001 FXUS65 KTFX 221719 AFDTFX Area Forecast Discussion National Weather Service Great Falls MT 1116 AM MDT Sat Jul 22 2017 Aviation Section Updated .SYNOPSIS... Look for dry and calm conditions areawide today. Temperatures will not change much from yesterday with highs continuing 5 to 15 degrees above average. Patchy smoke from neighboring wildfires may cause hazy conditions at times. Expect a gradual warm up again by late next week...along with a better chance for showers and thunderstorms. && .UPDATE... Shortwave ridging aloft and weak high pressure at the SFC should keep the area dry through tonight and no major changes were needed for the update. As for smoke impacts, I tried to fine-tune the areas that are more likely to see smoke from area fires (as opposed to keeping smoke in across the entire CWA). For now, it looks like the better chance of seeing some smoke impacts looks to be from Helena to Dillon through this evening and then in the greater Lewistown area tonight. Kept the mention to patchy for now, but this may need to be refined in later forecasts if impacts become more certain. MARTIN && .AVIATION... Updated 1716Z. VFR conditions are expected through Sunday afternoon areawide. Smoke/FU may cause reduced VIS at times, especially in the vicinity of KHLN/KLWT, but confidence remains too low to include in the TAFs for now. Distant mountains may be obscured/harder to see with hazy conditions just about anywhere through Sunday. MARTIN && .FIRE WEATHER... Decent mixing is expected once again this afternoon, but winds aloft are weak/modest and even with deep mixing, winds at the SFC only look to reach 10-15 mph for most areas. Additionally, RH may only fall to 15 to 25 percent. All this paints more of a marginal threat, fire weather wise, for today, so we'll hold off on any Red Flag Warnings. On Sunday...expect increasing winds over North Central MT along with hot temperatures and windy conditions. Thus a fire weather watch has been issued for locations along the I-15 corridor north of Great Falls. We'll take a closer look at conditions on Sunday and determine if the current Fire Weather Watch needs upgrading. On Sunday night a dry front with a wind shift is expected to move southward through the region. Winds will be strong over North Central MT overnight...but with increasing humidities I will hold off on additional fire weather highlights at this time. Isolated thunderstorms with very warm temperatures are then expected for much of the second half of next week. Brusda/MARTIN && .PREV DISCUSSION... /ISSUED 428 AM MDT Sat Jul 22 2017/ Today through Monday...Fairly quiet weather will be over the region today through Sunday afternoon...as a weak upper level ridge moves over the region. Temperatures will be very warm today and hot on Sunday afternooon. The upper level ridge breaks down by Sunday evening, as a wind shift moves southward through the region Sunday night, along with increasing winds...especially over North Central MT. For Monday expect seasonable temperatures along with decreasing winds. Little/no precipitation is expected during the short term. Brusda Monday night through Saturday...Taking a look at recent model trends from yesterday to tonight, there have been a few slight changes that have led to a few noticeable modifications to the long range forecast package. Beginning late on Monday, the advertised potent closed upper low swinging across southwestern Canada has really picked up speed. This idea seems feasible given how the NAM also speeds this system through, even faster than the latest GFS/Euro solutions. Meanwhile, a closed upper low will continue spinning off the coast of Northern California. This low will help to continue to pump increasing moisture our way. However, given the quick speed of the shortwave passing to our north versus the closed low slowly spinning to our southwest, there could be a distinct dry period for northern and central areas during the day on Tuesday. With that said, it is still looking likely showers and storms will arrive to far southwestern areas by late Tuesday afternoon and evening, and I have matched PoP's to illustrate this. A few storms could still be strong at times, with gusty winds the main threat. This activity will likely continue into the overnight hours on Tuesday and into the Wednesday for southwestern areas, with more spotty shower and storm chances possible areawide Wednesday afternoon. The main idea Tuesday, Wednesday and even lesser into Thursday is that latest model runs are not as optimistic on how widespread the rain and storms will be, as this is not expected to be a drought-breaking rain and storm event. Additionally, given the drought situation, lightning strikes may cause an increase in wildfire potential. At the end of the forecast period late in the week and weekend, we begin to dry out with ridging building back again, with temperatures creeping back up into the 90's for some. KLG && .PRELIMINARY POINT TEMPS/POPS... GTF 87 59 95 56 / 0 0 0 0 CTB 84 56 90 51 / 0 0 0 10 HLN 88 59 96 59 / 0 0 0 10 BZN 87 53 94 54 / 0 0 0 0 WEY 81 44 84 43 / 0 0 0 0 DLN 84 52 91 53 / 0 0 0 0 HVR 88 59 98 57 / 0 0 0 10 LWT 84 57 94 57 / 0 0 0 0 && .TFX WATCHES/WARNINGS/ADVISORIES... Fire Weather Watch from Sunday afternoon through Sunday evening Eastern Glacier/Toole/Central/Eastern Pondera/Liberty...Lewis and Clark National Forest Rocky Mountain District-Rocky Mountain Front. && $$ weather.gov/greatfalls |