Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 222334
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
534 PM MDT SUN MAY 22 2016

AVIATION SECTION UPDATED

.DISCUSSION...

TONIGHT THROUGH TUESDAY...

A strong upper level low is spinning just north of our forecast
area, and slowly drifting northeast into Saskatchewan. A strong
pressure gradient at the surface has produced widespread west-
southwest wind gusts of 30 to 45 mph. Isolated gusts could reach
near 55 mph this evening, and have otherwise remained below high
wind warning criteria. Winds will stay brisk but gradually taper
later tonight through Monday as the surface low begins to fill and
move further away.

Deep moisture wrapping around the west side of the upper low is
producing record rainfall, per NWS MSO, at some locations west of
the Continental Divide. Snow levels over the Northern Rockies may
be as low as 5500 feet. Thus, there is potential for heavy snow
accumulation overnight into Monday crossing over to the east side
of the Continental Divide. A Winter Weather Advisory for
elevations above 5500 feet remains in effect to cover this hazard.

Radar and satellite trends show scattered light rain showers with
a few embedded lightning strikes over our southwest and eastern
zones. This activity is expected to dissipate after sunset, but
then redevelop once again on Monday and Tuesday afternoon.
Temperatures continue to remain below average with mostly cloudy
skies through Tuesday. PN

TUESDAY NIGHT THROUGH SUNDAY...Forecast models continue to show an
unsettled period during this time, with the greatest potential for
showers and thunderstorms occurring during the peak instability of
the afternoon and early evening hours. A broad upper level trough
with two distinct low pressure areas will set up over the western
and central United States through Friday. One low pressure area will
move east across the southwestern U.S. during this period, while the
second one dives south along the Pacific Northwest coast. A
disturbance over Montana and southern portions of Alberta and
Saskatchewan will keep a chance of showers and thunderstorms over
the forecast area through Wednesday night, with the best chances
over western and southwest Montana. As this disturbance moves east
out of the area with the first low pressure center beginning on
Thursday, the second low will continue to move south over the
Pacific Coast states and a high pressure ridge will build over the
Great Plains. As a result, the flow aloft will become more
southerly, which will bring unstable and steadily warming air with
increased (potentially monsoonal) moisture to Montana. This will
continue the good chance of showers and mainly afternoon/evening
thunderstorms over the forecast area. Temperatures will remain near
normal for most of the period, but warming temperatures into the
Memorial Day weekend could cause highs to reach the lower to mid 70s
in some areas by Sunday. However, with this warming, there will be
an increased threat of strong thunderstorms over the weekend. Will
continue to monitor this situation. Coulston

&&

.AVIATION...UPDATED 2332Z.

A low pressure center will continue to move northeast of the region
tonight although a broad area of low pressure and strong southwest
flow will continue through Monday. The airmass will remain moist and
unsettled with a chance of showers through the period but especially
Monday afternoon. Local MVFR conditions are possible near showers
and thunderstorms. Elsewhere, VFR conditions will prevail through
the next 24 hours.

&&

.HYDROLOGY...
Periods of showers and isolated thunderstorms will continue to
affect the region over the next few days. A Flood Warning
continues for Clear Creek where the level remains just above
flood stage. It is expected to drop below flood stage by this
evening. Meanwhile, other locations near small creeks could see
minor low land flooding or agricultural field flooding. However,
with breaks in the precipitation, major rivers/creeks are not
expected to rise above flood stage at this time.

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  44  54  39  61 /  10  50  20  30
CTB  40  51  37  59 /  40  60  30  50
HLN  43  55  42  61 /  20  40  20  40
BZN  38  57  38  63 /  20  40  30  30
WEY  31  49  32  52 /  40  40  30  40
DLN  36  57  37  59 /  20  40  20  40
HVR  44  56  42  61 /  30  40  20  30
LWT  41  56  39  58 /  10  30  20  40

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until noon MDT Monday for MTZ009-048.

Flood Warning for Clear Creek in Blaine County through Sunday
night.


&&

$$

weather.gov/greatfalls



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