265
FXUS63 KBIS 170543
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
1243 AM CDT Thu Aug 17 2017

.UPDATE...
Issued at 1230 AM CDT Thu Aug 17 2017

Widely scattered showers showing up on the Stanley radar that have
been moving southeast through western North Dakota past few hours.
Appears to be associated with mid level warm advection and the
surface trough in eastern Montana. Added slight chance of showers
and more cloudiness to the rest of tonights forecast with low
POPs. Patchy fog still forecast by CAM models across teh east so
left in place.


UPDATE Issued at 939 PM CDT Wed Aug 16 2017

Little change with this update other than for observed trends
through 02 UTC. The 01 UTC RAP/HRRR within their visibility
forecasts favor the potential for fog development across the
Turtle Mountains through the James River Valley where surface
dewpoints in the 60s are in place, with already small temperature
and dewpoint spreads.

UPDATE Issued at 635 PM CDT Wed Aug 16 2017

No major changes were needed with this update. Most of the
precipitation has moved out of the southeast part of our forecast
area, with the exception of light shower possible in extreme
eastern Dickey county. Otherwise, just blended the latest
observations with the going forecast.

&&

.SHORT TERM...(This evening through Thursday)
Issued at 343 PM CDT Wed Aug 16 2017

Small thunderstorm chances and minimal fire weather concerns
highlight the short term period.

Low pressure over the eastern Dakotas will move slowly east
tonight. clouds over eastern ND will give way to clearing skies as
high pressure builds over the region tonight. With light winds and
mostly clear skies, we lowered forecast minimum temperatures from
given guidance. With drier air working in, the threat of fog
appears less than the past couple of days. The exception being
eastern portions of central ND, from the Turtle Mountains south
through the James River Valley. Previous shift added a mention of
fog and see no reason to deviate. We did extend the mention of
patchy fog back a little farther west, to the Missouri River
Valley given the recent rainfall and expected light winds and
clear skies.

After a cool start, we are expected to warm into the 80s across
most of the forecast area, ahead of a shortwave trough and
associated weak surface cold front dropping down a building
western North America ridge. With warm surface temperatures, we
should become slightly unstable ahead of the boundary. Have
maintained our small chance of pops across the west. The severe
potential looks to be low at this time, but with an inverted V
type sounding, we could get some gusty winds with any storms that
do develop. Behind the front we could see a couple hours of gusty
northwest winds, with dropping humidities to around 15 to 20
percent. With our recent rains, and only a small timeframe of
strong winds and low humidities, concerns remain low.

.LONG TERM...(Thursday night through Wednesday)
Issued at 343 PM CDT Wed Aug 16 2017

Warmer conditions are still in store over the upcoming weekend.

Min RH values will dip into the low 20s again Friday and Saturday
across southwest North Dakota. Warm and breezy conditions
Saturday may lead to elevated fire danger across the far southwest
North Dakota where less than an inch of rain has fallen recently.
However, fire weather managers have noted a greenup over the far
southwest, although a few dry spots remain, specifically around
the National Park.

Another weak wave may produce scattered showers and storms Sunday
night through Monday evening. Deterministic models are in
reasonable agreement in upper level ridging pushing into the
northern plains Tuesday and Wednesday signifying mainly dry
conditions.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday evening) Issued
at 1235 aM CDT THU Aug 17 2017

Hazards to aviation include patchy MVFR/IFR conditions in fog at
KJMS between 09-13Z. Otherwise surface low pressure in eastern
Montana at 06Z will move east to western North Dakota by noon
Thursday. The low will be the focus for widely scattered -TSRA
KMOT-KDIK-KBIS after 22Z. Too much uncertainty to include this in
TAFs instead used VCTS.

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...WAA
SHORT TERM...TWH
LONG TERM...TWH
AVIATION...PA