Damaging Wind and High Wind in Montana, April 27, 2020

Area Forecast Discussion
National Weather Service Great Falls MT
940 AM MDT Mon Apr 27 2020

.UPDATE...

A weak upper level disturbance will bring some isolated to
scattered showers and thunderstorms today. Initial round of
moisture will push across the west and southwest through the
afternoon. This may bring some showers and thunderstorms to these
areas during this time period. Meanwhile breezy, dry, and warming
conditions will be found across central portions. Later this
afternoon through the evening, the mentioned disturbance will move
across the region. This could provide for more scattered
thunderstorm activity to the area. There are some concerns these
storms may bring gusty to isolated severe wind gusts. The threat
overall is isolated, and made mention of gusty winds for any
areas with thunderstorms. Isolated showers may linger tonight in
central portions, then high pressure brings a dry and warm day on
Tuesday. The fire weather concerns will continue through mid week.
Today's cloud cover may limit critical fire danger, although
breezy winds and lowering RH may at least elevate the threat.
Anglin

&&

.SYNOPSIS...

Winds will become quite gusty today into this evening with the
passage of a cold front, which will also bring scattered showers
and thunderstorms mainly to Southwest and Central Montana. High
pressure ridging will bring mostly clear skies and continued above
normal temperatures later tonight into Tuesday, with temperatures
warming up to 20 degrees above normal for Wednesday. However,
somewhat cooler and more unsettled conditions are likely later
this week.

&&

.AVIATION...
Updated 517 AM MDT Mon Apr 27 2020 (27/12Z TAF Period)

Extensive mid-level clouds continue ahead of the next disturbance
approaching from the west today. Scattered showers with a few
thunderstorms develop over Southwest Montana after 15Z, with an
isolated shower or two moving into Central Montana after 18Z. VFR
conditions expected to continue but there is some chance for brief
IFR/MVFR conditions and gusty and erratic winds in showers and
isolated thunderstorms. Mountains become and remain obscured for
much of the period. Gusty westerly winds can be expected in North
Central Montana this afternoon and extending well into the evening
and overnight, especially over the plains.

NOTE: Amendments not scheduled for Ennis (KEKS) due to ongoing
runway closure.

&&

.FIRE WEATHER...

Westerly winds will increase significantly for today into this
evening, as a disturbance moves over the area with an associated
cold front. However, skies will be cloudy for much of the day,
which should keep afternoon relative humidity mostly in the 20 to
35 percent range and green-up is occurring across much of the
area. Therefore, near-critical fire weather conditions are
possible for a period of time, but fire weather highlights are not
expected at this time. Scattered thunderstorms are also possible
across much of Central and Southwest Montana (zones 115 through
118), which may mix strong erratic wind gusts down to the surface.
However, again, the moderate humidity and mostly green vegetation
should hinder rapid spread of fires if any should start. Winds and
any storms should start to decrease after sunset. Sunny skies on
Tuesday will help decrease afternoon relative humidity more so
into the 15 to 25 percent range, but winds will remain relatively
light. Wednesday will likely be the warmest day of the year so
far, which could cause low relative humidity once again, but winds
are not expected to be strong at this time.

Anyone with burn plans will want to consult the forecast for
their location and consider delaying plans. Those outdoors should
also be mindful of any errant sparks that can cause unwanted
fires.

&&

.PREV DISCUSSION...
/ISSUED 517 AM MDT Mon Apr 27 2020/

Today through Wednesday...Winds will increase significantly today
with the passage of an upper level disturbance and a surface cold
front. (This may cause near-critical fire weather conditions; for
more details on this please see the Fire Weather portion of this
discussion product.) This is due to the passage of a weak
shortwave trough (which will increase mid level westerly winds
into the 40 to 45 kt range) and its associated cold front (which
will help translate these winds down to the surface). Winds of 25
to 35 mph will be common over the plains with gusts up to 40 mph,
but gusts in excess of 50 mph are possible on the Rocky Mountain
Front. Slightly lesser winds of 15 to 25 mph winds are likely in
the southwest valleys with gusts to 35 mph. These winds will help
warm temperatures up to 10 degrees above normal. The cold front
will also cause scattered showers and thunderstorms to develop
over Western Montana this morning and spread over Central and
Southwest Montana (mainly along and south of a Great Falls to
Lewistown line) this afternoon into this evening. A few storms may
also develop over the plains late this afternoon through this
evening in the immediate wake of the disturbance. A high pressure
ridge will then start to move back into the area later tonight
through Tuesday night, which will keep skies mostly clear with
decreasing winds and continued above normal temperatures. The
ridge will shift a bit to the east on Wednesday, which will allow
cloudiness to increase. However, lingering subsidence from the
ridge will help increase temperatures to their warmest levels so
far this year (mostly mid 70s to around 80 for lower elevations).
Coulston

Wednesday Night through next Monday...This period looks to be more
unsettled than the early week period, with an increased chance for
showers and thunderstorms and gradually cooling temperatures. A
low pressure trough in the Gulf of Alaska will periodically deepen
and swing shortwave troughs over the forecast area in a more
unstable southwest flow aloft. The first shortwave is forecast to
bring scattered showers and thunderstorms Wednesday night into
Thursday, but temperatures should remain around 10 degrees above
normal. The chance for showers and thunderstorms will linger into
Friday as the shortwave starts exiting the area, but temperatures
will cool about 5 degrees in the wake of its associated cold
front. High pressure ridging will decrease the chance of showers
further on Saturday, but the next shortwave will bring cooling
temperatures and an increased chance for showers and thunderstorms
Sunday into Monday. Coulston

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  65  38  67  44 /  10  20   0   0
CTB  61  35  64  43 /  20  30   0   0
HLN  65  39  69  44 /  20  10   0   0
BZN  62  36  67  39 /  60  20   0   0
WYS  50  26  57  28 /  70  40   0   0
DLN  61  36  66  39 /  30  20   0   0
HVR  69  41  68  43 /  10  30   0   0
LWT  62  37  61  39 /  20  30  10   0

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
None.
&&

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