Storm Prediction Center Forecast Products Page (2024)

 SPC AC 251631 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1131 AM CDT Thu Jul 25 2024 Valid 251630Z - 261200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PARTS OF CENTRAL AND NORTHEAST MONTANA... ...SUMMARY... Scattered severe thunderstorms capable of 60-75 mph gusts are forecast across portions of central and northeast Montana late this afternoon into the evening. ...Montana/Northern Rockies to Great Basin... Water-vapor imagery this morning shows an upper-level trough moving east from British Columbia toward Alberta/Saskatchewan, with strengthening cyclonic westerlies overspreading the northern Rockies/Montana. Model guidance continues to indicate scattered thunderstorm development initiating off the higher terrain this afternoon, and in advance of a cold front across central Montana. Forecast soundings shows large to very large surface temperature-dewpoint spreads (40-60 F) later this afternoon. A downward mixing of 30-40+ kt ambient southwesterly to westerly flow in the 700-500 mb layer may contribute to severe-caliber wind gusts in consolidating outflows, as convection spreads eastward into this evening toward eastern Montana and possibly western North Dakota. Farther south over the Great Basin, model guidance appears to be trending towards greater storm coverage (numerous) and associated ability for storm outflow. The 12 UTC HREF in particular (and recent HRRR runs) shows a potential corridor of outflow surging convection from northeast NV into northwest and northern UT during the 23-04 UTC period. Some consideration for a Slight Risk was given but uncertainty precludes an upgrade at this time. ...Arizona... Lingering early day outflow/cloud cover via yesterday's relatively active convection should generally abate by afternoon. As the boundary layer diurnally warms and destabilizes, thunderstorms are again likely to initiate across the Mogollon Rim and adjacent mountains of southwest New Mexico this afternoon. Given the position and movement of the mid-level high, somewhat stronger (around 15 kt) northeasterly steering flow will remain focused across southeast into adjacent portions of central Arizona. Severe gusts will be possible later this afternoon into the mid-late evening as storms progress south-southwestward across the lower deserts of central and southern AZ. ...Carolinas/Mid-Atlantic States... Midday visible-satellite imagery shows and extensive cloud shield across much of NC into the southern half of VA. The 12 UTC GSO raob featuring poor lapse rates and meager buoyancy contrasted with the MHX raob (2000 J/kg MLCAPE) and a much more moisture-rich airmass. Thinner cloud cover near the coast will aid in widely scattered storms developing this afternoon largely removed from the southern fringe of large-scale troughing over the Mid-Atlantic states/Northeast. An isolated risk for locally severe gusts may develop for several hours this afternoon into the early evening. Farther north, breaks and thinning of cloud cover will promote stronger heating across northern VA into the northern half of the Chesapeake Bay vicinity than areas farther south. Widely scattered storms are forecast to develop per the latest 12 UTC HREF guidance within this corridor by mid-late afternoon. A belt of 40-50 kt southwesterly 500-mb flow may enhance storm vigor, and a few downdrafts may yield a risk for isolated 45-60 mph gusts capable of localized damage. ...Upper Texas Coast and Southwest Louisiana... Extensive showers and some thunderstorms are ongoing along the Texas coast early today. Influenced by a weak mid-level disturbance, some guidance suggests that a strengthening of low-level winds/shear may occur. However, mid-level winds will remain weak, while the aforementioned convection should considerably limit destabilization inland. These factors seem likely to minimize the potential for anything beyond a very weak/transient circulation. ..Smith/Karstens.. 07/25/2024 CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 2000Z