Special Weather Statement, NWS Great Falls, MT

Area Forecast Discussion
National Weather Service Great Falls MT
917 AM MDT Sat Jul 28 2018

.UPDATE...
Updated forecast is out. No significant changes to the morning
package. Pops were increased to at least a slight chance for areas
mainly north of Great Falls through this afternoon, as an upper
level disturbance moves through the region. Thunderstorms should
become a bit more widespread during the afternoon/evening hours.
Otherwise, the rest of the forecast looks on track. Brusda

&&

.SYNOPSIS...
Isolated to scattered showers and thunderstorms and below-normal
temperatures persist today as multiple disturbances affect the
area. A warming and overall drying trend begins Sunday through the
middle of next week as high pressure builds from the west.

&&

.AVIATION...
Updated 1530Z.
With an upper level disturbance moving through the region, expect
scattered showers/thunderstorms through this evening. The storms
should begin to decrease in coverage area after 06z Sunday.
Overall, VFR conditions are expected, but some MVFR conditions are
possible in/near showers. Brusda

&&

.Fire Weather...
Isolated to scattered thunderstorms are expected through this
weekend, especially today. Any lightning strikes, especially those
that occur well away from the center of a storm, may spark new
fire starts. Fire weather concerns may become elevated this Sunday
through the middle of next week, as a warming and overall drying
trend is accompanied by minimum RH values of about 10 to 20
percent. However, winds still look to remain light enough to
prevent critical fire weather conditions.
- Jaszka

&&

.PREV DISCUSSION...
/ISSUED 457 AM MDT Sat Jul 28 2018/

Today through Sunday...Westerly to northwesterly flow aloft persists
over our CWA today as a mid- to upper-level trough with axis
extending west-southwestward from southern SK to WA's Olympic
Peninsula moves little. Multiple low- to mid-level disturbances
embedded within this trough traverse our region today, contributing
to the development of isolated to scattered showers and
thunderstorms, especially over and near higher terrain. Greatest
coverage of showers and storms will be this afternoon and early
evening, when daytime heating will result in weak to moderate
instability. Similar to yesterday, moderate vertical wind shear may
allow a storm or two to become severe over central and southwest MT.
Damaging wind gusts up to 60 mph and hail up to quarter-size will be
the threats from any severe storm. An overall drying trend then
commences tonight into Sunday as the trough shifts southeastward
and high pressure aloft builds from the west. However, a few
showers and thunderstorms may develop via daytime heating of
higher terrain late Sunday morning through afternoon. Temperatures
undergo a warming trend through this weekend, but are expected to
remain below-normal.
- Jaszka

Sunday Night through Saturday...A high pressure ridge will build
over the western United States through Wednesday. This will keep the
area mostly dry and very warm, as temperatures warm to between 5 and
10 degrees above normal. Winds are not expected to be very breezy,
so fire weather concerns remain minimal at this time. However, a
disturbance with a weak Canadian cold front may bring few weak
showers and thunderstorms to the forecast area Tuesday afternoon and
evening, which is delayed a bit from the previous forecast. A
shortwave low pressure trough will then slowly move a weak Pacific
cold front east through the area Wednesday through Thursday. This
may bring a few more showers and thunderstorms during the afternoon
and evening hours. The passage of this shortwave will likely flatten
the high pressure ridge, which may help cool temperatures back
closer to normal Friday into Saturday with a chance for breezy
west winds, but very little chance of showers.
- Coulston

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  80  51  82  53 /  30  30  10   0
CTB  78  47  82  50 /  50  40   0   0
HLN  79  54  82  54 /  30  30  10  10
BZN  78  49  78  49 /  20  20  10  10
WEY  74  40  71  36 /  30  30  10  20
DLN  78  47  78  47 /  20  30  10   0
HVR  81  52  84  54 /  30  10   0   0
LWT  74  50  76  51 /  20  40  10   0

&&

.TFX WATCHES/WARNINGS/ADVISORIES...

None.

&&

http://www.weather.gov/greatfalls

Special Weather Statement
National Weather Service Great Falls MT
1221 PM MDT SAT JUL 28 2018

MTZ014-052-281915-
Jefferson-Central and Southern Lewis and Clark-
1221 PM MDT SAT JUL 28 2018

...A STRONG THUNDERSTORM WILL AFFECT SOUTH CENTRAL LEWIS AND CLARK
AND NORTH CENTRAL JEFFERSON COUNTIES...

At 1220 PM MDT, a strong thunderstorm was located 24 miles west of
Helena, moving east at 25 mph.

Winds near 30 mph, brief heavy rainfall, lightning and pea size hail
are possible with this storm.

Locations near the path of this storm include, but not limited too,
Helena, Canyon Creek, East Helena and Clancy.

This storm should affect the city of Helena between 1245 PM and
115 PM.

This includes the following highways...Interstate 15 between mile
markers 174 and 210 and Highway 12 between mile markers 29 and 52.

Reminder, lightning can strike 10 miles away from a thunderstorm.
Seek a safe shelter inside a building or vehicle.

LAT...LON 4684 11193 4653 11185 4629 11211 4644 11233
      4652 11230 4662 11230 4666 11233 4666 11241
      4670 11242 4670 11253 4683 11253
TIME...MOT...LOC 1819Z 281DEG 20KT 4673 11251

Brusda