Area Forecast Discussion
Issued by NWS Bismarck, ND
Issued by NWS Bismarck, ND
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486 FXUS63 KBIS 201353 AFDBIS Area Forecast Discussion National Weather Service Bismarck ND 853 AM CDT Thu Jun 20 2024 .KEY MESSAGES... - Chances for showers and thunderstorms will increase through this afternoon and evening. A stronger storm with small hail and gusty winds will be possible across the northwest this evening. - Widespread showers and scattered thunderstorms are expected on Friday, with a Marginal Risk (level 1 of 5) for isolated severe storms over portions of the southwest and south central. - Showers and thunderstorms will continue through Saturday morning, before diminish in the afternoon. - Daily chances for thunderstorms Sunday through early next week, with strong to severe storms possible on Monday. - Temperatures will continue warming through the weekend, with expected highs on Monday in the 80s to lower 90s. && .UPDATE... Issued at 853 AM CDT Thu Jun 20 2024 An overcast deck of clouds has formed and begun to build north into the area a bit quicker than expected, particularly across the southwest and far southern James River Valley, so cloud coverage has been bumped up a bit in those areas to account for this early arrival. Otherwise, the forecast remains on track. Relatively light winds and clear skies are present across the rest of the area. It is also worth noting that the SPC has introduced a small Marginal Risk area (level 1 of 5) to eastern Montana, but this area does not reach the western North Dakota border, so the threat for any strong to severe storm has not changed very much, remaining minimal at this time. .UPDATE... Issued at 625 AM CDT Thu Jun 20 2024 The forecast remains on track at this time, and with no updates needed for this update. Generally dry conditions are observed across western and central North Dakota. Lows have been from the mid 40s west to the lower 50s east. Some lingering mid to high level clouds remain over central North Dakota, but have been diminishing over the past hour. Winds are generally light, and out of the south southeast at this time. && .DISCUSSION... Issued at 400 AM CDT Thu Jun 20 2024 The northern Plains lies under a southwesterly flow pattern this morning, as a near stationary H5 trough over the Rockies is expected to gradually diminish through the end of the workweek. Some weak radar returns linger over portions of the northwest and southeast, though are expected to quickly dissipate by the mid morning hours. Cloud cover is clear out from the west, and winds winds are light and generally out of the south. Lows this morning are forecast from the mid 40s west to lower 50s east. Today, an inverted trough will approach from the west as a slow moving warm front begins to push into the northern Plains from the south. Chances (20 to 40%) for showers and a thunderstorms will gradually increase across the west and south as moisture streams northward ahead of the warm front. With the inverted trough approaching from the west, modest model MUCAPE values around 1000 to 1500 J/KG in the northwest and north central, and 0 to 6 KM Shear of 25 to 30 knots, there will be a short window this afternoon where a stronger storm with small hail and gusty winds could develop over the northwest in the late evening to early morning hours. Chances for showers and thunderstorms will continue across the north through the early morning hours. Showers will be more widespread across the south this afternoon and evening, also with the occasional embedded thunderstorm, before briefly diminishing overnight. Highs this afternoon are forecast from around 70 in the southern James River Valley up the mid 70s in the north and west. Overnight lows Friday morning are expected to be broadly in the 50s. Winds are generally light, though will briefly become breezing in portions of the south, and will gradually turn out of the south into the east through the afternoon and evening. Chances for showers will redevelop across the south and west early Friday morning as a energetic shortwave digs across the northern Plains, expanding to encompass the entire forecast area by the early afternoon. The highest chances for these showers will be across the southwest and much of the north. Modeled MUCAPE broadly around 500 to 1000 J/KG will allow for widespread chances for thunderstorms Friday afternoon and evening. An axis of higher MUCAPE, from modeled from 1000 to 2000 J/KG, will drape itself across the South Dakota border Friday afternoon, and currently represents the highest, yet still limited, risk for severe thunderstorm development in the short term. Baseline hazards of quarter sized hail and isolated gusts up to 60 MPH would be expected with any severe storm, with the period of opportunity being from around 12 to 8 PM CDT. With morning showers and thunderstorms expected across our southern counties, however, we currently think that the worked- over atmosphere and prevalent cloud cover could work against development of severe thunderstorms. Thus, the risk for severe weather remains on the lower side, with the SPC Day 2 Outlook assigning only a sliver the southwest a Marginal (level 1 of 2) at this time. Highs on Friday are similar to today`s, from the upper 60s to mid 70s. Overnight lows temperatures on Saturday morning are forecast to be from the mid 50s northwest, to the lower 60s southeast. Winds will generally remain easterly, with modest speeds from 10 to 15 MPH expected through the afternoon and evening hours. Chances for showers and thunderstorms will continue overnight into Saturday morning, before diminishing through the afternoon as the inciting upper level shortwave exits to our northeast. There currently little to no severe weather concerns on Saturday as any potential is expected to be far to our east. Shortwave ridging will establish itself across the northern Plains Saturday morning, promoting both west southwesterly flow and a warming trend. Highs on Saturday are forecast from the lower 70s south to the lower 80s north. Winds will become westerly Saturday morning as surface high pressure moves in from Montana. The overall ridging pattern squashes down early Sunday, with a series of shortwaves traveling down the overall westerly flow pattern that will promote chances for showers and thunderstorms each day through Tuesday next week. There is fairly good agreement in the ensemble for seasonably warm temperatures, with highs broadly in the upper 70s to lower 90s each day, and high moisture availability across the forecast area as we get a little taste of the heat dome here in North Dakota. Exact timing and locations of any severe threat is difficult to place this far out, though Monday, as the peak of the heating trend, currently looks to have the highest severe potential in the long term. We will have to continue monitoring trends over the next few days. && .AVIATION /12Z TAFS THROUGH 12Z FRIDAY/... Issued at 625 AM CDT Thu Jun 20 2024 VFR ceilings and visibility are expected at all terminals at the start of the 12Z TAF period. This afternoon, chances for showers and potentially some thunderstorms will increase across the south and the west. MVFR to LIFR ceilings and MVFR visibility are expected to move over the southern terminals of KDIK, KBIS, and KJMS with these showers this afternoon and evening. Scattered thunderstorms are also expected across the south today, though the confidence is currently too low to place it at any given TAF site. KXWA may briefly experience showers and MVFR ceilings this afternoon, along with the potential for a stronger thunderstorm with small hail and gusty winds through the early evening. Showers and thunderstorms will diminish overnight, before redeveloping and becoming widespread over the forecast area Friday morning. Winds are generally light and out of the south southeast this morning, but will turn easterly through the afternoon and overnight into Friday morning. Where showers or thunderstorms do develop, gusty and erratic winds are expected. && .BIS WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Besson DISCUSSION...Adam AVIATION...Adam