SPC Jun 25, 2019 0600 UTC Day 2 Convective Outlook

SPC 0600Z Day 2 Outlook

Day 2 Outlook Image

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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