Area Forecast Discussion
Issued by NWS Rapid City, SD

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454
FXUS63 KUNR 080524
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1024 PM MST Wed Dec 7 2016

.UPDATE...
Issued at 843 PM MST Wed Dec 7 2016

Main fcst challenge for the evening revolves around the wind chill
advry. Added Mellette Co a little earlier this evening as winds
there will stay up a bit longer and with current cold temps fcst
and ABR expanding their advry...it made sense to add Mellette to
the mix. Latest NAM12 shows weakening sfc pressure gradient as the
night wears on...so winds should relax toward sunrise. However
will need to keep an eye on temps over areas that currently have
snowcover as 850-700hpa cond pressure defs show drying low layers
leading to a good radiational cooling night. Remainder of fcst
appears to be on track and only hourly tweaks needed to grids.

&&

.SHORT TERM...(This Evening Through Thursday Night)
Issued at 300 PM MST Wed Dec 7 2016

Current surface analysis shows strong low pressure now over
southern Ontario, with 1045 mb high over southern Alberta. Tight
pressure gradient between the two systems is continuing to produce
breezy to windy conditions across the SD plains. Large upper level
trof now covers much of Canada and the United States, with strong
jet stretching from the Pacific NW to the Southern Plains to the
northeast US. Skies are variably cloudy across the area. Temps are
in the single digits to mid teens, with wind chill values near or
below zero in most areas.

Frigid weather will continue through the short term period, with
temps 20 to 30 degrees below average through Thursday night. Arctic
high will slowly move southeast into the Northern Plains tonight and
Thursday, with winds finally diminishing overnight. This will allow
for bitter cold temps in most areas overnight, from around zero to
as low as 15 below or so by Thursday morning. The lighter winds will
still produce wind chills as low as 25 below to 30 below zero in
many areas overnight into Thursday morning. Will issue a wind chill
advisory for most of the cwa, excluding parts of south central SD
and the Rapid City area to Hermosa, where the combination of temps
and wind will keep values above the criteria of -25.

Skies will be mostly sunny on Thursday, with high temps similar to
today, mostly in the 5 to 15 degree range. However, there will be
less wind across the area as the high moves into eastern MT. Lows
Thursday night will drop to near or below zero again as the high
moves across ND. With relatively light winds, it looks like the only
areas that may approach wind chill advisory criteria will be across
northwest SD.

.LONG TERM...(Friday Through Wednesday)
Issued at 300 PM MST Wed Dec 7 2016

Warm front pushes into the cwfa Friday ahead of an approaching
low pressure system. Temps are expected to warm up 5 or ten
degrees higher than Thursday...but pinpointing the location of the
front will be difficult. Light snow associated with the baroclinic
zone and low pressure will develop across the area Fri night into
Sat. Accumulations will generally be light with up to an inch or
two. Colder air will push back into the region Sat night/Sunday
behind the departing low. Below average temperatures are expected
to remain across the region through the rest of the long term with
occasional light snow early next week.

&&

.AVIATION...(For the 06Z TAFS Through 06Z Thursday Night)
Issued At 1024 PM MST Wed Dec 7 2016

Good VFR conds are expected at KRAP and KGCC terminal
locations through valid TAF period. Cold high pressure will continue
to slide into the region...allowing winds to slowly diminish and
will keep skies clear.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...Wind Chill Advisory until 11 AM MST /noon CST/ Thursday for
     SDZ001-002-012>014-024-025-027>029-031-032-041>044-046-047-
     072-073.

WY...Wind Chill Advisory until 11 AM MST Thursday for WYZ054>058-071.

&&

$$

Update...Hintz
SHORT TERM...26
LONG TERM...13
AVIATION...Hintz



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