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Area forecast discussion 
National Weather Service Bismarck ND
649 am CDT Tuesday Jul 22 2014

Update...
issued at 643 am CDT Tuesday Jul 22 2014

Patchy areas of fog continue across west and central North Dakota
this morning. Will maintain the fog through 9 am CDT. Current
forecast trending OK.

&&

Short term...(today and tonight)
issued at 445 am CDT Tuesday Jul 22 2014

Forecast issues today are patchy dense fog this morning...and
thunderstorm chances this afternoon along the Montana border counties.

The rains of Monday...and light winds overnight...have brought
temperatures down close to the dew point levels. Patchy fog had
formed at Tioga...Williams County...at Dickinson...and around
Jamestown. Patches of low cloud were advancing south and west
through the state.

Early morning fog will dissipate by middle morning with low cloud
patches also drying up as lower dew point air makes its way in and
daytime heating begins.

For this afternoon...a weak trough of low pressure forms over
eastern Montana with a thermal ridge axis pushing north just west
of the state line. This will be sufficient for some surface
convergence...while a weak middle level vorticity maxima approaches
with middle level forcing. The combination...in slightly increasing
unstable air...could lead to isolated thunderstorms...especially
over southwest North Dakota...Bowman-Hettinger areas.

Any convection dissipates this evening with cooler lows...in the 50s.

Long term...(wednesday through monday)
issued at 445 am CDT Tuesday Jul 22 2014

Closed upper low off the Washington/or coasts will be the defining forecast
feature for most of the extended period. The upper low is forecast
by GFS/European model (ecmwf) to migrate across the northwest US through Idaho by
Thursday then into Saskatchewan/mant by Friday/Saturday. It then meanders
south across the northern plains Sunday into early next week
bringing a coolish weather pattern for July. As this low begins its
journey northeast into the northern plains and the prairie provinces
of Canada it will flatten an h500 ridge over the northern plains by
Thursday. At the surface this means a cold front will approach from
the west and force a low level thermal ridge across western North
Dakota Thursday. This should be the warmest day of the week with
highs middle 90s southwest to west central. Cold frontal passage
Thursday afternoon/night will also bring a chance of thunderstorms
through the region. Currently going 30-40 probability of precipitation for this. After
Friday will only be a small chance of thunderstorms as the upper
low slide southeast keeping the region on its southern side which
will be generally dry. Spotty 20 probability of precipitation Friday through Tuesday with
highs in the 70s to lower 80s.

&&

Aviation...(for the 12z tafs through 12z Wednesday morning)
issued at 643 am CDT Tuesday Jul 22 2014

Main issue this morning will be fog leftover from rain cooled air.
Visibilities have been as low as 1/4 mile in fog at kdik prior to 12z.
The fog will end by 14z most areas. Then VFR.

&&

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

$$

Update...warm air advection
short term...jpm
long term...warm air advection
aviation...warm air advection

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