Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Bismarck ND
333 am CST Friday Nov 21 2014
Short term...(today and tonight)
issued at 333 am CST Friday Nov 21 2014
Low pressure was over northern Saskatchewan with a warm front
extending south along the Montana/Dakotas border. The warm front is
forecast to move east across the state today. The front should reach
the James River Valley around noon. South winds ahead of the front
will become southwesterly and increase to 10 to 20 miles per hour. Highs should
reach the low to middle 30s from The Turtle mountains through the James
River Valley...and around 40 for much of the western part of the
A weak cold front follows the warm front tonight...but cold air
intrusion is expected briefly along the northern tier of counties.
Warm advection begins again in the west tonight with the approach of
another low pressure system. Lows tonight should be in the upper
teens to middle 20s across western and central North Dakota.
Long term...(saturday through thursday)
issued at 333 am CST Friday Nov 21 2014
After a mild start on Saturday...the main forecast highlights in the
extended period will be the potential hazardous winter weather
Saturday night through Monday.
Middle level shortwave trough pushing east across the Pacific northwest into
the Montana rockies tonight into Saturday will trigger Lee side
low pressure development from southern Alberta south-southeast
through the northern High Plains of Montana and Wyoming. Increasing
southerly flow/warm air advection ahead of the low pressure...coupled with a shortwave
ridge moving east ahead of the middle level trough...will result in
mild daytime highs Saturday...mid/upper 30s most locations. A few
low 40s possible southwest.
With increasing surface moisture and diffluent flow aloft will see
chances for precipitation materializing in the afternoon west.
Will keep p-type as all rain with the boundary layer up through
800-750mb above freezing.
Forecast becomes tricky regarding precipitation chances and p-type
Saturday evening through early Sunday morning. With the surface low
tracking to generally southwest Saskatchewan by 00 UTC Sunday and
far north central ND/southeast Manitoba by 12 UTC Sunday...the greatest
threat of precipitation will exist from the west central and
northwest into the north central Saturday evening. Forecast BUFKIT
soundings indicate profiles that would support freezing rain at
Minot and Devils Lake. Farther south...global models are generally
dry...but the latest 21 Nov 06 UTC NAM is depicting an area of warm
frontal precipitation spreading west to east and extending south to
the South Dakota border. Surface temperatures will be a big factor
as to if there will be a threat of mixed precipitation in the south
if the NAM should verify. For the time being used a model blend
which keeps precipitation confined to the west and north central.
This does result in a period of mixed precipitation Saturday
evening...into the early overnight hours. At this time the more
favorable area for light ice accumulations would be across the
northern third of west/central ND with forecast quantitative precipitation forecast on average
closer to a trace to the south.
Cold air will overspread the entire area between 12-18z Sunday and
models are not spreading the quantitative precipitation forecast ahead of the cold air...thus will
not mention any mix after 12 UTC Sunday. Will mention the wintry mix
in the severe weather potential statement Saturday night and closely monitor model runs over the
Next weather impact quickly develops across the west and north
Sunday morning and into the rest of the region Sunday afternoon
through Sunday night with wrap around snow showers and strong
northwest winds developing on the backside of the middle level low. The
strong winds and snow showers could still be an issue over eastern
portions of central North Dakota into Monday. Will continue to
monitor for possible highlights for the late Sat night-Sunday night
period as we move forward into this weekend. For blowing snow
impacts...think it will depend on how much snow we get with this
system...as the current snowpack should have crusted with the warm
temperatures Friday and Saturday.
Afterwards...Tuesday-Friday...another clipper tracks from eastern
Montana into eastern South Dakota during the Tuesday-Tuesday night
timeframe which would bring another swath of light snow across the
area...this will be followed by another surge of cold air lasting
into Thanksgiving. Late in the extended period...models are having a
hard time resolving the cold air over the northern plains. Both the
GFS/European model (ecmwf) agree that Thanksgiving will be cold...but they have
flipped their solutions beyond with the European model (ecmwf) now bringing upper
ridging and warmer temperatures into the region...while the GFS
keeps it cold.
Aviation...(for the 06z tafs through 06z Friday night)
issued at 1229 am CST Friday Nov 21 2014
At 06z an area of MVFR/IFR ceilings was moving northward through central
North Dakota. Latest short term models indicate the kbis and kjms
terminals will be most affected...and have tempo ceilings at 700 feet
and 1200 feet. Only made mention of scattered 1200 feet at kmot. Otherwise
VFR conditions as south winds become southwest later on Friday with
mainly broken middle/high clouds that should scatter out with time
during daylight hours.