903 
FXUS63 KUNR 110851
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
251 AM MDT Mon Mar 11 2019

.DISCUSSION...(Today Through Sunday)
Issued at 250 AM MDT Mon Mar 11 2019

Weak sfc ridge currently over the region supporting clear skies. 
Patchy fog has developed across portions of the SD plains, with 
some expansion expected over scentral SD. WAA ongoing aloft as 
shortwave ridging continues across the region. Partly to mostly 
sunny skies expected the next two days with warming temps, esp in 
locations in the west and on higher terrain. Snow pack will 
continue to influence max t potentials although increasing flow 
Tues will allow for more expansive deeper mixing and warmer temps,
esp in the eastern Black Hills. The main concern in the forecast 
period is the looming winter storm expected in the 
Central/Northern Plains Wed into Thur. Forecast models continue to
offer varying solutions to the height/momentum and resulting 
thermal fields, supporting varying totals for snow and ice accums.
The latest ECMWF has shifted the track of the storm more NW in 
line with a more negatively tilted height pattern. If this were 
the case, heavier snow totals would shift west as indicated in its
progs. The uncertainty in the degree of southern/norther stream 
trough phasing and the associated upper jet dynamics will continue
to offer varying track solutions the next few model runs. One 
thing that is certain is that heavy snow and very strong winds can
be expected in the region Wed-Thur esp given a GOMEX connection 
supporting PW’s near 1 inch toward central SD, it’s just a 
question of exactly where. There is also the potential for a 
period of ice accums SE of the main FGEN band which at this time 
favors central SD. Perhaps the most concerning thing is the 
progged wind speeds, with gusts exceeding 60 mph for a period of 
12 hours or more. Coupled with snow totals over 6 inches, this 
would support blizzard to near blizzard conds. Outside of the 
plains, the northern and central Black Hills are set up well for a
period of heavy upslope enhanced snow which could extend further 
SE than usual given the strong flow and steep ll lapse rates. 
Given the potential impacts from this system, felt a winter storm 
watch is certainly warranted for part of the FA. 

After the mid week storm, massive western NOAM ridging is favored
toward next weekend in all deterministic models, which would 
allow for much warmer conds by early next week if the ridge axis 
shifts east over the Rockies, as the ECMWF is indicating. This 
will all hinge on the eventual position of the blocking western 
Atlantic ridge.

&&

.AVIATION...(For the 06Z TAFS Through 06Z Monday Night)
Issued At 1014 PM MDT Sun Mar 10 2019

Areas of MVFR conditions in light snow across south central SD
will end by 09z. Other than some patchy fog later tonight into 
early Monday across the SD plains, VFR conditions will continue
through Monday.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...Winter Storm Watch from late Tuesday night through Thursday 
     afternoon for SDZ024>028-030>032-041>044-046-047-049-
     072>074.

WY...Winter Storm Watch from late Tuesday night through Thursday 
     afternoon for WYZ057.

&&

$$

DISCUSSION...JC
AVIATION...Johnson