119 FXUS65 KTFX 240446 AFDTFX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREAT FALLS MT 1050 PM MDT Sat Mar 23 2013 Aviation section updated .UPDATE... Tonight...Isolated showers continue over and west of the Divide. A few showers over Southwest Montana as well but very minor coverage. Showers will diminish by midnight. Only made a few changes on the update...freshened POPs, WX, QPF, and Snow Amts. Zelzer && .AVIATION... UPDATED 0500Z. VFR conditions will prevail over the region through the period. Expect a few isolated snow showers over the western/southwestern mountains through 07z Sunday. Otherwise...mid/high level cloudiness can be expected over the region...along with a few areas of scattered low clouds. Brusda && .PREV DISCUSSION... /ISSUED 800 PM MDT Sat Mar 23 2013/ Tonight through Monday...Rather quiet weather pattern to end the week. Upper trof over northeast Montana will continue to move south and east overnight. Circulation from this feature is bringing moisture, in the form of low and mid clouds as well as isolated snow, to the northeast portions of the county warning area. Southwest Montana will also see a threat for scattered showers this evening as the airmass has destabilized with CAPE values of 200-400 J/kg. The upper trof should exit the area by late Sunday afternoon with conditions improving over southwest Montana and over the eastern county warning area. High pressure aloft will begin to influence the area Monday bringing dry and warmer conditions. Temperatures tonight will be cool but with just enough wind and an influx of drier air to inhibit fog formation. Surface winds will remain light Sunday and Monday. Temperatures will remain below seasonal averages Sunday before warming to near Seasonal averages to start the week. Emanuel Monday Night through Friday Night...Medium range models continue to be in good general agreement for the period. A broad upper level ridge of high pressure over the western and central CONUS will gradually build into Montana through the early week period, which will keep the area about 5 degrees above normal through the week. Models are hinting at an enhanced warm-up late in the week with a greater strengthening of the ridge. However, am holding off on any significant warm-up at this time, as models are only just coming into agreement with the potential warm-up this model run, and it is a day later than the GFS run last night. Will continue to monitor this situation. Otherwise, disturbances moving through the resulting westerly flow aloft will keep a slight chance of showers around the area for most of the period. The first disturbance will be fairly weak and only bring a chance of snow showers to the mountains Monday night through Tuesday night. The next disturbance will be slightly stronger but slower moving, bringing an increasing chance of showers to the entire area for Wednesday through Thursday. A large scale upper level trough will then deepen along the Pacific coast for Thursday night through Friday night, and the resulting moist southwesterly flow aloft will keep a chance of mainly mountain showers over the area. Strong winds do not appear to be a concern during this time, as a northwest-to-southeast oriented surface frontal boundary moves only slightly southwest and northeast through the period with the passage of these disturbances. Overall, winds should remain easterly over the plains and southerly in the southwest valleys. Coulston && .PRELIMINARY POINT TEMPS/POPS... GTF 9 32 16 46 / 0 10 0 0 CTB 8 32 13 42 / 0 10 0 0 HLN 15 37 18 46 / 10 10 0 0 BZN 10 31 9 40 / 10 20 10 0 WEY -1 28 -4 32 / 30 20 20 10 DLN 11 34 12 42 / 10 10 10 0 HVR 10 29 12 42 / 10 10 0 0 LWT 9 25 10 39 / 10 30 10 0 && .TFX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ weather.gov/greatfalls