop during the day along the front with additional convection forming further east across the moist sector. Model forecasts suggest that a low-level jet will increase in strength, moving north-northeastward across Alabama during the late afternoon. Convective development may be favored on the nose of the low-level jet during the late afternoon and early evening. Additional storms may develop further to the west across the lower Mississippi Valley. Low-level and deep-layer shear profiles should be favorable for severe storms across those two areas. The main threats would be for tornadoes and wind damage. At this point, there is some uncertainty concerning how far the quality moisture can advect northward. For this outlook, have drawn the 15 percent contour across central Alabama, where there appears to be a good chance surface dewpoints will reach the lower to mid 60s F. On Friday, the upper-level low is forecast to move north-northeastward into the mid Mississippi Valley as southwest mid-level flow remains entrenched across the eastern Seaboard. Thunderstorm development will be possible along and ahead of a cold front as a low-level jet moves northward across the Carolinas. Low-level and deep-layer shear profiles are forecast to be favorable for severe storms with the main threats being tornado and wind damage. Have placed the 15 percent contour in the area where the chance for quality moisture and convective potential is maximized, according the latest ECMWF solution. ...Saturday/Day 6 to Monday/Day 8... On Saturday, an upper-level trough is forecast to move eastward across the southern Plains and mid Mississippi Valley as southwest flow remains over much of the Southeast. The upper-level trough is forecast to move across the Southeast on Sunday as a cold front advances southward across the Florida Peninsula. Severe storms can not be ruled out during the day on Sunday in central Florida but uncertainty concerning the model solutions is substantial at this time. On Monday, surface high pressure across much of the eastern third of the nation should limit thunderstorm potential.
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