362 FXUS65 KTFX 190033 AFDTFX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREAT FALLS MT 630 PM MDT Mon Mar 18 2013 UPDATE TO AVIATION .DISCUSSION... Monday night through Wednesday...Afternoon convection beginning to initiate off of some of the higher terrain. This activity should continue ahead of the next shortwave trough that will move through the area later tonight. Atmosphere should continue to increase in moisture at the mid latitudes ahead of the next system. Shower activity should remain relatively scattered with light precipitation dominating the area....some bands of heavier precipitation due have a chance of developing though under the weak cape westerly winds. Will continue the winter weather advisory for elevations above 5000 feet at this time due to the radar returns over the area. Temperatures will climb through the rest of the short term as a moist ridge moves into the area from the pacific. Some showers will occur especially over the mountains terrain due to the moisture aloft. Temperatures will continue to rise above seasonal averages by Wednesday afternoon before the next system moves into the area late Wednesday. Suk Wednesday Night through Sunday...A system approaching from the west will begin to affect Central Montana Wednesday night. Models remain in very good agreement with moisture entering Central Montana from the west Wednesday night with chances for precipitation spreading to Central and North Central Montana by overnight Wednesday into Thursday morning. Chances for precipitation and accumulating mountain snow look to remain over most of the area into Thursday afternoon as this system slowly moves over Montana. Showers Thursday night into Friday may remain along the Rocky Mountains and the Southwest Montana mountains. Precipitation over the plains of North Central Montana looks to still be showery in nature with the mountains likely getting the brunt of any precipitation. Models keep a generally unstable northwesterly flow and scattered chances of mountain showers over the region into Sunday. Scattered periods of gusty westerly winds will also be seen through the extended forecast period as surface flow remains generally west to northwest in nature. The strongest winds over the extended period look to be Thursday into Friday associated with the incoming system. Temperatures have cooled quite a bit throughout the long term on this model run with highs generally in the low 40s over the plains with low 20s to low 30s in the mountains. Low temperatures will generally be in the 20s to 30s with teens and even single digits possible in colder Southwest Montana valleys. && .AVIATION... UPDATED 0030Z. The moist northwesterly flow aloft will keep at least mountain tops obscured in clouds/snow showers through around 12Z, with snow showers occasionally bringing MVFR conditions to the terminals of southwest Montana (KHLN KBZN). The initial round of scattered snow showers east of a KCTB-to-KGTF line, also with occasional MVFR conditions, will decrease from the northwest through 03Z. However, a disturbance will move south out of Canada between 03Z and 06Z with an associated cold front, which will shift winds more northerly over the north central Montana plains. This more upslope flow will cause more widespread light snow showers to develop over this area, mainly between 06Z and 12Z. Some showers may be heavier at times due to lingering weak instability, causing conditions to become low MVFR/high IFR at times. The disturbance will exit the area after 12Z and an upper level ridge of high pressure will move in from the west, for improving conditions with clearing skies across the area. Coulston && .PRELIMINARY POINT TEMPS/POPS... GTF 17 43 28 55 / 30 10 10 20 CTB 12 40 25 53 / 30 10 10 10 HLN 24 46 30 54 / 40 10 10 20 BZN 18 40 23 50 / 30 10 20 30 WEY 4 36 13 41 / 30 10 30 60 DLN 18 43 26 50 / 20 10 20 40 HVR 16 39 22 50 / 20 10 0 20 LWT 14 34 20 47 / 30 10 10 20 && .TFX WATCHES/WARNINGS/ADVISORIES... WINTER WEATHER ADVISORY until 9 PM MDT this evening FOR ELEVATIONS ABOVE 5000 FEET FOR Northern Rocky Mountain Front... Southern Rocky Mountain Front. && $$ SHORT TERM...Suk LONG TERM...WARANAUSKAS AVIATION...COULSTON weather.gov/greatfalls