Area Forecast Discussion
Issued by NWS Glasgow, MT
FXUS65 KGGW 220316 AAA
Area Forecast Discussion...UPDATED
National Weather Service GLASGOW MT
816 PM MST Sat Jan 21 2017
.SHORT TERM...for northeast Montana...tonight through Mon...
Sent an update tonight to incorporate the latest model data and
include the mention of freezing fog, freezing drizzle and
scattered flurries. I believe that most of the depiction of
reflectivity in the models may simply be frost or fog. Scaled back
our PoPs accordingly. Some of our river valley locations are now
seeing reduced visibilities. Should get worse as the night
Previous short term discussion: An area of low pressure continues
to sit off to the east of the forecast area this afternoon as the
CWA remains in fairly clear conditions with temperatures hovering
around freezing. These relatively mild temperatures have resulted
in snow melt and added moisture to the low level boundary layer.
On the edge of this low pressure system where skies remain clear,
patchy dense freezing fog is expected to develop. It may also
occur in some of the river valleys where snow pack is more
prevalent. Further to the north and east, low stratus is expected
to back into the area and if ceilings lower enough there
occasionally could be some patchy freezing fog as well. Other
concern is light snow/flurries or isolated freezing drizzle that
may accompany the cloud on the edge of the storm system as it
passes through the area.
Bufkit forecast soundings continue to show an elevated warm nose
which cools sufficiently late tonight and Sunday morning. Light
precipitation will allow evaporative effects, but may not be
enough to keep all precipitation in the form of snow. Therefore,
due to the combination of cloud microphysics and thermal
properties of the column, some freezing drizzle appears possible,
though probability is low. Will mention the combination of patchy
dense freezing fog and freezing drizzle in an HWO in the eastern
zones to get the word out on low probability impactful weather
conditions tonight which could create difficult travel conditions.
This is especially true if patchy freezing drizzle creates slick
roadways and combines with reduced visibility in freezing fog.
Again, probability is low at this time but worth monitoring and
worth messaging due to potential impacts should it occur.
Regardless, system will push east on Sunday and an upper ridge
will move into the area allowing for drying weather conditions. A
closed low off the Pacific Northwest and upper trough will head
east across the Western U.S. and knock the ridge down by Monday
with a new chance for snow showers spilling into the area from
west to east.
.LONG TERM...Mon night through Sat...
Models continue to show an upper low with a moist NW flow,
therefore increased pops slightly for light snow Wednesday-
Wednesday Night. With an upper ridge folding over into the region
late in the period, warmer and drier conditions continue to look
Upper trof moves across the western states midweek with slight
chances of snow and cooler temperatures. Best energy will be to
the south, but snow could spread northward on Tuesday.
Upper ridge then pushes over the Rockies for drier weather through
the end of the week. Cooler temperatures should persist until the
weekend before another chinook begins to develop across Alberta.
Low stratus clouds drifting S-SE out of Saskatchewan and across
NE Montana are forecast to reach a southward line roughly from
Malta to Jordan to Glendive overnight and may combine with some
fog to bring lowering ceilings and visibility overnight into
Sunday morning with local LIFR AND IFR conditions tonight. Fog and
low ceiling are forecast for the Yellowstone river valley through
Sunday morning. Freezing drizzle is a slight possibility in any
foggy areas, primarily over Daniels, Roosevelt and Sheridan
Winds will be light, less than 10 kts W-NW thru the forecast