Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 280924

Area Forecast Discussion
National Weather Service Great Falls MT
324 AM MDT Sun May 28 2017


An upper level ridge of high pressure currently over the Pacific
Northwest will slowly move eastward over the next few days. As a
result, scattered showers and thunderstorms today, will become more
isolated for Monday and Tuesday. Afternoon temperatures will be near
normal today, then gradually warm to near 10 degrees above normal by
Tuesday afternoon.



Today through Tuesday...The main focus in the short term is the next
24 hrs or so. Beyond that, an upper level ridge will gradually build
in with shower and thunderstorm activity expected to be limited to
the higher terrain.

Latest SFC analysis shows one cold front stretching from Cut Bank to
Great Falls and then east through the remainder of Montana. To the
north, a secondary cold front was dropping south through central
AB/SK. Showers associated with the first front have remained
isolated, with a general decreasing trend in coverage noted. A few
lightning strikes have been noted over southern AB early this
morning, but much of our area remains fairly stable and for now,
opted to keep out any mention of thunder for the rest of the AM, but
this will be closely monitored.

The second front will push into central Montana by early this
afternoon, then reach SW MT by this evening. Ahead of this front,
isolated to scattered showers and thunderstorms will likely develop
with the heating of the day, mainly along and south of a Cut Bank to
Lewistown line. While instability still looks better today compared
to the past couple of days, it remains on the weaker side, as does
shear. Still, any stronger storm today could produce gusty winds of
30-40 mph and small hail. In the wake of the front, a tightening
pressure gradient and steep lapse rates will lead to breezy
conditions from Havre to Lewistown with 30+ mph gusts likely. High
pressure then builds in tonight with much cooler temperatures,
lighter winds, and perhaps some patchy fog. Martin

Tuesday night through Sunday...An upper level ridge of high pressure
will be over the region to begin the period, but then gradually
breaks down by next weekend. How much the ridge breaks down
differs quite a bit when you compare the GFS/EC models. However,
the GFS continues to prog a fairly good chance for precipitation
Thursday afternoon/evening...thus pops have been raised closer to
the National Blend solution for this period. Isolated showers
continue for Fri/Sat...while another round of a better chance for
showers/thunderstorms arrives next Sunday afternoon/evening.
Temperatures will likely be above normal through the extended
period, with Wednesday likely being the warmest day with afternoon
temperatures about 8 to 12 degrees above normal. Brusda


Updated 0425Z.

VFR conditions are mostly expected over the next 24 hours across the
area, unless otherwise mentioned. A cold front will continue to move
slowly southwest out of Canada across the area overnight, reaching
the north- and east-facing slopes of the Rockies by 15Z. Increasing
mid level clouds and scattered showers with the potential for
occasional MVFR ceilings will accompany the front and its associated
energy embedded in the northwest flow aloft. A few thunderstorms
with brief heavy rain and gusty winds have also developed this
evening, but it is unlikely that they will directly impact any of
the terminals before they diminish overnight. Ahead of the front, in
the warmer and more unstable airmass across Southwest Montana, the
threat for showers (with some possible thunderstorms and MVFR
ceilings) will mainly occur after 16Z. Clouds, showers, and
thunderstorms will gradually diminish from the northwest across
North Central Montana after 20Z.


Updated 324 AM

The Big Hole River near Melrose is forecasted to go above
flood stage later this week. The rate the river rises this week
is greatly dependent on how fast the higher elevation snow pack
melts. Thus we will continue to monitor for possible flood
highlights later this week. Brusda


GTF  69  43  73  45 /  40  10   0   0
CTB  69  42  72  43 /  20  10   0   0
HLN  73  47  77  48 /  20  10   0   0
BZN  70  41  74  42 /  30  20   0   0
WEY  61  34  66  34 /  30  10  10  10
DLN  71  43  74  44 /  20  10  10  10
HVR  74  39  73  41 /  10   0   0   0
LWT  65  39  67  41 /  20  10   0   0



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