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Area Forecast Discussion
Issued by NWS Glasgow, MT
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FXUS65 KGGW 261532 AAA
AFDGGW

Area Forecast Discussion...UPDATED
National Weather Service Glasgow MT
932 AM MDT Fri Apr 26 2019

.DISCUSSION...

Sent an update this morning to bring the forecast for today
through tonight more into line with the latest observations and
near/short term models. Tried to align with the best model
agreement I could find. First wave of precipitation will be today
through tonight. Some areas from Malta through Glasgow through
Sidney could get a wetting rain out of this first wave.
Temperatures will be cold enough tonight for some of that rain to
mix with snow. More concern will be with the next wave
accompanying a much stronger low pressure system from Saturday
evening through Sunday morning. Accumulating snow will be possible
near and north of Highway 2.      BMickelson

Previous discussion: An initial low pressure system will bring
rain showers and possible thunder to the region as early as this
afternoon and evening. A pause is expected for many locations
tonight and early Saturday before a second low pressure system
brings higher impact precipitation to the area.

Rain will initially begin on Saturday, continuing into Saturday
night. However, as temperatures fall as the low lifts north and
east, rain will begin to transition to snow, especially along the
Canadian border. Models show particularly heavy precipitation
north of the low track, and evaporative cooling of the column may
also help assist in changing precipitation type over to snow,
particularly in locations where precipitation rate is the
heaviest. That said, low temperatures for many will range on
either side of freezing to the mid 30s, and so the forecast will
remain a challenge going forward. Highest confidence on
accumulating snowfall would be along the Canadian border where 1
to 4 inches may be a solid bet, with isolated higher amounts.
Further south toward Highway 2, around an inch of wet snow may
also occur but it may take longer for the changeover to occur.
Right now the best estimate is that patchy locations along Highway
2 may see a wet inch, with very little except for the wrap around
precipitation on Sunday occurring to the south of Highway 2.
Regardless of precipitation type, a weekend precipitation total
is expected to, on average, range between 0.25" and 0.75" for
most.

An important caveat to consider, a closer look at the 06Z NAM
shows at least one scenario in which the low tracks far enough
north for the dry slot to make it all the way to the Canadian
border. Should this occur, the steadiest snowfall totals would
remain on the Canadian side of the border, with lesser snowfall
impacts to northeast Montana. However, even in this scenario, wrap
around precipitation will likely affect northeast Montana as the
system pulls away on Sunday and Sunday evening, and Bufkit
forecast soundings suggest that thermal profiles would support
snow or a mix. So, future shifts will indeed need to monitor
precise thermal profiles Saturday night and Sunday in the presence
of the steadiest QPF, as well as the northern extent of the dry
slot. These factors will have important considerations on
precipitation type and snowfall amounts in the forecast going
forward.

Gusty northwest winds will likely develop late Sunday as the
system pulls away, with drier conditions and cool temperatures
expected to be in place for Monday. Models show yet another storm
system approaching Tuesday or Wednesday, with the southern and
eastern zones most impacted by that event. Given uncertainties at
larger time scales, and increased focus on the short term period
and coming event, have elected to trend the longer range forecast
toward consensus blends. Maliawco



&&

.AVIATION...

Flight Category: VFR to MVFR.

Discussion:
VFR flying conditions are expected to begin with today, but
ceilings will lower to MVFR this afternoon and tonight, possibly
down to IFR as low pressure approaches the region. Rain showers
with isolated thunder will move in from the west this afternoon
and evening as well.

Wind: Southeast, 5 to 10 kts this morning, increasing to 10 to 15
kts after 18Z.

Maliawco


&&

.GLASGOW WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

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