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Area forecast discussion
National Weather Service Great Falls Montana
818 PM MDT Wed may 24 2017


Main update is to cancel the high wind warnings for north-central
Montana. Winds are safely below warning criteria but will slowly
diminish through tonight and into Thursday. Also made a minor
update in accordance with latest pop/quantitative precipitation forecast observed and model
trends. Cassell



Synopsis...a strong low pressure system moving slowly east across
the Canadian prairies will maintain windy conditions through tonight
with some potential for damaging winds across north central Montana
through this evening before winds diminish slightly and turn to the
northwest. Moisture wrapping around the low pressure system will
spread showers south across the region overnight with a period of
rain showers likely cross much of central Montana late tonight
through Thursday morning. Breezy to windy and cooler than average
conditions persist on Thursday with a gradual warming and drying
trend anticipated through the upcoming Holiday weekend.


updated 2323z.

Strong low pressure system tracking east across southern Canada will
maintain strong westerly flow aloft with gusty west winds across
much of the region today. Strongest winds of 30-40kts sustained with
gusts to around 50kts will across north-central Montana terminals. Winds
will be slow to subside this evening while veering to northwesterly.
VFR conditions prevail through early this evening, then moisture
wrapping around the back side of the low will spread south bringing
MVFR cigs and a chance for rain showers from north to south late
tonight into Thursday morning. Hoenisch/Cassell


Previous discussion...
/issued 523 PM MDT Wed may 24 2017/

Tonight through Friday...vigorous/stacked low pressure system
centered along the ab/sk border this afternoon will slowly track
southeast across sk tonight, maintaining strong westerly/veering to
northwesterly wind flow aloft and a tight pressure gradient at the
surface. Overall high wind potential will decrease through this
evening with the loss of surface heating, though a few stronger wind
gusts to near 50kts remain possible and the High Wind Warning will
remain in effect though midnight. Flow aloft shifting to the northwest will
shift focus for strongest winds from areas along the rocky mtn front
to more isolated areas, particularly in the vicinity of the island
mtn ranges of N-central Montana. Trowal-like feature wrapping around the
back side of the low will spread precipitation south into northern
portions of the forecast area this evening and south through central
and SW Montana late tonight through Thursday morning. Have increased pops
some tonight with most areas seeing less than 0.10" precip, but some
localized higher amounts in excess of 0.25-0.50" are possible across
the central Montana mtn ranges, including the little belts, where some of
this will fall as snow at the highest elevations late tonight into
Thursday morning. Unsettled north/northwest flow aloft with embedded
disturbances continues across the region Thursday afternoon through
Friday as the low slowly moves east across S-central Canada. Breezy
to windy conditions are likely on Thursday, though winds should be
below high wind thresholds. A few showers and thunderstorm are
possible during the afternoon period on both days with a greater
focus for convection over the higher terrain areas of SW and western
Montana. Hoenisch

Friday night through Wednesday...overall a large upper level low
will influence our weather through the Holiday weekend...with a
ridge trying to build in next week. Friday night through Saturday a
large upper low in Canada will attempt to enter the states keeping
US in an unsettled northwest flow pattern to start Memorial Day
weekend. Limited moisture and instability will be found with this
pattern...bringing some scattered showers and a few weak
thunderstorms through Saturday. Best chance for precip is still west
and south of a line from about Cut Bank to Lewistown to Billings,
with more isolated activity east of this Line. Ridge tries to build
in the region on Sunday and Memorial Day...although with the large
upper low across the northern plains we never fully escape the north
to northwest flow. Models now indicate enough of the ridge enters
our cwa making for a decent second half to Memorial Day weekend with
warming temperatures and only isolated shower and thunderstorm
activity. More of the ridge moves into the area for Tuesday into
Wednesday, however, it flattens quickly leaving US vulnerable to
weak disturbances riding over the top of it. The result will be
chances for scattered afternoon and evening shower and thunderstorm
activity each day. Thunderstorms and this point look to be weak and
limited in coverage. Each day will be warmer than the previous in
the long term. Memorial Day high temperatures in the 70s are
expected...with this warming trend looking to continue into next
week. The large disturbance to our east may linger some breezy NW
flow on Saturday...and to a lesser extend on Sunday. Lighter winds
should then be found on Memorial Day into next week. Anglin


Preliminary point temps/pops...
gtf 43 60 40 64 / 60 30 20 20
ctb 41 58 38 62 / 70 30 20 20
hln 44 62 41 66 / 40 30 20 20
bzn 39 58 38 61 / 20 50 10 30
wey 29 50 30 53 / 10 30 40 40
dln 36 57 38 60 / 10 30 20 30
hvr 45 62 39 66 / 40 30 10 20
lwt 40 56 37 60 / 40 50 10 20


Tfx watches/warnings/advisories...

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