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Area forecast discussion 
National Weather Service Bismarck ND
1150 PM CDT Tuesday Jun 2 2015

Update...
issued at 1150 PM CDT Tuesday Jun 2 2015

The airmass over the western half of the forecast area was
becoming more stable. Thunder was removed from that area with just
isolated rain showers possible the rest of the overnight. In the
east...a line of showers and isolated lighting strikes was moving
through rollette and Pierce counties.

A large area of low clouds was advancing southwest across the
area. Sky grids were increased to mostly cloudy the rest of the
night.

Update issued at 943 PM CDT Tuesday Jun 2 2015

Severe threat has now pushed well to the east of the area...so
will allow the Tornado Watch to expire. Areas of showers with
some weak thunderstorms will continue through tonight.

Update issued at 906 PM CDT Tuesday Jun 2 2015

Severe threat continues to push off to the east and diminish.
Still a little concern of something strong developing over the
James River Valley where the greatest instability exists...but
the chances for this continue to diminish with the easterly
pushing surface boundary. Therefore...have cancelled most of the
Tornado Watch with the exception of the James River Valley
counties...which I expect to be dropping by the top of the hour.

&&

Short term...(this evening through wednesday)
issued at 206 PM CDT Tuesday Jun 2 2015

Main forecast problem in the short term period is risk of severe
weather this afternoon and this evening. Very moist and unstable
atmosphere is setting up over central North Dakota this afternoon.
Surface based cape values are exceeding 3000j/kg as of 1 PM this
afternoon...with 30-35 knots of bulk shear south central...and
precipitable waters in excess of an inch over all but southwest North
Dakota...and over 1.3 in over the James River Valley. A surface
boundary remains from west central into north central North Dakota
with showers and embedded thunderstorms continuing along and north
of this boundary. To the south... surface low pressure is situated
near Mobridge South Dakota with clear to partly cloudy skies over
the far southwest and south central...aiding in the surface
destabilization. Will be sending up a special 18z sounding today.

Mesoscale models are giving various solutions on how convection may
evolve this afternoon/evening. In general...mesoscale models have
tried to develop a few supercells over western North Dakota along
the frontal boundary and tracking southeast across south central
North Dakota during the middle to late afternoon. Then additional
convection develops late afternoon/early this evening over the
James River Valley into South Dakota and tracks east. Latest WRF
develops a qlcs over western North Dakota and tracks it across the
state. The 12z hopwrf keeps convection pretty much out of the County Warning Area
today with cells developing just southeast of Jamestown and
tracking into southeast North Dakota. No matter what eventually
happens...any thunderstorms that do develop across the southern
half of the state will have the potential to become severe. Large
hail...damaging winds will be the most obvious threats...but very
heavy rain will also be a threat and a tornado cannot be ruled out
with any discrete supercell thunderstorm that develops.

The severe weather threat should lessen from west to east this
evening...much earlier than last nights round of severe weather. As
the surface low pressure system tracks east late tonight and
Wednesday models are indicating abundant low level stratus
developing in a north flow. Expect a much cooler day Wednesday
with showers ending across the north central into the James River
Valley Wednesday morning.

Long term...(wednesday night through tuesday)
issued at 206 PM CDT Tuesday Jun 2 2015

An active weather pattern will highlight the long term.

Earlier model runs indicated an upper level ridge over North
Dakota through late week. Now indications are this ridge will be
further to east...allowing most of North Dakota to reside in
southwest flow aloft as a deep upper level longwave trough
develops across the West Coast. This will allow numerous
shortwave troughs to traverse the northern plains. This will bring
a nearly daily chance for thunderstorms.

Temperatures should generally be in the 70s and 80s during the
afternoon hours through the weekend.

&&

Aviation...(for the 06z tafs through 06z Wednesday night)
issued at 1150 PM CDT Tuesday Jun 2 2015

The airmass over the western half of North Dakota was becoming
more stable and so the thunderstorms will be taken out of the
tafs. A large area of low stratus clouds was advancing southwest
through the area with MVFR and IFR ceilings.

&&

Bis watches/warnings/advisories...
none.
&&

$$

Update...jpm
short term...twh
long term...aj
aviation...jpm

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