Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 231133

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
433 AM MST Mon Jan 23 2017

.SHORT TERM...(Today Through Tuesday Night)
Issued at 303 AM MST Mon Jan 23 2017

Water vapor shows deep upper trof along the west coast with
disturbed sw flow extending through the cntrl Rockies. Week upper
ridge axis currently pushing through the wrn Dakotas. At the
sfc...ridge is located over the cntrl Dakotas with deepening lee
trof over ern WY/ern CO. Expanding area of low stratus/fog
across the plains of wrn SD. upper wave embedded in the sw flow aloft will move
through the ridge and may spread a band of light pcpn newd across
the cwfa. Thermal profiles suggest mainly snow, although temps may
warm enough for a mix of rain/snow in our srn zones. Thermal
profiles also suggest some lower level drying after passage of
this wave, and with the low stratus/fog currently spreading sewd
through wrn SD there is a some chance for an area of -fzdz/-dz to
develop. However, chances seem slim enough and will leave out of
forecast for now. High temps will be tricky given expanding area
of low stratus.

Tonight and Tuesday...strong upper jet pushing through the desert
sw through the cntrl Rockies/cntrl plains will develop an upper
low over the cntrl Rockies tonight, with the low continuing to
deepen as it tracks ewd across Neb on Tuesday. Models continue to
converge on this solution, which would bring wdsprd accumulating
snow to much of the cwfa. The heaviest snow is likely to fall
across scntrl SD during the day on Tuesday as upper low deepens
further over ern Neb. At this time, still thinking rather wdsprd
2-6 inches across the cwfa, with the higher amounts over scntrl SD
and possibly the nrn Blkhls. The least amount of snow with this
system will likely be from nern WY through far nwrn SD, with areas
along the ND border only receiving an inch or two. Northerly winds
will increase late tonight into Tuesday and may lead to areas of
blowing snow, especially on the plains east of the Blkhls into
scntrl SD. System will pull out rather quickly Tuesday night with
snow dissipating from west to east. Will keep the current Winter
Storm Watch in place and allow the day shift one more look at
model data before issuing any warnings/advisories.

.LONG TERM...(Wednesday Through Sunday)
Issued at 303 AM MST Mon Jan 23 2017

Low pressure moves quickly away from the region by Wednesday
morning. However, the broad upper trough will remain across the
region Wednesday, with a chance for mostly upslope snow showers
over far northeast WY and the northern Black Hills area through
Wednesday night as upper level energy slides through the area.

Temperatures will be below average Wednesday and Thursday. As trough
moves out of the area and building ridge over the west coast slowly
shifts east late in the week, temperatures should gradually rise to
average levels over the weekend. Dry weather is still expected from
Thursday through the weekend.


.AVIATION...(For the 12Z TAFS Through 12Z Tuesday Morning)
Issued At 433 AM MST Mon Jan 23 2017

An extensive area of low clouds from northwest to south central
SD, with IFR/LIFR conditions, will slowly slide south and west to
the Black Hills area today and eventually across much of the CWA
by this evening. Some uncertainty as to when these clouds will
reach KRAP and KGCC terminals, but at this time it looks to be
late morning to early afternoon at KRAP and mid afternoon at KGCC.
A weak disturbance will bring areas of light rain and snow to the
forecast area today, mainly during the morning. Snow will become
more widespread and heavier later tonight, especially across
northeast WY and the Black Hills, as a stronger system approaches
the region.


SD...Winter Storm Watch from this evening through late Tuesday night
     for SDZ024>032-041>044-046-047-049-072>074.

WY...Winter Storm Watch from this evening through late Tuesday night
     for WYZ057.



SHORT TERM...Johnson
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