Area Forecast Discussion
Issued by NWS Grand Forks, ND
Issued by NWS Grand Forks, ND
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802 FXUS63 KFGF 281748 AFDFGF Area Forecast Discussion National Weather Service Grand Forks ND 1248 PM CDT Fri Jun 28 2024 .KEY MESSAGES... - There is a level 1 out of 5 risk for severe thunderstorms across the region today in the late afternoon and evening. - There is a low chance for severe thunderstorms again Monday across the region. && .UPDATE... Issued at 1248 PM CDT Fri Jun 28 2024 Clouds beginning to clear with SFC heating kicking across eastern North Dakota ahead of the severe threat later on. Two main scenarios have become favored with a discrete mode or a more clustered mode. For discrete convection the thought is that weak funnels and hail as large as ping pongs would be possible with transient supercell structures following along the inverted trough across eastern North Dakota. Should we get more of a cluster mode wind would be predominant as straight hodographs and storm motions parallel to the inverted trough seem to conceptually favor this outcome. The problem is CAMs seem to favor the discrete mode more leading to a spilt in confidence. Either way a low end threat with a 5% threat for severe storms this evening. UPDATE Issued at 947 AM CDT Fri Jun 28 2024 No change in thoughts for today`s severe risk with rain mostly clear of the forecast area now aside from a few showers in the Lake of the Woods area. Has been a persistent area of sub 2 mi visibility in Pembina and Kittson though seems to be more mist related than fog based on webcams currently so no SPS needed. Mist will continue across much of the area through noon as clouds lift. UPDATE Issued at 641 AM CDT Fri Jun 28 2024 Patchy fog has started forming this morning thanks to last nights moisture. There are lingering showers slowly working their way out of northwest Minnesota. Expecting by this afternoon this fog to lift or dissipate as we are mixing out. The severe risk still seems very conditional and heavy rain showers or strong thunderstorms may still be the more likely scenario. && .DISCUSSION... Issued at 404 AM CDT Fri Jun 28 2024 ...Synopsis... The wave responsible for last nights showers is moving off to the east into the great lakes region. The upper level low is currently on the border of Alberta,Canada and Montana. Convective guidance shows the low moving directly over the Northern Plains and then exiting the region via the arrowhead before moving back into Canada over the great lakes. Starting this afternoon this low is depicted as entering North dakota from the West and having this narrow band of instability off the frontal boundary that extends into the valley. However, the moisture and theta-e axis is being pulled across the arrowhead potential leaving our area with very little to lift. Looking at model soundings our mixed layer Cape is around 500 joules which could lead to showers and some pretty lightning bolts but not really severe. However, the catch is the shear profile ahead of the low is about 30-40kts which is sufficient to sustain storms if convection were to initiate. With this upper low passing directly conceptually we can obtain more forcing and instability ahead of the low but I`m not quite to sure if we have a long enough destabilization period to help the dynamics produce more than heavy showers. The model soundings better support heavy rain but SPC did keep the marginal risk over the majority of that CWA because of the low passing through. Because of this going to message severe potential of quarter sized hail and 60 mph just because if we do reach a long enough destabilization period then we might hit severe but another round of heavy rain with lightning is probably more likely. ...Severe threat Monday.... Another mid/upper wave follows a very similar track and evolution as the system Friday, with a period of widespread showers or embedded thunderstorms. There is a signal for a deeper warm sector building into our region within most clusters, and higher probs for SB CAPE to exceed 1000 J/KG during the peak heating/diurnally favored period of the afternoon/evening. CSU GEFS based machine learning (15-30% severe probs) are supported by 100% chance for greater than 55 NBM CWASP and 50-60% probability for NBM CWASP values exceeding 65. That aligns with a threat for isolated to scattered severe convection. This is still farther out, so details/impacts are still inherently uncertain. && .AVIATION /18Z TAFS THROUGH 18Z SATURDAY/... Issued at 1248 PM CDT Fri Jun 28 2024 As clouds clear this afternoon in eastern North Dakota ceilings briefly become solidly MVFR everywhere with a few sprinkles remaining until 20Z in BJI. Gusty NW winds at all sites until 03Z with gusts near DVL already topping 25kts at times. Could see a few thunderstorms form near DVL around 00Z tracking southeast towards GFK and FAR by 03Z end ending 06Z accordingly have added VCTS to the TAFS though further adjustment may be needed later on for timing. Post storm overnight cigs drop between 005 and 015 leading to widespread IFR to MVFR with LIFR still a 20% chance. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. && $$ UPDATE...TT DISCUSSION...MM AVIATION...TT