Flood and Heavy Rain in Montana, June 18 to 20, 2020

Area Forecast Discussion
National Weather Service Great Falls MT
1130 PM MDT Wed Jun 17 2020

Aviation Section Updated.

.UPDATE...

The surface low that has been impacting the region continues to
slowly rotate through the area, causing widespread precipitation.
Expect snow at elevations above 7000 feet, and rain at lower
elevations. The forecast is working as intended; therefore, no
changes will be made, at this time.
- Fogleman

.SYNOPSIS...

Scattered to widespread showers are expected over the area tonight
through Thursday. Some snow is possible over Southwest Montana
but will likely remain above pass level. Temperatures will also
remain 10 to 15 degrees below normal during this time. High
pressure ridging will then bring warmer and drier weather starting
Friday and continuing into early next week, with some scattered
showers possible at times.

&&

.DISCUSSION...

Tonight through Friday...Large upper level trough will begin to
wrap up into a large upper low overnight tonight and gradually
progress eastward. The result is still widespread rain showers,
although with somewhat diminished coverage than earlier today.
Snow levels tonight will generally be above 7000 feet and bring
limited impacts to the area. Thus have continued with no winter
weather highlights for the night. Overnight lows will again be
below normal, and generally in the 30s and 40s. The mentioned
upper low then spins around in Canada leaving MT in northwest flow
for Thursday. The result will be continued cool temperatures with
scattered rain showers and perhaps an isolated thunderstorm. Due
to scattered activity of showers QPF values are a little tricky to
pinpoint, although and additional 0.25 to 0.50 inch of rain is
possible for some reasons. Showers then become more isolated
Thursday night while temperatures again remain below normal. Some
areas of fog are also possible for Thursday night into Friday
morning. As the trough exits the area on Friday, the northwest
flow will keep a chance of showers mainly during the afternoon
hours. Daytime heating will bring weak instability during the
afternoon, causing a chance for a few thunderstorms each day.
However, any storms should remain weak. Temperatures will remain
10 to 15 degrees below normal today through Thursday, with a
warming trend starting on Friday. Anglin

Saturday through next Wednesday...Forecast models continue to
indicate that weak high pressure ridging will gradually build over
the western United States during this period. This will continue
the drying and warming trend, allowing temperatures to warm to
between 5 and 10 degrees above normal. However, weak energy in the
resulting westerly flow aloft will keep at least a slight chance
of mainly afternoon and evening showers and thunderstorms.
Coulston

&&

.AVIATION...
Updated 1130 PM MDT Thu Jun 17 2020 (18/06Z TAF Period)

VFR to MVFR conditions in light rain and low clouds are becoming
more widespread across North-central Montana tonight. Expect areas
of light rain to continue expanding southward through Thursday
morning. Mountain obscuration continues. Precipitation and clouds
begin to decrease in coverage with partial clearing by Thursday
afternoon and evening.

NOTE: Amendments not scheduled for Ennis (KEKS) due to
ongoing runway closure.

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  46  62  44  70 /  70  60  40  30
CTB  45  62  44  69 /  70  40  50  40
HLN  47  62  45  72 /  80  70  30  20
BZN  42  61  40  72 /  80  50  20  10
WYS  35  57  31  65 /  70  40  20  10
DLN  38  60  39  69 /  60  30  10  10
HVR  47  63  44  72 /  80  30  30  30
LWT  44  57  41  66 /  90  60  30  40

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
None.
&&

http://www.weather.gov/greatfalls