682 FXUS65 KTFX 201611 AFDTFX Area Forecast Discussion National Weather Service Great Falls MT 1011 AM MDT Fri Oct 20 2017 .UPDATE... Windy conditions of late will remain more calm today ahead of the next system coming from the west late Saturday into Sunday. Expect winds to become more westerly through the day and a chance of precipitation along the Continental Divide and Southwest Montana. Winds look to pick up significantly once again Sunday and thus a High Wind Watch has been issued for much of Central Montana. && .SYNOPSIS... A frontal boundary crosses the region today, bringing a chance for showers for the Rocky Mountains and Southwest Montana. Windy conditions persist through the weekend with cooler temperatures. && .AVIATION... Updated 1125Z. Scattered to broken high cloud-cover will prevail overnight. A cold front moves through the forecast area by mid-day Friday with winds shifting to the west and increasing behind the front. Widespread snow and mountain obscurations expected along the Continental Divide after 12Z Friday, while isolated to scattered showers accompany frontal passage through the plains. VFR conditions expected to prevail at all forecast terminals through the period, except for brief IFR/MVFR conditions possible in showers. Mountain wave turbulence and low level wind shear expected to redevelop in favored locations as west winds increase behind frontal passage. mpj/PN && .PREV DISCUSSION... /ISSUED 417 AM MDT Fri Oct 20 2017/ Today through Sunday...Breezy conditions overnight maintained mild temperatures and remarkably low humidity overnight for much of the forecast area. A cold front associated with an Alberta Clipper system will advance across the area this morning through early afternoon. Hence, forecast high temperatures may be reached early this morning, with cold advection driving temperatures gradually lower through the day. Pressure rises behind the front will produce a period of gusty west winds. Wind reports will be monitored closely today, but the vertical wind profile does not support any more than a few isolated gusts nearing 50 mph. Despite another breezy day, fire concerns are slightly lower today due to increasing humidity. Along with these rapid changes in temperature and winds today, expect rain and mountain snow to develop up to, and along the Continental Divide, and across southwest Montana with the passing trough. Sprinkles are possible across the N-central plains, but otherwise suppressed by the downslope winds. All this activity tapers downward tonight into Saturday as the Clipper system pulls further away to the east. A remarkably strong zonal jet pushes across the PacNW and reaches across the Northern Rockies Saturday night. Confidence continues to increase that a widespread, potentially damaging high wind event could develop late Saturday night through the day Sunday. A high wind watch is appropriate for this potential event, but opted to hold off for now to avoid confusion compared to today's passing front. PN Sunday night through Thursday...The main concerns during this period center around wind and the potential for continued elevated fire weather concerns. An impressive upper level jet and associated moisture/precip aimed at the Pacific NW will gradually shift south away from the area Sunday night, with precip diminishing in the mountains. NW flow takes over aloft as the upper level trough pushes into the central US. This is followed by an anomalously strong ridge (for late- October) TUE/WED which will likely yield a return to above normal temps (60s/70s at lower elevations) both days. The models are then in very good agreement in bringing a sharp trough SE out of Canada later WED into THU. In this transition, another wind event appears possible late Tuesday night into Wednesday, especially along the Rocky Mtn Front where a 60-80kt mid-level jet and strong pressure gradient are forecast to be co-located. Out over the plains, high wind criteria may not be met, but as has been seen in previous breezy/windy days, relative humidity values may fall low enough to warrant elevated to near-critical fire weather concerns. The shortwave forecast to dive SE out of Canada will likely be accompanied by a strong northerly jet. Where the models differ is where the upper jet and coldest air is directed (ie. right over our area or further east across eastern MT and the Dakotas). Regardless, the mild temps TUE/WED should quickly be replaced by much cooler temps late-week. The potential then exists for yet another wind event late in the week as well. MARTIN && .PRELIMINARY POINT TEMPS/POPS... GTF 60 37 51 45 / 20 10 10 20 CTB 53 37 48 38 / 10 10 10 20 HLN 51 35 51 41 / 30 10 20 20 BZN 59 30 50 38 / 50 30 10 20 WEY 43 25 35 27 / 90 60 40 60 DLN 53 28 45 36 / 30 20 20 20 HVR 61 39 54 36 / 30 20 10 20 LWT 66 34 49 38 / 20 10 0 20 && .TFX WATCHES/WARNINGS/ADVISORIES... High Wind Watch from Sunday morning through Sunday evening Blaine...Cascade...Central and Southern Lewis and Clark... Chouteau...Eastern Glacier...Eastern Pondera...Eastern Teton... Fergus...Hill...Judith Basin...Liberty...Meagher...Toole. High Wind Watch from late Saturday night through Sunday evening Northern Rocky Mountain Front...Southern Rocky Mountain Front. && $$ weather.gov/greatfalls |