Area Forecast Discussion
Issued by NWS Bismarck, ND
Issued by NWS Bismarck, ND
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466 FXUS63 KBIS 310234 AFDBIS Area Forecast Discussion National Weather Service Bismarck ND 934 PM CDT Thu May 30 2024 .KEY MESSAGES... - Areas of frost in low-lying areas of southwest North Dakota tonight. - Seasonably cool temperatures on Friday with scattered afternoon showers and thunderstorms. - Dry Saturday, then chances for showers and thunderstorms return later Saturday night through early next week. && .UPDATE... Issued at 932 PM CDT Thu May 30 2024 Latest satellite trends show a mostly clear sky over southwest North Dakota this evening. Some mid level clouds are developing from the northern Black Hills to the Standing Rock Reservation. These clouds are forecast to remain southeast of Hettinger through much of the night, with clouds increasing from Sioux and Grant Counties to the north and east. There is still a bit of a west-northwest breeze as of this writing, but winds should weaken and turn more to the west-southwest as surface high pressure builds over southeast Montana. Dewpoints in southwest North Dakota are in the lower to mid 30s, and HRRR/RAP/NBM projects these values to hold through the night. Taking all this into consideration, we have issued a Frost Advisory for most of southwest North Dakota, in effect from 2 AM to 7 AM MDT. Areas outside the advisory could possibly see some patchy frost, mainly in the favorable Glen Ullin to Beulah-Hazen corridor, but the highest probabilities for temperatures falling near freezing tonight are in low-lying areas in the southwest, including Mott, Hettinger, Bowman, Amidon, and Medora. UPDATE Issued at 655 PM CDT Thu May 30 2024 Shower activity is now confined to northwest North Dakota. One batch of showers with occasional lightning has lifted into southeast Saskatchewan, while another batch with no lightning observed is entering from northeast Montana along and north of the Missouri River. With up to 500 J/kg still present, will maintain a slight chance of a thunderstorm in the forecast for the evening. All showers are forecast to dissipate or lift north into Canada later this evening. We will continue to monitor satellite trends this evening for the possible need of a Frost Advisory in southwest North Dakota later tonight into early Friday morning. The main area of focus is a batch of mountain wave clouds from the Bighorns to Black Hills, extending north toward the ND/SD border. If these clouds remain south of the state, which latest RAP guidance favors, temperatures could easily fall into the mid 30s in low lying areas. && .DISCUSSION... Issued at 233 PM CDT Thu May 30 2024 A blocking upper level pattern will keep an upper level low situated over the central Canadian Prairie Provinces through the weekend. A combination of shortwaves rotating around this low, and impulses coming off the Pacific, tracking across the Northern Rockies and below the Canadian low will influence the weather over our area through the weekend. This low eventually gets pushed east as a stronger wave coming off the Pacific moves into the Region early to mid next week. Currently, showers and a few thunderstorms are lingering over the far southern James River Valley but should exit the area this afternoon. This activity is situated along a warm front/trough that is currently exiting the JRV. Breezy westerly winds behind this front have developed over most of western and central North Dakota. A trailing cold front will sweep through the area later this afternoon and tonight. There may be a few showers trying to move into western ND late this afternoon/early this evening, but with very dry air southwest, the potential for shower activity will likely be limited to the west central/northwest and any thunderstorm activity should be limited to the far northwest corner. Late tonight and early Friday the focus shifts to temperatures. Current forecast trends clear out much of western and central ND tonight. By 12Z Friday, surface high pressure is situated over western SD with mid and high level clouds beginning to work back into western ND from the southwest. However, very dry air is situated over the area overnight. The NAEFS SA table shows a signal for dry PWATs over western ND. IF winds drop off tonight, which it looks like they may in the southwest, and skies remain clear, we could see some temperatures in the middle 30s southwest, resulting in Frost. Given our normally cool areas west of the Missouri River extend north and east to the Beulah/Hazen area and towards eastern Lake Sakakawea, the area of mid 30s could extend even farther north and east than we are currently advertising. NBM 10th percentile was only depicting some upper 30s and no frost, so we combined some MOS based guidance to trend temperatures down a bit over the southwest. MET/MAV guidance for Hettinger is 34. There is the potential that mid level clouds could move into the area, keeping temperatures from dropping into the 30s at all. Will hedge towards the cool side and pass along to the evening shift. Potentially we could see a frost advisory if ideal conditions are met. After a cool start Friday, diurnal heating, combined with another upper level impulse will fire afternoon showers and thunderstroms. The lack of heating is expected to keep the severe threat to a minimum and SPC is currently carrying a general thunderstorm risk and this looks reasonable. Saturday will bring mostly sunny skies with warmer temperatures. Highs should be mainly in the 70s statewide. Late Saturday night and Sunday, an impulse emanating from the Pacific will move into the area bringing another round of showers and thunderstorms, with a stronger wave moving into the Region early next week. There is some some indication that the far southeast could see a few stronger storms on Sunday but this remains quite a ways out. Still something to monitor as we head into the weekend. Uncertainty in the deterministic models and ensembles increases as we head into next week, but the pattern will likely remain active through at least Monday and Tuesday. && .AVIATION /00Z TAFS THROUGH 00Z SATURDAY/... Issued at 655 PM CDT Thu May 30 2024 VFR conditions are expected to prevail through the forecast period. Scattered showers remain possible across northwest North Dakota this evening, and another round of afternoon showers with a few thunderstorms is possible across most of western and central North Dakota on Friday. Strong westerly winds will diminish to around 10 kts later this evening and only increase slightly on Friday. && .BIS WATCHES/WARNINGS/ADVISORIES... Frost Advisory from 2 AM to 7 AM MDT Friday for NDZ031>033-040- 041-043-044. && $$ UPDATE...Hollan DISCUSSION...TWH AVIATION...Hollan