Area Forecast Discussion
Issued by NWS Bismarck, ND

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000
FXUS63 KBIS 231814
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
114 PM CDT Fri Sep 23 2016

.UPDATE...
Issued at 104 PM CDT Fri Sep 23 2016

Little change to the forecast for the remainder of the day other
than to blend to observed trends through 17 UTC. Two areas of
convection, one across northwest North Dakota and another across
the south central and southeast will continue to propagate
northeast through the afternoon. Somewhat of a lull in
precipitation is expected across the southwest and south central
until early evening. Thereafter, elevated convection associated
with a strengthening low level jet and the arrival of greater
upper level forcing continues to be suggested on the 13-16 UTC
operational and experimental HRRR iterations across southwest
North Dakota, with additional storms initiating across eastern
Wyoming this afternoon propagating northeast into the southwest,
also sustained by the level jet and resurgence of upper level
forcing. SPC has again expanded the Marginal Risk across the
southwest and has now included the far southwest in a Slight Risk
in their Day 1 Convective outlook.

UPDATE 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
Saturday.

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
east.

.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 18Z TAFS through 18Z Saturday afternoon)
Issued at 104 PM CDT Fri Sep 23 2016

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


&&

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

$$

UPDATE...AYD
SHORT TERM...JPM
LONG TERM...JPM
AVIATION...AYD



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