106
FXUS65 KTFX 142324
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
523 PM MDT Tue May 14 2024

UPDATED AVIATION SECTION

.SYNOPSIS...

Showers and a few isolated weak thunderstorms will continue to
track southeast across central and southwest Montana through this
evening with decreasing clouds and precipitation changes
overnight. A return to above normal temperatures is then expected
from Wednesday through Friday, with a daily chance of showers and
thunderstorms. Unsettled weather conditions persist through the
weekend, with temperatures falling below normal.

&&

.DISCUSSION...

The large scale weather pattern features a seasonably strong
upper level ridge/high anchored offshore of the west coast with
multiple disturbances moving over the ridge and tracking E/SE
through western Canada and the Northern US Rockies. Numerous
showers and a few isolated thunderstorms associated with the
shortwave disturbance moving across the area this afternoon will
decrease later this evening as the disturbance exits the area with
a few showers lingering through later in the overnight period
mainly across portions of SW MT. With little support for storm
organization (skinny CAPE/low shear) expect any thunderstorms
through early this evening to be short-lived and relatively weak.
Clouds decrease from NW to SE across the area overnight with
generally light surface winds creating a window for some patchy
fog development

A warmer and mainly dry period is expected Wednesday and Thursday as
the next disturbance tracks eastward primarily north of the
International Border. There is 20-30% probability of thunderstorms
across northern Hill/Blaine counties Wednesday night as this
disturbance passes by to the north with a 20% or less probability for
showers across remaining portions of north-central MT.  Westerly
flow aloft across the Northern Rockies and MT gradually increases
through Thursday with breezy west winds developing across most of
the area Wednesday and windy conditions likely Thursday as low
pressure moves east across southern Alberta. Temperatures warm back
to above seasonal averages Wednesday with additional warming
expected Thursday before the next frontal system and mid to upper
level disturbance begin to move into the area Thursday night.

A Pacific cold front moves east across the area Friday in
association with the incoming upper level wave which also helps
deepen the surface low through Friday as it moves across southern
SK. The main impacts here will be an additional increase in winds
both with the frontal passage and following it Friday afternoon as
the low wraps up NE of the area. There is still some uncertainty
in the coverage of showers and likely a few thunderstorms with
the system on Friday, though current timing would favor SW MT for
better thunderstorm chances. Another shortwave looks to quickly
follow through the area Friday night, maintaining at least some
chance for showers across the area and particularly across the
mountains near the the Continental Divide and across eastern
portions of SW MT where there is a small risk (15-25%) for wet
snow accumulations of 2" or more as snow levels fall to around
5000ft Friday night. While widespread strong winds are not
anticipated, probabilities for wind gusts in excess of 40 mph
range from 30-50% across portions of north-central MT near the
Rocky Mtn Front Thursday with potential for more widespread
coverage on Friday across the area.

Looking ahead, the active weather pattern looks to persist into next
week with the next series of upper level disturbances arriving as
early as late this weekend. While medium range model-ensembles are in
fair agreement on maintaining and potentially deepening the upper
trough across the region into next week there is large amount of
spread in the timing and details of the individual waves, leading
to lower than average confidence in timing, though a continued
unsettled pattern with higher than average precipitation chances
and near to somewhat below average temperatures is likely. Hoenisch

&&

.AVIATION...
15/00Z TAF Period

VFR conditions are generally expected to continue across North
Central (KCTB, KHVR), Central (KLWT, KGTF, KHLN), and Southwest
(KBZN, KEKS, KWYS) Montana through at least 16/00Z.

Scattered lingering showers will continue to diminish through around
04Z, possibly producing some brief mountain-obscuring MVFR
conditions as a disturbance exits the area. A few weak thunderstorms
are also possible, with the main threat being erratic wind gusts,
but the likelihood that any storm will directly impact a terminal is
low, so have not mentioned it in TAFs. Otherwise, clouds and breezy
northerly winds should also decrease through around 06Z. This
partial clearing could allow some patchy fog to form in areas that
received the most precipitation (mainly along and south of a KHLN-
KLWT line). Any fog should diminish after 16Z, leaving skies mostly
clear with breezy westerly winds through the remainder of the
period. -Coulston

Refer to weather.gov/zlc for more detailed regional aviation
weather and hazard information.

&&

.HYDROLOGY...

A small stream Flood Advisory remains in effect for Belt Creek in
southeastern portions of Cascade County, generally from just north
of Neihart to Sluice Boxes State Park. The Monarch Fire
Department reported that fallen trees in the creek from the recent
snowstorm are causing log jams in the creek. This is resulting in
the creek coming out of its banks in locations that normally do
not flood. The flood advisory will remain in effect until the
water returns back to the creek or the impact has been reduced.
- Brusda/Moldan

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  43  71  48  75 /  10  10  20  30
CTB  40  69  46  70 /  20  10  20  30
HLN  45  74  51  80 /  40  10  10  20
BZN  41  69  43  77 /  60  10  10  20
WYS  32  63  34  67 /  40  10  10  20
DLN  40  69  43  76 /  40   0   0  10
HVR  43  73  46  75 /  20  20  50  40
LWT  40  66  45  70 /  30  20  40  40

&&

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

$$

http://www.weather.gov/greatfalls