Weather Service Report


001 
FXUS65 KTFX 221719
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1116 AM MDT Sat Jul 22 2017

Aviation Section Updated

.SYNOPSIS...
Look for dry and calm conditions areawide today. Temperatures will 
not change much from yesterday with highs continuing 5 to 15 degrees 
above average. Patchy smoke from neighboring wildfires may cause 
hazy conditions at times. Expect a gradual warm up again by late
next week...along with a better chance for showers and 
thunderstorms.

&&

.UPDATE...

Shortwave ridging aloft and weak high pressure at the SFC should
keep the area dry through tonight and no major changes were needed
for the update. As for smoke impacts, I tried to fine-tune the
areas that are more likely to see smoke from area fires (as
opposed to keeping smoke in across the entire CWA). For now, it
looks like the better chance of seeing some smoke impacts looks to
be from Helena to Dillon through this evening and then in the
greater Lewistown area tonight. Kept the mention to patchy for
now, but this may need to be refined in later forecasts if impacts
become more certain. MARTIN

&&

.AVIATION...
Updated 1716Z.

VFR conditions are expected through Sunday afternoon areawide. 
Smoke/FU may cause reduced VIS at times, especially in the vicinity 
of KHLN/KLWT, but confidence remains too low to include in the TAFs 
for now. Distant mountains may be obscured/harder to see with hazy 
conditions just about anywhere through Sunday. MARTIN

&&

.FIRE WEATHER...

Decent mixing is expected once again this afternoon, but winds
aloft are weak/modest and even with deep mixing, winds at the SFC
only look to reach 10-15 mph for most areas. Additionally, RH may
only fall to 15 to 25 percent. All this paints more of a marginal
threat, fire weather wise, for today, so we'll hold off on any 
Red Flag Warnings.

On Sunday...expect increasing winds over North Central MT along 
with hot temperatures and windy conditions. Thus a fire weather 
watch has been issued for locations along the I-15 corridor north 
of Great Falls. We'll take a closer look at conditions on Sunday
and determine if the current Fire Weather Watch needs upgrading.

On Sunday night a dry front with a wind shift is expected to move
southward through the region. Winds will be strong over North
Central MT overnight...but with increasing humidities I will hold
off on additional fire weather highlights at this time.

Isolated thunderstorms with very warm temperatures are then 
expected for much of the second half of next week. Brusda/MARTIN

&&

.PREV DISCUSSION...
/ISSUED 428 AM MDT Sat Jul 22 2017/
Today through Monday...Fairly quiet weather will be over the
region today through Sunday afternoon...as a weak upper level
ridge moves over the region. Temperatures will be very warm today
and hot on Sunday afternooon. The upper level ridge breaks down 
by Sunday evening, as a wind shift moves southward through the
region Sunday night, along with increasing winds...especially 
over North Central MT. For Monday expect seasonable temperatures 
along with decreasing winds. Little/no precipitation is expected
during the short term. Brusda

Monday night through Saturday...Taking a look at recent model trends 
from yesterday to tonight, there have been a few slight changes that 
have led to a few noticeable modifications to the long range forecast 
package. Beginning late on Monday, the advertised potent closed 
upper low swinging across southwestern Canada has really picked up 
speed. This idea seems feasible given how the NAM also speeds this 
system through, even faster than the latest GFS/Euro solutions. 
Meanwhile, a closed upper low will continue spinning off the coast 
of Northern California. This low will help to continue to pump 
increasing moisture our way. However, given the quick speed of the 
shortwave passing to our north versus the closed low slowly spinning 
to our southwest, there could be a distinct dry period for northern 
and central areas during the day on Tuesday.

With that said, it is still looking likely showers and storms 
will arrive to far southwestern areas by late Tuesday afternoon 
and evening, and I have matched PoP's to illustrate this. A few 
storms could still be strong at times, with gusty winds the main 
threat. This activity will likely continue into the overnight 
hours on Tuesday and into the Wednesday for southwestern areas, 
with more spotty shower and storm chances possible areawide 
Wednesday afternoon. The main idea Tuesday, Wednesday and even 
lesser into Thursday is that latest model runs are not as 
optimistic on how widespread the rain and storms will be, as this 
is not expected to be a drought-breaking rain and storm event. 
Additionally, given the drought situation, lightning strikes may 
cause an increase in wildfire potential. At the end of the 
forecast period late in the week and weekend, we begin to dry out 
with ridging building back again, with temperatures creeping back 
up into the 90's for some. KLG

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  87  59  95  56 /   0   0   0   0 
CTB  84  56  90  51 /   0   0   0  10 
HLN  88  59  96  59 /   0   0   0  10 
BZN  87  53  94  54 /   0   0   0   0 
WEY  81  44  84  43 /   0   0   0   0 
DLN  84  52  91  53 /   0   0   0   0 
HVR  88  59  98  57 /   0   0   0  10 
LWT  84  57  94  57 /   0   0   0   0 

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Fire Weather Watch from Sunday afternoon through Sunday evening 
Eastern Glacier/Toole/Central/Eastern Pondera/Liberty...Lewis 
and Clark National Forest Rocky Mountain District-Rocky Mountain 
Front.

&&

$$

weather.gov/greatfalls

Return to Home page


Western Regional Climate Center, wrcc@dri.edu