Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 271019
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
419 AM MDT Wed Aug 27 2014

.DISCUSSION...

Cut-off upper-low continues to rotate over the Central Rockies and
is centered over Utah as of 10Z/Wednesday. This feature will have
little influence on Montana`s weather with sct showers/storms only
reaching as far north as Idaho and Wyoming.

Today...Zonal flow and negligible pressure gradient from the sfc up
through the troposphere will result in clear skies, light winds, and
seasonal temps. SREF 1000-500 mb thicknesses rise to near 573-576
dam...700 mb temps increase to ~8 C.

Thursday...Cold air advection in the 1000-500 mb layer looks to hang
mainly west of the forecast area through Thursday aftn, allowing
temps to reach the mid 80s. The tail end of an upper jet will brush
north-central MT during the evening/nighttime and a 500 mb vort max
will traverse through MT from west to east. These features should
produce isolated showers during this time.

In concert with these mid/upper level disturbances, a low-level
cold front, albeit a weak one, will slide through north-central
MT, increasing dewpoints to the lower 50s. NAM has MUCAPE values
up to 1 K J/kg along the boundary. Therefore, there is a slight
chance for thunder.

Friday...As the sfc boundary stalls just south of GTF Friday
morning, a SE flow will develop in response to a high pressure
center moving through the Dakotas. This flow will support low-level
moisture advection and should sustain 50-55 F dewpoints which will
create an unstable air mass over my eastern forecast area during the
aftn...MUCAPE may exceed 1 K J/kg. However, showers/storms should
remain isolated. Uttech

Friday Night through Wednesday...Cool and unsettled conditions are
expected for this period.  The primary weathermaker will be
a longwave trof that gradually moves into the region on Sat and will
persist across the Northern Rockies and the Great Basin areas
through much of next week.  A series of quick-moving shortwaves
embedded within the larger trof pattern will bring scattered showers
and thunderstorms on Saturday, Monday, and Wednesday with isolated,
lingering showers possible on Sunday. An autumn-like cooling trend
begins with passage of a cold front in the early aftn on Sat, and is
then maintained by northwest flow aloft through at least Mon.  After
near-normal temperatures on Sat, high temps each following day will
be about 10-15 degrees below normal, with highs only reaching the
low-mid 60s.  Will also be keeping an eye on possibility of
breezy-to-gusty surface winds along the Rocky Mtn Front and adjacent
foothills and plains on Mon and Tues as a leeside trof develops over
central MT with high pressure ridging west of the Continental
Divide. Waranauskas

&&

.AVIATION...
UPDATED 0500Z.
High pressure will continue to dominate the weather pattern for the
next 24 hours and will keep the air mass dry and stable. VFR
conditions will prevail for the next 24 hours.

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  84  55  85  53 /   0   0   0  20
CTB  85  53  79  50 /   0   0  20  20
HLN  85  55  87  54 /   0   0   0  20
BZN  81  47  84  48 /   0   0   0  20
WEY  70  38  72  39 /   0   0  10  20
DLN  79  49  82  50 /   0   0   0  10
HVR  86  55  85  53 /   0   0  10  30
LWT  82  55  84  54 /   0   0  10  20

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

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