957 FXUS65 KTFX 081127 AFDTFX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREAT FALLS MT 425 AM MST Wed Jan 8 2014 AVIATION SECTION UPDATED .DISCUSSION... Today through Friday...West to northwest flow aloft will continue over Montana throughout the short term forecast. Moisture and upper level energy moving in from the Pacific will combine with orographic lift to bring periods of snow to the Continental Divide. Mostly cloudy conditions, with the chance for a few isolated light snow showers, will be seen over the plains. Strong westerly down-slope winds should keep most precipitation from reaching the plains through the period. Winds along the Rocky Mountain Front will pick up speed Thursday but are expected to remain below high wind criteria through Thursday night. There may be some risk of strong and gusty winds through a few favored passes and canyons overnight Thursday before approaching a more widespread chance early Friday. With this increased chance a High Wind Watch has been issued for the Northern Rockies from early Friday morning into the weekend. With strong winds across the region, expect relatively warm temperatures to continue with highs in the mid to upper 40s across much of Central Montana. Friday Night through Wednesday...Confidence is increasing on the likelihood of a significant wind event for the Rocky Mtn Front and most/all of central and north central MT through early Sunday morning. Forecast models have been consistent for several runs now in showing a high pressure ridge moving across the length of the Treasure State on Saturday. Flow aloft over our area will initially be northwesterly, but transition quickly to zonal (westerly) flow as the ridge axis passes through Sat morning. Tight gradients in both the upper-level and surface pressure fields between the ridge and a sharp Pacific shortwave trof coming ashore in WA/OR/BC will accelerate the mid-level (700 mb, or about 10kft MSL) winds to 70-90+ mph. As these winds crest the Continental Divide and move down-slope, widespread strong and possibly damaging winds will occur along/over the Rocky Mtn Front and the adjoining central plains. The period of peak winds is expected to be Sat aftn and eve, with gusty winds occurring late Fri through early Sun. It looks like southwest MT will stay out of the strongest winds, although a few wind-prone passes (such as Norris Hill in Madison County) may reach warning criteria (58 mph) on Sat. Models continue to struggle with the timing of the Pacific shortwave and its associated cold front, with the GFS model bringing those features through our region about six hours earlier (approx. late Fri evening) than the ECMWF model. However, the models are in decent agreement on the expected coverage and amounts of precipitation, with most of the valley rain/mtn snow staying over the Rocky Mtn Front and southwest mtn ranges. The strong, drying down-slope flow will limit precip over the central/Hiline counties to some isolated and very light showers Sat night. As usual, the down-slope winds will also bring pronounced warm air advection, pushing high temps on Sat into the upper 40s to mid 50s, about 15-20 degrees above normal, before cooling back to low-mid 40s on Sun & Mon. A secondary, backdoor (moving northeast to southwest) cold front is forecast to push across the northern half of the region late Mon, bringing some scattered showers, but it dissipates quickly as high pressure ridging returns with dry conditions for the midweek period. Waranauskas && .AVIATION... UPDATED 1125Z. VFR conditions expected today with BKN-OVC mid- and high-level clouds remaining over all of central and southwest MT. Isolated light snow showers will occur along the Rocky Mtn Front through the day, with occasional MVFR ceilings there. Winds turning breezy this afternoon over the central plains, with gusts of 20-25 kts vcnty KGTF/KLWT/KHVR and 30-35 kts vcnty KCTB, before diminishing again tonight. Waranauskas && .HYDROLOGY... A flood warning continues for portions of the Gallatin River near Gallatin Gateway. An ice jam on the Gallatin River has caused the river to go out of its banks. Axtell-Gateway Road from Gateway- South road to Deer Spring Lane remains closed. Ice jams are unpredictable and thus the flood warning will remain in effect until the river recedes back into its banks. && .PRELIMINARY POINT TEMPS/POPS... GTF 44 34 45 30 / 0 0 0 10 CTB 42 31 44 28 / 0 0 0 0 HLN 41 28 43 27 / 10 0 10 10 BZN 37 22 38 17 / 10 0 20 20 WEY 28 17 29 10 / 60 60 70 30 DLN 37 26 35 20 / 10 10 40 10 HVR 32 23 37 22 / 0 0 0 0 LWT 39 26 40 24 / 10 0 0 10 && .TFX WATCHES/WARNINGS/ADVISORIES... HIGH WIND WATCH from early Saturday morning through early Sunday morning Blaine...Broadwater...Cascade...Central and Southern Lewis and Clark...Chouteau...Eastern Pondera...Eastern Teton... Fergus...Hill...Judith Basin...Liberty...Meagher...Toole. HIGH WIND WATCH from early Friday morning through early Sunday morning Eastern Glacier...Northern Rocky Mountain Front...Southern Rocky Mountain Front. FLOOD WARNING until further notice for a portion of the Gallatin River near Gallatin Gateway. && $$ weather.gov/greatfalls www.twitter.com/NWSGreatFalls www.facebook.com/US.NationalWeatherService.GreatFalls.gov