Fire Weather Outlook Discussion
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FNUS21 KWNS 251624

Day 1 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
1123 AM CDT Tue Jul 25 2017

Valid 251700Z - 261200Z

...Western US Dry-Thunderstorm Potential...
The ongoing isolated dry-thunderstorm area is expanded southward
across parts of the Sierra Nevada, where thunderstorms will likely
develop later today. Although previous rainfall and some modest
increase in PW values suggest conditions will be less favorable for
ignitions/fire spread today versus prior days, thermodynamic
profiles should still support some enhanced potential for
lightning-induced starts. The 12Z REV sounding sampled PW of 0.75
inches, and forecast soundings suggest around 0.75-0.85 inches
across the area later today. Thus, while storms will continue to
become wetter with time, strikes outside of precipitation cores will
combine with gusty outflow winds to exacerbate the fire-weather

...Central Plains Gusty Winds/Low RH Potential...
Ahead of a cold front, a tightening pressure gradient will support
breezy southerly winds across parts of western Nebraska.
Additionally, with this area on the western edge of deeper moisture,
diurnal mixing will allow RH values to fall below 30% this
afternoon. Pockets of dry fine fuels may encourage locally elevated
fire-weather concerns. However, the threat appears too spatially
confined for highlights at this time.

..Picca.. 07/25/2017

.PREV DISCUSSION... /ISSUED 0227 AM CDT Tue Jul 25 2017/

Little change to the overall pattern is expected today, as a
slow-moving midlevel low edges eastward into northern California and
the Great Basin, while an upper ridge remains in place across the
Southwest into portions of the southern/central Plains. At the
surface, a trough will extend across much of the Plains south of a
surface low near Hudson Bay, while high pressure settles into the
Northeast. Generally weak surface features are expected across most
of the West.

...OR/Northern CA eastward into southern MT...
Scattered thunderstorms are again expected from OR/northern CA
eastward into southern MT, in proximity to the slow-moving midlevel
low and embedded smaller-scale features. Thermodynamic profiles are
again expected to support a mix of wet and dry thunderstorms, though
with potentially abundant lightning affecting areas with dry fuels,
the risk of ignitions away from the heaviest rain cores will
continue. The driest thunderstorm activity is expected on the
northern fringe of the isolated dry-thunderstorm area, where PW
values will be slightly lower and stronger heating/mixing will
occur, but coverage will also tend to drop off with northward
extent. Strong and erratic outflow winds will be possible in the
vicinity of any thunderstorms.

...Please see for graphic product...

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