Area Forecast Discussion
Issued by NWS Glasgow, MT
FXUS65 KGGW 192227
Area Forecast Discussion
National Weather Service GLASGOW MT
327 PM MST Sun Feb 19 2017
.SHORT TERM...for northeast Montana...tonight through Tue...
A westerly to southwesterly flow aloft will prevail through
Tuesday. A weak shortwave trough is expected to move across the
area tonight, bringing a slight chance of precipitation from the
west and south. The latest GFS model output keeps this mainly
along the North Dakota border, where other models keep this more
over our western and southern areas...so decided to leave a
slight chance in for both regions. Either way...as this spreads
north and east overnight, temperatures in the far northeast corner
of the state will likely get cold enough to see a wintry mix of
precipitation. With light winds expected across the area overnight,
areas of fog are also a potential concern, especially near river
valleys over the eastern part of the CWA.
Monday and Tuesday...Temperatures will again be above normal as a
ridge moves across northeast Montana. A stronger embedded shortwave
is anticipated to move across the region Tuesday, bringing
another chance of precipitation to the area. This may start out as
wintry precipitation in the morning along and north of Highway 2,
but should transition to rain area-wide throughout the day.
Accumulations are currently expected to be less than a tenth of an
.LONG TERM...Tue night through Sun...
Main forecast challenges in the extended period now revolve
around the increased chances for precipitation amid colder
temperatures after the middle of the week.
Models have now begun to line up showing some banded
precipitation, especially across our northern zones late Tuesday
night, then through our central and southern zones Wednesday
afternoon through Thursday.
Daily fluctuations between day warm and night cold will bring
changeovers between rain and snow each day. Some accumulation is
possible. At this time, expecting 2-4 inches of snow near the
Little Rockies / Zortman area.
Beginning Thursday, temperatures will struggle to reach above
freezing as the cold air mass from the Canadian Rockies sweeps
down through our region.
Previous long term discussion: A shortwave trough moves through
Eastern Montana Tuesday Night and drops a cold front south through
the area. Models have differences in track of the surface low
with GFS and NAM along the Canadian border while the ECMWF well to
the south in SE Montana and into South Dakota. Either way, it
looks like there will a good chance of either rain early and snow
late north of the Missouri River.
The cold front becomes quasi-stationary south of the forecast area
during the day and Wednesday and both the GFS and ECMWF want to
develop an area of overrunning precipitation but in different
locations of the forecast area. Temperatures will be borderline
for rain vs snow. Will mention a chance of rain and snow over
most of the region with the best chance in the north.
Upper trough moves inland from the Pacific on Wednesday and into
the Central and Northern Rockies on Thursday. The surface low
tracks well to the south across Colorado and Kansas which will
keep most of the precipitation to the south of the forecast area
with this system. However, flow aloft becomes split with this
system on Thursday and models are hinting at a northern stream
wave that could bring a chance of snow into Northeast Montana.
Friday is expected to be mainly dry and colder with temperatures
closer to normal with the forecast area between systems.
A shortwave trough in NW flow aloft moves through the area on
Saturday. There could be enough moisture for a slight chance of
snow. Another wave late Sunday could bring a slight chance of
Flight Category: LIFR for KGGW and KOLF. VFR for KGDV and KSDY.
Synopsis: Lingering low clouds and fog seem likely to persist
through the overnight hours, especially across the lower elevation
area in our NE portion of our CWA. KGGW and KOLF will likely be
impacted more than KSDY and KGDV.
Winds: Light and variable winds tonight will set up from the west
at 5 to 10.
Ice jams have developed on the Milk River near Glasgow and the
Yellowstone River near Terry. As of 730 am MST, no flooding has
been reported from either jam. The Milk River has risen to 21.25
feet in the Glasgow area at 730 AM with a flood stage there of 25
feet. The Yellowstone River at Glendive has been holding steady
between 47 and 48 feet overnight with a flood stage there of 53.5
feet. Will need to watch both rivers carefully for the
possibility of ice jam flooding over the next few days.
Additional concerns are rising for possible flooding on the
following rivers and streams: Big Muddy in Sheridan County,
Yellowstone in Prairie and Dawson County, and the Milk River in
With the Milk River steadily rising, a Flood Watch is in effect through
Monday, and may be expanded.
Flood Watch through Monday afternoon for Central and Southern