Area Forecast Discussion
Issued by NWS Bismarck, ND
Issued by NWS Bismarck, ND
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093 FXUS63 KBIS 300926 AFDBIS Area Forecast Discussion National Weather Service Bismarck ND 426 AM CDT Tue Apr 30 2024 .KEY MESSAGES... - Widespread rain showers are expected to move across the state from west to east through the day. A rumble or two of thunder is possible. - Windy across southwest North Dakota today, with critical fire weather conditions expected in the afternoon and early evening. A Red Flag Warning has been issued. - Daily chances (low to medium) for rain (and maybe an isolated thunderstorm or two) through the rest of the week, with temperatures slightly below normal. && .DISCUSSION... Issued at 425 AM CDT Tue Apr 30 2024 An upper level ridge axis will continue to move off to our east early this morning while western and central North Dakota settles into southwest flow aloft. A surface cold front is currently located near the Montana/North Dakota border and this boundary will cross this state from west to east this morning and afternoon. Widespread rain showers will accompany the cold frontal passage with radar returns now currently approaching the Montana/North Dakota border. Some of the CAMs have been aggressive in ramping this activity up in the 12 to 14 UTC time frame and beyond, even suggesting the potential for some embedded lightning strikes. That being said, instability will be limited as the RAP is only showing the potential for a couple hundred J/kg MUCAPE. Still, an embedded rumble of thunder or two isn`t out of the question and much of the forecast area has been highlighted in a general thunderstorm outline by the Storm Prediction Center. We will clear out rapidly late this morning and early afternoon across the west behind the front, especially the southwest where modest pressure rises and cold air advection will lead to some gusty west northwest winds. These winds will team up with the dry airmass behind the front to usher in some near critical to critical fire weather conditions across the southwest and portions of the south central. See the Fire Weather section below for more details. Most of the rain will move out to the northeast by late this evening. The heaviest totals continue to look probable across portions of the northwest and north central where the NBM is suggesting a 40 to 60 percent chance of a half inch of rain or more. The NBM suggests that almost all of western and central North Dakota has a 50 to 90 percent chance of a quarter inch of rain or more. The one exception will be across the far southwest and south central where probabilities drop off quickly. Most will see a break in rainfall on Wednesday but we could see some lingering showers across the far north. The next wave then rotates around the very slow moving upper low that will be centered near the Montana/North Dakota/Saskatchewan border by Wednesday night. We will then see our next round of low to medium rain shower chances Wednesday night through at least Friday, if not Saturday, as the upper low slowly moves across the region. Thursday looks to be the wettest day of the aforementioned period and the NBM suggests that much of the central and southeast could see a medium chance for another quarter inch of rain or more on Thursday. We will also start to see a bit more instability towards the middle to end of the week so some more isolated thunder will be possible as well. Regarding temperatures, we will see highs close to normal for this time of year on Wednesday, ranging from the upper 50s northwest to the mid 60s southeast. However, in the Thursday through Saturday time frame, we will be a bit cooler than normal with highs mainly in upper 40s to around 60. The NBM then suggests a return of highs in the mid 60s to lower 70s range by Sunday and Monday. That being said, considerable ensemble spread continues to be noted this far out. && .AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/... Issued at 100 AM CDT Tue Apr 30 2024 An upper level disturbance and surface cold front will cross the state from west to east Tuesday morning and afternoon, bringing widespread rain showers and MVFR to IFR ceilings. MVFR visibilities will also be possible under any heavier showers. Winds will shift to out of the northwest behind the front, becoming gusty across most of the west. Sustained winds will approach 30 mph with gusts to 40 mph over portions of the southwest Tuesday afternoon. Winds will decrease fairly quickly Tuesday evening. Most areas will see improvement into VFR categories (from west to east) late Tuesday afternoon and into the evening. && .FIRE WEATHER... Issued at 425 AM CDT Tue Apr 30 2024 A cold front will cross the state from west to east this morning and afternoon. While the passage of this boundary will bring widespread rain showers to much of western and central North Dakota, the lowest chances for wetting rains will be across the southwest. A dry airmass will then push into the southwest behind the cold front by mid to late morning, rapidly clearing any lingering cloud cover out. Winds will also increase with sustained winds up to 30 mph and gusts to 45 mph by the afternoon hours. With the gusty winds and a dry airmass in place, locations that experience little to no wetting rains should dry out quickly. If the wetting rains are limited in coverage across the southwest as expected, then the winds will overlap with low afternoon humidity (values dipping as low as 18 percent) for three hours or more across significant portions of Bowman, Adams, Hettinger, Slope, Golden Valley, Billings, and Stark counties. For these factors, we decided to go ahead and upgrade these counties to a Red Flag Warning today from 1 PM MDT to 8 PM MDT. It was decided to not upgrade Grant and Sioux counties but we could still see a couple hours of near critical fire weather conditions here this afternoon and we will message the potential in the Hazardous Weather Outlook. As a final note, the northern portions of Golden Valley, Billings, and Stark counties may only see near critical fire weather conditions. Critical fire weather conditions may be confined to southern portions of these counties. && .BIS WATCHES/WARNINGS/ADVISORIES... Red Flag Warning from 1 PM this afternoon to 8 PM MDT this evening for NDZ031>033-040-041-043-044. && $$ DISCUSSION...ZH AVIATION...ZH FIRE WEATHER...ZH