Day 1 Convective Outlook
Issued: · Valid: –
Summary
Severe thunderstorms capable of producing damaging winds, large hail, and occasional tornadoes are expected across parts of the Mid-Atlantic and Northeast today. Additionally, strong to severe thunderstorms with the potential for damaging gusts and large hail are forecast for the Central Plains and parts of Montana through this evening.
Product Text
000 ACUS01 KWNS 271625 SWODY1 SPC AC 271624 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1124 AM CDT Thu Aug 27 2026 Valid 271630Z - 281200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE MID-ATLANTIC/NORTHEAST...THE CENTRAL PLAINS...AND CENTRAL MONTANA... ...SUMMARY... Scattered strong to severe thunderstorms are possible across parts of the Northeast and Mid-Atlantic today. Damaging winds, severe hail, and a tornado or two may accompany these thunderstorms. Large to very large hail and severe gusts are also possible across parts of northern High Plains and central Plains. ...Mid-Atlantic/Northeast... Recent surface analysis places a low over western Quebec, with a cold front arcing from this low southwestward through the middle OH Valley, western TN Valley and then westward across central AR and central OK. Satellite imagery reveals a shortwave trough extending from northeastern Ontario through western PA, just west of the analyzed surface low. There also appears to be a more subtle shortwave trough farther south moving through WV towards VA. Expectation is for the primary shortwave trough and cold front to continue eastward, interacting with the very moist airmass across the Northeast to support thunderstorm development this afternoon. 12Z ILN and PIT soundings sampled the moderate westerly flow aloft, supporting the potential for strong multicells along both the cold front and pre-frontal troughing. A few supercells are possible if warm sector development can mature without too much interaction with other convection. Primary risk will be damaging gusts, although the modestly cool temperatures aloft (i.e. -10 to -12 deg C at 500-mb) suggest some hail is possible as well. A somewhat displaced area of earlier thunderstorm development is manifesting across the northern Mid-Atlantic. As mentioned in MCD #2145, a broken band of thunderstorms is ongoing as of mid-morning from the New York City vicinity southwest toward Baltimore, with that activity potentially being aided by forcing for ascent associated with the subtle shortwave trough moving into VA. Airmass across this region is very moist, and instability is steadily building under modest diurnal heating. Most guidance suggests this activity gradually increases in coverage and intensity over the next few hours. The presence of a vertically veering wind profile with around 30 to 35 kt of effective bulk shear would support a conditional risk for embedded supercell structures capable of locally damaging winds, marginally severe hail, and perhaps a brief tornado. ...Northern Rockies/High Plains... Recent satellite imagery depicts a shortwave trough progressing across eastern OR towards ID and western MT. Moderate mid-level moisture and forcing for ascent associated with this wave are forecast to initiate thunderstorms across the northern Rockies this afternoon. This activity is then forecast to progress northeastward off the higher terrain into central MT, where a deeply mixed airmass is forecast to be in place. Despite this deep mixing and somewhat limited low-level moisture, the mid-level moisture associated with the shortwave will allow for at least modest buoyancy (i.e. MLCAPE over 500 J/kg). This should support storm maintenance off the terrain, with a trend towards outflow-dominant bowing segments with time. Primary severe risk is damaging gusts, including the potential for gusts from 65 to 75 mph. ...Central Plains... Moist southerly flow will help maintain moderate low-level moisture through the NE Panhandle and into southwest SD amid the strong heating and boundary-layer mixing expected this afternoon. Additionally, this modest, but persistent, warm-air advection is likely to force convective initiation this afternoon over the western NE/SD border vicinity. Low-level southerly flow veering to moderate northwesterlies aloft will support deep-layer shear of 40 to 50 kt, more than adequate for supercell development with any mature convective. Any sustained supercells will be capable of producing large hail (some 2+ inches) as they track south-southeastward through the late afternoon into the evening. Upscale growth into one or more bowing segments appears likely this evening, with strong to severe gusts (65 to 75 mph) possible. An isolated threat for severe hail/gusts may also exist farther west/south across the CO Front Range to Raton Mesa vicinity. Weaker buoyancy and deep-layer shear should keep any more organized updrafts confined to the higher terrain and Foothills. -- No other changes needed to the outlook with the text for the additional areas appended from the 13Z Outlook below -- ...Great Basin... High-based thunderstorms should also develop this afternoon across portions of northeast NV into northwest UT and southeast ID. While low/mid-level winds and related thunderstorm organization will likely be somewhat weaker/limited compared to areas farther north, steep lapse rates and large DCAPE will support potential for strong to severe outflow gusts as this convection spreads northeastward into the early evening. ...South-Central/Coastal Texas into Southern Louisiana... Ongoing thunderstorms across southern LA may pose a threat for gusty winds this morning before they move offshore. Additional thunderstorms may develop this afternoon from parts of south-central TX towards the upper TX Coast, with isolated severe/damaging downburst winds possible given ample moisture/instability forecast. Weak deep-layer shear should limit the overall severe threat. ..Mosier/Chalmers.. 08/27/2026 $$