Area Forecast Discussion
Issued by NWS Bismarck, ND

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000 FXUS63 KBIS 050334 AFDBIS Area Forecast Discussion National Weather Service Bismarck ND 934 PM CST Thu Mar 4 2021 .UPDATE... Issued at 934 PM CST Thu Mar 4 2021 There are some hints of fog developing in northwest North Dakota, and to the south and west of the Devils Lake Basin. Based on previous nights` model vs. observation performance of low-level moisture fields, we are very reluctant to increase messaging of fog potential until we see something more prominent. The greatest potential for impactful visibility reductions is across the 4 northwestern-most counties of North Dakota, where snow cover still exists and dense fog is climatologically more common (at Stanley and Tioga). Model consensus for sky cover remains very poor. It is under-performing on high clouds across southwest North Dakota and over-performing on low clouds across northern North Dakota, although there are signs of developing fog in some similar locations. The first several hours were adjusted to more closely follow observed trends. UPDATE Issued at 622 PM CST Thu Mar 4 2021 Some minor adjustments were made to the coverage of patchy fog tonight through tomorrow morning. The HRRR and RAP visibility fields were relied upon, as they have been trending well with observed surface dewpoints. However, it`s worth noting that all guidance, especially non-HRRR/RAP solutions, has been far too aggressive with both the coverage and duration of low stratus and fog the past few nights. For this reason, we also trended sky cover down with this update. Even though our forecast grids will contain 30-70% sky cover for much of the area, think that most locations will either be completely overcast or completely clear at any given time. && .SHORT TERM...(This evening through Friday) Issued at 113 PM CST Thu Mar 4 2021 Low stratus and fog tonight and continued mild temperatures tomorrow highlight the short term forecast. Tonight, easterly surface flow will bring in a shallow layer of moisture (enhanced by continued snow pack melting) across central and eastern ND. Forecast sounds depict low stratus between 500-1000 feet AGL and some fog as a result. There is some uncertainty as to the extent and duration of the stratus/fog. Some short-term models want to take it as far west as Dickinson and leave Jamestown clear, while the majority maintain a further east solution. How long clouds/fog persist will play a significant role in temperatures tomorrow. We still maintained a warmer forecast than what the NBM is providing due to its continued cold bias, but we elected to go below the higher end thresholds we`ve been trending with as of late. We still expect the southwest will see temperatures in the 60s tomorrow, but further east where cloud cover is more likely and more likely to linger longer, temperatures could struggle to get out of the 40s to lower 50s. .LONG TERM...(Friday night through Thursday) Issued at 113 PM CST Thu Mar 4 2021 Mild and dry conditions continue through much of the long term before a potentially more active pattern sets up next week. Saturday will likely be the warmest day through the next week as an upper-level ridge axis moves directly overhead. Therefore, maintained higher than straight NBM temperatures which brings widespread upper 60s into portions of the west and widespread upper 50s to low 60s everywhere else, except for the Turtle Mountains. This is slightly cooler than the previous forecast as the cold front appears to be slightly delayed. This means compressional warming will be maximized a bit further west and a southeasterly (which doesn`t mix down as well as southwesterly) wind will be favored all day. Winds will be quite breezy Saturday afternoon with southeasterly winds around 25 mph gusting to 35 mph. This may lead to near critical fire conditions across the southwest Saturday afternoon where temperatures will be in the upper 60s, relative humidity around the low 20s and winds around 30 mph. Sunday will not be as warm, but highs should remain well above normal with widespread readings in the upper 40s to upper 50s. The flow becomes more zonal on Monday as a broad western trough approaches Tuesday into Wednesday. This could be the start of a more active period. The 12z suite of deterministic global models have trended towards the flow staying split over the Dakotas before phasing across the Great Lakes, keeping the strongest cyclogenesis well to our east. Still, warm air advection associated with the northern wave stream would still bring us a brief period widespread precipitation in this scenario, but the impacts would be fairly tempered. The 12z ensemble guidance has shifted their favored storm track a bit north and lowered their expectations of more meaningful precipitation. Overall, expectations remain low in this system producing impacts or much needed rain, but a great deal of uncertainty remains so there is still the possibility however small it might be. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 622 PM CST Thu Mar 4 2021 Patchy fog with associated LIFR ceilings may develop across much of western and central North Dakota tonight through Friday morning. Confidence in impacts at any given terminal remains low, so have opted to include VCFG and SCT003 mentions for this set of TAFs. Otherwise, VFR conditions and light easterly winds are expected through the forecast period. && .BIS WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...Hollan SHORT TERM...AJ LONG TERM...AJ AVIATION...Hollan

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