Area Forecast Discussion
Issued by NWS Glasgow, MT
FXUS65 KGGW 261517
Area Forecast Discussion
National Weather Service GLASGOW MT
917 AM MDT TUE JUL 26 2016
.SHORT TERM...for northeast Montana...today through Thu...
Forecast was updated to increase pops a bit for this afternoon.
Scattered thunderstorms have popped around fort peck lake and will
likely increase in coverage into the afternoon. Echoes over
southern Sask should also move into the north or NE zones over the
next several hours. Models were not agreement with coverage and
placement so confidence isn`t as high as I`d like it to be.
Rest of forecast looked good. TFJ
Synoptic setup: a large high pressure heat dome continue to be
stationed over the western half of the conus with its center
positioned over Nevada. To the north, zonal flow exists across
southern Canada and the far northern CONUS. Weak shortwaves are
constantly flowing though this stream along with a mix of Pacific,
Monsoonal Moisture at the mid and upper level and Gulf of Mexico
Moisture in the lower levels.
A back door cold front Monday evening has turned winds to the
northeast over most of Northeast Montana overnight. The front
which was just south of the forecast area at 08z has interacted
with a shortwave to produce thunderstorms that were tracking along
and south of Highway 200. Another wave that was over North Central
Montana at 08z has produce scattered thunderstorms between the
Bears Paw Mountains south of Havre and the Cypress Hills to the
north. The wave will move through Northeast Montana this morning
and some of these storms should hold together with an unstable
atmosphere over the area.
The frontal boundary will stay to the south of the forecast area
the next few days allowing for somewhat cooler temperatures.
Frequent shortwaves will move through Northeast Montana with an
unstable atmosphere which will provide chances for showers and
thunderstorms. The atmosphere will be unstable enough at times for
a few severe storms but it will be difficult to time any specific
storms with the frequent waves. The upper level ridge is expected
to expand north across the Rocky Mountains Wednesday and Thursday
which will gradually turn the flow aloft to the northwest over
Eastern Montana. Forrester
.LONG TERM...Thu night through Tue...
The extended period begins Thursday evening with northwest flow
aloft over Northeast Montana. This flow pattern is based on the
area of persistent high pressure and hot desert air over the
Southwest and the large eastern Canada trough anchored by the
Hudson Bay low. This places the local area near the boundary
between the two air masses. Thus, the frequent weak short-waves
and embedded disturbance will find enough instability to kick off
isolated to scattered thunderstorms.
Conditions begin to change for the weekend when the ridge moves
east over eastern Montana. This push is caused by a deepening
trough off the Pac-NW and BC coast. Thickness heights ramp up and
upper flow backs around to the southwest. Weekend temperatures
become hot again.
By the end of the weekend the Pac-NW trough sends a cold front
across the Divide. This will lead to more chances for storms and
possibly cooler temperatures by mid-week.
Short-wave disturbances will find unstable conditions resulting
in isolated thunderstorms today and more widespread thunderstorms
tonight. Expect amends when storms threaten the terminal areas.
Winds: easterly 5-10 kt. Expect erratic winds near storms.