Severe Storm Outlook Narrative (AC)
Issued by NWS
Issued by NWS
377 ACUS03 KWNS 260731 SWODY3 SPC AC 260730 Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0230 AM CDT Sun May 26 2024 Valid 281200Z - 291200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS TUESDAY AFTERNOON AND EVENING ACROSS PARTS OF THE TEXAS EDWARDS PLATEAU INTO EASTERN NEW MEXICO AND ACROSS PARTS OF NORTHEASTERN OREGON....CENTRAL AND NORTHERN IDAHO...AND WESTERN MONTANA... ...SUMMARY... Strong thunderstorms may impact parts of the Texas Edwards Plateau and Permian Basin into eastern New Mexico, as well as portions of the northern Rockies, Tuesday afternoon into Tuesday evening, accompanied by at least some risk for severe weather. ...Synopsis... Mid/upper flow across the northern mid-latitudes of the Pacific into western North America is forecast to remain modestly amplified and slowly progressive into and through this period. This appears likely to include larger-scale troughing migrating inland of the Pacific coast through the northern Rockies, and downstream ridging shifting eastward across the eastern Canadian Prairies and northern U.S. Great Plains. Downstream troughing, across and east of the upper Mississippi Valley, may be a bit slower, with one notable embedded short wave impulse forecast to dig southeast of the Upper Midwest into the lower Ohio Valley, but another notable impulse may accelerate east-northeast of the lower Great Lakes through the St. Lawrence Valley. This will be accompanied by a weakening surface cyclone and trailing reinforcing surges of cooler/drier air into the Northeast and across the Ohio Valley into the Southeast. Cooler and drier air may also advance southward through the southern Great Plains, beneath ridging within weaker westerlies across the southern mid- into subtropical latitudes. Seasonably high boundary-layer moisture may be in the process of shifting offshore of the southern Atlantic coast at the beginning of the period, and becoming confined to parts of the Edwards Plateau, Permian Basin and adjacent Rio Grande Valley. However, there is notable spread among the model output concerning this and other synoptic/sub-synoptic details. ...Southwest Texas into Eastern New Mexico... It currently appears that the dryline within weak lingering surface troughing across parts of eastern New Mexico through the Permian Basin/Edwards Plateau vicinity will become the focus for strong thunderstorm development Tuesday afternoon. It is possible that this may be aided by forcing for ascent associated with a weak perturbation progressing through the larger-scale ridging aloft. In the presence of steep lapse rates, it appears that the low-level moisture to the east of the dryline may be sufficient for moderate to large CAPE with daytime heating, with deep-layer shear, aided by veering winds with height in lower through mid-levels, conducive to the evolution of a few supercells. It is possible that severe probabilities could be increased further in later outlooks for this period. ...Northern Intermountain Region/Rockies... Models suggest that weak destabilization ahead of the inland advancing mid-level trough will support increasing thunderstorm development Tuesday afternoon and evening. The latest NAM, in particular, suggests that activity may consolidate across the mountains of central Idaho into western Montana, where evaporative cooling within a well-mixed sub-cloud boundary layer may contribute to downward mixing of 40-50 kt southwesterly lower/mid-tropospheric flow and a strengthening cold pool. It is possible that strong to severe surface gusts may spread east of the continental divide Tuesday evening, even as more weakly unstable inflow begins to weaken convection. ..Kerr.. 05/26/2024 $$