Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 281156
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
555 AM MDT THU JUL 28 2016

Updated Aviation Section

.DISCUSSION...

Today through Saturday...Northwest flow aloft continues over the
region with weak embedded disturbances. Mid-level temperatures are
gradually warming, but still expect just enough instability to
generate isolated to scattered afternoon showers and
thunderstorms. Most of this activity will be confined to the
higher terrain, but any storms that can develop could produce
brief downpours as precipitable water remains above about 0.8 inches.
Temperatures remain near to just below seasonal averages today,
but then trend warmer through the weekend. The warmest
temperatures are expected Saturday as highs reach the mid-90s for
many locations. PN

Saturday night through Thursday...Not a lot of change regarding the
medium range forecast. Very warm westerly flow aloft develops Sunday
as a closed upper low moves across central Canada. Precipitation
from this feature continues to look as though it will stay north of
the border. Winds will increase a bit Sunday as the pressure
gradient tightens and the combination of the very warm temperatures,
low relative humidity, and increasing winds could raise fire weather
concerns. Also Sunday, monsoonal moisture is drawn up into southwest
Montana where isolated afternoon thunderstorms will be possible.
Monday will be dry and not as warm as cooler air will make its way
across the area in the wake of the upper low pushing east. By
Tuesday, another closed upper low approaches western Montana as it
moves along the international boundary. The models differ in their
structure and movement of this feature. The GFS depicts this feature
as a closed upper low while the ECMWF depicts it as a broad upper
trof. Regardless, scattered afternoon and evening thunderstorms will
be possible across the north and over the eastern portion of the
county warning area. By Wednesday, isolated thunderstorms will be
confined to the Hi-Line as the upper disturbance continues to slowly
move east. 500 mb heights rise on Thursday bringing dry conditions
but, as was the case with the earlier scenario, cooler air will
filter across the area as the second upper disturbance moves east.
Temperatures will be above seasonal averages Sunday but afternoon
readings will slowly decline to below seasonal averages by the end
of the period.

&&

.AVIATION...
Updated 1155Z.
Somewhat unstable northwest flow aloft will continue. Enough low
level moisture around for isolated showers and thunderstorms to
develop after 20z. Convective activity should end by 04z with
clearing skies. VFR conditions prevail with MVFR conditions possible
in the vicinity of thunderstorms with gusty erratic winds.

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  83  55  88  58 /  30  20  10  10
CTB  81  54  84  56 /  40  20  10  10
HLN  85  60  91  61 /  30  30  10  10
BZN  83  51  89  53 /  30  20   0   0
WEY  78  43  79  44 /  20  20  10  10
DLN  83  52  87  54 /  10  10   0   0
HVR  82  57  86  60 /  30  20  10  10
LWT  76  55  83  58 /  30  20  10  10

&&

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

$$

weather.gov/greatfalls



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