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260 
ACUS02 KWNS 260643
SWODY2
SPC AC 260642

Day 2 Convective Outlook CORR 1
NWS Storm Prediction Center Norman OK
0142 AM CDT Thu Apr 26 2018

Valid 271200Z - 281200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM EASTERN
OREGON INTO SOUTHWEST IDAHO...

CORRECTED FOR OUTLOOK GRAPHIC

...SUMMARY...
Isolated strong thunderstorms capable of downburst winds and some
hail may occur from parts of eastern Oregon into southwestern Idaho
later Friday afternoon and evening.

...Synopsis...

Upper pattern is forecast to be characterized by a synoptic upper
trough over the eastern U.S., a ridge over the Intermountain West
and a closed upper low moving into the Pacific Northwest region
Friday. A significant shortwave trough located within the base of
the eastern U.S. synoptic trough will advance through the Gulf Coast
region. A cold front will move off the Atlantic Seaboard early in
the period with trailing portion continuing through FL. Farther west
a cold front will advance through the Pacific Northwest and Great
Basin regions.

...Eastern Oregon through southwest Idaho and northern Nevada...

Model consensus is that another in series of vorticity maxima will
rotate through the closed upper low circulation and into northwest
NV and central to eastern OR near peak heating. Steep lapse rates
and deeply mixed boundary layers will support marginal instability
with MLCAPE from 300-500 J/kg. The development of more numerous
high-based convection should occur in response to the ascent
accompanying the vorticity maximum being favorably timed with
maximum afternoon and evening destabilization. Some of this activity
could produce a few instances of downburst wind and hail through mid
evening.

...Central through southern Florida...

A gradual moistening will occur across south FL through Friday as
the Gulf boundary layer modifies and surface winds return to
southwesterly, though models have trended drier, suggesting more
limited prospects for thunderstorms. Nevertheless, modest
instability is expected in pre-frontal warm sector with MLCAPE below
1000 J/kg. Upper forcing will remain weak during the day promoting a
shallow frontal circulation, but at least a few showers and isolated
thunderstorms might occur especially along the east coast where
frontal convergence will be augmented by the seabreeze circulation.
An upstream shortwave trough will move through the Peninsula
overnight, but the forcing with this feature will remain in
post-frontal zone.

..Dial.. 04/26/2018

$$