Area Forecast Discussion
Issued by NWS Great Falls, MT
FXUS65 KTFX 200524
Area Forecast Discussion
National Weather Service Great Falls MT
1025 PM MST Sun Feb 19 2017
UPDATED AVIATION SECTION
Shortwave in WSW flow and associated cold pool aloft has
triggered several bands of convective showers across the region
this evening. Regional radar imagery currently shows what is
likely the final round of this activity currently extending from
the Rocky Mtn Front SW into central ID. This activity should move
east across the forecast area through the rest of this evening
while weakening over the next several hours as shortwave ridging
embedded within the fast WSW flow aloft moves over the northern
Rockies later tonight. Precipitation associated with areas of
convection is very short lived with rain/snow/graupel observed at
lower elevations with likely less than an inch of snow accumulation
over some mountain passes. Main updates this evening were to
short term pops/weather through the rest of tonight based on
observed trends with minor adjustments to min temps in some areas
as well. Hoenisch
VFR conditions are mostly expected through the next 24 hours.
However, the moist southwest flow aloft will continue mainly
mountain rain and snow showers. A disturbance in the flow will
continue to bring isolated to scattered showers (with the
possibility of a thunderstorm that could produce gusty winds) to the
eastern terminals (KHVR KLWT) through around 09Z. Another surge of
moisture with a weak associated disturbance will then bring a chance
of showers to much of the area once again after 18Z.
/ISSUED 450 PM MST Sun Feb 19 2017/
Tonight through Monday...Skies are generally clearing across the
forecast area this afternoon with subsidence following the passage
of a shortwave trough. Scattered rain and mountain snow showers
linger over the forecast area but are expected to dissipate while
exiting to the northeast this evening. Additional new convection
is observed upstream over Idaho. Some of this activity could move
into the western and southwest mountains during the evening hours.
Subtle ridging aloft with weak warm advection maintains generally
fair and mild weather for Monday.
Monday night through Wednesday..Another atmospheric river sends a
surge a Pacific moisture into the region amid a strong southwest
flow aloft. Most of the accumulating rain and mountain snow will
remain along and west of the Continental Divide, though areas of
light precipitation are expected to move across central Montana at
times. A period of strong winds are expected Tuesday afternoon
across much of central, southwest and south-central Montana. This
is a somewhat atypical path for strong winds as the surface low
tracks through North-central MT with a lightning of the 700 hPa
gradient. If this feature arrives during the daytime, boundary
layer mixing will help bring these strong winds to the surface.
Temperatures trend cooler on Wednesday as this system weakens and
cooler air begins to move into the Pacific Northwest.
Wednesday night through Sunday...A northerly flow develops
bringing a return to more normal late-winter temps areawide. This
northerly flow will likely be accompanied by enough moisture for
periods of snow at times through next weekend.
.PRELIMINARY POINT TEMPS/POPS...
GTF 31 52 39 54 / 60 20 20 30
CTB 28 43 31 44 / 10 10 20 40
HLN 27 43 30 46 / 30 30 40 30
BZN 26 43 32 47 / 40 40 50 40
WEY 21 35 31 37 / 70 90 90 90
DLN 27 43 36 46 / 20 40 60 40
HVR 31 50 34 51 / 20 10 10 40
LWT 29 52 36 55 / 30 20 20 30