Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 09/21/21
Area Forecast Discussion
National Weather Service Great Falls MT
753 PM MDT Mon Sep 20 2021
.SYNOPSIS...
Lingering shower and thunder activity ends by this evening and
skies begin to clear as high pressures begins to build into the
region. Temperatures begin to moderate on Tuesday, and by
Wednesday, afternoon highs could be in the 80s once again at lower
elevations. Additionally, little to no precipitation is expected
for the next several days after today.
&&
.UPDATE...
The weather producer of the last couple days, moves eastward out of
the area, and upper level ridging gradually becomes the dominant
feature for The Treasure State. The forecast is performing nicely;
therefore, no updates will be made, at this time.
- Fogleman
&&
.DISCUSSION...
Remainder of this afternoon and tonight...The exiting Pacific
trough continues to bring an unsettled northwesterly flow aloft
for broken clouds, isolated showers/thunder, and another day of
below average temperatures. Mostly maintained pops from the
morning update but did increase them over the northeastern portion
of the CWA as some showers and even a few thunderstorms approach
the Canadian border. Current mesoanalysis shows some modest CAPE
here as well, so increased the chance for thunder to roughly match
the remainder of the region. Impacts from any shower/thunder
activity should be limited to brief gusty winds, brief rainfall,
occasional lightning, and some graupel or snow pellets with the
heavier showers. An isolated cold air funnel can`t be ruled either
out given the weak surface instability and cold air aloft,
especially along the eastern half of the Hi-Line. Showers should
quickly end by sunset and partial clearing is expected to take
place tonight as high pressure begins to build back over the
Northern Rockies. Some patchy fog will be possible over the
southwest valleys and other areas that receive precipitation
followed by clearing skies tonight. Temperatures will cool to the
20s and 30s for most areas, with colder readings in the higher
valleys along the Divide and southwest MT. Frost and freezing
temperatures will be most widespread in the southwest. -RCG
Tuesday through next Monday...Overall expect dry conditions
starting on Tuesday and continuing into next week. An upper level
ridge of high pressure is expected to be the primary weather
influencer over the Northern Rockies during this period, resulting
in dry conditions and near to above average temperatures. A weak
disturbance is expected to temporarily dampen the ridge for
increased westerly winds and potential elevated fire weather
conditions on Wednesday. Then a weak surface frontal boundary
moves southward into North Central MT and may bring brief
northerly wind shift to the plains. Overall, this front is not
expected to move into the southwest at this time. With dry air in
place, overnight lows may be on the chilly side, especially in the
higher valleys of Southwest MT and along the Rocky Mountain
Front. -RCG/Brusda
&&
.AVIATION...
658 PM MDT Mon Sep 20 2021 (21/00Z TAF period)
VFR conditions prevail at all airfields, with the exception of KWYS,
where intermittent MVFR conditions are expected in light rain
showers during the first few hours of this TAF period. Some areas of
virga are present throughout the region. Expect the associated
hazards. Overnight and into the early morning hours, predominant
MVFR conditions are expected at KWYS, due to mist. Expect mountain
obscuration, especially across the mountains of southwest Montana.
It is likely that light aircraft will encounter morning fog when
flying through valleys. After 21/14Z, VFR conditions are expected at
all airfields, with mostly clear skies across the region. Gusty
winds along The Northern Rocky Mountain Front, and some breezy winds
funneled through passes, impact light aircraft aviation ops on
Tuesday.
- Fogleman
Refer to weather.gov/zlc for more detailed regional
aviation weather and hazard information.
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 37 73 44 80 / 0 0 0 0
CTB 38 70 41 75 / 0 0 0 0
HLN 37 74 43 81 / 0 0 0 0
BZN 31 71 36 78 / 20 0 0 0
WYS 19 58 23 65 / 10 0 0 0
DLN 28 70 36 76 / 10 0 0 0
HVR 39 71 43 82 / 10 0 0 0
LWT 34 69 41 80 / 10 0 0 0
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
http://www.weather.gov/greatfalls