Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 180456

Area Forecast Discussion
National Weather Service Bismarck ND
1156 PM CDT Mon Jul 17 2017

Issued at 1155 PM CDT Mon Jul 17 2017

Have increased pops south of Interstate 94 for the overnight based
on radar trends over the past hour. Returns were increasing
rapidly across Bowman and Adams counties in response to several
factors including a surface convergence trough, mid level short
wave positive vorticity advection, 1,000-2,000 J/KG CAPE, and weak
shear. Latest CAMS runs support the idea that this convection will
push east, mainly south of the interstate, into south central
sections of the forecast area.

Issued at 1002 PM CDT Mon Jul 17 2017

No big changes from earlier forecast discussions. Forcing aloft
and at the surface are both on track to move across southern ND
now through the early morning hours of Tuesday. Latest CAM output
continues to track convection across southern ND, roughly along to
south of I94. Have noticed some north/south shifts of high res
qpf/future radar reflectivity, so opted to keep POPs below
`likely` and more scattered. Updraft Helicity signatures for a few
organized updrafts are still depicted, so strong storms remain
very possible over the next several hours through 10-12Z, again
roughly along to south of I94.

Issued at 710 PM CDT Mon Jul 17 2017

Scaled back considerably on POPs southeast for this evening.
Appears all activity will now remain to our south and east.

As mentioned in the previous discussion, we will see increasing
chances for convection southwest and south central later this
evening and especially during the overnight. Easterly upslope flow
north of low pressure over southern SD combined with upper level
support via an easterly moving embedded wave and right-entrance
region upper jet dynamics should trigger a decent area of showers
and thunderstorms south. Some of the high res guidance continue
to indicate decent updraft helicity streaks 08-12Z near the ND/SD
border area over my south central and southeast so will be
something to monitor later on tonight. Mentioned possible strong
storms in the HWO.


.SHORT TERM...(This evening through Tuesday)
Issued at 238 PM CDT Mon Jul 17 2017

An upper and surface low were located over the Hudson Bay over
Canada with a cold front extending south across western Ontario,
the northeast corner of Minnesota, eastern North Dakota, and into
central South Dakota. This cold front will be the focus of
scattered showers and thunderstorms later this afternoon. The
front has moved east faster than initially forecast, so any
thunderstorm development in our forecast area will likely be
limited to our far southeast counties, if that. The Storm
Prediction Center has maintained a marginal risk of severe weather
over McIntosh, Lamoure, and Dickey counties, but there is
considerable uncertainty regarding thunderstorm formation in these
areas. Still, with CAPE exceeding 2000-3000 J/kg and 35-40 knot
shear in place at the moment, if something does go it will have to
watched closely. One other thing to note is that there could be
some smokey issues due to some Canadian wildfires, especially in
the north.

Overnight, the upper level ridge continues to flatten with
embedded shortwaves propagating through the fast flow. Another
area of showers and thunderstorms will develop late over
southeastern Montana and move into southwestern North Dakota along
the South Dakota border. Some of the high resolution models
suggest this activity could strengthen overnight and sustain
itself as it moves across the southern part of the state through
the early morning hours. Confidence is low regarding this
solution, but some of the models do show these storms becoming rather
strong to marginally severe. Therefore, we will be monitoring.

Tuesday may see some lingering showers and storms early, with
relatively cooler temperatures during the afternoon. Highs will
mainly be in the low 80s, which should be a nice relief from the
recent hot weather.

.LONG TERM...(Tuesday night through Monday)
Issued at 238 PM CDT Mon Jul 17 2017

A weak, broad ridge briefly tries to build in on Tuesday night,
before another embedded shortwave trough travels through the flow
on Wednesday, bringing more shower and thunderstorm chances. The
progressive pattern will remain through the long term with brief
ridging and troughing alternating and near daily chances of hit
and miss thunderstorms. Conditions will likely be favorable for
strong to severe thunderstorm on a few of these days, but model
discrepancies on wave timing and strength preclude any confidence
in the potential at this time. Either way, it looks like and
active weather pattern will be in place for through the extended.


.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1155 PM CDT Mon Jul 17 2017

Scattered thunderstorms will be over southern North Dakota,
including KBIS-KJMS through 18/1500Z. Some haze north due to smoke
from Canadian wild fires. Otherwise VFR all terminals.




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