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FNUS21 KWNS 101651

FWDDY1



Day 1 Fire Weather Outlook  

NWS Storm Prediction Center Norman OK

1151 AM CDT Sat Apr 10 2021



Valid 101700Z - 111200Z



...CRITICAL FIRE WEATHER AREA FOR WESTERN NEW MEXICO AND FAR EASTERN

ARIZONA...



Only minor changes have been made to the current forecast. The

Critical area was moved west and trimmed on the eastern side to

better account for critical meteorological conditions across the

higher terrain of the Southwest. Locally elevated fire weather

conditions will be possible across portions of the northern/central

High Plains. The sporadic nature of strong winds/RH will preclude

the addition of an elevated area at this time.



..Lyons.. 04/10/2021



.PREV DISCUSSION... /ISSUED 1252 AM CDT Sat Apr 10 2021/



...Synopsis...

A mid-level trough and associated surface cyclone will continue to

move across the eastern CONUS, with ample low-level moisture and

widespread precipitation limiting major wildfire spread concerns

across much of the Mississippi Valley towards the Appalachians.

Another mid-level trough will deepen across the northern Rockies,

promoting dry downslope flow across much of the northern into the

central High Plains. Strong west-northwesterly mid-level flow will

also overspread a dry boundary layer across the southwest U.S,

promoting surface conditions favorable for wildfire spread. Lastly,

dry, occasionally breezy conditions are expected around afternoon

peak heating across portions of the Florida Peninsula, before

isolated to potentially scattered thunderstorms arrive.



...Portions of the Southwest U.S...

By afternoon, adequate diurnal heating will promote RH values

dropping to the 10-20% range across much of central and eastern

Arizona into central New Mexico and Far West Texas. Efficient

downward momentum transport of the mid-level flow is expected to

support widespread 15-25 mph sustained westerly surface winds.

Guidance consensus depicts the best overlap of critically low RH and

sustained 20+ mph westerly surface winds across western New Mexico,

where a Critical area has been delineated. Critical conditions are

most likely across lower-terrain areas, where fuels are most

receptive of wildfire spread. 



...Florida Peninsula...

By afternoon peak heating, RH is expected to drop into the 25-35%

range across central and eastern portions of the Florida Peninsula.

At the same time, surface lee troughing is expected to encourage a

strong enough surface mass response for a relatively stronger

surface wind field to develop. During this period, and before

thunderstorms develop or move into the area, there is a multi-hour

window of opportunity where 15+ mph sustained west-southwesterly

surface winds may coincide with the aforementioned RH to foster

favorable wildfire-spread conditions. An Elevated area has been

maintained to address this concern given that fuels remain receptive

to fire spread.  



...Northern High Plains...

With the approach of an upper trough, downslope flow is expected to

promote 15-25 mph sustained westerly surface winds coinciding with

15-25% RH during the afternoon hours. At least locally Elevated

conditions are likely from the Laramie Mountains to the

Montana/North Dakota/Canada border, potentially expanding as far

east as the western Dakotas into the Nebraska Panhandle. At the

moment, the primary mitigating factor for adding an Elevated area is

the lack of stronger surface winds on a more widespread basis.

However, given the receptiveness of fuels (especially in eastern

Montana into western North Dakota), an Elevated area may be added in

the Day 1 update should guidance show any increasing trends for wind

speeds.



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



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