SPC 1200Z Day 1 Outlook

Day 1 Outlook Image

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1127 PM CST Fri Jan 08 2021

Valid 091200Z - 101200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Scattered weak thunderstorm activity is possible this afternoon
through tonight across parts of the southern Rockies into central
and southeastern Texas, and perhaps near northern California coastal
areas.

...Synopsis...
Another initially vigorous short wave impulse, emerging from a
strong mid-latitude Pacific jet, appears likely to progress into
amplified branching flow across the eastern Pacific into western
North America during this period.  As it does, models indicate that
it will weaken substantially and split, with one portion
accelerating north-northeastward across the British Columbia coast,
and another turning eastward, inland across the southern
Oregon/northern California coast.  It appears that this will be
accompanied by a weakening surface front preceded by a moist plume
emanating from the subtropical Pacific, though richer moisture
return may become cut-off before reaching the Pacific coast.

Downstream, and ahead of inland advancing mid-level ridging, the
fairly vigorous southern portion of a preceding perturbation is
forecast to dig across the southern Rockies into the Permian Basin
by late tonight.  Models suggest that this will be preceded by
moisture return emanating from the southwestern Gulf of Mexico. 
However, this initial moistening is expected to be elevated above a
cool and dry low-level environment.

Beneath otherwise broadly confluent mid/upper flow across and east
of the Rockies, cold surface ridging is forecast to prevail across
much of the U.S., in the wake of a cyclone migrating northeastward
away from the Mid Atlantic coast.  This will maintain generally
stable conditions across most areas, with negligible risk for severe
thunderstorms.

...Texas...
Particularly east of the Edwards Plateau and Hill Country vicinity,
forecast soundings indicate that initial moistening will largely be
rooted in the 850-700 mb layer.  However, beneath modestly steep
mid-level lapse rates, it appears that this may contribute to
thermodynamic profiles marginally sufficient for weak convection
capable of producing lightning.  Aided by mid-level warm advection
ahead of the approaching short wave impulse, this may initiate
across parts of south central Texas into the middle Texas coastal
plain this evening, before spreading northward and northeastward
through tonight.

Farther west, mid-level cooling in the exit region of the cyclonic
jet accompanying the short wave impulse may contribute to scattered
weak thunderstorms across parts of the Edwards Plateau and Hill
overnight.

...New Mexico...
The mid-level cold core of the digging short wave trough is forecast
to overspread the higher terrain of northwestern through south
central New Mexico today.  This may contribute to weakly unstable
thermodynamic profiles at least marginally conducive to convection
capable of producing lightning this afternoon.

...Pacific Northwest...
Latest model output suggests that the mid-level cold core with the
splitting/weakening inland advancing perturbation may not be
particularly cold, with richer moisture return becoming cut off
before reaching coastal areas.  This seems to limit the potential
for thunderstorms.  However, a couple of lightning flashes might
still be possible late tonight across southern Oregon/northern
California coastal areas, coincident with the stronger mid-level
forcing for ascent.

..Kerr.. 01/09/2021

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