Special Weather Statement, NWS Great Falls, MT

Area Forecast Discussion
National Weather Service Great Falls MT
249 PM MDT Thu Jun 6 2019

.SYNOPSIS...

A strong Pacific cold front continues to traverse our region through
tonight and should exit to our southeast by daybreak Friday.
Scattered showers and thunderstorms occur ahead of this front
through this evening. Some of the storms should become severe.
Behind the front, periods of rain and mainly mountain snow occur
through Saturday. Warm temperatures today will turn sharply colder
for Friday and Saturday, especially in the mountains. A warming
trend and drier weather are expected next week Sunday through
Thursday.

&&

.DISCUSSION...

Through tonight...The Pacific cold front appears to be situated
in vicinity of Glacier County at time of writing. This front will
continue moving southeastward and should exit our area to the
southeast by about daybreak Friday. Simultaneously, a mid- to
upper-level trough begins overspreading our region from the west.
Along and ahead of this front, scattered showers and thunderstorms
ahead of the front will transition to periods of rain and
mountain snow as temperatures drop sharply and snow levels lower
toward 6000 feet MSL behind the front. Through this evening, some
severe thunderstorms are expected ahead of the front, where weak
to moderate instability and strong vertical wind shear exist.
Damaging wind gusts and quarter-size or larger hail remain the
primary severe threats. In addition, abundant Pacific moisture
ahead of the front will likely allow downpours to accompany
showers and thunderstorms. Localized flash flooding remains
possible where showers and thunderstorms train (i.e. follow the
same path).

Friday through Saturday...The aforementioned, eastward-moving trough
aloft traverses our area during this period as colder air continues
to overspread our CWA behind the cold front. Below-normal
temperatures will be accompanied by snow levels as low as about 5000
to 6000 feet MSL. Periods of rain and mountain snow occur Friday
through Saturday, but forecast rainfall and snowfall totals continue
to trend downward since the precipitation does not look to be as
widespread or persistent as previously thought. Nevertheless, winter
weather advisories may be needed for some of our mountain passes
later Friday into Saturday.

Sunday through next Thursday...Northwesterly flow aloft resides
over the region through Wednesday as the aforementioned trough
exits to our east and a high pressure ridge aloft builds from the
west. This ridge may then crest over our CWA on Thursday, allowing
flow aloft to become westerly. Subtle disturbances will also
traverse our area during this period. This pattern will promote
drier weather, although a few showers and thunderstorms are
possible essentially each afternoon and evening, especially
over/near our mountains. Temperatures rebound, with readings
returning to normal or above- normal for Tuesday through next
Thursday.
- Jaszka

&&

.AVIATION...
Updated 1125 AM MDT Thu Jun 6 2019 (18Z/Thu TAFs)

Mainly VFR and southwesterly to westerly flow aloft expected next 24-
hours as a larger trough approaches from the west and multiple
disturbances embedded in this trough traverse our area. Isolated to
scattered showers and thunderstorms are expected through about
06Z/Fri before transitioning to periods of steadier rain thereafter.
Brief MVFR CIGS/VSBY are possible in any shower or thunderstorm. In
addition, severe thunderstorms with erratic gusts up to 60 knots and
hailstones of quarter to ping pong ball-size are possible between
roughly 20Z/Thu and 03Z/Fri, especially over southwest MT and the
eastern-half of north-central MT. Even outside showers and
thunderstorms, surface winds will be breezy at times at most
terminals. Lastly, mountain obscuration is possible at times.
- Jaszka

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  47  57  40  55 /  90  60  20  70
CTB  42  57  37  55 /  80  20  30  60
HLN  45  56  37  57 /  70  70  40  50
BZN  47  57  34  56 /  60 100  80  50
WEY  41  57  27  48 /  60  90  80  60
DLN  45  53  31  53 /  70 100  80  30
HVR  47  65  39  59 /  80  30  20  40
LWT  46  56  37  53 /  50  70  50  60

&&

.TFX WATCHES/WARNINGS/ADVISORIES...

None.

&&

http://www.weather.gov/greatfalls

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