Day 1 Severe Weather Outlook

Valid 021300Z – 031200Z

…NO SEVERE THUNDERSTORM AREAS FORECAST…

…SUMMARY…
Severe storms are not expected across the U.S. mainland today.

…Synopsis…
As the synoptic trough off the Atlantic coast moves farther away
from the CONUS, a progressive upper-air pattern will continue. The
next substantial perturbation is apparent in moisture-channel
imagery offshore from the Pacific Northwest, with its height/
vorticity axes generally between 132W-135W. Satellite imagery shows
abundant glaciated convection over Pacific waters between the trough
and the coastline, indicating a broad field of favorable large-scale
ascent/destabilization aloft for supporting deep convection. With
the trough forecast to amplify as it approaches the coast, then
moves inland between 18-00Z, that ascent plume should at least
maintain its strength. By the end of the period, the trough should
extend from the northern Rockies south-southwestward across northern
NV and eastern CA.

…Coastal Pacific Northwest…
Isolated thunderstorms are possible, predominantly through the day
to about 00Z. This activity will be supported by marginal boundary-
layer theta-e accompanying the Pacific marine layer, as well as weak
but supportive buoyancy from that layer into areas of -20C and
colder temperatures aloft. Time series of near-coastal forecast
soundings prior to the passage of the 500-mb trough show steepening
low/middle-level lapse rates (compared to 12Z UIL RAOB) and little
or no CINH, from the Pacific marine layer upward to near a
tropopause located between 450-500 mb. Thereafter, the tropopause
will descend toward the -20C isotherm, concurrent with weakening of
lapse rates, thereby removing sufficient magnitude/depth of CAPE to
support thunder potential.

..Edwards/Kerr.. 02/02/2020

$$

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.