Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 120857
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
257 AM MDT Tue Mar 12 2024

.KEY MESSAGES...
252 AM MDT Tue Mar 12 2024

- Warm, dry today with elevated fire weather conditions
- Splitting upper-trough brings precipitation as well as cooler
  and windy weather for Wednesday and Thursday

&&

.DISCUSSION...(Today Through Monday)
Issued at 252 AM MDT Tue Mar 12 2024

08z surface analysis had weak trough/cool front from southern MT
into southern ND with weak low over southeast MT. Surface features
supported by weak upper-level trough from eastern MT into CO per
water vapour loop. System moisture-starved with some mid-high
clouds passing through. Looking upstream, upper trough dropping
into southwest Canada/northwest CONUS. This will be the main
weather concern this week.

Today/tonight, surface lows slips southeastward dragging
trough/cool front into the CWA, hanging up over northern NE
tonight. Result will be slightly cooler temperatures over the
northern two-thirds of the CWA with far southern SD near 70F.
Temperatures will be near guidance.

Wednesday/Thursday, main upper trough drops into the Rockies and
splits as main energy wraps up over the four corners region by
Thursday morning. Northern stream energy passes through with a
potential lead shortwave spinning into modest upper low over
eastern NE Wednesday. The disposition of the lead shortwave most
uncertain with a variety of ensemble outcomes. For now, forecast
will reflect middle ground with best chances of >0.10" QPF over
parts of northeast WY/Black Hills and along the SD/NE border,
which is where best synoptic forcing/low level frontogenisis
coincide. Initial lift may be wasted on saturation. >0.25" QPF
chances ~50% over the northern Black Hills where froude numbers
>1 and 0-2km mean RH >90% Wednesday night/Thursday morning could
promote enhanced upslope flow and much needed snow. Wet bulb zero
heights support best snow chances over northeast WY/Black Hills,
which is inline with most probabilistic guidance. 50% chance of 4"
of snow over the northern Black Hills late Wednesday to Thursday
morning. Temperatures will be slightly below guidance over
southwest half of the CWA for highs Wednesday give pops/clouds,
but near guidance elsewhere. Looks like a good chance of 40+ MPH
wind gusts just east of the Black Hills as the main storm system
wraps up southeast of the CWA Thursday.

Friday into the weekend, temperatures rebound some, but decent
upper trough sweeps into from central Canada to the Midwest which
will drop a cold front through the northern Plains. Gusty winds a
good bet with minimum QPF given lack of moisture this far west.
Temperature spreads quite large by the weekend given low
confidence in eventual location of coldest air over the CWA.

&&

.AVIATION...(For the 06Z TAFS Through 06Z Tuesday Night)
Issued At 1143 PM MDT Mon Mar 11 2024

VFR conditions will continue through the forecast period. Breezy
west to southwest winds will develop on Tuesday from southern
parts of northeast WY to far southern SD.

&&

.FIRE WEATHER...
Issued At 252 AM MDT Tue Mar 12 2024

Elevated fire weather conditions expected today as minimum
relative humidities drop into the upper teens to mid 20s over far
southern portions of the CWA near the NE border and west winds
average 10-20 mph. Much higher minimum relative humidities
expected Wednesday and Thursday, although gusty northerly winds
are expected Thursday. Elevated fire weather concerns return
Friday into the weekend as drier air returns.

&&

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

$$

DISCUSSION/KEY MESSAGES...Helgeson
AVIATION...26
FIRE WEATHER...Helgeson


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