Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Bismarck ND
124 am CDT Thursday Jul 24 2014

issued at 104 am CDT Thursday Jul 24 2014

Have updated to refine probability of precipitation.

Update issued at 925 PM CDT Wednesday Jul 23 2014

While convection has remained low in coverage through 230 UTC
across central and eastern Montana into southwest has increased in intensity over the past hour.
Storm Prediction Center has just issued a Severe Thunderstorm Watch across north
central Montana. See Storm Prediction Center mesoscale discussion 1452 for details regarding trends
through 345 UTC as storms propagate east. All model guidance has
had a tough time handling the convective scenario this
evening...with storms now expected to approach the North Dakota
border around 07-09 UTC.

Update issued at 539 PM CDT Wednesday Jul 23 2014

No significant changes with this forecast update. Still monitoring
for convective initiation across central into eastern Montana over
the next one to two hours. The 20 UTC hrrr would suggest
Montana surface based convection approaching the North Dakota border
by 03-04 UTC...continuing to propagate into central North Dakota
by 08-09 UTC sustained by a 30-35 knots low level jet. The best
chance for large hail and damaging winds are generally along and
west of Highway 85 as the Montana convection propagates into
western North Dakota.


Short term...(this evening through thursday)

Issued at 320 PM CDT Wednesday Jul 23 2014

Forecast issues in the short term are thunderstorm chances...and
possibility of severe storms.

Currently...surface high was over Manitoba southward through the Red
River valley...with low pressure in the Lee of The Rockies.
Southeasterly flow was keeping moist low levels with dewpoints in
the 60s over western and central North Dakota. At upper levels...a
Sharp Ridge was in place from Saskatchewan to the western Dakotas
and eastern Mt/WY. Best shear and middle level lapse rates were over
the Front Range this afternoon...with most unstable convective available potential energy over the
Front Range into the western Dakotas.

Latest model runs suggest thunderstorms developing over central and
eastern Montana this evening in the vicinity of a middle level
shortwave energy impulse forecast to move/develop into northeastern
Montana during the evening. Once convection becomes better
established...the scenario is for storms to migrate eastward into
western North Dakota later this evening...then spread into central
North Dakota after midnight. The western third of North Dakota has
the best potential for severe storms late this evening into the
early morning hours.

Ongoing convection daybreak Thursday over much of central North
Dakota expected to continue moving eastward. Then...attention turns
to the west as a significant upper low emerges into the Front Range
from The Rockies with strong southwest flow aloft into the Dakotas.
At the same time...the aforementioned surface low over the Front
Range will have moved/developed eastward into the western Dakotas.
These ingredients will be favorable for plenty of shear...cape
(especially with surface dewpoints in the 65 to 70 degree
range)...and upper level impulses. Good chance of thunderstorms
Thursday afternoon over the western third of the state. This will
continue into the evening hours as well...with severe weather
possible over much of the forecast area Thursday afternoon/night.

Long term...(thursday night through wednesday)

Issued at 320 PM CDT Wednesday Jul 23 2014

The main features in the long term period continue to be an upper
low off the Washington/or coast and its interaction with the downstream
h500 ridge over the northern plains. As the upper low moves east
and flattens the ridge...a cold front at the surface will
position itself across eastern Montana by Thursday afternoon. The
front will then push east across North Dakota Thursday
evening and overnight into Friday morning. Thunderstorms...a few
possibly severe with strong winds and hail the main threats will
accompany the front as it progresses east through the state
Thursday afternoon and evening. On Friday cooler but still
reasonably mild temperatures in the upper 70s to lower 80s should
be the rule. Any showers and isolated thunderstorms should be
limited to the east. One more day of showers/scattered
thunderstorms on Saturday as the slow moving upper low tracks
south across Minnesota. While the state will generally be on the
dry side of the upper low cant rule out showers as cool air aloft
should support some instability...especially north. As the upper
low drifts east and a ridge probability of precipitation up in Montana Sunday through
Tuesday...should be dry with generally pleasant temperatures and
humidity for this time of year.


Aviation...(for the 06z tafs through 06z Thursday night)
issued at 104 am CDT Thursday Jul 24 2014

VFR conditions outside of thunderstorms are forecast for the 06utc
taf cycle across western and central North Dakota. Isolated
thunderstorms in northeast Montana were moving into northwest
North Dakota and will spread east and south through 12utc. See
tafs for timing and threat details. Another round of storms is
expected late Thursday afternoon and into the evening.


Bis watches/warnings/advisories...


short term...jv
long term...New Hampshire

National Weather Service Glossary of Abbreviations