Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 261802
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1201 PM MDT TUE JUL 26 2016

...Aviation Section Updated...

.UPDATE...
Updated forecast is out. Only changes where to freshen
pops/temperatures for today. Light showers will affect the divide
area between Butte and Helena through Noon, while showers around
Hays are moving out of our region. Otherwise, expect another round
of showers/thunderstorms this afternoon/evening...with the best
chance for storms over North Central MT. Some storms could produce
small hail and brief heavy rainfall. Brusda

&&

.AVIATION...
Updated 1801Z.

An upper level shortwave will bring isolated to scattered TSRA to
the forecast area through Wednesday morning. The greatest coverage
is expected across north-central Montana with a lower coverage
across SW MT. Added TEMPO groups for TSRA at KCTB/KHVR due to the
higher confidence at those sites. For the remainder of the TAF
sites, later amendments may be needed if confidence in TSRA
increases. Any TSRA that develops today, especially across north-
central Montana, may bring a short period of MVFR or lower VIS.
Gusty winds and small hail will also be possible with any storm that
develops. Of note, some short term models move a broken line of
storms across the Hi-Line later this afternoon/evening. If this does
pan out, there could be an increased threat of wind gusts over 40kt.
Martin

&&

.PREV DISCUSSION...
/ISSUED 525 AM MDT TUE JUL 26 2016/
Today through Thursday Evening...Quiet conditions this morning,
except for small area of slow-moving showers and weak, pulse-type
thunderstorms through parts of Hill/Chouteau/Blaine counties. This
activity should exit into eastern MT later this morning, with little
rainfall expected. Meanwhile, current water vapor satellite imagery
shows the next Pacific shortwave trof is already into central WA and
is on track to arrive this aftn/eve, bringing another round of
showers and thunderstorms.  Storm coverage should be more widespread
today, especially over the central and Hiline counties, where broad,
moist airmass with dewpoints in the 45 to 58F range is already in
place. Storms should trend a bit wetter today as latest models have
further increased precipitable water (PW) values into the 0.75-1.0
inch range for much of the forecast area. This should lead to more
occurrences of moderate to briefly heavy rainfall as storms move
through our region today.

Pattern repeats itself on Wed as another shortwave tracks across the
Northern Rockies.  PW remain favorably high for decent rainfall
amounts, except for southwest MT where storm coverage and PW values
are forecast to be lower.  The final shortwave in the parade shows
up on Thurs aftn, but this one looks to be the weakest of the three,
with less accompanying moisture too, so storms should be more
isolated in coverage.  Finally, after another day in the upper 80s
to low 90s today, the combination of precip and slightly cooler air
behind the Wed system will provide a brief break in the hot
temperatures.  Look for highs on Wed/Thurs to reach the more
comfortable mid 80s.
Waranauskas

Thursday Night through Tuesday...The last in a series of shortwave
disturbances exits to the east Thursday night. Temperatures trend
back into the lower 90s Friday and Saturday amid a generally stable
westerly flow. However, isolated weak afternoon thundershowers may
be possible during this period over our northeast zones associated
with a weak baroclinic zone. A stronger weather system moves across
the Canadian Rockies Saturday night into Sunday, forcing a southwest
flow aloft over the region. This will help to draw monsoonal
moisture into southwest Montana, with enhanced chances for afternoon
showers and thunderstorms through the weekend. Temperatures trend a
few degrees cooler to start next week with lower heights over the
northwest and isolated to scattered showers. PN

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  89  59  85  56 /  40  40  20  30
CTB  83  56  81  53 /  60  50  30  40
HLN  90  61  89  60 /  30  20  10  20
BZN  89  55  87  53 /  20  20  10  20
WEY  83  48  79  44 /  30  30  10  20
DLN  87  55  87  53 /  20  20  10  20
HVR  88  62  84  58 /  40  50  30  40
LWT  83  59  82  57 /  40  50  20  30

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

weather.gov/greatfalls



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