872 
FXUS65 KGGW 272038
AFDGGW

Area Forecast Discussion
National Weather Service Glasgow MT
238 PM MDT Mon Aug 27 2018

.DISCUSSION...

Afternoon Update (2pm MDT): The afternoon update was just as
tricky and difficult as the morning update. The rain better
penetrated the northeast than had been realized, and with the slow
moving system, more QPF has been realized than was previously
expected. However generally the forecast does fall within reason
to previous iterations. Rain chances were extended tomorrow to
last for many areas through the morning and in the southeast
through the early afternoon, before the region totally dries out
for the following several days. Otherwise, the rest of the grids
were appropriately updated to reflect current trends and recent
model output.

Bigelbach

PREVIOUS DISCUSSION: A few forecast challenges do exist for 
today, but overall expect cool and wet condition for today with an
upper level trough feature situated over the region. This system 
will lend dynamic support within a very moist boundary layer. 
Bufkit forecast soundings show low and mid levels near saturated 
across much of the region with precipitable water values around an
inch for the southern zones. This evidence, combined with solid 
00z model consensus, leads to increased confidence in the 
steadiest rainfall to occur today somewhere south of Highway 2, 
particularly this afternoon. This is where wetting rains are most 
likely. Closer to the Canadian border, periods of rain are still 
expected, but it may be more showery in nature and lighter, and 
therefore rainfall totals will probably come in lower than places 
to the south.

Given a near saturated low level boundary layer and moist
conditions through much of the column, even when it is not
raining, patchy fog may still result. Have included mention for
some, but could consider expanding this coverage in future updates
to include patchy fog throughout more of the CWA today.

A final word about the forecast for today is with regard to high
temperatures. Have trended toward latest consensus blends for now,
but given abundant clouds and precipitation, and low heights
proximal to the upper level trough, the high for today may be a
bit optimistic. Will have a look at tweaking the numbers in coming
updates.

Tonight and Tuesday, rain will end as the trough axis slides
downstream of the region. This will lead to drier weather
conditions by Tuesday with clearing skies. Even with some sunshine
by late in the day, highs will still likely be well below average
for this time of year.

Wednesday and beyond: The forecast for this period was trended
toward consensus model blends given the focus on the near and
short term periods. Tweaks were made to targets of opportunity
such as the potential next shortwave and associated cold front to
approach late Thursday or Thursday night. Have included a slight
chance mention of rain showers at that time for portions of the
CWA. Model consensus for QPF placement at these time scales is 
poor, so did sort of a broad brush across a larger portion of the 
CWA for now rather than try to confine to a smaller location 
provided by the initial blends. Maliawco

&&

.AVIATION...

FLIGHT CAT: Currently IFR to near shutdown conditions, with MVFR
to IFR expected later

DISCUSSION: Cool and rainy conditions, with a surplus of moisture
in the air currently, is causing fog, rain and extremely low
ceilings across the sites and region. Temporary airport shutdown
is possible periodically through the rest of the afternoon. 
Sometime this evening, relief in visibility and ceiling height 
looks likely, but expect continued IFR to low MVFR conditions 
through tomorrow with persistent periods of rain showers through 
at least tomorrow morning.

WINDS: Expect the possibility of gusty and erratic winds
associated with rain activity for the rest of the afternoon today.
In general, expect east to southeast winds to turn to the north- 
northwest by this evening with speeds generally in the 7-12 kt
range.

Bigelbach

&&

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

&&

$$

weather.gov/glasgow