Area Forecast Discussion
Issued by NWS Bismarck, ND
Issued by NWS Bismarck, ND
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771 FXUS63 KBIS 091725 AFDBIS Area Forecast Discussion National Weather Service Bismarck ND 1225 PM CDT Sun Jun 9 2024 .KEY MESSAGES... - High temperatures the next few days near normal for early June (normal is mid 70s). Above normal temperatures are expected with increasing confidence for Wednesday (80-85 degrees). - Widespread showers and thunderstorms (80 percent chance) expected Monday through Monday night. Isolated severe thunderstorms are possible across most of western and central North Dakota (level 1 out of 5 risk). - Chance for showers and thunderstorms (30 percent) return late Tuesday night through Wednesday, before higher chances for precipitation at the end of the week. && .UPDATE... Issued at 1225 PM CDT Sun Jun 9 2024 The forecast remain on track at this time. High clouds linger over the south central, while scattered mid level clouds have spread over the west. Winds across the west have begun to turn to the east northeast while as a weak high pressure center continues to intrude into the northwest. UPDATE Issued at 830 AM CDT Sun Jun 9 2024 Other than minor edits to the sky grids in accordance to the latest satellite trends, the forecast remains on track at this time. The bank of scattered to broken mid level clouds that will continue expanding across western and central North Dakota through the early afternoon has begun to intrude into the west. Winds remain light across the area. UPDATE Issued at 642 AM CDT Sun Jun 9 2024 Quiet weather continues this morning with surface high pressure pushing into northwest North Dakota. A few midlevel clouds continue over the south central and James River Valley, with additional clouds slowly approaching from Montana. Keeping POPs as is for this afternoon for now, with CAMs painting a similar picture of isolated to scattered showers across southwest North Dakota, with forecast soundings still showing cloud decks around 8-10k feet and a very dry layer below that. Tweaked sky cover with this update otherwise no changes to the forecast needed. && .DISCUSSION... Issued at 414 AM CDT Sun Jun 9 2024 This morning, the synoptic pattern was characterized by northwest flow aloft, with one closed low over southern Saskatchewan and a second low over eastern Ontario. Broad surface high pressure is building in over the Canadian Prairies, while a weak stationary front is draped west-east across the forecast area. Nighttime satellite imagery shows a swath of mid-level clouds in this same area, and although there were some light radar returns earlier in the night, these have all diminished. Additional, more widespread cloud cover is visible upstream. Highs today will be a touch cooler than yesterday, with highs in the upper 60s north to mid 50s south. We are carrying a mention of isolated showers in the southwest this afternoon, with many CAMs advertising precipitation chances as a vort max embedded in northwest flow moves through. Similar to yesterday, cloud bases are expected to be relatively high (around 9-10k feet), so unless these showers become heavier we would expect the majority of precipitation to remain as virga. A brief upper ridge will build in overnight before a shortwave trough approaches from Montana, with an attendant surface low progged to deepen in Wyoming and move east. Strong low-level warm air advection ahead of the low and trough axis is expected before a cold front sweeps west to east across the forecast area late Monday. With this warm advection and upper ascent, showers and thunderstorms are expected to become widespread, with blended POPs starting early Monday morning and increasing to 70 to 90% Monday afternoon and evening. Most of western and central North Dakota has been upgraded to a Marginal Risk (level 1 of 5) for isolated severe thunderstorms on Monday, with a sliver of level 2 out of 5 (Slight Risk) in southern Bowman and Adams Counties. One main area of concern regarding severe potential is how early widespread cloud cover and scattered showers and thunderstorms are expected to begin on Monday morning, and if that will limit instability later in the day. For now, deterministic guidance is advertising MLCAPE around 1000 J/kg and strong 0-6km shear of 35-45 knots, with marginal mid level lapse rates. Of note is rather high SRH, which is also shown in CSU Machine Learning probabilities highlighting a low but non- zero tornado threat across western North Dakota. However, we are thinking the main threats are large hail up to the size of half dollars and damaging wind gusts up to 60 mph. Updated rainfall probabilities for Monday through Monday night are similar to the previous shift, with generally a 30-50% chance of exceeding at least 0.50" of rain across most of western and central North Dakota, with the exception of the southwest and southeast. The highest probabilities are currently in the northwest part of the state. We will have to keep an eye out for any areas that get multiple rounds of heavier precipitation, with forecast PWATs at the high end of climatology. Precipitation chances end early Tuesday morning as the trough axis moves through, with a bit of a breeze in the east but otherwise a pleasant day with highs in the 70s. Rain chances return on Wednesday as an embedded shortwave moves through zonal flow, while a surface low and associated front moves through the Dakotas. Current model guidance has shifted Wednesday`s severe potential slightly to the southeast, with a quicker front and limited instability in our forecast area. Timing changes could lead to a short-lived threat in the James River Valley area but for now, the highest potential is outside of our forecast area. Highs on Wednesday are forecast to be in the upper 70s north to mid 80s south, although the timing of the front could impact how warm we get. Ensemble guidance is in good agreement on a southwest flow pattern dominating the end of this week and into the weekend, with a more active pattern expected. Blended POPs are already showing widespread 30 to 40 percent chances of precipitation late Friday night through Saturday night. NBM temperature ranges keep highs near to slightly above average through the weekend, in the lower 70s to lower 80s. && .AVIATION /18Z TAFS THROUGH 18Z MONDAY/... Issued at 1225 PM CDT Sun Jun 9 2024 VRF conditions are expected to begin to 18Z TAF period. Isolated showers are possible across the southwest, but there is not sufficient confidence in it impacting any terminals at this time. Winds will become breezy across the west this afternoon, but will then diminish through the evening. Overnight into early Monday, chances for showers will push into the west, first impacting the terminals of KXWA and KDIK then spreading to KMOT and KBIS by 18Z tomorrow. Beyond the end of the TAF period, showers and eventually thunderstorms will become widespread, with strong to severe thunderstorms possible Monday afternoon and evening. && .BIS WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Adam/Jones DISCUSSION...Jones AVIATION...Adam