Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 03/13/20

Area Forecast Discussion
National Weather Service Great Falls MT
849 PM MDT Thu Mar 12 2020 .SYNOPSIS... A major winter storm is expected to impact portions of the Northern Rockies, especially the plains of Central and North Central Montana to end the work week and through the weekend. Snow, blowing snow, and cold temperatures are expected to accompany this storm. Motorist should be prepared for hazardous driving conditions, especially from Friday through Saturday && .UPDATE... The evening update has been published. Snow showers over the Little Belts and the eastern portions of the CWA will continue to wind down for the remainder of the evening into the overnight. Then the focus turns to the winter storm, which moves in from northwest to southeast tonight through Saturday night. No changes were made to the current winter weather headlines but the situation will continue to be monitored for the potential of blizzard conditions along and west of the I15 corridor northwest of Great Falls to the Canadian border. && .AVIATION... Updated 600 PM MDT Thu Mar 12 2020 (13/00Z TAF Period) A few lingering snow showers may persist over North-central Montana through 4Z but should mostly stay in between terminals. Mostly VFR conditions will begin to degrade toward MVFR/IFR from north to south tonight into Friday morning as a major winter storm approaches the region. KCTB may see consistent IFR/LIFR conditions due to snow and blowing snow from 12Z Friday through the end of the TAF period. Other Central/North-central terminals will see more sporadic snow and associated low ceilings and visibility but conditions will worsen as the day progresses. Mostly VFR or MVFR are expected for KBZN and KEKS for this period but condtions will likely degrade just beyond that. North to northeasterly surface winds develop over most Central/North-central locations Friday morning. Mountian obscurations and aircraft icing will increasingly become more widespread, especially for areas receiving snow. && .PREV DISCUSSION... /ISSUED 617 PM MDT Thu Mar 12 2020/ Rest of this afternoon through Saturday night...biggest concern and focus with the afternoon forecast was on the major winter storm set to impact the region beginning late tonight and persisting through much of the day on Saturday, only to be followed by record to near record low temperatures Saturday night/Sunday morning across North Central and Central Montana. First, not to be ignored or slept under the proverbial rug of the "major winter storm", is the on-going snow showers over North Central and Central Montana this afternoon. These snow showers, which are being drive by a combination of moist, northwest flow aloft and steep low-level lapse rates, will likely continue into the late evening hours before gradually decreasing in areal coverage. Brief reductions in visibility and some accumulations on road surfaces are the primary impacts with these showers, but given the scattered nature and briefness of said showers we will continue to just highlight through Special Weather Statements. As the showers gradually dissipate in coverage this evening over the plains of Central and North Central Montana, expect snow to begin to fill in along the Rocky Mountain Front around midnight as the low level flow becomes more east to northerly. Snow will spread south (east) along (away from) the Rocky Mountain Front Friday morning through Friday afternoon, continuing into Saturday morning/afternoon. Of biggest concern with today`s forecast issuance is the potential for blizzard condtions, especially along and west of the Interstate 15 corridor. For these areas, a push of pressure 6hr rises of 3-6mb along the Rocky Mountain Front combined with H850 winds of 25-35kts is expected to lead to a prolonged period strong and gusty northerly winds. The one question that remains is whether or not a sustained period of blizzard condtions can be observed, but given uncertainty and that the onset of the winds are still 18-24hrs out I will defer possibly upgrading (to a Blizzard Warning) to future shifts should trends continue. Regardless of if a Blizzard Warning is needed, I have continued to message within the current Winter Storm Warning that near-blizzard conditions are possible and could lead to hazardous conditions for both driving and ranching interests. Otherwise, snowfall amounts continue to remain relatively steady across the region, with the only major change being an increase in amounts along and west of Interstate 15. Finally, a very cold night is expected Saturday night/Sunday morning as a strong surface high settles over the area, with the potential for record or near-record temperatures. - Moldan Sunday through next Thursday...The low pressure area will continue to move south along the Pacific coast Sunday through Tuesday, which will help decrease the snow across the area. High pressure at the surface will also start to slowly exit the area to the east, relaxing the surface pressure gradient and allowing the winds to decrease. However, cold air will remain in place over much of the area due to the expected widespread snow cover. Temperatures over the plains could potentially fall into the teens below zero Sunday night and Monday night, with even colder temperatures possible if skies clear out and winds stay light. A weak westerly flow aloft will then reside over the forecast area through the middle of the week, keeping much of the area dry with only gradually warming temperatures. Daytime temperatures should warm above freezing in Southwest Montana, but they should remain below freezing over the plains. - Coulston && .PRELIMINARY POINT TEMPS/POPS... GTF 18 24 0 8 / 20 100 100 100 CTB 12 14 -8 3 / 80 100 100 100 HLN 20 29 4 14 / 10 70 80 90 BZN 17 33 15 28 / 0 20 40 70 WYS 2 34 17 36 / 10 0 60 80 DLN 19 35 18 35 / 0 0 20 60 HVR 16 24 9 18 / 50 70 100 100 LWT 16 25 12 20 / 40 90 90 90 && .TFX WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory from noon Friday to 4 PM MDT Saturday Broadwater...Jefferson. Winter Storm Warning from 9 AM Friday to 4 PM MDT Saturday Central and Southern Lewis and Clark...Meagher. Winter Storm Warning from 9 AM Friday to 4 PM MDT Saturday Blaine...Cascade...Chouteau...Fergus...Hill...Judith Basin... Liberty. Winter Storm Warning from midnight tonight to 4 PM MDT Saturday Eastern Glacier...Eastern Pondera...Eastern Teton...Northern Rocky Mountain Front...Southern Rocky Mountain Front...Toole. && $$