Area Forecast Discussion
Issued by NWS Bismarck, ND
Issued by NWS Bismarck, ND
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627 FXUS63 KBIS 190929 AFDBIS Area Forecast Discussion National Weather Service Bismarck ND 429 AM CDT Wed Jun 19 2024 .KEY MESSAGES... - Frost Advisory for western and portions of south central North Dakota early this morning. - A slow warming trend into the weekend but seasonably cool temperatures continue through Saturday. Warmer Sunday and into early next week. - Hit and miss showers (20 percent) today through Thursday. Better chances for showers and thunderstorms (30 to 75 percent) return Thursday night through Saturday. && .DISCUSSION... Issued at 224 AM CDT Wed Jun 19 2024 A broad southwest upper level flow will persist across the Northern Plains through much of the forecast period. This will bring a series of waves across the local area but with a low confidence in the timing and placement of resulting shower and thunderstorm activity. In general though it looks to be mostly dry early in the period (today through Thursday daytime). Chances for showers and thunderstorms then increase Thursday night through Saturday. Within the broad southwest upper flow, one could imagine a southern and a northern track within our local area. Today into this evening a shortwave will lift through Wyoming and southeast Montana and into the Dakotas. Another wave is forecast to lift from Montana into southern Saskatchewan. As surface high pressure over the forecast area today exits to the east, a return flow will set up over the western Dakotas and eastern Montana. CAMS are showing some reflectivities into southwest ND late this afternoon/evening and northwest ND mainly this evening and into the early overnight hours. QPF with this activity looks minimal at best. We utilized the NBM blend for pops but kept pops broader (3 hour duration) instead of hourly. Impacts will be minimal with non-zero, but very low probabilities for thunder. On Thursday, we start the day mostly dry but we do see moisture increasing from south to north through the day. Southern portions of the forecast area will see more clouds and cooler daytime highs. Low pressure from the Central Rockies moves into the plains and we see increasing precipitation chances Thursday evening into Friday across South Dakota and possibly into southern portions of North Dakota. Meanwhile in the north, temperatures will be warmer and instability higher in the Thursday afternoon so a few thunderstorms could be found along the International Border, but the greatest instability appears to remain over Canada. It`s possible that a good portion of the forecast area remains dry Thursday afternoon into Friday, contrary to our current NBM guidance. As we get into the Friday through Saturday timeframe, confidence continues to diminish as we remain within the aforementioned broad southwest upper flow but we see some rather significant differences in the deterministic models. A DESI cluster analysis was not available, but the WPC Day 3 cluster analysis for the 24 hour period ending 00Z Saturday shows that the far south central into southeast ND is the general favorite for qpf placement, but there are scenarios that would keep this area dry as well. All scenarios also keep some light precip right along the International border and this could certainly sneak south into northern portions of the forecast area. On Saturday there is a signal for a stronger northern wave moving east along the International Border, which could bring a chance of showers and thunderstorms. As for the potential for severe storms, SPC has a general risk in the far west today, which is covered earlier. Thursday the general risk is situated over the southern two thirds of the state. Friday there is a marginal risk just south of the southern James River Valley, with a general risk pretty much statewide. There is abundant bulk shear across the forecast area through the period. Thursday and Friday, instability is highest just to the north and just south of the forecast area. If we would get a stronger storm either of these days, it would be favored along either our southern or northern border. Depending on the timing/placement of the stronger wave on Saturday, there could be a window for a stronger storm or two. Overall the risk for strong to severe storms late Thursday through Saturday looks to be low at this time. With the higher temperatures Sunday and Monday we will see and increase in instability and our broad upper level flow will remain over the area. Will need to monitor. As for temperatures. we start out quite cool today but see a gradual warming trend Through the weekend and into early next week. There is a signal for some above normal temperatures Sunday and Monday with some 90 degree readings possible in the south on Monday. Ensemble spreads are actually not very wide Sunday into Monday. NBM temperatures drop quite a bit after Monday, but ensemble spreads also increase significantly, so confidence in a warm couple of days Sunday and Monday is pretty high, but whether we cool off significantly thereafter, or remain warm, is murky at best. && .AVIATION /06Z TAFS THROUGH 06Z THURSDAY/... Issued at 1211 AM CDT Wed Jun 19 2024 Low pressure over the Great Lakes Region will continue to lift northeast as high pressure builds over western and central ND tonight. Low VFR ceilings to begin the 06Z TAF period will clear from west to east overnight. A few areas of MVFR cigs could be possible over central ND, as well as some patchy fog in the west as clouds clear. However at this time confidence is to low to mention. West to northwest flow to begin the TAF period will transition to a southeast flow this afternoon/early evening. && .BIS WATCHES/WARNINGS/ADVISORIES... Frost Advisory until 8 AM CDT /7 AM MDT/ this morning for NDZ001-002-009-010-017>020-031>034-040>044. && $$ DISCUSSION...TWH AVIATION...TWH