Area Forecast Discussion
Issued by NWS Glasgow, MT

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FXUS65 KGGW 230912
AFDGGW

Area Forecast Discussion
National Weather Service Glasgow MT
312 AM MDT Sun Jul 23 2017

.SHORT TERM...for northeast Montana...today through Tue...

Synoptic Setup: A hot high pressure airmass resides over the
western half of the CONUS. A ridge spur will run north out of
western Wyoming through central Montana and into southern Alberta
and Saskatchewan. to the west a closed low will break into a open
trough over central British Columbia.

Today: A the opening BC trough moves over the front range it will
amplify the ridge over eastern Montana this afternoon and force
prefrontal heating. This will lead to near 100 degree temperatures
at the surface just ahead of the developing lee side trough over
the central Montana Mountains. RH will also be very low and
therefore a Red Flag Warning was put out to reference this.

Tonight into Monday: As the open trough steps off over the Alberta
front range it will latch onto the lee sides surface trough and
convert it into a dry front with slightly cooler air being pulled
in behind it. This front will be moved across the region early
Monday morning and could easily drag any lift mechanism that form
isolated thunderstorms along with it leading to an ignition source
for fire. Gusty winds that develop behind the dry front further
solidify the need for a Fire Weather Watch.

With conditions being tinderbox dry have gone one step further in
edging up a degree, percent, or knot or two beyond the average
blend and towards the more dangerous FireWx conditions in most
grids over the next two days. Basically biasing on the side of
caution. GAH


.LONG TERM...Tue night through Sun...
The extended forecast starts Monday night and Tuesday with zonal
flow residing across the state of Montana with a closed upper low
pushing further downstream into Manitoba. This pattern will
feature seasonable temperatures, though continued dry conditions.

The concerns arising from the dry airmass will only amplify as an
upper ridge builds and strengthens across the western U.S. and
extends into Montana and adjacent portions of southern and
central Canada into the middle of next week. Expect increasing
temperature trends, with highs returning to the 90s for most
places by Wednesday or Thursday. The large scale subsidence will
drive afternoon minimum relative humidity values down into the 10
to 25 percent range each day.

Precipitation chances appear minimal throughout the long range,
though 00z deterministic models suggest a weak embedded shortwave
could eject into eastern Montana on Thursday on southwest flow
aloft as the ridge axis shifts just downstream of the CWA. In any
case, rainfall amounts would be light, if anything at all were to
materialize. The forecast was trended toward consensus blends
which produced isolated pops for this time.

The bottom line: overall, the continuation of dry weather
conditions and occasional hot temperatures look to continue for
the foreseeable future. Maliawco


&&

.AVIATION...
FLIGHT CAT: VFR.

SYNOPSIS: A ridge will be in place today and exit overnight. A
frontal passage is expected early Monday morning.

HIGH DENSITY ALTITUDE: With temperatures approaching the upper
90s to near 100, takeoff may take longer than expected Today.

WIND: Veering to the south this morning around 10 kts or less,
backing to the southeast and increasing to 10 to 15 kts this
afternoon and evening, Switching to the northwest behind a front
early Monday morning.

GAH


&&

.FIRE WEATHER...

...A Red Flag Warning remains in effect today until 9pm for Fire
Weather Zones 122, 134, 135, 136, and 137...

...A Fire Weather Watch is in effect for all Fire Weather Zones
on Monday from 6am through 9pm...

Light southeast winds this morning will trend more southerly by
the afternoon and increase to 10 to 15 kts. This will occur ahead
of a cold front, and as such expect a very hot afternoon due to
effects from compressional warming with high temperatures nearing
100 degrees. The combination of hot temperatures, persistent south
winds, and minimum relative humidity values as low as 10 percent
will create critical fire weather conditions for today.

Fire weather concerns are particularly strong for Monday at this
point. The front will track east across northeast Montana
tonight, reaching the North Dakota/Montana border on Monday
morning. Isolated dry thunderstorms are possible tonight and
Monday ahead of and with the frontal passage, and any lightning
could result in new fire starts as well as complicate current
wildfire containment efforts. Gusty and shifting winds are also
possible with any isolated storms that do occur. Otherwise, expect
a steady northwest wind to develop on Monday behind the front in
a range of 10 to 20 mph with gusts to near 30 mph. These winds
will continue from about mid morning through early evening before
diminishing in magnitude and turning north Monday night. Maliawco


&&

.GLASGOW WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 9 PM MDT this evening for MTZ136-137.

Fire Weather Watch from Monday morning through Monday evening
for MTZ120-122-134>137.

Dense Smoke Advisory until 9 PM MDT this evening for Garfield.

Red Flag Warning from 9 AM this morning to 9 PM MDT this evening
for MTZ122-134-135.


&&

$$

weather.gov/glasgow


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