Area Forecast Discussion
Issued by NWS Great Falls, MT
FXUS65 KTFX 181142
Area Forecast Discussion
National Weather Service Great Falls MT
545 AM MDT Tue Apr 18 2017
Aviation Section Updated.
Today through Thursday...Shortwave ridging currently over the
region is rapidly giving way to a moist southwest flow aloft
with an upper low along the West Coast continuing to eject
disturbances to the northeast. Short term models continue to
indicate that the airmass will become slightly unstable,
especially over Southwest portions of the state, this afternoon.
The combination of disturbances and instability is expected to
fuel scattered to numerous showers and isolated thunderstorms
this afternoon and overnight. Another shortwave ridge builds over
the region for mostly dry conditions Wednesday and Wednesday
night. The upper low along the West Coast transforms into an open
trough and moves inland on Thursday with another round of
scattered showers and a few thunderstorms anticipated.
Temperatures will remain near or slightly above seasonal averages
through the short term period and winds will be generally breezy.
Thursday Night through Tuesday...A progressive flow pattern
continues over the forecast area, with periods of fair weather
interrupted by rounds of rain and mountain snow showers. Overall
forecast confidence remains moderate to high through the weekend.
The period begins Thursday night as a Pacific shortwave trough
brings scattered showers and possible thunderstorms through
southwest Montana. The trough splits and deepens over Wyoming. A
cold front associated with the northern branch will bring cooler
temperatures Friday while maintaining rain and mountain snow
showers. Snow levels Thursday night and Friday morning drop to
around 6000 feet, with up to two inches of new snow generally
above mountain passes. Showers end Friday night, while upper level
ridging brings fair and warmer weather for Saturday. The ridge
flattens on Sunday with chances for isolated to scattered
afternoon showers and possible thunderstorms. Ridging aloft
returns on Monday, with a larger Pacific system producing more
widespread precipitation on Tuesday. PN
Mainly VFR expected next 24-hours as zonal flow aloft persists, but
periods of mountain precipitation and obscuration are expected. An
upper level disturbance will cross the region this evening through
early Wednesday, producing showers and possible MVFR ceilings.
Isolated thunderstorms are possible over SW MT this afternoon, but
do not have enough confidence to place at terminals. PN
.PRELIMINARY POINT TEMPS/POPS...
GTF 61 37 60 35 / 10 30 10 0
CTB 58 35 59 32 / 20 20 0 0
HLN 60 37 60 36 / 30 30 10 0
BZN 59 36 58 33 / 30 50 20 0
WEY 44 29 44 25 / 50 50 30 10
DLN 55 34 56 34 / 20 30 10 10
HVR 63 36 63 34 / 10 10 10 0
LWT 60 36 57 32 / 20 40 30 0