FXUS63 KBIS 031501 AFDBIS Area Forecast Discussion National Weather Service Bismarck ND 1001 AM CDT Thu Oct 3 2024 .KEY MESSAGES... - Near to sub-freezing temperatures are possible again tonight into Friday morning, mainly west and north. - It is looking more and more likely that Saturday will be very windy, with critical fire weather conditions possible over portions of western and central North Dakota. - A High Wind Watch has been issued for western and much of central North Dakota. A Fire Weather Watch has been issued for a good portion of western and south central North Dakota. - Very little to no measurable precipitation is expected through most of next week. && .UPDATE... Issued at 1001 AM CDT Thu Oct 3 2024 The Freeze Warning has been allowed to expire as temperatures have recovered to above freezing in the warned area. Otherwise, sunny skies generally prevail everywhere except along the ND/SD border. These clouds should clear out over the next few hours. With very dry near-surface air, any returns under this cloud cover are generally producing virga, though an occasional sprinkle may be observed as well. UPDATE Issued at 638 AM CDT Thu Oct 3 2024 The main update early this morning was to remove portions of the southwest and south central from the Freeze Warning. Cloud cover ended up being thicker than anticipated overnight across southern North Dakota. Temperatures here remained mainly in the 40s and clouds are not expected to clear before sunrise, this the threat of sub-freezing temperatures is quite low. We bumped up sky cover in the south early this morning. Otherwise no changes to the going forecast. && .DISCUSSION... Issued at 321 AM CDT Thu Oct 3 2024 Currently, surface high pressure was building eastward from Montana and southern Saskatchewan, into western North Dakota. A shortwave trough also over Montana was producing mid level cloudiness extending from central and eastern Montana into western and southern portions of North Dakota. As of yet, no precipitation has been noted below this mid level cloudiness. The clouds are also keeping temperatures well above freezing over southwest and south central ND, but areas north of the clouds have dropped into the middle and lower 30s so for now will leave the current Freeze Warning as is. It will be cooler today, especially south, with highs generally in the 60s. If there is any precipitation, it will mostly likely evaporate before reaching the ground, but a few sprinkles here and there can't be completely ruled out. Winds will be generally light today as surface high pressure traverses the forecast area. By tonight, the surface high will slide to our southeast with a return southerly flow beginning over western ND. Expect less clouds tonight over the area, with another chance for lows to drop down to or below freezing. With the current Freeze Warning continuing and some uncertainty as to whether a warmer return flow develops or not, will hold off on a Freeze Warning for tonight into Friday morning and let the day shift revisit this. Whether we see another freeze warning or not, we will see a quick warmup with temperatures climbing back into the 70s over much of the forecast area. Breezy southerly winds are expected to lift into the state behind a warm front that lifts north Friday. The strongest winds Friday look to be over the south central portion of the state with sustained winds of 20 to 25 mph, which combined with humidities down to 25 to 30 percent will result in near critical fire weather conditions over the south central portion of the state. There remains some uncertainty in the extent of the warm temperatures and dry air. It's possible that we could see a few hours of Critical fire weather conditions over portions of Grant, Sioux and Emmons counties. If trends point to warmer, or drier conditions a Small RFW may be needed, but at this time we will limit this to near critical and pass it along to the day shift to monitor. Late Friday night through Saturday evening a shortwave trough will deepen with an upper level low closing off over the southern Prairie Provinces of Canada and tracking quickly off to the east. This will bring a period of strong west to northwest winds to western and central North Dakota from early Saturday morning through late Saturday evening. In addition to the strong winds, the position of the surface low will be favorable for dry conditions over much of western and central North Dakota. It will be cooler, especially north, with the potential for light shower activity along the International Border, but by and large, it looks like most of western and central ND will remain dry with temperatures generally in the 60s. The combination of the strong winds and humidities dropping down to around 25 percent will result in critical fire weather conditions being possible from around mid morning Saturday through Saturday evening. Currently the most likely area to see an extended period of low humidities and strong winds looks to be areas south and west of Lake Sakakawea and the Missouri River, in addition to Williams county in northwest ND and Emmons county in south central ND. Because of the potential for the strong winds and low humidities, we have issued a High Wind Watch and a Fire Weather Watch for portions of western and central North Dakota for Saturday. There remains some uncertainty in the track of the surface and upper low. A more northward track may lessen the southern extent of the strong winds, but currently these differences look negligible. The NAEFS SA table shows strong winds at 85H and 70H over western North Dakota at 18 UTC Saturday afternoon. The ECMWF EFI SA page shows values of 0.8 over most of western and central North Dakota and 0.9 centered over the northwest into north central ND. Local research has shown that values of 0.9 correlate well with high wind warning criteria winds. A strong isallobaric component and strong cold advection will be congruent with the initial surge of strong winds Saturday morning, while through the day Saturday we see a strong gradient wind develop with steep lapse rates developing, resulting in very strong winds aloft, potentially being pushed down to the surface. The strong winds aloft linger over central ND well into the evening but by this time we begin to lose the mixing potential. East of the High wind watch, over eastern portions of central ND there is more uncertainty as to whether or not we see warning criteria winds, but if current trend continue, we would expect at least advisory criteria winds, and HWW winds are not out of the question. Beyond the wind on Saturday, high temperatures for this weekend will be mostly in the 60s with a warming trend into the next workweek. Low 80 degree readings may return for parts of the area by mid-week. Mainly dry conditions are also expected to continue through the work week. && .AVIATION /12Z TAFS THROUGH 12Z FRIDAY/... Issued at 638 AM CDT Thu Oct 3 2024 VFR conditions are expected through the 12Z TAF period. Mid level clouds will diminish across southern North Dakota, including KDIK, KBIS and KJMS. Otherwise mostly clear skies are anticipated through the period. Generally west to northwest winds today 5 to 15 mph. Winds will diminish early this evening and shift southerly. && .BIS WATCHES/WARNINGS/ADVISORIES... High Wind Watch from late Friday night through Saturday evening for NDZ001-002-009-010-017-018-031>033-040-041-043-044. High Wind Watch from Saturday morning through late Saturday night for NDZ003-004-011-012-019>022-034>036-042-045>047-050. Fire Weather Watch from Saturday morning through Saturday evening for NDZ009-017>020-031>034-040>046. && $$ UPDATE...Telken DISCUSSION...TWH AVIATION...TWH