Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 290442

Area Forecast Discussion
National Weather Service Great Falls MT
1040 PM MDT Sun May 28 2017

Updated Aviation Discussion


Main update this evening is to significantly trend down the
isolated shower and thunderstorm activity along the east slopes of
the Rockies and into Southwest Montana. The main area of activity
currently is in the vicinity of Great Falls, and it should
diminish after sunset as it loses daytime heating and moves into
the area of the Big/Little Belt Mountains. Any lingering showers
and thunderstorms should be done by midnight. The rest of the
forecast remains in good shape.



An upper-level ridge of high pressure currently over the Pacific
Northwest will slowly move eastward over the next few days. As a
result, scattered showers and thunderstorms over our area today will
become more isolated for Monday through Wednesday. Temperatures
trend gradually warmer through Wednesday. Chances for showers and
thunderstorms increase again late in the week.


Updated 0440z.

With upper level ridging exerting its influence on the area,
tranquil conditions with VFR cigs and visibility should predominate
all terminals through the next 24 hours. Enough instability remains
over the mountains after 18z Monday to trigger a few showers/storms.
However, with light winds aloft any shower/storm activity will
remain confined to the mountainous terrain.  Cassell



The Big Hole River near Melrose is forecasted to go above
flood stage later this week. The rate the river rises this week
is greatly dependent on how fast the higher elevation snow pack
melts. Thus we will continue to monitor for possible flood
highlights later this week. Brusda


/ISSUED 500 PM MDT Sun May 28 2017/

Tonight through Tuesday...Scattered rain showers and thunderstorms
have been most concentrated today over Fergus County and along
central portions of the Rocky Mountain Front. Satellite imagery
reveals boundary layer cumulus marking a convergence line running
from near Cut Bank to Havre to Lewistown. This is providing a
source of initiation for the observed showers. Short-term model
guidance suggest that a minor short wave feature aloft, combined
with northeasterly upslope is responsible for the showers along
the Rocky Mountain Front. All of this activity will continue to
drift slowly SSE into central Montana through this evening. Gusty
winds may be possible in the vicinity of some of the stronger
showers or thunderstorms. The large scale upper level ridge axis
drifts over the forecast area Monday and Tuesday, providing mainly
dry and warmer conditions, except for isolated mountain showers.

Tuesday Night through Sunday...An upper-level ridge of high pressure
will be over the region Tuesday night into Wednesday, resulting in
fair weather for most. Just a few showers and thunderstorms are
possible over and near higher terrain Tuesday evening and again
Wednesday afternoon/evening. The EC and GFS are in good agreement
that a Pacific disturbance will then overspread our area Thursday
into Friday, resulting in a somewhat higher potential for scattered
showers and thunderstorms. The aforementioned models then disagree
on the timing of additional shortwaves for the upcoming weekend.
However, the potential of scattered showers and thunderstorms should
persist. Temperatures look to be above normal through the extended
period, with Wednesday likely being the warmest day.


GTF  45  71  46  79 /  20   0   0   0
CTB  44  71  43  77 /  10   0   0   0
HLN  48  75  49  82 /  20   0   0   0
BZN  43  72  43  79 /  20   0   0   0
WEY  36  63  34  70 /  30  10  10  20
DLN  44  72  45  78 /  10   0   0  10
HVR  41  71  41  79 /   0   0   0   0
LWT  41  67  41  73 /   0   0   0   0



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