Scientific Forecaster Discussion
fxus65 ktfx 240425
Area forecast discussion
National Weather Service Great Falls Montana
1025 PM MDT Fri Jun 23 2017
..aviation section updated...
Only minor adjustments to going forecast overnight. Main change
was to lower lows for tonight, mainly in the colder mountain
valleys along the Rocky Mountain front and south into southwest
Montana, as those areas should remain mostly clear. Clouds
currently along the east slopes of The Rockies seem to be being
reinforced by clouds moving south from the east slopes of the
Canadian rockies in Alberta. Have therefore kept skies mostly
cloudy along our east slopes overnight. Only a very small chance
of a passing light rain shower over the plains. Winds also appear
to remain light overnight with high pressure at the surface.
An upper level ridge of high pressure will gradually build over
the northern rockies over the weekend. As a result, expect a few
isolated showers over the region early this evening and again on
Saturday, while it will be mostly dry on Sunday. Afternoon
temperatures will gradually warm over the next several days, from
the mid 70s on Saturday to around 90 degrees by Monday.
Northwest flow aloft will remain in place over the northern rockies
and northern High Plains through the 2406/2506 taf period. VFR
conditions will prevail, however, lowering ceilings to around 5000ft
above ground level are expected to occur at the kctb, khvr, and klwt terminals
after 12z Saturday. Ceilings at the kctb terminal may approach MVFR
for a brief period during the early morning hours on Saturday, but
confidence is to low to mention at this time (outside of using
sct030). Some mountain obscuration is possible, especially along the
northern Rocky Mountain front. Otherwise, winds are expected to be
light and variable. - Moldan
/issued 535 PM MDT Fri Jun 23 2017/
Tonight through Sunday...a northwesterly flow aloft continues to
reside over the region...resulting in a few light rain showers
along The Divide. These showers will drift to the southeast this
evening...but should generally remain west of I-15. Otherwise
mostly clear skies will prevail...especially over southwest Montana.
Another cool/crisp night is expected, especially for the valleys
of the southwest...thus some delicate/sensitive vegetation could
be at risk once again. On Saturday, the upper level ridge builds
a bit further North/East resulting in slightly warmer
temperatures. A few spotty light showers will once again be
possible...mostly over north central Montana. On Sunday, the upper
level ridge continues to drift further east, resulting in mostly
dry and warm conditions over the region.
Sunday night through Thursday...the weekend warming trend peaks
on Monday as the upper level ridge axis passes over the region.
Warm temperatures Monday afternoon will produce adequate
instability to cause scattered afternoon and evening
thunderstorms. Some of this activity could persist late Monday
evening, aided by a shortwave trough approaching from the pacnw.
A large scale trough develops over western Canada on Tuesday,
then drops into the High Plains through mid-week. Diverging model
solutions provide little useful guidance regarding the passage of
shortwave features embedded within the broadly northwest flow aloft.
Overall, temperatures trend cooler Tuesday through Thursday, with
slight chances for showers and thunderstorms associated with the
minor shortwave disturbances.
Preliminary point temps/pops...
gtf 43 73 47 81 / 0 0 0 0
ctb 41 72 45 80 / 0 10 10 0
hln 46 77 50 84 / 0 0 0 0
bzn 42 75 44 82 / 0 0 0 0
wey 31 71 36 77 / 0 0 0 0
dln 42 75 45 81 / 0 0 0 0
hvr 44 75 47 82 / 0 10 0 0
lwt 41 69 43 77 / 0 10 10 0