SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook CORR 1 NWS Storm Prediction Center Norman OK 0116 AM CDT Tue Jun 25 2019 Valid 261200Z - 271200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF NORTHERN INTO CENTRAL MONTANA WEDNESDAY AFTERNOON AND EVENING... CORRECTED FOR GEN THUNDER LINE ERROR ...SUMMARY... Widely scattered severe storms capable of wind and hail are possible across parts of the central High Plains into the northern Plains, and over much of Montana on Wednesday. Additional strong storms are expected from northern Indiana into the lower Great Lakes vicinity. ...Northern Rockies/Montana... An upper low off the Pacific Northwest coast will shift eastward only slightly on Wednesday as height rises reinforce the upper ridge over the Plains. As the upper low slowly pivots inland, strengthening southwesterly midlevel flow will overspread the Great Basin and northern Rockies. East/southeasterly low level flow across the northern Plains will bring mid 40s to mid 50s dewpoints eastward across much of MT into northern ID and portions of the Columbia Basin. Strong heating and steep midlevel lapse rates will result in MLCAPE values from around 500-1500 J/kg. A deeply mixed sub-cloud layer (i.e. inverted-v thermodynamic profile) and strong midlevel flow will support strong downdrafts, and strong to severe wind gusts are possible from northeast OR/southeast WA eastward across much of MT. Shear profiles indicate high-based supercells are possible, and elongated hodographs above 3-4 km in the midst of 7.5-8.5 C/km midlevel lapse rates will support large hail as well, especially across parts of northern/central MT where a Slight risk has been included. ...Northern Plains to Central High Plains Vicinity... Height rises are expected across the Plains but temperatures aloft will remain cool, maintaining a large area of very steep lapse rates atop a moderate EML in the 850-700 mb layer. Some guidance suggests convection may be ongoing, but decaying, at the beginning of the period in the vicinity of the mid-MO Valley. This activity could pose a marginal severe threat, but more likely will result in various outflow boundaries overlying the region. Southerly low level flow will maintain rich boundary-layer moisture, with dewpoints in the 60s to mid 70s F across all but the western portions of the Plains states where a surface trough and dryline will extend north to south from far eastern WY/western NE through western KS and into the OK/TX Panhandles. Mid to upper level west/southwesterly flow across the central/southern Rockies will be rather modest, but there is some evidence of a weak impulse ejecting across the region during the afternoon. Strong heating/instability could lead to isolated storms during the late afternoon/evening hours if forcing becomes strong enough to overcome moderate capping. Strong wind gusts and hail would be possible with any storms that form. Some guidance suggests the as a southerly low level jet increases during the evening/overnight, a complex of storms could emerge from dryline convection perhaps in NE, or develop along outflow from aforementioned morning convection. The overall conditional and uncertain nature of the threat across the region will preclude higher severe probabilities at this time. ...Northern Indiana/OH into PA/NY/VT... A couple of weak impulses associated with northern Ontario mid/upper low will migrate through westerly flow in the Great Lakes vicinity on Wednesday afternoon. This will result in a moderate midlevel flow around 30-40 kt downstream of Lake Michigan toward western PA/NY. Southwesterly low level flow will maintain 60s dewpoints and strong heating will result in 1500-2500 J/kg MLCAPE. As a result, one or more bands of storms are expected to develop and shift east/southeast across the region. Strong wind gusts will be the main threat but some near-1 inch hail is possible as well. ...MAXIMUM RISK BY HAZARD... Tornado: 2% - Marginal Wind: 15% - Slight Hail: 15% - Slight ..Leitman.. 06/25/2019
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