FXUS63 KUNR 100439

AFDUNR



Area Forecast Discussion For Western SD and Northeastern WY

National Weather Service Rapid City SD

1039 PM MDT Fri May 9 2025



.KEY MESSAGES...



- Unseasonably warm conditions through this weekend with near

  record/record highs possible Sunday and Monday



- Period of elevated to near critical fire wx conditions possible

  over most of the area through this weekend into early next week.



- Chances for storms Sunday evening with marginal risk for

  damaging wind gusts in far northwestern SD.



- Unsettled weather pattern will move into the region by mid week

  with increasing chances for wetting precip



&&



.DISCUSSION...(This Evening Through Friday)

Issued at 215 PM MDT Fri May 9 2025



Radar and IR satellite imagery show a few storms bubbling up over

the Black Hills. Very weak upper level shear (values <10 kt per 

18z sounding) and upper level winds will preclude any severe 

threat from these storms but a few of the stronger storms could 

produce small hail and gusty winds. Upper level analysis depicts 

broad, somewhat positively tilted ridging over the western CONUS 

while a messy trough lingers over the eastern US. SFC analysis 

depicts trof/weak frontal boundary draped over central/eastern SD 

with sfc high sitting to the northwest over southern SK.



Upper ridging will remain in place over the Northern Plains as 

cutoff upper low loiters to the south over TX/LA. On Saturday, the

aforementioned upper high over southern SK slides eastward as sfc

low develops in the lee of the Canadian Rockies. A tightening W-E

oriented pressure gradient will facilitate breezy southerly winds

and WAA into the Northern Plains. H85 temps progged to reach the 

low 20sC by Saturday afternoon, translating to highs in the mid 

80s to low 90sF over much of the region. Stronger southerly flow 

and WAA occurs Sunday as deepening trof over the PNW forces the 

upper ridge eastward. H85 temps climb to the mid to upper 20sC 

which will correspond to highs in the upper 80s to 90sF. EFI MaxT 

values still show much of the CWA in the 90th+ percentile for 

Sunday into Monday, we could see a few daily temperature records 

broken Sunday and Monday. Could see a few storms develop Sunday 

evening along a sfc trof, deep layer moisture and shear will be 

marginal so don't have any widespread severe wx concerns at this 

time. Deep boundary layer mixing and inverted-V profiles do point 

at a marginal risk for damaging wind gusts, especially up in far 

northwestern SD near the MT/ND border. 



The hot, dry, and breezy to windy conditions this weekend will 

lend to elevated to near critical fire wx conditions across much 

of the area. More details in the Fire Wx discussion.



Upper trof will continue to deepen and slowly move its way into 

the western US through the beginning of next week. Slow moving 

frontal bndy will cross the CWA Tuesday, leading to a rather 

pronounced temperature gradient with NE WY experiencing highs in 

the low 70s while the western SD plains see highs in the upper 80s

to low 90s. There will be a chance for showers/storms Tuesday 

evening into Wednesday as the front slowly crosses the region. 

Cooler and unsettled conditions develop over the region by the mid

to late week as the upper trof moves overhead. LREF shows medium 

chances (40-60%) of QPF exceeding 0.1" across much of the CWA Wed-

Thu with a 30-50% chance for QPF to exceed 0.25" across 

northwestern SD. 



&&



.AVIATION...(For the 06Z TAFS Through 06Z Saturday Night)

Issued At 1039 PM MDT Fri May 9 2025



VFR conditions are expected through the forecast period.



&&



.FIRE WEATHER...

Issued At 215 PM MDT Fri May 9 2025



Extended period of elevated to near critical fire wx expected 

this weekend into early next week as unseasonably warm 

temperatures, dry conditions, and breezy/gusty southerly winds 

develop. Expecting minimum RHs to drop into the teens for much of 

the region. Deep boundary layer mixing will bring gusty southerly 

winds at times, especially Sunday/Monday east of the Black Hills. 

Fuels are in green up which will preclude fire wx headlines at 

this time, though locally critical fire wx concerns may exist in 

patches where fuels are still receptive. 



&&



.UNR WATCHES/WARNINGS/ADVISORIES...

SD...None.

WY...None.

&&



$$



DISCUSSION/KEY MESSAGES...Wong

AVIATION...13

FIRE WEATHER...Wong