895 FXUS65 KTFX 201621 AFDTFX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREAT FALLS MT 921 AM MST Sun Jan 20 2013 .UPDATE...Cold Canadian air will continue to push into Montana today. As feared, it appears that snow amounts are much lower than models anticipated so have updated to lower pops and snow amounts across much of the forecast area. have also updated forecast highs to reflect the likelihood of temperatures falling during the day. At this time it also appears that wind speeds may be lower than anticipated and wind chill advisory criteria may not be met in Blaine and Hill Counties. However, will leave the advisory going in case winds pick up a bit this afternoon. mpj && .AVIATION... Updated 1155Z. A cold front continues to move across North Central and Central Montana during the TAF period. Winds will continue to originate out of the north or north east. Clouds and visibility conditions will remain difficult for much of the morning hours. Conditions will generally improve around 15z through 20z Weak upslope flow will continue to promote low clouds and IFR/LIFR CIGS along with the possibility for light snow and fog though little snow accumulations are expected during this time frame. At KBZN and KHLN conditions are expected to remain VFR. Suk && .PREV DISCUSSION... /ISSUED 455 AM MST Sun Jan 20 2013/ TODAY THROUGH TUESDAY...An upper level high pressure ridge will be in place over the West Coast with northwest flow aloft over the zones. At the surface, a cold front will be moving through the zones and temperatures behind the front will be much colder. Currently, pressure rises over Alberta are very strong and surface pressures are also 1045+ mb across northern Alberta. The main questions for today will be snow amounts and temps. The upper level support for this system is very weak and precipitation will be generated mainly by the low level upslope flow. Temperatures will be highly dependent upon the frontal positioning with very cold temps to the north and much more mild temps to the south. Low level moisture will spread through the north and central zones by this morning. Snow reports to the north have so far been scanty although Medicine Hat an Calgary have both reported snow. By midday today, the northwest zones will be drying. Most precip will likely occur along the frontal boundary--across the central zones--and best snow amounts will be over the higher terrain of this region. The upper level high pressure ridge will remain over the West coast through Monday and slowly move over the Pacific Northwest Tuesday. This will keep the zones underneath the northwest flow aloft. However, by Monday the ridge will be near the Idaho panhandle and the jet will be east of the zones so the airmass be trending warmer. The cold airmass moving into the area and breezy conditions could cause some low wind chills across the northeast zones and will continue the current wind chill advisory. Zelzer Tuesday Night through Sunday...A large scale ridge axis begins to move over the Rocky Mountains and in to the area Wednesday. By the middle of the day Wednesday a fast moving shortwave trough will move across the area bringing a quick decrease in temperatures and windy conditions Wednesday Night and Thursday. Some precipitation is possible too although it should be limited to area along the high line and the elevated terrain. This unsettled system will be relatively short lived as the large scale ridge once again build back into the are bringing warmer than average temperatures into the area Friday and Saturday. Model solutions are in general agreement through the bulk of the long term...by Sunday models do have significant differences. It should be noted though that both models due have a large scale low pressure system off the pacific coast...with the European retrograding and cutting off the low...and giving us more days under the high pressure ridge...while the GFS continues to move it across the continent as a large scale trough. Will continue to see how subsequent model runs address this discrepancy. Suk && .PRELIMINARY POINT TEMPS/POPS... GTF 23 8 35 27 / 40 10 0 0 CTB 11 -3 35 19 / 20 10 0 0 HLN 25 12 33 15 / 10 0 0 0 BZN 26 9 32 8 / 10 10 0 0 WEY 25 0 26 -6 / 0 0 0 0 DLN 35 15 38 12 / 10 0 0 0 HVR 10 -14 11 4 / 60 10 10 10 LWT 16 2 30 20 / 70 10 10 10 && .TFX WATCHES/WARNINGS/ADVISORIES... WIND CHILL ADVISORY until 6 PM MST this evening Blaine...Hill. && $$ weather.gov/greatfalls