Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

FXUS63 KUNR 192303

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
403 PM MST Sun Nov 19 2017

.DISCUSSION...(This Evening Through Sunday)
Issued at 256 PM MST Sun Nov 19 2017

Current surface analysis shows weak low pressure over south 
central Canada, with warm front north and east of the area. Upper 
level analysis shows large scale trough over the eastern US, with 
broad ridge covering the western US. Warmer air has pushed into 
the area, with temps in the 50s across the plains, 40s over the 
Black Hills. High clouds are spilling over the ridge to the west, 
with some filtered sun at times in most areas. Winds have mostly 
turned to the southwest across the area, breezy over northeast WY.

A dry and mostly mild pattern will continue this week as general 
pattern aloft remains in place across the region. The main weather 
feature for the next several days will be a passing cold front 
Monday afternoon and evening, bringing a chance of rain and snow 
showers over parts of the area. The one cold day of the week will be 
Tuesday, otherwise above average temps will persist through at least 
Friday. Medium range models are in pretty good agreement through 
much of the period. 

Skies will be mostly clear to partly cloudy tonight into Monday 
morning. Milder conditions can be expected tonight, with lows mostly 
in the mid 20s to mid 30s. Monday highs will be in the mid 50s to 
mid 60s, with increasing clouds by the afternoon as cold front 
approaches. Breezy west-southwest winds can be expected tonight into 
Monday across much of northeast WY. Winds will increase by late 
Monday afternoon across northwest SD as cold front begins to push 
through. There will be a chance for rain and snow showers Monday 
night, mainly from northeast WY through the Black Hills area, as 
post-frontal shortwave slides through western and southern portions 
of the area. There could be a light snow accumulation across some of 
the higher elevations, but should generally be less than an inch. 
Breezy conditions can be expected late Monday into Tuesday as cold 
front pushes through with strong cold advection. Tuesday will be a 
chilly day, with highs in the 30s to mid 40s, warmest over northeast 
WY and far southwest SD.  

The colder air will be short-lived as ridge rebuilds over the 
western states. Highs will be back in the 50s and 60s for Wednesday 
through Friday, with highs possibly near 70 in a few spots south and 
east of the Black Hills on Thanksgiving day. Another cold front is 
progged to cross the area on Friday, dropping temps back to more 
seasonable levels for the weekend. There are some differences 
between the medium range models as far pcpn chances go Friday into 
the weekend. GFS now mainly dry, while EC shows chances mostly with 
the front. Will keep some pcpn chances on Friday for now. 


.AVIATION...(For the 00Z TAFS Through 00Z Monday Evening)
Issued At 402 PM MST Sun Nov 19 2017

VFR conditions will continue through Monday afternoon.


Issued At 256 PM MST Sun Nov 19 2017

Mild and dry conditions can be expected across the area Monday, 
ahead of an approaching cold front. Relative humidities will drop 
to around 20 percent Monday afternoon across southwest SD, with RH
values in the 20s elsewhere. West to northwest winds will 
increase as the front moves into the area during the afternoon. A 
period of elevated fire weather conditions is likely across a good
portion of the forecast area Monday afternoon, with high to very 
high grassland fire danger across the western and south central SD




National Weather Service Glossary of Abbreviations