New York, NY...Philadelphia, PA...Columbus, OH...Baltimore, MD...Boston, MA...
SPC AC 051730
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1230 PM CDT Fri Jul 05 2019
Valid 061200Z - 071200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
NEW ENGLAND AND THE CENTRAL HIGH PLAINS...
Isolated strong to severe storms may occur on Saturday across the
northern/central Rockies into the adjacent High Plains, and over
much of the Northeast into the Mid Atlantic and Ohio Valley,
accompanied by some risk for large hail and potentially damaging
...Northeast into the Mid Atlantic and OH Valley...
An upper trough/low will move eastward over Quebec and the Northeast
on Saturday. At the surface, a cold front is expected to develop
east-southeastward across the Northeast into parts of the Mid
Atlantic and OH Valley through the period. The strongest mid-level
flow is expected to generally remain in Canada, but some enhancement
to mid/upper-level winds should occur across parts of New England by
Saturday afternoon. A moist low-level airmass, characterized by
upper 60s to lower 70s surface dewpoints, should exist ahead of the
surface front. As diurnal heating warms surface temperatures into
the lower to mid 80s, destabilization of the warm sector will occur.
MLCAPE in the 1000-1500 J/kg range seems plausible in a narrow
southwest/northeast corridor across parts of New England, with poor
mid-level lapse rates likely limiting the development of stronger
Current expectations are for storms to form by late Saturday morning
across the Northeast along the cold front, and subsequently
strengthen as they approach the Atlantic Coast by mid afternoon.
Isolated strong to damaging winds should be the main threat with
this convection, as 25-35 kt of mid-level flow and related bulk
shear act to modestly organize updrafts. A relatively greater
potential for damaging winds may exist across parts of ME into NH
where the best combination of instability and modest shear is
forecast to occur. A small Slight Risk has been included across this
area to account for this potential. Farther south/west into the Mid
Atlantic and parts of the OH Valley, shear will be even weaker. This
will tend to limit storm organization, but isolated strong/gusty
winds producing occasional damage could still occur as storms move
southeastward through Saturday evening.
...Northern/Central Rockies into the Adjacent High Plains...
An upper trough/low will remain over the West Coast and British
Columbia Saturday. Small-scale perturbations embedded within this
large-scale upper troughing and orographic lift will likely
encourage convective initiation along the higher terrain of the
northern/central Rockies by early Saturday afternoon. These isolated
to scattered storms will subsequently move eastward across the High
Plains through Saturday evening. Steep mid-level lapse rates should
once again be present over much of the northern/central High Plains.
Relatively greater low-level moisture should exist across parts of
eastern CO/WY into western NE/KS, and moderate to locally strong
instability will probably develop through peak heating across these
areas. Although low-level winds will remain generally weak, a
strongly veering wind profile and enhanced mid/upper-level flow
should result in about 35-40 kt of effective bulk shear. This
forecast combination of instability and shear will probably support
supercells initially, with mainly an isolated large hail threat.
Some possibility for clustering into one or more small bowing
segments may exist early Saturday evening, with a potentially
damaging wind threat.
Across the northern High Plains, low-level moisture is expected to
remain more limited, which should temper instability somewhat. While
some risk for hail and gusty winds should exist with the strongest
convection, this threat should remain quite isolated. Farther south,
mid-level flow should be comparatively weaker from southern CO into
northeastern NM. While loosely organized storms could pose an
isolated severe threat across this region, the overall threat should
...MAXIMUM RISK BY HAZARD...
Tornado: 2% - Marginal
Wind: 15% - Slight
Hail: 15% - Slight
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