185 FXUS65 KTFX 031622 AFDTFX Area Forecast Discussion National Weather Service Great Falls MT 922 AM MST Thu Jan 3 2019 .UPDATE... No significant changes from previous forecast. Strong winds continue downwind (E and NE of the Rocky Mtn Front and Little Belt Ranges). One of several low level wind maximums moved through the region early this morning and while lowest level winds have decreased some, mixing this afternoon should keep the threat for strong winds going through later today across these same areas. Strongest and most widespread period of winds still looks to occur overnight tonight through Friday morning and current set if High ind Highlights covers this well. Hoenisch && .SYNOPSIS... Strong westerly winds over ridge tops and along the east slopes of the Rockies will continue to spread east over the plains of north central Montana today and persist into Friday, with the strongest winds likely tonight. However, these winds will likely not impact the southwest valleys. Light snow will also accumulate over the mountains along the Rocky Mountain Front, likely causing blowing snow over Marias Pass. Winds will decrease Friday night into Saturday and any light mountain snow will diminish as a high pressure ridge builds back into Montana. Temperatures will be well above normal in the windy areas, but the southwest valleys will remain near normal. && .DISCUSSION... && .AVIATION... Updated 1145Z. The main impact to aviation during this period will be due to a strong westerly flow aloft. Significant mountain wave turbulence, low level wind shear, and potential rotors are expected over ridge tops and the Rocky Mountain Front. Winds of 40 to 60 kt with gusts to 80 kt will be likely, which will cause mountain obscuring blowing snow at and north of Marias Pass. Somewhat lesser, but still strong, winds will spread east over the plains of north central Montana today, where 25 to 40 kt winds will be likely with occasional gusts to 60 kt will be possible, along with low level wind shear and mountain wave turbulence. The southwest Montana terminals will not have nearly as strong winds, but low level wind shear will remain a threat. Coulston && .PREV DISCUSSION... /ISSUED 445 AM MST Thu Jan 3 2019/ Today through Saturday...Disturbances moving over a high pressure ridge spreading east across the southwest and south central U.S. will keep a strong westerly flow aloft over Montana through Friday. As a result, westerly winds over ridge tops will remain strong. A strong surface pressure gradient will also continue along the Rocky Mountain Front, making wind gusts of 75 to at times 90 mph possible there. Strong winds will also mix down to the surface over the remainder of the north central Montana plains at times today. Have therefore expanded the High Wind Warning to include all of this area, with the eastern TFX zones going into effect around 8 am. A weak surface low pressure area associated with a shortwave trough will move east across far southern Alberta and Saskatchewan tonight into Friday Morning, which will most likely bring the strongest winds of the period. Gusts to 70 mph will be possible over most plains, but gusts to 100 mph will be possible through favored wind areas along the Rocky Mountain Front. Accumulating snow will accompany this shortwave, likely bringing 6 to 10 inches above 6000 feet over the northern Rocky Mountain Front. Only a few inches are possible over Marias Pass, but the greater threat there will be from significantly reduced visibility due to blowing snow. With the passage of the shortwave Friday night into Saturday, the high pressure ridge will build into Montana, allowing winds to decrease quite a bit and causing that mountain snow to diminish. These winds will help keep temperatures 10 to 20 degrees above normal over the plains. However, winds will likely not mix down into most of the southwest valleys during this event, which will keep temperatures near to slightly below normal. Coulston Saturday Night through Thursday...Medium range models continue to suggest that central and southwest portions of Montana will remain generally quiet with no major weather systems anticipated. As has been the case over the last few days, am expecting that precipitation will primarily affect the mountains near the Continental Divide while lower elevations remain dry and windy. Model guidance indicates that temperatures through the medium range period will remain above seasonal normals. As was the case yesterday, the GFS pushes a Canadian airmass and some light precipitation into north central Montana Monday and Tuesday. However, this continues to be the only model that shows this solution as the ECMWF, Canadian, SuperBlend, WPCGuide, and National Blend of Models all support continuing the mostly dry and windy scenario over the plains. By mid week all models begin to develop a strong weather system along the West Coast with shortwave ridging over the Northern Rocky Mountain region. mpj && .PRELIMINARY POINT TEMPS/POPS... GTF 50 36 52 26 / 0 0 0 0 CTB 49 32 46 23 / 0 0 0 0 HLN 42 26 41 22 / 0 0 0 0 BZN 35 18 38 18 / 0 0 0 0 WEY 20 4 25 5 / 10 10 0 0 DLN 34 18 35 18 / 0 0 0 0 HVR 52 37 51 26 / 0 0 0 0 LWT 50 33 50 25 / 0 0 0 0 && .TFX WATCHES/WARNINGS/ADVISORIES... High Wind Warning until 5 PM MST Friday Cascade...Eastern Pondera...Eastern Teton...Judith Basin...Liberty...Toole. High Wind Warning until 5 PM MST Friday Northern Rocky Mountain Front...Southern Rocky Mountain Front. High Wind Warning until 5 PM MST Friday Blaine...Chouteau... Fergus...Hill. High Wind Warning until 5 PM MST Friday Eastern Glacier. && $$ http://www.weather.gov/greatfalls