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Area forecast discussion 
National Weather Service Bismarck ND
643 am CDT Tuesday Aug 4 2015

issued at 642 am CDT Tuesday Aug 4 2015

Considered adding a brief mention of patchy fog for an hour or two
this morning towards the southern James River Valley. Kjms and
kbac briefly reported visibility restrictions in fog...but they
have since climbed back to 10sm...and area webcams do not show
reduced visibilities. Decided to leave out the fog mention for
now since any fog should be very isolated...and is not expected
to persist.

Blended current observations into the grids...with the forecast
generally still on track.


Short term...(today and tonight)
issued at 305 am CDT Tuesday Aug 4 2015

Currently...surface high pressure extended from Manitoba southward
through the Red River valley. Low pressure continued to develop in
the Lee of The Rockies. At upper levels...a ridge was maintained
over the Canadian rockies and Front Range...but was being undercut by
a shortwave low/trough moving northeastward out of Utah into
Wyoming. A low level jet was established across the High Plains of
eastern Colorado/Wyoming and western NE/South Dakota nudging into eastern Montana. A line
of thunderstorms had developed along the nose of the h850
jet...arcing from the Black Hills southeastward into northeastern

The models move the upper level ridge eastward today...reaching
eastern Saskatchewan/western Dakotas by this evening. The models
continue its eastward March across the state...with the ridge
flattening as a strong upper level impulse...extending from central
Saskatchewan southward into Nebraska...enters far western North
Dakota early this evening and moves into central North Dakota before
daybreak Wednesday morning.

Expect mostly sunny skies over central North Dakota with east winds
becoming southeast...bringing higher surface dewpoints into the
region. Chances of thunderstorms begin late this afternoon in the
far west...with increasing chances this evening in the west and
spreading to central North Dakota late tonight. Increasing
cape/instability with the approach of the upper level impulse. Bulk
shear values are modest and we may see a strong storm or two...but
not expecting a severe weather outbreak with this scenario.

Look for highs today in the lower 80s north central through the
James Valley to the upper 80s in the southwest. Lows tonight should
be in the upper 50s to lower 60s.

Long term...(wednesday through monday)
issued at 305 am CDT Tuesday Aug 4 2015

Showers and thunderstorms from Tuesday night will continue into
Wednesday as an 500 mb wave moves across the state. Instability
increases Wednesday afternoon...especially across the eastern
half of the forecast area...while 0-6km shear is forecast to be
35 to 40 kts. The latest day 2 Storm Prediction Center outlook places eastern portions
of the forecast area in a marginal risk for severe
thunderstorms...and will mention the potential for a few strong
storms in the hazardous weather outlook.

Thunderstorm chances diminish behind this initial wave...but the
next wave is already moving into eastern Montana / western North
Dakota later Wednesday night into Thursday. The model blend paints
40-50 percent probability of precipitation across much of western and central North
Dakota on Thursday...and could see those rising in parts of the
forecast area with relative agreement already seen among the
deterministic runs of the NAM / GFS and European model (ecmwf).

A weak 500 mb ridge moves into the northern plains this weekend...but
the progression of waves continues. There is some disagreement
among the various model solutions in the details...and will again
favor the blended model approach which keeps much of Saturday
dry...with thunderstorm chances increasing Saturday night into


Aviation...(for the 12z tafs through 12z Wednesday morning)
issued at 642 am CDT Tuesday Aug 4 2015

A brief period of light fog is possible at kjms through 14z this
morning. Otherwise...VFR conditions are expected through the
forecast period as high pressure remains in control. Light surface
winds will become southeast later today. Showers and thunderstorms
are expected to move into the far southwest late Tuesday afternoon
but should reach/approach kisn/kdik by around 03z. Did not mention
thunderstorms in the vicinity for kbis or kmot as precipitation chances do not increase
significantly until after 12z Wednesday morning.


Bis watches/warnings/advisories...

short term...jv

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