Area Forecast Discussion
Issued by NWS Great Falls, MT

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119
FXUS65 KTFX 260555
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1155 PM MDT WED MAY 25 2016

Aviation section updated

.UPDATE...Upper level low remains over eastern portions of
Montana with an unstable north-northwest flow aloft over central
and southwest Montana. Radar imagery suggests that shower and
thunderstorm activity is beginning to diminish a bit. Latest
models support diminished activity but keep isolated showers over
portions of the forecast area overnight. Have updated forecast
based on latest models and observed conditions to fine tune pops,
weather, qpf and temperatures for tonight through Thursday
morning. No major changes as the going forecast anticipated
isolated showers continuing through morning. mpj

&&

.AVIATION...
UPDATED 0555Z.
Light showers are diminishing over the region at 06z. Expect
showers/isolated thunderstorms to redevelop after 17z and then
continue to around 03z Fri. Most showers will be brief, but short
periods of gusty winds and quick downpours will be possible with
heavier showers. Some mountains will be obscured at times during the
afternoon/evening hours, otherwise VFR conditions will prevail.
Brusda

&&

.PREV DISCUSSION...
/ISSUED /

Today Through Friday...A cluster of scattered thunderstorms has
developed along and north of a line from Helena to Judith Gap...as
a result from weakly unstable air combined with an upper level
disturbance. Strong 0-6 KM shear from a sneaky jet streak is
currently overhead...however...100-200 J/KG cape in the hail
growth zone will limit any severe potential for storms today.
Gusty winds...and small hail...along with brief heavy rain the
likely main threats through this evening. Upper low...now position
along the MT/SK border...continues slowly SE across NE MT
Thursday. A somewhat moist NW cyclonic flow aloft will remain
across the forecast area through Thursday with afternoon airmass
destabilization resulting in a greater coverage of showers and
possibly a few weak thunderstorms again on Thursday. Limited
instability...and weak shear...with result in just generic type
thunderstorms. Temperatures through Thursday will remain near to
somewhat below seasonal averages. By Friday, upper level energy
now moving SE along the AK Panhandle will dig into WA/ID, shifting
upper level flow across the region to the SW. A surface Pacific
cold front associated with the incoming upper level trough will
likely cross the Continental Divide Friday for increased chances
for showers and thunderstorms by Friday afternoon. Models still differ
some on the degree of instability ahead of the front with GFS/GEFS
indicating higher CAPE and a marginal risk for stronger
thunderstorms while the NAM/SREF is not as aggressive in coverage
of convection or its strength. Hoenisch/Anglin

Friday night through Wednesday...A rather unsettled weather pattern
will continue to reside over the region through Tuesday, before
drier and warmer conditions start to move into the region by next
Wednesday. We will be in transition between upper level disturbances
from Friday night through Sunday night, with a chance for a passing
shower expected over the weekend. Right now, the precipitation
activity should be on the low side on Sunday, and pops have been
reduced a bit for this period. However, both the GFS/EC prog an open
trof moving through the region on Memorial Day. As a result, pops
have been increased a bit on Monday. Temperatures will remain a bit
below normal over the weekend, and than rather cool on Monday.
Additionally, some snow will be possible, especially for elevations
above 6000 feet during the late night/morning hours. For late Tue
into Wednesday, both the GFS/EC are showing a weak upper level ridge
of high pressure building over the region. This ridge will allow
drier and warmer air to move into the region, which will be a nice
change from current weather pattern. By next Wednesday, afternoon
highs will be near normal over the Southwest, and near/slightly
below normal over the North. Brusda

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  44  67  45  60 /  30  40  20  70
CTB  42  66  41  59 /  20  60  50  30
HLN  47  68  45  60 /  40  40  30  50
BZN  42  67  41  61 /  30  40  30  60
WEY  32  57  35  54 /  40  50  40  30
DLN  40  64  41  58 /  30  30  30  60
HVR  42  69  46  67 /  10  20  10  50
LWT  41  64  43  61 /  30  20  20  60

&&

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

&&

$$

weather.gov/greatfalls



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