Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 201759

Area Forecast Discussion
National Weather Service Bismarck ND
1259 PM CDT Thu Apr 20 2017

Issued at 1235 PM CDT Thu Apr 20 2017

Mid/upper level synoptic pattern favors a brief omega type block
forming over western and central North Dakota. This will result in
a dry forecast, with prospects of fog formation increasing tonight
into Friday morning.

Latest suite of satellite imagery shows a closed upper level low
in northeastern Minnesota and another shortwave trough in western
Idaho forming into a closed low as it traverses into Wyoming
later tonight into Friday. In between a brief omega block pattern
evolves across western and central North Dakota. Prospects for fog
formation will increase tonight through Friday morning. Concern
will be for dense fog after midnight, especially central and
southern North Dakota where recent rainfall and low level moisture
remains with radiational fog formation favored.


.SHORT TERM...(Today and tonight)

Issued at 337 AM CDT Thu Apr 20 2017

Forecast highlights/challenges in the short term period will be
cloud cover and continued chances for showers today.

Currently, S/WV trough over the Northern Plains with two embedded
impulses, one over southeastern ND and a secondary wave over
western ND. Associated showers with the western ND impulse persist
over central ND with subsidence drying things out far west. Most
shower activity previously over my southeast have moved east with
the wave but should see redevelopment this morning. Cloudy
conditions persist over all but my southwest. Low clouds (via
HRRR/NAM/RAP/GLAMP25) are still on track to develop over western
ND now through 14Z from north to south as the mid level cloud deck
moves slowly east. This already is occurring over southern
SK/northeastern MT with stratus building south-southeast
towards/into western ND.

BUFFER soundings along with diurnal cloud development procedures
(lapse rates/boundary layer moisture) all show a strong signal
for diurnal CU development today in the wake of the mid level
deck. Along with the CU, we will likely see diurnally driven
showers as well with several models indicating as such. Showers
may linger across the James River Valley into the early evening
until the nocturnal inversion forms and mid level forcing rotates
south. Daytime highs were tweaked to reflect the likely colder
temperatures central and east where cloudy conditions are
expected. Warmer west where we expect more sun along with
southerly return flow.

Dry conditions tonight with a ridge of surface high pressure over
the central and eastern Dakotas.

.LONG TERM...(Friday through Wednesday)

Issued at 337 AM CDT Thu Apr 20 2017

Upper level ridging/high pressure will result in dry and mild
conditions Friday. Ridge breaks down Friday night into Saturday
bringing some precipitation chances to the region which continues
into Sunday. Vigorous S/WV trough moving into the Pacific
northwest Sat night will push east Sunday into Monday, resulting
in a very active/wet period Sunday night - Monday evening over the
Dakotas. Colder air is pulled south into the region so may see a
mix of rain/snow or all snow some places during the nighttime or
early morning hours. Active pattern continues through the work
week, though lots of uncertainty. Temperatures generally in the
50s and 60s with lows in the 30s to mid 40s through the weekend,
cooler for early to mid next week.


.AVIATION...(For the 18Z TAFS through 18Z Friday)
Issued at 1235 PM CDT Thu Apr 20 2017

Widespread stratus across central and eastern North Dakota will
gradually break up as the shallow cool boundary layer mixes out
this afternoon. However this weather pattern will be favorable for
fog and stratus to reform/return tonight into Friday morning.
Widespread IFR/LIFR is forecast KDIK-KBIS with KISN-KMOT-KJMS more
on the fridge of MVFR to locally IFR late tonight and Thursday
morning. Conditions VFR or gradually improving to vfr by 15Z.




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