Area Forecast Discussion
Issued by NWS Rapid City, SD

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000
FXUS63 KUNR 191101
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
501 AM MDT Wed Apr 19 2017

.SHORT TERM...(Today Through Thursday Night)
Issued at 306 AM MDT Wed Apr 19 2017

Current surface analysis shows low pressure over far northeast
CO, with frontal boundary extending across the Central Plains.
Inverted trough stretches north from the low across eastern WY.
Upper level analysis shows southwest flow across the region, with
main shortwave located across western WY, moving to the east-
northeast. Initial shortwave is moving through the area now. KUDX
radar showing scattered to numerous showers spreading northeast
across the area, with a few thunderstorms from the Neb panhandle
into far southern SD. Regional radars show more pcpn across
central WY with the main wave, pushing into northeast WY now.
Temps are mostly in the 40s, with some 30s across the higher
elevations of the western Black Hills.

Latest model guidance and current trends show that the somewhat
weaker, faster, and further north solution that the EC was showing
24 hrs ago is likely to materialize today. This means that pcpn
amounts will not be as high as was expected in most areas and the
heavier potential will be a bit further north across the CWA,
generally from far northeast WY and parts of the northern BH area,
into northwest SD, where best forcing and frontogenesis will be
later this morning. Potential amounts there will be near to over
an inch in many areas, with amounts of mostly a quarter to three-
quarters of an inch further south across southern portions of the
forecast area. Still a good rainfall event for much of the area.
The heaviest and most widespread rainfall looks to be from early
this morning through midday for most areas, and into the afternoon
across northwest SD. A few thunderstorms are still expected
across southern SD through midday. The highest elevations of the
BH, mainly above 6000 ft, could still see some snow and light
accumulations this morning, though the system is a bit warmer and
temperatures are struggling to drop there. Highs today will be in
the 40s across much of the area, some 50s across the far southern
CWA.

Pcpn will taper off and end quickly from southwest to northeast this
afternoon and early evening as the system pulls away. Skies will
clear tonight with lows in the 30s. A brief break from the unsettled
weather on Thursday as shortwave ridge tracks across, bringing
mostly sunny skies and warmer air. Highs will be in the upper 50s to
mid 60s, with 50s over the BH. Clouds will increase from the west
late in the day and evening as the next system slides southeast from
the Pacific NW through the Northern Rockies. Chances for rain will
increase across northeast WY and possibly spread into parts of
southwest SD late at night. Lows will mostly be in the 30s, with
some light snow possible across the higher BH if pcpn makes it
there late at night.

.LONG TERM...(Friday Through Tuesday)
Issued at 306 AM MDT Wed Apr 19 2017

Storm system will continue to dig southeast across the Rockies
and into the central high plains on Friday, with a low developing
across KS by the afternoon. Latest models in pretty good agreement
on system mostly just clipping northeast WY and far southwest SD
as high pressure sinks southeast into the Dakotas. Will keep
slight chance to chance pops across these areas, best chances
toward southern parts of northeast WY. The weekend looks mainly
dry, though a few light showers could still linger into Saturday
across northeast WY. Warm conditions will return briefly on
Sunday, with highs in the mid 60s to mid 70s. Still looks like an
unsettled and seasonable pattern for at least the first half of
next week as the next series of disturbances push through the
area, starting later Sunday night.

&&

.AVIATION...(For the 12Z TAFS Through 12Z Thursday Morning)
Issued At 500 AM MDT Wed Apr 19 2017

Widespread showers are expected this morning with MVFR
conditions. Local LIFR/IFR conditions expected near the Black
Hills and under the heaviest precipitation, especially near TSRA
over southern SD this morning. Conditions will improve from west
to east later this afternoon into tonight as the storm system
pulls away.

&&

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

$$

SHORT TERM...26
LONG TERM...26
AVIATION...Helgeson



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