Severe Thunderstorm Warning 31, NWS Glasgow, MT

Area Forecast Discussion
National Weather Service Glasgow MT
208 PM MDT Sat Jul 29 2017

.SHORT TERM...for northeast Montana...tonight through Mon...

Disturbance moving across the CWA this afternoon has flattened the
upper ridge across the area and provided some relief from the
searing heat. But the disturbance moves to the east tonight,
allowing the sun to heat things back up for Sunday.

Clouds were abundant across the CWA this afternoon with most of
the showers from Garfield to Dawson/Richland counties.
Instability axis was just east of the Montana/North Dakota border
with a surface trough signaled by a broken line of strong/severe
storms.

Clouds will move out tonight to our east allowing for a mostly
clear skies tonight.

Sunday will be sunny with generally light winds under the ridge. A
surface low will enter SW Sask and bring a dry-line or trough
across north-central Montana. But it is not expected to reach the
NW zones, so no worries in regards to Fire Weather here. See Fire
Weather Discussion below for more details. TFJ

.LONG TERM...Mon night through Sat...
The inherited forecast for the extended period remains largely on
track, though temperatures were trended lower for Tuesday into the
second half of next week to come into better alignment with the
12z consensus model blend guidance. This should occur as the upper
ridge across the western U.S., while remaining amplified into
British Colombia and Alberta, becomes narrower. This will lead to
lowering 500mb heights across eastern Montana with north to
northwest upper flow for much of next week. Maliawco

Previous Long Term Discussion...

The general upper-level flow pattern in the extended forecast
period continues to show a strong ridge of high pressure over the
US Great Basin and a substantial trough of low pressure anchored
over Hudson Bay. As these two features jockey for position, NE
Montana finds itself mostly under the influence of the high
pressure ridge, but occasionally, a few small scale disturbances
riding around the far side of the ridge, or down the leading side
of the trough, could bring a few periods of scattered rain showers
and isolated thunderstorms to portions of our CWA.

These chances for limited precipitation seem lined up the best on
Monday evening over our southern and SE zones, and on Wednesday
evening over our NE zones. Otherwise, model discrepancies are too
great to allow for such confidence.

Throughout the extended forecast period, winds look to be of no
great consequence, all at or below 15 mph. A bit of a cool front
seems evident in the model data leading into the middle part of
the week.

BMickelson

&&

.AVIATION...
VFR conditions will prevail through the night. Expect isolated to
widely scattered thunderstorms near KOLF, KSDY, and KGDV at times
through 04Z before ending as they shift east into North Dakota.
Light south winds will develop after 06Z and persist through the
remainder of the weekend. Maliawco

&&

.FIRE WEATHER...

Isolated showers and clouds will depart the area this evening with
clear skies and light southeast winds tonight.

An upper ridge will build back into the area Sunday, allowing for
sunshine to heat the area well into the 90s tomorrow. South then
southwest winds will increase over zone 134, but not expecting
them to be of concern.

Monday will see a wind shift to the west then north along with
lowering temperatures. The cooler conditions will last through
midweek. TFJ

&&

.GLASGOW WATCHES/WARNINGS/ADVISORIES...
&&

weather.gov/glasgow