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PNSTFX
MTZ008>015-044>055-150014-
Public Information Statement
National Weather Service Great Falls MT
1120 AM MDT Mon May 3 2021
...April 2021 and Water Year Seasonal Weather Summary for North
Central and Southwest Montana...
Northwesterly flow aloft prevailed for much of April. Typically a
weak ridge of high pressure dominates. Temperatures averaged below
normal with precipitation largely below normal. Wind speeds averaged
below near normal most areas, except along the Rocky Mountain Front.
April started warm, with a few record high temperatures on the 1st
and 4th. Very dry air produced some very low relative humidity
values so early in the season on the 1st and 3rd. A cold front on
the 5th brought cooler and wetter weather for much of the month. Up
to 13-inches of snow fell at Beagle Springs on the 5th and 6th,
while West Yellowstone picked up 7-inches. Strong winds prevailed on
the 8th, with gusts reaching 73-mph at Deep Creek. Another weather
system moved through on the 18th and 19th, producing as much as 15-
inches of snow near Wolf Creek. After this system, while not the
coldest of the month, a low of 1F was recorded at Elk Park on the
20th, and a new record low of 14F at Bozeman on the 22nd. Even a
little freezing drizzle fell on the 22nd at Great Falls. This was
the first instance of this since 1996 in April at Great Falls. A few
thunderstorms moved through the southwest on the 24th, with some pea-
sized hail reported in Beaverhead and Madison Counties. Temperatures
pushed above 80F for the first time of the year on the 30th.
#### Temperature
In April, temperatures were generally below average. Yellow Mule
(Gallatin) recorded the coldest average temperature of 25.9F. The
coldest temperature of the month was -1F at West Yellowstone on the
1st. The warmest was 83F at Bozeman on the 30th. Helena averaged
0.6F above normal while West Yellowstone averaged 2.7F below normal.
The areas warmest average temperature was 44.9F at Armells Creek
(Fergus). All areas were close enough to their average, so no
notable rankings were seen.
Very dry air prevailed in early April. Some record low relative
humidity values so early in the season occurred.
Bozeman 1 8.3% Second earliest and lowest RH so early.
Cut Bank 1 9.1% Earliest and lowest RH so early in the season.
Dillon 3 8.8% Earliest and lowest RH so early in the season.
Havre 1 10.2% Earliest and lowest RH so early in the season.
Helena 1 6.5% Earliest and lowest RH so early in season.
Lewistown 1 6.3% Second earliest and lowest RH so early.
The water-year-to-date temperature averages are 0.5F above normal.
The areas composite average temperature for this period was 30.8F,
the 55th warmest of record, and warmest since 2012.
#### Precipitation
Precipitation amounts were generally lighter than normal. The
heaviest precipitation was over the the northern Rocky Mountain
Front and some of the mountains of the southwest. Black Bear SNOTEL
(Gallatin) reported 4.20-inches and St Mary recorded 2.43-inches.
Dryness continued many areas. Dillon had their 6th driest April. Cut
Bank was driest since 2015 and West Yellowstone since 2005. For the
area, this was the 36th driest April of record. Last years April was
drier.
Water-year precipitation for the area is 84-percent of normal and
37th driest of record. Dillon continues their driest water-year of
record, while Lewistown has seen their 16th driest. Cut Bank has had
its 25th wettest.
As with precipitation, snowfall was light. The area composite of 5.0-
inches was 2.7-inches below normal and lowest since 2016. West
Yellowstone had one-inch of snow on the ground on the 30th. They had
none on May 1. Their normal melt-out date is May 3. Snowfall for the
season (Jul-Apr) has been near normal, totaling 65.2-inches, 0.9-
inches above normal. This is the 49th highest seasonal amount of
record.
#### Wind
Wind speeds averaged near to slightly below normal most areas. At
airport locations, Cut Bank recorded the highest monthly average of
13.3 mph. The highest average at other locations was 15.9 mph at
Deep Creek RAWS /Glacier County/, which is abount one mph lower than
normal for April. The highest wind gust for the month was 73 mph at
Deep Creek RAWS on the 7th. Gusts reached 66-mph near East Glacier.
The area average speed for April was 10-mph, the 23rd calmest of
record and 0.3-mph above normal. Lewistown had their 4th calmest
April of record and calmest since 2007.
The areas average wind speed for the water-year is 10.1 mph, the
30th windiest of record...and windiest since 2007. Great Falls has
had their windiest water-yeaer since 2002, while Havre has had their
windiest since 1979.
