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Area forecast discussion 
National Weather Service Bismarck ND
104 PM CDT Tuesday Jul 7 2015

Update...
issued at 1253 PM CDT Tuesday Jul 7 2015

Atmosphere continues to slowly destabilize over western North
Dakota. Couple of areas of congested cumulus developing...one over
northeast Montana and another in southeast Montana. Have again
backed off on the ignition time a little over western North
Dakota this afternoon. Made some timing and placement adjustments
tonight and limited the thunder potential as the precipitation
moves into central North Dakota. Did keep some isolated thunder
central but the potential for thunder looks limited at this time.

Update issued at 941 am CDT Tuesday Jul 7 2015

06 UTC NAM and latest iterations of the rap/hrrr seem to be a
little too aggressive in developing and moving convection across
western North Dakota this morning. Latest rap shows 600-800 j/kg
of cape and 30kts of 0-6km bulk shear over west central into
southwest North Dakota late this afternoon so there is still
potential for thunderstorms with a few stronger cells. For now
trimmed back on the eastern extend of convection through this
afternoon.

Also extended the mention of smoke through the afternoon for all
but the far eastern County Warning Area. Smoke had abated across most of central
and eastern North Dakota overnight...but remained over the west. A
west to northwest flow aloft will bring the smoke over the
west...back into central North Dakota today. Smoke is from the
Canadian fires...in addition to fires over the northwest U.S.

Update issued at 633 am CDT Tuesday Jul 7 2015

Adjusted smoke density a bit up to patchy smoke from areas of
smoke as other than the southwest visibilities were generally 6
miles or better. NAM continues to shoe 1500 or better cape across
the southwest by noon today which should support afternoon/evening
thunderstorms.

&&

Short term...(today and tonight)
issued at 300 am CDT Tuesday Jul 7 2015

The main forecast issue in the short term period will be chances
for convection.

Currently...surface high pressure was centered over the
central/eastern Dakotas. Skies were clear over the state.
Visibilities were reduced to around 4 miles due to smoke at
Dickinson and Hettinger in southwestern North Dakota...and also at
Sidney Montana. Will still keep a mention of smoke through the
morning over mainly western North Dakota...and with south winds
increasing a bit this afternoon will take the mention of smoke out
for the afternoon.

At upper levels...northwest flow continues with the tail end of a
jet streak oriented northwest to southeast across North Dakota early
this morning.

Today an upper level shortwave trough is forecast to approach
western North Dakota later this morning and move east across the
region tonight and Wednesday. The leading edge of upper level
impulses associated with the trough reaches western North Dakota
late this morning. By this afternoon...southwestern North Dakota is
in the right rear quadrant of the aforementioned jet streak. Another
jet streak moving out of Wyoming moves across South Dakota and into
central/southern Minnesota this afternoon and tonight. This
scenario will enhance instability across the region and induce
surface low pressure from southern Saskatchewan to Wyoming this
afternoon. This surface low pressure trough is forecast to
move/develop eastward into the western Dakotas tonight.

Introduced some slight chance mention of thunderstorms in the far
southwest late this morning. Isolated to scattered thunderstorms
expected this afternoon over the western half of the state...and
across all of western and central North Dakota tonight. Best cape
remains in the western part of the state more aligned with the
surface trough. Best shear is across southern North Dakota and into
South Dakota. The best chance of strong storms would be across
southwestern North Dakota...mainly late afternoon and early evening
when bulk shear is forecast to be strongest at around 40-45 knots.

Long term...(wednesday through monday)
issued at 300 am CDT Tuesday Jul 7 2015

The prominent upper low across Canada begins to fill and migrate
north as a Pacific flow begins to emerge across western North
America in the extended period. This will eventually bring
southwest flow aloft with impulses moving into the northern
plains by the end of the work week into the weekend. This will be
followed by a retrograding h500 ridge over the Southern Plains
north into the northern plains by Monday which should bring in a
more typical July warmth. Wednesday will see highs in the
70s...gradually warming through the 80s into the weekend and
possibly 90 by Monday. The best chances for thunderstorms will be
Saturday and Sunday when the Pacific/tropical flow reaches the
northern plains.

&&

Aviation...(for the 18z tafs through 18z Wednesday afternoon)
issued at 1253 PM CDT Tuesday Jul 7 2015

It appears the smoke from Canadian and northwest U.S. Fires in
more aloft today than the past few...thus visibility restrictions
are not as widespread across the region. However smoke remains and
would not be surprised to see some MVFR visibilities due to fog
through 18z Wednesday. Scattered convection is expected to develop
over western North Dakota this afternoon and move east tonight.
Limited the mention of thunder to kisn and kdik this
afternoon/evening. As precipitation moves into central ND taf
sites the threat of thunder diminishes. Could be some patchy fog
on the back side of the precipitation 06-12z before north to
northwest flow increases.

&&

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

$$

Update...twh
short term...jv
long term...warm air advection
aviation...twh

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