FNUS28 KWNS 132156

Day 3-8 Fire Weather Outlook  
NWS Storm Prediction Center Norman OK
0454 PM CDT Tue Apr 13 2021

Valid 151200Z - 211200Z

An upper low across the northern Great Basin will move south and
intensify through Day3/Thursday before ejecting across the
central/southern Rockies as an open wave Day4/Friday. At the
surface, low pressure across the southern Great Basin will fill
slightly before moving eastward across New Mexico as a cold front
and trailing high pressure move south across the central US.
Increasing mid-level flow over the Great Basin and southwest will
align with dry surface conditions to support increased fire weather
potential into early next week. Meanwhile, cooler and wetter than
average conditions should limit fire potential over much of the rest
of the lower 48.

As the upper-low continues to move southeastward toward the southern
Rockies early in the period, mid-level flow will increase
substantially as a 70 kt jet ejects eastward. Models soundings
across eastern Arizona and western New Mexico show a deep and dry
PBL with widespread surface RH ranging from 7-15%. With the increase
in flow aloft, and the close proximity to the surface low, winds of
20-25 mph are expected. Widespread dry fuels, low RH, and strong
low-level flow will support critical fire weather conditions across
the lower and middle elevations through much of the day. 

Locally elevated fire weather conditions may continue into
Day4/Friday across eastern New Mexico and far west Texas as
lingering surface flow shifts to the east. RH of 10-15% behind a
weak surface trough will likely support some potential through the
afternoon before cooler temperatures behind the cold front increase

...Great Basin...
Behind the departing upper-level low Day3/Thursday, winds should
remain relatively weak (10-15 mph) with little surface pressure
gradient and waning mid-level flow. However, the depth of dry air at
the surface with RH near 10-15% should be sufficient for locally
elevated fire weather conditions through the day. 

A shortwave impulse embedded within the northerly flow aloft is
expected to intensify as it nears the backside of the upper low
drifting onto the High Plains. The weakening surface low is expected
to reinvigorate slightly with the approach of the secondary trough.
While at the same time, surface high pressure across the central
Rockies is expected to increase substantially. The result should be
an uptick in low-level northerly winds late Day4/Friday through
Day6/Sunday. With dry air in place it appears plausible that some
areas of elevated to critical fire weather conditions may develop
across the southern Great Basin within this time frame. Though
models vary significantly on the strength of the secondary trough
and the resulting surface flow. Offshore flow may also spill into
portions of southern California with low humidity and near critical
winds but confidence in the overall scenario remains low.

Dry post frontal conditions may occur across portions of the
Carolinas early this weekend. Winds are expected to be mostly light,
but fuels across the area are very dry. Surface RH as low as 20-25%
suggests elevated fire weather potential may exist. Some potential
for precipitation may limit this threat, though most model
projections show little accumulation greater than 0.1 inches.

..Lyons.. 04/13/2021

...Please see www.spc.noaa.gov/fire for graphic product...