Area Forecast Discussion
Issued by NWS Glasgow, MT

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FXUS65 KGGW 261505

Area Forecast Discussion
National Weather Service GLASGOW MT
905 AM MDT THU MAY 26 2016

.SHORT TERM...for northeast through Sat...

Morning Update... changes to the forecast began with the larger
analysis of the wrap around low. Precipitation on Canadian radars
has rapidly moved into the northwest quadrant but appears to be
light. A trowal may form on this but appears to be rather diffuse
at the moment. Afternoon thunderstorms will likely be less
plentiful with the excess of cloud coverage preventing surface
instability, best chances for a clap of thunder will be over the
Yellowstone Valley where a few breaks in the clouds due to a
possible dry slot sucked into the low aloft may briefly be able to
help heat the surface layer. GAH

Previous Short Term Discussion...
Closed upper low currently over eastern Montana is producing
isolated showers over the area. This low will drift east today and
will be in North Dakota by evening. Air mass across the forecast
area today will become more unstable with daytime heating which
will allow showers and thunderstorms to increase over the area
during that day. Look for scattered to numerous showers and
thunderstorms. Most areas should see precipitation at some point
today but all day rain is not expected at any one location.

With the upper low over North Dakota tonight and weak high
pressure and shortwave ridge over Eastern Montana, the chances for
showers will diminish. The northeast corner of the state will stay
within the upper low circulation and a chance of showers could
linger all night.

The upper low retrogrades somewhat back towards Northeast Montana
on Friday before it dissipates. This will allow a chance of
showers to return to the eastern half of the forecast area in the
morning. Meanwhile, the next upper trough moves into Western
Montana during the day with a frontal system that moves into
Central Montana during the afternoon. This could bring showers and
thunderstorms to the western zones.

The upper trough and frontal system moves through Eastern Montana
Friday Night and Saturday with a good chance of showers and
thunderstorms. Forrester

.LONG TERM...Sat night through Thu...

As the next major Rocky Mountain low pressure trough emerges
eastward over the northern High Plains region, there is some hint
of a brief short-wave ridge in-between embedded disturbances.
Indeed, model precip consensus shows high confidence in keeping
most of our CWA dry Saturday night through Sunday.

Beginning Sunday night and lasting through the remainder of the
forecast period, significant model differences emerge regarding
precipitation chances. This lack of forecast confidence for next
week is based primarily on the evolution of another major low
pressure trough set to descend through our northern Rocky
Mountains and northern High Plains regions.

The most glaring difference is with the GFS bringing down a much
stronger closed low much earlier than that EC which brings a much
weaker open trough and does not mature it until it moves well to
our east. The GFS solution is similar to the DGEX and is very wet
with some strong and efficient rain makers late Monday night
through Wednesday.

Overall, I chose to lean toward the wetter solution when models
disagreed with some average to less-than-average confidence. Found
highest confidence with best model consensus early in the forecast
period, even if it shows dry. BMickelson



SYNOPSIS: Isolated to widely scattered showers and thunderstorms
will be possible as a low pressure system spins over northeast
Montana today and this evening. VFR conditions will mainly
prevail, but will reduce to IFR or MVFR if a shower passes
directly over a TAF site.

WINDS: northwest to north at less than 15 kts today... veering to
the northeast and diminishing to less than 10 kts overnight.





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