923
FXUS65 KTFX 190814
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
214 AM MDT Sun May 19 2024

.SYNOPSIS...

Seasonably cool temperatures will be around the next week or so,
with opportunities for precipitation most days. There is still some
uncertainty in amounts, but Wednesday into Thursday looks to be
the most impactful from a precipitation perspective.

&&

.DISCUSSION...

Through Tuesday... To start the period, a series of upper level
disturbances are in places from the Pacific NW northeastward across
much of southern Canada, forming a congealed mess of a broad upper
level trough. The next disturbance in the parade will shift eastward
from the Pacific NW toward the Northern Rockies this morning,
shifting eastward away from the region late today.

A brief period of frontogenesis in the 700-600 mb layer will
result in a band of precipitation early this morning, generally in
the Helena area east-northeastward toward Lewistown. This band
will slowly shift southeastward through the morning, dissipating
as mid-level support diminishes and shifts eastward late morning.
High resolution ensembles give high confidence in snow as the
precipitation type in terrain. The Kings Hill Pass area has the
best chance for a couple inches of snow with this band. A mix of
rain and snow looks to be a good bet at lower elevations of
Central Montana south toward the I-90 corridor through late
morning. Given warm roadways I am not expecting too many impacts
outside of reduced visibility at lower elevations where snow does
mix in.

Given the cool temperatures aloft working in with this system,
numerous showers and a few thunderstorms look to develop late
morning into the afternoon, especially in areas that see less cloud
cover early in the day. Most showers will diminish by sunset.

The next in the parade of upper level disturbances will largely miss
the region to the south cool Monday into Tuesday. Although this is
the case, cool temperatures aloft stick around into Monday and
Tuesday, allowing additional showers to develop late morning through
early evening across much of the region each day. Overall, not
expecting much impact from these showers. Cool temperatures at the
surface trend a touch warmer Monday, and get close to average for
Tuesday.

Wednesday into next weekend... Ensembles are converging on a
solution where a closed upper low dives southward from northern BC
late Tuesday into the Pacific NW Wednesday, eastward across
Southwest Montana Wednesday night into Thursday, finally exiting
eastward late Thursday night or early Friday. This solution would
bring a round of accumulating precipitation to the region, largely
rain at lower elevations, with high mountain snow. The chance for a
half an inch of total precipitation Wednesday through Thursday night
is largely greater than 50% across much of the plains and across
terrain.

Ensembles get a bit murky on the Friday through Sunday period,
though temperatures near to slightly below normal with chances for
lingering precipitation look reasonable at this point. -AM


&&

.AVIATION...
19/06Z TAF Period

Note: The NWS Great Falls Weather Forecast Office manages the
following TAFs: KCTB, KHVR, KGTF, KLWT, KHLN, KBZN, KEKS and KWYS.

Beginning at 19/12Z, TEMPO groups, PROB30s and/or predominant
conditions due to light rain/snow and mist are introduced into all
of our TAFs. Most airfields remain VFR throughout this TAF period,
even as they fall into the low VFR category range. Intermittently,
MVFR conditions are forecast for KHLN during the period of, 1912Z to
1915Z, while periods of MVFR conditions are included in the KEKS
TAF, and the KWYS TAF includes a PROB30 with MVFR conditions for a
one hours period that begins at 19/22Z. General thunderstorm
activity is forecast to occur across our region during today`s
afternoon and evening hours, with thunderstorm mentioned in the
following TAFs: KCTB, KGTF and KHLN. Aside from the strong and
erratic gusty winds associated with thunderstorm, breezy to gusty
northwesterly winds up to 25KT develop across portions of central
and southwest Montana, during today`s afternoon and evening hours.
The winds at KWYS, generally, remain light and southeasterly to
southwesterly.
- Fogleman

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

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  55  35  59  37 /  80  30  60  20
CTB  55  33  57  35 /  70  30  50  10
HLN  57  37  60  39 /  70  30  60  20
BZN  55  32  56  34 /  80  20  70  40
WYS  52  27  51  28 /  40  30  70  50
DLN  53  31  55  33 /  40  20  60  30
HVR  59  37  60  38 /  60  20  40  10
LWT  52  32  54  33 /  80  30  70  20

&&

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

$$

http://www.weather.gov/greatfalls