Area Forecast Discussion
Issued by NWS Bismarck, ND

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702
FXUS63 KBIS 131706
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
1206 PM CDT Sun Aug 13 2017

.UPDATE...
Issued at 1151 AM CDT Sun Aug 13 2017

Minor adjustments to pops in the southern James River Valley this
afternoon as the mid/upper level low slowly shifts into southeast
ND later this afternoon. Plenty of sunshine north, with mostly
cloudy conditions along and south of Interstate 94. Followed the
high resolution solutions with improvements in sky conditions
through the afternoon. Have begun coordinating fog issues with
neighboring offices for the tonight period. More on that in the
afternoon update.

UPDATE Issued at 923 AM CDT Sun Aug 13 2017

Upper low continues to track slowly east across eastern North
Dakota. Precipitation over our southeastern CWA continues to wane,
but also continues to push back west along and north of the
Interstate. Utilized a blend of short term pops with the previous
forecast to depict a continued slow overall dissipation through
the morning. We did keep a mention of afternoon thunder over the
far southeast. Removed the mention of fog and lowered sky cover
across the north.

UPDATE Issued at 635 AM CDT Sun Aug 13 2017

Area of rain continues to dissipate south of Bismarck while the
area over the James River Valley was spiraling around the mid
level low centered over eastern LaMoure County. Question for
today is how far west, toward Bismarck, does the wrap around
extend. Have maintained low pops for the morning and trended down
and out, stage east, for the afternoon.

Other issue is low clouds and patchy fog. Updated the weather
grids to take dense fog up to fog as visibilities were slowly
improving. look for fog erosion from the northwest by mid
morning.

&&

.SHORT TERM...(Today and tonight)
Issued at 430 AM CDT Sun Aug 13 2017

H5 low remains over the forecast area as it was pushing just very
slowly east as of this writing. Two significant short waves were
rotating in the closed flow with one continuing the rain south of
Bismarck and the other resulting in an expansion and
intensification of rain through the James River Valley.

Low clouds and fog will be slow to burn off this morning with
erosion coming from the northwest as sunshine there works to
evaporate the northern periphery.

The low moves into Minnesota this evening ending the rain east.

Weak H5 ridging moves in for a mainly clear sky tonight, but with
high low level moisture in place fog will likely result,
especially across the south.

.LONG TERM...(Monday through Saturday)
Issued at 430 AM CDT Sun Aug 13 2017

As the weak H5 ridge passes Monday southwest flow aloft becomes
established, and with increasingly diffluent flow, upward motion
results. This is aided by the nose (left front) of an H2 jet.
Surface support is also present in the form of, by Monday
afternoon, a surface boundary advancing to the Montana and North
Dakota border with convergence, lifting, and moisture pooling.
This results in thunderstorm development. With lapse rates
steepening and shear profiles increasing, strong to near severe
storms could be possible along and west of highway 85 by mid to
late afternoon.

This long wave trough advances with a parade of short waves
keeping the chance for storms going right through Monday night
and into Tuesday. With that comes a lot of clouds and temperatures
only in the 70s for most places.

Beyond that, less organized systems and triggers for the end of
the week should spell more hit or miss showers and storms rather
than the widespread ones of late. With that is more solar
insolation and the expectation that lower 80s for highs will be
more common.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1151 AM CDT Sun Aug 13 2017

High pressure situated over northern ND into southern Saskatchewan
and Manitoba will move southeast through the forecast period.
MVFR ceilings at KBIS should lift to low VFR around 19Z, with KDIK
and KJMS lifting to VFR around 20Z and 21Z respectively. As the
surface high drifts southeast, a southerly return flow will set up
tonight setting the stage for another round of IFR ceilings and
fog again tonight into Monday morning. For now will hit KJMS
hardest followed by KBIS. Confidence in low ceilings and fog not
as high at KDIK, KISN and KMOT at this time, thus will hold off on
low ceilings and fog for these sites.

&&

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

$$

UPDATE...KS
SHORT TERM...JPM
LONG TERM...JPM
AVIATION...TWH



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