Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 192341

Area Forecast Discussion
National Weather Service Great Falls MT
545 PM MDT Sun May 19 2019

Aviation Section Updated


Mostly cloudy conditions, some scattered showers, and cool
conditions are expected to be found tonight through Monday. A few
thunderstorms are also possible at times, mainly across the
southwest. Another storm system will begin to impact the region on
Tuesday, bringing the next chances for widespread rain and
mountain snow along with continued cool temperatures. This
unsettled weather could linger through mid to late week.



Tonight through Monday night...An east southeast flow pattern from
a low across the Great Basin and a high in Canada will continue to
impact the weather tonight through much of Monday. The end result
will be scattered showers and a few thunderstorms across the
southwest, and some scattered rain or mountain snow showers across
western and some central portions through tonight. This mentioned
low moves further eastward for Monday bringing a widespread
scattered shower threat to much of the area, with perhaps an
isolated thunderstorm. Shower activity then diminishes somewhat
Monday night. QPF values look to be fairly light to near normal
through Monday night. This should limit the potential for any
flooding concerns, although some river, creeks, and streams may
remain on the high side with fast flowing currents. Temperatures
also look to remain below normal throughout Monday, with some
lower elevation areas approaching freeing tonight and again Monday
night. Anglin

Tuesday through Sunday...The attention then turns to the potential
unsettled pattern for mid to late week. Forecast models continue
to indicate that a second upper level low will merge with the Four
Corners trough by Tuesday. These merged systems will develop into
a broad cyclonic circulation that dominates western and central
portions of the USA for much of the week. Depending on how far
north this low can get, periods of rain and (mainly) mountain
snow can be expected Tuesday through Thursday with temperatures
remaining unseasonably cool. QPF amounts of 0.5 to 1.5 inches are
still being forecasted From Tuesday through Thursday, with snow
amounts over 6 inches possible across the mountains. This may need
to be watched for any hydro concerns, and travel/recreation
concerns. Medium range models continue to show the broad upper
level circulation breaking down into a positive-tilt trough late
in the week. From Thursday through Sunday model agreement remains
relatively poor with the various models disagreeing on where and
when the best energy will eject to the northeast. The overall
forecast will continue to keep unsettled and cool conditons in
place for much of Montana during this time period. However, models
do indicate that temperatures should gradually warm through the
late week and weekend period, with perhaps less shower coverage
(except across the south) by late weekend. With warmer
temperatures may come some chances for a few thunderstorms during
any unsettled period. mpj/anglin


Updated 545 PM MDT Sun May 19 2019 (00Z TAF)

A slow moving upper level trof over the Great Basin will slowly
drift northward towards MT tonight. Expect increasing chances for
rain and mountain snow to move northward into Southwest MT this
evening and into Central/North Central MT Monday morning. Overall
precipitation will be light with this event, but low IFR/LIFR
ceilings are possible. Scattered showers will continue in many areas
on Monday afternoon. Mountains/passes will be obscured at times
through the period. Brusda


GTF  33  50  36  48 /  20  40  20  50
CTB  31  47  35  46 /  20  40  40  60
HLN  34  53  37  52 /  30  40  20  50
BZN  35  52  35  53 /  40  50  20  30
WEY  32  49  27  50 /  60  80  40  40
DLN  33  51  34  52 /  50  60  20  30
HVR  34  54  38  51 /  10  20  20  60
LWT  32  43  33  42 /  40  60  50  70




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