Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 110533
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
1133 PM CST Sun Dec 10 2017

.UPDATE...
Issued at 1133 PM CST Sun Dec 10 2017

Latest water vapor imagery shows a potent mid/upper level low
with the center of circulation in the corner of southeastern
Saskatchewan. Associated surface low was in southern Manitoba
with pressure falls continuing over western and central ND,
although the delineation between pressure falls/rises was not far
behind, now shifting into far western ND and southeast Saskatchewan.
Strongest winds are right along/within the isallobaric rise/fall
transition zone. Models are in good agreement with shifting the
center of the pressure bubble rise in south central into southern
Manitoba by 12z/6AM CST Monday. Current wind advisory placement
looks good based on upstream observations. So far, the highest
winds have occurred in Tioga with a 53 mph gust and at Crosby
with a 50 mph gust. The 03Z Bufkit soundings are too slow with
the strong winds that are already occurring in northwest and far
north central ND, thus will continue to watch stations upstream
and adjust if necessary.

UPDATE Issued at 936 PM CST Sun Dec 10 2017

With wind gusts upstream in Saskatchewan this past hour close to
50 mph will issue a wind advisory for nw and north central North
Dakota tonight.

UPDATE Issued at 611 PM CST Sun Dec 10 2017

No major changes were needed with this update cycle. Blended the
latest observations with the previous forecast and trimmed back
precipitation chances over the next hour as most radar returns in
my north are likely not reaching the ground. Did keep an area of
slight chances in my north central as Rolla was reporting light
rain with their last observation. As ceilings continue to lower,
precipitation chances will continue to increase.

&&

.SHORT TERM...(This evening through Monday)
Issued at 324 PM CST Sun Dec 10 2017

Highlights in the short term include the strong northwest winds to
develop for tonight and Monday, as well as chances of light rain and
snow with patchy blowing snow.

Currently, an Alberta Clipper was over central Alberta, with
continued warm advection ahead of it across much of the Northern
Plains. A north-south warm front extended from northern
Saskatchewan, across western Manitoba, and along the Devils Lake
Basin and James Valley in the Dakotas. Temperatures ranged from the
50s in the southwest to the 30s in the Turtle Mountains and James
Valley.

The clipper low is forecast to dive southeast tonight, reaching
central/southern Minnesota by daybreak Monday morning. As the
clipper approaches, the associated upper level shortwave`s leading
edge was associated with some light radar returns - especially along
the warm frontal boundary. Some initial chances of light rain or
snow late this afternoon into this evening are possible in north
central ND into eastern ND. Then as the main center of the vigorous
shortwave moves southeast across ND, some light scattered snow -
possibly mixed with light rain - is forecast to develop.

As the main shortwave exits the state by daybreak Monday morning, a
secondary shortwave will follow after daybreak, continuing the
chances for light snow. The loss of mid-level clouds later on Monday
with low level clouds may result in supercooled low levels, allowing
light snow to mix with some light freezing drizzle Monday afternoon
before the precipitation ends.

Decent 3-hour pressure rises of 3-7 mb late tonight through early
Monday afternoon, cold advection, and forecast soundings indicating
mixing from the surface to around H825 will result in northwest
winds of 25 to 30 mph with wind gusts to 35-40 mph tonight into
Monday morning/early afternoon. There is a chance for patchy blowing
snow, but the uncertainty lies in any impacts...mainly because of
the relative wet nature of the expected snow and whether any
visibility impacts might occur outside of any areas of falling snow.
This may be a case of good visibility most of the time, but flurries
or light snow showers in the strong winds might lower visibilities
for brief periods of time.

The strong winds keeping the lower levels well-mixed will keep
temperatures from dropping much tonight. Overnight lows should be in
the upper 20s to lower 30s most areas of western and central ND.
Highs Monday may not reach 30F in the Turtle Mountains, with highs
in the 30s across the remainder of western and central ND.

.LONG TERM...(Monday night through Sunday)
Issued at 324 PM CST Sun Dec 10 2017

The impacts of two more clipper systems highlight the extended
forecast.

The first clipper system is forecast to move southeast across the
Northern Plains Tuesday night through Thursday, with the global
models differing on placement of associated upper level shortwaves
and, in turn, placement of the surface low track. The consensus of
the models are in agreement on a quick recovery in temperatures on
Tuesday, with highs near 50 in far southwestern ND and 40s mainly
across the western half of the state.

The next clipper system looks to be at the Friday night/Saturday
timeframe, with gusty winds and chances of rain and snow. The models
hint that the west coast ridge may be breaking down next weekend,
with another possible low pressure system bringing chances of rain
and snow next Sunday/Monday.

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1133 PM CST Sun Dec 10 2017

Hazards to aviation include low level wind shear to 55kts and
northwest surface winds gusting 40-45kts KISN-KMOT through 12Z.
Gusty northwest winds to 30-35kts KDIK-KBIS-KJMS. This wind
associated with a cold front sweeping through the region. MVFR to
locally IFR conditions will prevail after the frontal passage. Brief
Visibility reduction due to snow and blowing snow are possible,
however did not add to TAFS due to uncertainty in timing.

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
Wind Advisory until 6 AM CST /5 AM MST/ Monday for NDZ001>004-
009>012-017.

&&

$$

UPDATE...KS
SHORT TERM...JV
LONG TERM...JV
AVIATION...WAA



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