###############
During April, the average sky cover at Great Falls was 4.5-octas.
The average is 3.8-octas. Air quality PM2.5 concentrations (courtesy
of Montana Department of Environmental Quality) averaged 5.7
micrograms per cubic meter at Great Falls. This was the ninth lowest
of a 22-year period of record. Average for April is 5.6 micrograms
per cubic meter.
At Great Falls, the April high and low temperatures were 80F and
14F, for a range of 66F. This is the smallest range since 2019 and
slightly above the average of 62F.
Severe convection occurred on zero days, which is normal.
Rankings are shown below for individual locations if ranked within
the 15th highest or lowest of the respective element.
Average temperature...degrees Fahrenheit...
Apr Nrml Rank Oct-Apr Nrml Rank
Bozeman......41.1..42.2... 31.1...30.8...
Bozeman MSU..41.5..43.3... 32.9...33.5...
Cut Bank.....40.1..40.2... 30.8...30.2...
Dillon.......40.1..40.1.. 30.8...30.5...
Great Falls..41.5..42.4... 33.7...33.2...
Havre........43.6..44.0... 31.8...30.2...
Helena.......44.5..44.5... 34.6...33.2...
Lewistown....39.9..40.9... 31.6...31.7...
W Yellowston.31.4..34.1... 21.9...22.8...
Area Avg.....40.3..41.0...48th coolest 30.8...30.3...55th warmest
Precipitation...Inches...
Apr Nrml Oct-Apr Nrml
Bozeman.......0.99..1.68... 4.03....5.75...11th driest
Bozeman MSU...1.74..2.53... 7.40....9.52...
Cut Bank......0.40..0.95... 4.12....3.06...
Dillon........0.24..1.18... 6th driest 0.77....3.49... 1st driest
Great Falls...1.10..1.73... 5.46....5.83...
Havre.........0.45..1.01... 3.00....3.96...
Helena........1.00..1.02... 5.01....4.18...
Lewistown.....1.04..1.71... 4.21....6.10...16th driest
W Yellowstone.0.68..1.80... 13.01...13.60...
Area Avg......0.85..1.51...36th driest 5.28....6.26...37th driest
Snowfall...Inches...
Apr Nrml Jul-Apr Nrml
Bozeman....... 1.8.. 6.2...13th lowest 54.3....43.4...
Bozeman MSU... 8.5..13.2... 82.3....89.0...
Cut Bank...... 4.0.. 5.2... 62.6....44.4... 7th highest
Dillon........ 0.2.. 3.7... 21.5....31.9...14th lowest
Great Falls... 7.5.. 9.4... 65.5....63.9...
Havre......... 1.5.. 2.7... 34.3....40.6...
Helena........ 3.9.. 2.9... 56.1....37.1...
Lewistown..... 9.1.. 8.6... 64.8....66.2...
W Yellowstone. 5.0..11.7... 134.7...143.5...
Area Avg...... 5.0.. 7.7...61st lowest 65.2....68.1...49th highest
Average Wind speed...mph...
Apr Nrml Rank Oct-Apr Nrml Rank
Bozeman.......6.8....6.9... 5.3.... 5.5...
Cut Bank.....13.3...13.7... 14.7....14.2...
Dillon.......11.0... 9.8... 10.2.... 9.6...
Great Falls..11.9...11.3... 13.5....12.6...
Havre........10.4...10.7... 11.1....10.2...15th windiest
Helena....... 7.9....8.3... 6.8.... 6.5...
Lewistown.... 8.4... 9.9 .. 4th calmest 10.1....10.0...
W Yellowstone M M
Area Avg.....10.0... 9.7...23rd calmest 10.1.... 9.4...30th calmest
Temperature and precipitation records for Bozeman began in
1935, Cut Bank began in 1903, Dillon began in 1939, Great Falls
began in 1891, Havre and Helena began in 1880, Lewistown began in
1896, and West Yellowstone began in 1905. Wind records at Bozeman
and Dillon began in 1948, Cut Bank and Lewistown in 1938, Great
Falls in 1937, Havre in 1889, Helena in 1880 and West Yellowstone in
2010. The normal period for all elements is 1991 to 2020.
These data are preliminary and have not undergone final QC by NCEI.
Therefore these data are subject to revision. Final and certified
climate data can be accessed at the National Centers for
Environmental Information.
$$
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