Flood in Montana, March 12, 2018

Area Forecast Discussion
National Weather Service Glasgow MT
246 PM MDT Mon Mar 12 2018

.DISCUSSION...
With an amplified ridge moving into the region overnight and
Tuesday, skies will remain clear with little to no wind. Most if
not all of the near term models are suggesting widespread fog
across the area. The main question is how dense and widespread
the fog will be tonight and Tuesday morning. Model RH just above
the surface of only 50 to 60 percent and only a very narrow layer
of higher RH at the surface suggest that while fog may be dense,
it should also be shallow. Keep in mind that anyone traveling may
go from areas of good visibility to very poor visibility suddenly.
Have issued a Dense Fog Advisory for all of northeast Montana
except the Little Rockies and Petroleum County from 9PM this
evening to noon tomorrow.

Otherwise, the forecast has not changed very much. Still expect
increasing temperatures over the next couple of days with the
ridge moving through the area. By Wednesday, most of northeast
Montana will finally be seeing high temperatures above freezing.

Thursday, confidence is increasing regarding a trough quickly
moving across the area, with the potential for some light snow.

Beyond, model guidance diverges so populated with the latest model
blends.  Hickford

Previous Discussion...

An upper level ridge pattern over the U.S. with axis over the
Pacific Northwest will extend into northeast Montana with dry
weather and a warming trend in overall temperatures. This will
lead to a couple of different effects. First will be increasing
potential for patchy fog in the morning. As snow melts during the
warmer daytime hours, expect some increase in boundary layer
moisture which could increase the potential for fog formation as a
nocturnal inversion sets up. Second, in the coming days and weeks,
as snow melts and temperatures rise, an eye toward hydrology will
have to be maintained.

Shorter term forecast challenges however do include fog. That
said, early this morning, note some slight visibility reductions
in some areas, along with widespread relatively narrow dew point
depressions. Given these factors, have maintained patchy fog in
for the next few hours even as potential may become more favorable
in the coming days.

By Wednesday or Thursday, 00z models have the ridge axis reaching
eastern Montana. As heights continue to rise, temperatures will
follow along. In fact, daytime highs will likely be well above
freezing for most of the area at this time even in areas with snow
pack. The longer daytime hours and higher sun angle this time of
year are certainly going to help make a difference. Large scale
subsidence will also mean a continuation of dry weather across the
area.

Late in the week, the ridge will slide downstream of the CWA as a
new Pacific trough and/or upper level low pressure system takes
aim and the region. Therefore, expect a trend toward slightly
lower temperatures and increasing chances for rain and snow
showers during this time. Maliawco

&&

.AVIATION...
Category: VFR to potentially airport shutdown.

In general, expect VFR conditions to last through 02Z or 03Z.
Afterwards, fog is expected to develop, becoming dense by 06Z.
There may be periods of below one quarter mile visibility between
06Z and around 15Z, with fog slowly diminishing through 18Z
Tuesday. Winds will be variable to southeast at 5 kts or less through
the period. Hickford

&&

.GLASGOW WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory from 9 PM this evening to noon MDT Tuesday
for Central and Southeast Phillips...Central and Southern
Valley...Daniels...Dawson...Eastern Roosevelt...Garfield...
McCone...Northern Phillips...Northern Valley...Prairie...
Richland...Sheridan...Western Roosevelt...Wibaux.

&&

weather.gov/glasgow