Area Forecast Discussion
Issued by NWS Bismarck, ND
Issued by NWS Bismarck, ND
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822 FXUS63 KBIS 021755 AFDBIS Area Forecast Discussion National Weather Service Bismarck ND 1255 PM CDT Tue Jul 2 2024 .KEY MESSAGES... - There is a chance (30%) for showers and thunderstorms today. - Breezy northwesterly winds are expected during the day today, diminishing near sunset. - There is a chance (40%) for showers and thunderstorms Wednesday. An isolated strong storm is possible, mainly in the southwest. - The chance for showers and thunderstorms on Independence Day is 80 percent across all of western and central North Dakota. && .UPDATE... Issued at 1251 PM CDT Tue Jul 2 2024 More showers have developed in the cyclonic flow and are slowly moving south as they rotate around the low in Canada. Slight chance of thunder with these, the chance will increase some as more diurnal heating occurs. PoPs have been adjusted. UPDATE Issued at 940 AM CDT Tue Jul 2 2024 The very light isolated showers in the north continue, have not seen any observations of the rain making it to the ground. These showers chances will continue in the cyclonic flow. PoPs were reduced to slight chance through the late morning. UPDATE Issued at 628 AM CDT Tue Jul 2 2024 Minimal changes were made to the forecast for this update. Some radar returns have shown up across the far northwest, with a few instances of drizzle being recorded. We`ve kept the PoPs as is, as there may be some additional showers moving into the north over the next hour or so. Otherwise, just blended the current observations into the forecast along with some minor cloud coverage updates to account for latest satellite observations. && .DISCUSSION... Issued at 402 AM CDT Tue Jul 2 2024 Showers have since exited the area this morning, with generally clear skies and light westerly winds present across much of western and central North Dakota this morning. However, wraparound moisture associated with the low pressure system to our northeast has begun to push some additional low clouds and spotty showers into our northwest from southern Saskatchewan. As the low pressure system moves off to the east, these showers may continue across the northern tier of the area through the day today, with occasional rumbles of thunder associated with them. Severe weather is unlikely given the lack of forcing, but instability is just enough to allow for the development of some isolated thunderstorms. With the surface pressure gradient tightening on the back side of the aforementioned low, some breezy northwesterly winds are expected through the day today, with sustained winds generally around 20 mph, and gusts up to 30 mph. High temperatures will remain slightly below normal for this time of year, ranging from the lower to upper 70s. The overnight period is forecast to be rather uneventful, with precipitation chances and wind speeds gradually diminishing. Lows will mostly be in the 50s. Aloft, the northwesterly flow associated with the generally cyclonic pattern is expected to remain across the area through at least the work week. A shortwave embedded within the flow is expected to pass through southern Montana and northern Wyoming on Wednesday, helping initiate some more showers and thunderstorms across the region. Surface forcing and instability as a whole remain rather weak, with the most robust values staying to our south across Nebraska and South Dakota, thus keeping much of the severe threat to our south. However, 0-6km deep layer shear values of roughly 40 kts do encroach into our far southwest for a few hours, which may support a very isolated strong to severe storm threat near the South Dakota border Wednesday evening. Most of the CAMs keep convection well to our south, with a few solutions suggesting a few thunderstorms across our southwest in the evening hours. The severe threat, while remaining rather low, is non zero for that area. The SPC did maintain a Marginal Risk (level 1 of 5) area across our far southwest, but given the uncertainty in the exact location of convective initiation and the marginal makeup of the ingredients needed for strong to severe storms, the areal extent of this risk remains rather small. The CSU machine learning guidance has also removed the low risk of severe hail from our southwest, pushing it further south and out of our area. As the trough deepens and moves through the Great Plains through the middle of the week, we continue to see indications of Independence Day being cooler and wetter than usual. WPC cluster analysis has really begun to come into agreement with regards to where this upper level trough will set up across the Plains, which owes to the continued confidence in NBM PoPs ranging from 70 to 80% across the entire area during the day. Showers and thunderstorms are likely across nearly all of western and central North Dakota during the day, with mostly cloudy skies expected. Along with the deepening trough aloft, cooler midlevel temperatures are expected to filter in from the northwest, helping reduce highs on Independence Day to the lower to mid 70s. Winds, however, are expected to be rather light for much of the area. Even though the chances for precipitation overall has remained the same, the actual amount of precipitation that can be expected has decreased somewhat. NBM probabilities of exceeding 0.25" of rain on Independence Day has decreased to around 30 to 50%, with the highest chances in the south central and southern James River Valley. The chances for severe weather during the day is very low, given the cooler temperatures and cloud coverage helping stabilize the atmosphere. CSU machine learning guidance keeps severe probabilities entirely out of our area. While occasional rumbles of thunder can be expected, severe weather is not anticipated. Model precipitable water values range from around 1.00" to 1.10", which places it between 75th and 90th percentiles for this time of year, which helps support the widespread chances for precipitation and the chances for exceeding a quarter inch of rain. All in all, we can expect Independence Day to be rainy and cloudy, with chances for rain and cloud coverage decreasing overnight into Friday. The active cyclonic flow aloft will continue into the weekend, with daily chances for showers and thunderstorms continuing as a result. Long range guidance is indicating multiple shortwave troughs to pass through the Northern Plains during this period, with chances for rain returning to the area Friday into Saturday morning, Saturday into early Sunday morning, and Sunday afternoon into the overnight hours. Day to day high temperatures will remain in the mid 70s to lower 80s. Given the moisture return and instability each day, we can expect to see some rumbles of thunder with these waves, though its a bit too far out to really tell what the severe potential will be with them. This active pattern may finally break down next week, as the very prominent trough across the western CONUS may slowly build its way east into the Plains. WPC cluster analysis indicates that there is a 65% chance for this ridge to be influencing North Dakota by Wednesday, while the remaining 35% chance keeps the ridge to our west, building into the Northern Plains a day later. Generally, with a ridge pattern like this, we can expect to see a gradual warming in temperatures, clearer skies, and drier conditions, reducing the chances for the near-daily showers and thunderstorms we`ve been seeing for much of this summer. The NBM spreads in high temperatures do widen out heading into next week, but the overall trend does suggest a warming pattern, lasting through at least next Wednesday. Beyond this point, its hard to say whether or not the ridge pattern will continue. Needless to say, confidence continues to increase in the active pattern breaking down some time early next week, with a warmer and drier pattern taking its place. && .AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/... Issued at 1251 PM CDT Tue Jul 2 2024 Mainly VFR with scattered to broken cumulus clouds at 4000ft. Scattered showers around most terminals this afternoon then skies clear around sunset. Winds will gust near 30kts from the west until sunset. && .BIS WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Smith DISCUSSION...Besson AVIATION...Smith