Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 210823
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
223 AM MDT Fri Jul 21 2017

.DISCUSSION...(Today Through Thursday)
Issued at 222 AM MDT Fri Jul 21 2017

08z surface analysis had low pressure over southeast MT with
"cold" front into northwest WY and trough into central NE.
Convective complex moving east along trough early this morning.
Should be out of the CWA by 12z. Shortwave scooting across eastern
MT into the Dakotas will push surface low into eastern ND today
dragging "cold" front through the CWA. Much drier air will move in
behind the front with 20-30kt boundary layer winds. Expect deep
mixing given strong surface heating and weak cool air advection
from 800-600mb. Gusty northwest winds will result. Leftover
instability on tail end of shortwave may pop a few -TSRA in
central SD late this afternoon and early this evening. Clearing
skies are expected tonight. Temperatures will be above guidance
today and near guidance tonight.

Saturday and Sunday, upper ridge will rebuild over the Rockies as
westerly flow Saturday becomes northwesterly Sunday. Dry air in
place, so PoPs not warranted. Few breezy spots Saturday afternoon.
Temperatures will be near guidance.

Next week, upper ridge shifts into the plains and flattens. Series
of shortwaves moving across the US/Canadian border will push a few
frontal boundaries into the CWA, which may be the focus for
convection. Temperatures will peak early in the week and then cool
to near normal for the rest of the week.

&&

.AVIATION...(For the 06Z TAFS Through 06Z Friday Night)
Issued At 1118 PM MDT Thu Jul 20 2017

Thunderstorms with MVFR conditions will continue to move across
western SD tonight. Outside of any thunderstorms, VFR conditions
are expected. Northwesterly winds will become a little breezy on
Friday afternoon.

&&

.FIRE WEATHER...
Issued At 222 AM MDT Fri Jul 21 2017

Much drier air will push into the area this afternoon. Minimum
relative humidities in the teens will be common across the
northwest. Deep mixing will promote gusty northwest winds across
far northeast WY and northwest SD. Critical fire weather
conditions will result, so will hoist Red Flag Warning.

Few breezy spots will occur again Saturday with minimum relative
humidities from 15-25%.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...Red Flag Warning from 9 AM this morning to 6 PM MDT this evening
     for SDZ261.

     Heat Advisory from 11 AM MDT /noon CDT/ this morning to 7 PM MDT
     /8 PM CDT/ this evening for SDZ032-043-046-047-049.

WY...Red Flag Warning from 9 AM this morning to 6 PM MDT this evening
     for WYZ297-298.

&&

$$

DISCUSSION...Helgeson
AVIATION...Pojorlie
FIRE WEATHER...Helgeson



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