Severe Storm Outlook Narrative (AC)
Issued by NWS
Issued by NWS
860 ACUS02 KWNS 221729 SWODY2 SPC AC 221728 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1228 PM CDT Sat Jun 22 2024 Valid 231200Z - 241200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS IN THE CENTRAL NEW ENGLAND VICINITY... ...SUMMARY... Scattered damaging winds and a few tornadoes are likely across parts of the Northeast, mainly during Sunday afternoon. ...Northeast... A relatively more active severe weather day is anticipated on Sunday afternoon with increasing confidence in scattered damaging winds and a few tornadoes across parts of the region. A low-amplitude shortwave trough over the Upper Midwest will track east to the Saint Lawrence Valley by Sunday afternoon, as a more amplified upstream trough digs across the Great Lakes. Multiple belts of enhanced low-level flow will likely accompany each impulse, with the stronger strengthening occurring with the secondary wave. A deepening surface cyclone should track across southeast ON/south QC. While mid-level lapse rates will be weak, rich low-level moisture will yield moderate buoyancy with a broadening plume of MLCAPE of 1500-2000 J/kg by afternoon. 12Z CAM guidance is fairly consistent in suggesting that primary warm-sector development will occur with the lead wave by late morning into the afternoon. A secondary round of convection accompanying the cold front trailing southwestward should occur downwind of the Lower Great Lakes during the late afternoon to early evening. The most favorable parameter space appears centered on parts of the Hudson Valley through the central portion of New England. Here, low-level hodographs are progged to be most enlarged in combination with a favorable low-level thermodynamic environment. This may yield a few discrete supercells with a risk for tornadoes and damaging winds. Storm mergers and eventual clustering should maintain a threat for isolated to scattered damaging winds as convection approaches the coast. The degree of destabilization in the wake of the lead activity is somewhat uncertain. But moderate to strong southwesterly deep-layer shear should yield a threat for scattered damaging winds with late-day convection as the cold front shifts east of the Lower Great Lakes. ...OH Valley to Mid-South/TN Valley vicinity... The cold front trailing from the New England system will move across parts of the Ohio Valley during the afternoon and evening. Isolated to scattered thunderstorm development will be possible along/ahead of the front within a moderately unstable and modestly sheared environment. A few stronger cells or small clusters will be possible within this regime, with a threat of sporadic damaging winds and small to marginally severe hail. Primary change with this outlook is to expand the level 2-SLGT risk southwestward in the Upper OH Valley where confidence is greater in storm coverage and resultant damaging wind threat. ...East MT into northwest ND... A shortwave trough should move east across parts of WA and the southern Canadian Rockies. A deepening surface cyclone will accompany this wave over the southern AB and move into SK, with a cold front trailing southward into MT. Low-level southeasterly flow will transport a confined plume of modest low-level moisture into parts of east MT, resulting in a corridor of MLCAPE from 500-1500 J/kg. Deep-layer shear will be favorable for organized convection, but large-scale ascent attendant to the shortwave trough may tend to remain north of the international border. Development of a severe storm or two across east MT is possible by early evening, which would then potentially spread into northwest ND Sunday night. ...Northwest KS/southwest NE... Hot temperatures along a lee trough should yield at least isolated late afternoon thunderstorm development. A deeply mixed boundary layer with modest mid-level northwesterlies could foster small hail-loaded downdrafts capable of a few strong microbursts into early evening. ...North WI/northeast MN... On the backside of the Great Lakes mid/upper trough, favorable speed shear within the northwesterly flow regime should yield an elongated hodograph. Forecast soundings suggest mid-level lapse rates will be weak as the thermal trough shifts east. But isolated, low-topped convection might produce small hail and locally gusty winds, centered on late afternoon. ..Grams.. 06/22/2024 $$