Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 01/18/23
Area Forecast Discussion
National Weather Service Great Falls MT
852 PM MST Tue Jan 17 2023
.SYNOPSIS...
A weak disturbance will continue to bring light snow and rain to
parts of north-central and southwest Montana through this evening,
with total accumulations generally less than a half inch. Breezy
conditions will develop Wednesday along the Eastern Slopes, then
expand across north-central Montana Thursday. Strong winds develop
Friday night into Saturday along the Eastern Slopes once again,
then a cooler and snowier pattern develops late Saturday and
extending into the middle of next week.
&&
.UPDATE...
Have reduced overnight lows in accordance with scattering skies,
in order to allow for the loss of surface heating. I`ve, also,
adjusted hourly temperature grids accordingly. Considering the
tightening pressure gradient along The Rocky Mountain Front, and
portions of central Montana, I`ve increased winds, a bit, by
loading current observations and interpolating out for a few
hours. Finally, with moisture lingering across portions of Hill
and Blaine Counties, I`ve increased Probability of Precipitation
(POP) grids in that area, to include Havre, where I have 25% to
28% POPs, for a three hour period. My educated assessment is that,
over the next few hours, skies will scatter-out in that area as
well, and fog will likely develop. As winds increase during the
morning hours, fog should dissipate. Fog development is highly
dependent upon the loss of cloud cover, as well as, winds
remaining sufficiently light.
- Fogleman
&&
.AVIATION...
522 PM MST Tue Jan 17 2023 (18/00Z TAF Period)
KHVR:
The first few hours of this TAF period are characterized by
predominant MVFR condition and intermittent IFR conditions in light
snow and mist and with low ceiling. From 08/03Z skies scatter-out
and clear, allowing for surface cooling. There is moderate to high
confidence in the development of LIFR conditions in fog with
vertical visibility conditions. Winds remain light and variable
through 18/14Z, at which point winds become southwesterly at 9KT.
These southwesterly winds are expected to be just strong enough to
aid in the dissipation of fog/mist, allowing conditions to become VFR
and remain VFR through the remainder of the TAF period. Expect
mountain obscuration.
KCTB, KGTF, KLWT, KHLN, KBZN, KEKS:
VFR conditions are forecast for these airfields throughout this TAF
forecast period. Near MVFR conditions are expected due to low
ceiling. Ceilings slowly increase throughout the period. Expect
mountain obscuration. Confidence is moderate to high in
southwesterly to west southwesterly winds strong enough to inhibit
the formation of fog/mist. Periods of breezy to gusty winds are
forecast for KCTB and KGTF. Southerly breezy winds develop at KEKS.
In this region, southerly winds, when funneled through north-south
oriented mountain valleys/passes, impact light aircraft operations.
- Fogleman
Refer to weather.gov/zlc for more detailed regional aviation weather
and hazard information.
&&
.PREV DISCUSSION...
/ISSUED 522 PM MST Tue Jan 17 2023/
Rest of this Afternoon through Tonight...
The latest satellite, radar, and model analysis depicts a weak mid-
level low pressure system north of Havre moving slowly northeast
into southwestern Saskatchewan. Widespread drizzle and flurries and
isolated/scattered snow/rain showers continue to move east and
southeast across much of north-central and parts of southwest
Montana in association with the parent low. This low will continue
to move very slowly northeast over the next 24 hours, with light
precipitation moving east of the region overnight tonight. The
forecast problem for late tonight is fog reformation, both in
terms of intensity and spatial extent. Currently, highest
confidence for such fog reformation is along and near the Hi-Line
from the Shelby area east to, and including, the Milk River
Valley.
Wednesday through Friday Night...
This period will feature primarily breezy conditions across the
region, especially the Eastern Slopes. Winds will be strongest
along the Rocky Mountain Front, over and on the lee side of the
central ranges, and over portions of southwest MT. Exceedence
probabilities for gusts over 55 mph are running well below 50
percent for all locations on Wednesday and Thursday; however,
probabilities for gusts over 39 mph increase to 40 percent and
greater over the Rocky Mountain Front and portions of the plains
on Thursday as a cold front brings a sharp northwesterly wind
shift to these areas. A split flow aloft looks to send much of the
moisture and shortwave energy to our south on Thursday, but there
should be enough lift for some light, mostly mountain snow.
Saturday through next Tuesday...
Ensembles continue to suggest that a stronger system will dive
southward into the region Saturday into Sunday, bringing a period of
potentially strong and gusty winds followed by accumulating snow.
Currently, higher end probabilities for wind gusts over 55 mph on
Saturday are confined to the Rocky Mountain Front and the lee side
of the central ranges, but widespread gusts in the 35 to 55 mph
range are likely, especially over the plains. Snowfall amounts on
Sunday look to fall in the 1 to 3 inch range for lower elevations,
with higher amounts over higher terrain. The progressive
northwesterly flow aloft continues into early next week, maintaining
periods of light snow, breezy to windy conditions, and cooler
conditions, though not bitterly cold. It is important to note that
the chances for sub-zero low temperatures increases to 15 to 40
percent by the middle of next week across much of the forecast
area, with highest probabilities in the typically-colder sheltered
valley areas.
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 37 23 39 27 / 40 10 0 0
CTB 36 22 38 25 / 20 0 0 0
HLN 32 15 31 19 / 30 10 0 0
BZN 28 7 27 9 / 20 20 0 0
WYS 24 -2 21 6 / 0 0 0 10
DLN 26 6 26 12 / 10 10 0 0
HVR 32 14 28 13 / 50 50 0 0
LWT 36 21 37 22 / 10 40 0 0
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
http://www.weather.gov/greatfalls