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Area forecast discussion 
National Weather Service Bismarck ND
327 am CDT Wednesday Aug 5 2015

Short term...(today and tonight)
issued at 324 am CDT Wednesday Aug 5 2015

Timing and precipitation chances/areal coverage of showers and
thunderstorms today and tonight are the main challenges in today's
short term period. area of showers and thunderstorms continued over
southwestern North Dakota and northeastern Montana...though the
intensity of showers and thunderstorms has waned with time early
this morning. The convection was associated with an upper level
shortwave that is forecast to continue moving eastward slowly
across the state today.

The latest iterations of the hrrr and NAM suggest that the area of
convection will still be in western North Dakota but approaching
central North Dakota by daybreak today. The latest hrrr suggests the
convection would begin increasing in intensity before noon over
central North a wide line of convection extending from
western Manitoba to Minot to Bismarck before noon. The models
suggest that The Turtle mountains and James Valley and eastward will
be the favored area for convection during the afternoon.

Cape and shear values are modest this afternoon in central North
Dakota...thus a few storms could be on the strong side...but
ingredients are not favorable for a mention of a severe threat.

Attention then turns westward. Wednesday morning and afternoon a
rather potent series of upper level impulses emerging from a trough
over the West Coast moves eastward across Montana/Wyoming. These
upper level impulses enter the western Dakotas late this afternoon
or early evening (models differ on timing)...and expand eastward
across the state tonight. Precipitation chances for this evening
begin in the west by mid-evening...spreading east into central North
Dakota after midnight.

The best cape and shear with this potent wave appears to be
farther south into South Dakota and Nebraska...but the modest
values in North Dakota could be enough for a few of the storms to
be on the strong side.

Long term...(thursday through tuesday)
issued at 324 am CDT Wednesday Aug 5 2015

The long term period begins Thursday with showers and thunderstorms
across eastern Montana / western North Dakota moving their way
east during the day. These are in response to an 500 mb wave and
upper level jet streak moving across the northern plains. The
deterministic models have come into fairly good agreement in this will carry likely probability of precipitation from northwest North
Dakota...through the central part of the state and towards the
southern James River Valley. The day 2 convective outlook from the
Storm Prediction Center places much of central and eastern North
Dakota in a marginal risk...and that appears reasonable with
SBCAPE values of 1500-2500...though shear is rather marginal.

Considered going dry for Friday across all of western and central
North Dakota...but after collaboration with surrounding offices
opted to keep a slight chance of thunderstorms in the far south.
The 05.00z GFS and European model (ecmwf) bring a small chance of rain into the
far south...while the NAM is dry.

Rain chances should increase again Saturday night into Sunday as
the next 500 mb wave moves across the region. The higher rain chances
are expected to be in southern parts of the forecast area...closer
to the more robust forcing. An upper ridge builds into the
northern plains early next week...which will bring drier weather
to western and central North Dakota.


Aviation...(for the 06z tafs through 06z Wednesday night)
issued at 324 am CDT Wednesday Aug 5 2015

VFR conditions are expected through the forecast period outside of
thunderstorms. Showers and thunderstorms over southwestern North
Dakota and northeastern Montana are expected to approach kisn and
kdik around 06z-07z lasting for a few hours through 09z-10z. Area of
convection reaching kmot/kbis around 12z-14z...and kjms after 18z.

Late Wednesday night another round of showers and thunderstorms
expected to move into western North Dakota mainly after 06z Thursday.


Bis watches/warnings/advisories...


Short term...jv

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