Area Forecast Discussion
Issued by NWS Missoula, MT
FXUS65 KMSO 291310 CCA
Area Forecast Discussion...CORRECTED
National Weather Service Missoula MT
710 AM MDT SUN MAY 29 2016
...Cool, breezy & showery Monday with high mountain snow
...Quick warm-up expected later in the week...
.DISCUSSION...Showers and thunderstorms are in the forecast for
this afternoon as a shortwave trough moves into the region. Brief
heavy rain, small hail, and lightning can be expected out of the
stronger storms this afternoon. High resolution model guidance
show storms to form early this afternoon in northwest Montana,
while the same guidance show storms in north central Idaho and
west central/southwest Montana in the late afternoon and evening.
Most of the storms will move off to the east by the late evening
as the cold front moves through, but a few may linger near Butte.
There has been consistency for the trough to become a closed low
pressure system on the east side of the Continental Divide by
Monday. This low will clip Glacier National Park, which will
lower snow levels to around 6500 feet on Monday. Rain and high
elevation snow chances will extend along the Divide into Monday
night as the low moves off to the east.
An extended warm and dry spell is expected to begin Tuesday, as a
high pressure ridge builds overhead and lasts through at least
next weekend. Daytime high temperatures will rise to about 10
degrees above normal by Wednesday, climbing to 15-20 degrees above
normal late in the week through the coming weekend. This means
valley locations will see highs in the mid 80s to low 90s; certainly
the warmest temperatures seen so far this year!
Occasional surges of mid-level moisture will allow for a few
afternoon thunderstorms, mainly across the higher terrain beginning
on Thursday, but most areas will remain dry for an extended
period. Agricultural activities requiring dry stretches (such as
hay cutting), should be able to benefit from this pattern.
.AVIATION...Cloud cover will increase this morning as a trough and
cold front move into the region. Showers are forecast to first
develop near KMLP, beginning around 29/1600z. Simulated satellite
imagery then show showers and thunderstorms throughout northwest
Montana by 29/1800z. The rest of north central Idaho and western
Montana will see showers and thunderstorms develop during the
afternoon. Model guidance show the highest instability to be near
a line from KGIC to KBTM between 29/2100z-30/0000z, but with the
cold front`s expected passage, shower and thunderstorm development
should decrease in most areas by 29/0300z. Isolated storms may
linger until around 30/0600z in southwest Montana. Increased
westerly winds can be expected with the cold front passage today
as well. There has been model agreement that the trough will
become a closed low pressure system once it moves to the east
side of the Continental Divide tonight. This low will wrap
moisture and cloud cover into locations along the Divide, so
obscured terrain, high elevation snow, and rain will occur in the
Glacier Region and along the Divide through Monday night.