Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0352 AM CDT Tue May 04 2021 Valid 071200Z - 121200Z ...DISCUSSION... Models indicate that blocking mid-level ridging may linger, but it may redevelop east of the Labrador Sea into the southern Greenland vicinity during this period. Coincidingly, a deep mid-level closed low appears likely to redevelop eastward, from near James Bay into areas near/north of the Canadian Maritmes, with initially amplified large-scale troughing to its south de-amplifying and while shifting northeastward out of the eastern U.S. As this occurs, a belt of westerlies emanating from the northern mid-latitude Pacific may become more prominent across and east of the Rockies. Latest medium-range guidance now appears much lower in amplitude with mid-level troughing developing across the Intermountain West this weekend, before progressing east of the Rockies, as well as with ridging building north of a subtropical high center developing near the Yucatan peninsula. However, in association with the progression of the troughing, there remains at least some potential for severe thunderstorm development this coming weekend into early next week across parts of the central and southern Great Plains into the lower Mississippi Valley and Gulf Coast states. This may be focused near the intersection of a developing frontal cyclone and dryline across the central Great Plains on Saturday, when lapse rates will be steep, but CAPE may still be a bit modest. Boundary-layer moisture return off the Gulf may become supportive of more substantive CAPE on Sunday, when the focus for strongest convection begins to become a bit more unclear. It is possible that this may become confined to portions of central Texas into the Red River vicinity, before spreading into portions of the western and central Gulf states on Monday, ahead of the southward advancing front. Due to sizable uncertainties, severe weather probabilities are maintained at below 15 percent.
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