328 
FXUS63 KUNR 162233
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
433 PM MDT Sun Oct 16 2022

.DISCUSSION...(This Evening Through Sunday)
Issued at 218 PM MDT Sun Oct 16 2022

Water vapor imagery this aftn indicates a ridge building from the 
Pac NW nwd into BC, troughing from the Upper Midwest ewd to sern CN, 
and a northerly jet in-between, extending from cntrl CN into the nrn 
Plains. Visible and cloud phase distinction RGB satellite data 
reveal that this morning's persistent stratus deck from swrn SD 
extending nwwd toward the srn Black Hills supported by weak upslope 
flow has largely dissipated within the last hour. Mixing over the 
srn Black Hills has facilitated the development of a locally very 
dry air mass, with dew point depressions of approximately 50 F and 
associated relative humidity values in the low teens. Nearby, 
continued upslope flow has kept areas south and east of the Black 
Hills relatively cooler and more moist. Away from the hills, breezy 
N/NW flow has developed over the plains. Aftn temperatures area-wide 
range from the lower 40s to the mid 50s. Broad sfc ridging is 
analyzed from the wrn Dakotas nwd into SK/MB.

Sfc ridging continues to build sewd this evening thru tonight as 
upper jet shifts ewd. Combination of these factors should promote 
near-optimal nocturnal cooling tonight thru tomorrow morning, 
bringing lows in the 20s to even upper teens across much of the 
wrn/cntrl SD plains. As midlevel trof deepens over the Great Lakes 
region and transitions to a closed low tomorrow, longitude of the 
associated low-level thermal trof axis remains approximately 
unchanged. However, low-level temperature gradient tightens as 
thermal ridging over the wrn CONUS begins to expand. This should 
favor a wide range of highs tomorrow, from the mid 40s over our far 
east to mid 60s across the far west. A tightening pressure gradient 
between developing lee troughing east of the Rockies and the sfc 
high slowly shifting ewd across the ern Dakotas/Upper Midwest will 
promote the development of steady E/SE flow over much of the area. 
Upper-level and accompanying lower-level patterns are fcst to change 
only modestly on Tuesday, leading to an overall similar day. Main 
difference will be an ewd push of warmer low-level temps late in the 
day ahead of a shortwave trof digging thru N/NW flow aloft across s 
cntrl CN/n cntrl CONUS, which could raise highs 5 F or so compared 
to tomorrow.

Shortwave trof and attendant dry cold front are progged to cross 
the region Wednesday. Main impact to our sensible wx will be 
breezy/gusty NW winds. Despite northerly winds, fairly high 
confidence that temps will increase over most of the area as low-
level thermal ridging continues to expand ewd. WPC cluster analysis 
from 00z showed considerable agreement among ensemble suites, with 
only subtle differences across the four clusters amounting to 
temperature disparities of <4 F. Another, more amplified shortwave 
trof approaches late Wednesday into Thursday, facilitating stronger 
WAA and westerly downslope winds across the region. Based on 
ensemble consensus, this should bring well above average 
temperatures and increased potential for elevated or near-critical 
fire weather conditions. Generally zonal flow is expected to persist 
on Friday; however, confidence decreases substantially heading into 
the weekend as WPC clusters diverging solutions, mainly tied to the 
amplitude and motion of a trof across the wrn CONUS.

&&

.AVIATION...(For the 00Z TAFS Through 00Z Monday Evening)
Issued At 432 PM MDT Sun Oct 16 2022

VFR conditions through the period.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...None.
WY...None.
&&

$$

DISCUSSION...Sherburn
AVIATION...JC