685 FXUS65 KTFX 242110 AFDTFX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREAT FALLS MT 310 PM MDT Thu Oct 24 2013 ...UPDATE TO AVIATION... .DISCUSSION... Tonight through Saturday night...A dry northwest flow aloft is expected over the forecast area through Saturday evening. Cloudiness will increase near the Canadian border after midnight but am not expecting any precipitation. This cloudiness is associated with the weather system that will be affecting the area late in the weekend and early next week. A very weak front will move south over the area Friday morning and early afternoon. It will mainly bring a shift in light winds from the southwest to the north. High temperatures will still continue above normal the next two days. Blank SUNDAY THROUGH TUESDAY...THE WEATHER WILL CHANGE ABRUPTLY ACROSS THE AREA ON SUNDAY AS TROUGH OF LOW PRESSURE MOVES SOUTH OUT OF CANADA AND INTO THE NORTHERN ROCKIES. THERE WILL BE SUFFICIENT COLD AIR, MOISTURE, AND LIFT WITH THE SYSTEM TO BRING WIDESPREAD SNOW TO NORTH CENTRAL AND SOUTHWEST MONTANA. TEMPERATURES WILL START OUT MILD ON SUNDAY BUT WILL FALL RAPIDLY IN THE AFTERNOON OVER NORTH CENTRAL MONTANA AS A FRONT PUSHES SOUTH INTO THE AREA. RAIN WILL DEVELOP BEHIND THE FRONT BUT SHOULD TRANSITION TO SNOW BY LATE SUNDAY AFTERNOON. SNOW WILL CONTINUE TO DEVELOP SOUTHWARD SUNDAY NIGHT INTO SOUTHWEST MONTANA AS THE FRONT CONTINUES TO PUSH SOUTH. THE HEAVIEST SNOW APPEARS TO FALL ON SUNDAY NIGHT THROUGH MONDAY AFTERNOON. THERE IS STILL MODEL DISAGREEMENT WITH THE TIMING OF THE STORM AND HOW LONG THE SNOW WILL LINGER, HOWEVER, ALL MODELS ARE PRODUCING STRONG DYNAMICS AND HEAVY SNOWFALL ACROSS THE AREA. WITH INCREASED CONFIDENCE IN HEAVY SNOWFALL HAVE ISSUED A WINTER STORM WATCH FOR SUNDAY AFTERNOON THROUGH TUESDAY MORNING. IN ADDITION TO HEAVY SNOW WINDS WILL GUST OVER 35 MPH DURING MUCH OF THE EVENT OVER MUCH OF THE AREA WITH GUSTS OVER 40 MPH ALONG THE ROCKY MOUNTAIN FRONT. THIS WILL LEAD TO AREA OF BLOWING SNOW AND POSSIBLY BLIZZARD CONDITIONS NEAR IN THE HWY 89 CORRIDOR ALONG THE ROCKY MOUNTAIN FRONT. LANGLIEB && .AVIATION... UPDATED 1800Z. VFR conditions will continue over north central/central/southwest Montana through at least 12Z Friday under a dry northwesterly flow aloft. A light southerly winds will persist over the plains of north central/central Montana until a weak cold front moves south through the area after 00Z, shifting winds there more westerly, then northerly after 12Z Friday. Coulston/Suk && .PRELIMINARY POINT TEMPS/POPS... GTF 40 60 38 63 / 0 0 0 0 CTB 37 58 34 63 / 0 0 0 0 HLN 36 62 35 62 / 0 0 0 0 BZN 31 59 30 60 / 0 0 0 0 WEY 20 55 20 53 / 0 0 0 0 DLN 32 62 32 62 / 0 0 0 0 HVR 36 59 30 61 / 0 0 0 0 LWT 36 58 31 61 / 0 0 0 0 && .TFX WATCHES/WARNINGS/ADVISORIES... WINTER STORM WATCH from Sunday afternoon through late Monday night Beaverhead...Blaine...Broadwater...Cascade...Central and Southern Lewis and Clark...Chouteau...Eastern Glacier...Eastern Pondera...Eastern Teton...Fergus...Gallatin...Hill...Jefferson... Judith Basin...Liberty...Madison...Meagher...Northern Rocky Mountain Front...Southern Rocky Mountain Front...Toole. && $$ weather.gov/greatfalls www.twitter.com/NWSGreatFalls www.facebook.com/US.NationalWeatherService.GreatFalls.gov