Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 231501

Area Forecast Discussion
National Weather Service Bismarck ND
1001 AM CDT Fri Sep 23 2016

Issued at 950 AM CDT Fri Sep 23 2016

The biggest change with this update is associated with the
expansion of the SPC Day 1 Marginal Risk into a great portion of
southwest North Dakota with their 13 UTC outlook. The 11-14 UTC
HRRR iterations and the experimental ESRL HRRR within their 2-5km
updraft helicity forecasts have consistently shown tracks of
75-100+ m2/s2 across southwest North Dakota this evening,
pointing to the potential for organized convection. This is
plausible given increasing low level warm air advection and
moisture transport arching into the southwest north of the
surface low that will be propagating into western South Dakota
and Nebraska, coincident with the next surge of upper level
forcing. 850mb CAPE values around 1000 j/kg in a highly sheared
environment suggest low topped supercells could be possible. Large
hail is the most likely threat given the likely elevated nature of
the storms.

UPDATE Issued at 632 AM CDT Fri Sep 23 2016

For this update, no major changes were needed. Tweaked the
temperatures through the morning hours as well as the QPF
forecast. Otherwise, just blended the most current observations to
the inherited forecast. Decided to keep precipitation chances as is
for the time being, as showers should continue to become more
numerous over western and central North Dakota through the morning
and afternoon hours. Once the surface low begins to mature over
South Dakota, should have a better idea of eventual coverage by
later this afternoon. Isolated thunder is still expected with the
activity today, mainly in the south. Severe weather is not
expected at this time. Stronger shortwave approaches tonight,
bringing more widespread rain and thunderstorm potential to the
west as the low lifts into North Dakota.


.SHORT TERM...(Today through Saturday)
Issued at 515 AM CDT Fri Sep 23 2016

This Friday morning the mid level low, that began impacting our
weather with an increase in clouds yesterday, was over Utah and
progged to move northeast. This is consistent model to model. By
Saturday afternoon it is either over eastern Montana or western
North Dakota, depending on which model is followed, and ends up in
Manitoba by Sunday. The 150 mile difference in track of that mid
level low results in very little difference in sensible weather as
the surface low track is much more in line model to model.

Basically what this track and diffluent flow aloft means is a lot
of clouds and numerous showers. It also means warmer weather
ahead of the surface feature as winds veer to southerly, and an
increase in instability. We`d also expect a dry slot to work in,
likely through the central Dakotas, resulting in some sunshine on

The surface low track and tightening gradient would support windy
weather Saturday and Sunday, very windy southwest with an advisory
possibly needed.

As far as lightning, the better chances are along and south of
I-94 as CAPE and instability are highest, but still not
impressive, later today. storms could fire in the dry slot
Saturday, and conditions would favor strong storms, but they would
likely form in the central Dakotas, strengthening as they move

.LONG TERM...(Saturday night through Thursday)
Issued at 438 AM CDT Fri Sep 23 2016

Gusty wind in the wake of the low continues for Sunday, again,
possibly advisory levels. Behind the mid level low on monday we`d
typically expect cooler air, however, models agree on strong H5
ridging, in response to the deepening low, into the forecast
area. This means back to normal, and even above normal
temperatures, to end September.


.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
Issued at 950 AM CDT Fri Sep 23 2016

Widespread IFR/MVFR conditions in stratus, rain showers and
thunderstorms are forecast across western and central North
Dakota today and tonight. A brief improvement to VFR is possible
at KBIS Saturday morning as dry air works into the storm system
impacting the area.




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