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Area Forecast Discussion
Issued by NWS Grand Forks, ND
Issued by NWS Grand Forks, ND
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967 FXUS63 KFGF 150456 AFDFGF Area Forecast Discussion National Weather Service Grand Forks ND 1156 PM CDT Wed Aug 14 2024 .KEY MESSAGES... - Showers and thunderstorms will increase in coverage through this evening and last into Thursday. Heavy rain and lightning are the main impacts. - Wildfire smoke from Canada may return to the region Friday, with a chance for air quality impacts. && .UPDATE... Issued at 1156 PM CDT Wed Aug 14 2024 Low continues to push into the area, with rain across much of the southern Red River Valley and more scattered showers further north and east. Adjusted POPs and QPF to fit current trends a bit better, but soggy night continues. Got some reports of lower visibility around the Devils Lake area, so added in some patchy fog. Just have it along the western edge of the system for now but will watch and see how the rain evolves later tonight to see if a mention needs to be added further east. UPDATE Issued at 950 PM CDT Wed Aug 14 2024 As expected, storms entering southeastern ND have been on a weakening trend, no longer SPS worthy but bringing rain and lightning to our area. Northern shield of precip has been falling apart as the stronger cells from the south have been taking over, but there are still plenty of showers to bring rain to most of our counties. System will continue to slowly wrap up and push northeastward throughout the night. Should see decreasing instability and any lingering convection will be weakening. UPDATE Issued at 659 PM CDT Wed Aug 14 2024 Rain has pushed northeastward into the Devils Lake Basin, northern Red River Valley, and western MN. A bit of elevated instability in the 500-1000 J/kg range has entered southeastern ND, so we are getting some thunderstorm activity in that area. With the better CAPE remaining to the south and effective shear around 25 kts, think that we won`t see any severe impacts, but will monitor for heavy rain and anything popping up to produce some small hail. Adjusted for timing and placement of POPs but otherwise no major changes to overall messaging. && .DISCUSSION... Issued at 334 PM CDT Wed Aug 14 2024 ...Synopsis... A mid/upper level trough is slowly deepening over the Northern Plains, with a 700MB/500MB low eventually closing off over our region tonight into Thursday before moving east. A plume of deep moisture highlighted by PWATs in the 1.5-1.8" range extends over our CWA and several areas of showers and embedded thunderstorms will track through or develop over our area through tonight before coverage becomes more scattered Thursday. We remain on the northern fringe of centered over the southwest US, and progressive flow will returns in several shortwave ridge and trough passages. The amplitude of the ridging does vary in time between ensemble clusters with stronger ridging supporting drier and warmer conditions, while more clusters keep flow flatter/more progressive. This keeps near seasonal highs in place next week and allows for progressive waves and shower/thunderstorm chances. Regarding thunderstorm impacts today-Thursday: This afternoon/evening features an axis of steep to marginal mid level lapse rates and marginal instability (1000 J/KG) near our west and south through sunset. Deep layer shear is weak. There may be enough forcing for a few marginal cores/smaller hail, and eventually a linear MCS may pass to our south (as shown by some CAMs), but with the main axis of instability south and 0-3km shear is less than 20kt/DCAPE less than 1000 J/KG wind organized severe this evening. PWATs are very high but broader areas of moderate showers and embedded thunderstorms/locally heavy rain. As thunderstorm activity will tend to be more progressive/embedded within larger areas of moderate rain the signal has continued to decrease within CAMs for higher totals above 3" and 24hr PMM show a very "spotty" signal for 1.5"+, which lowers confidence in even localized excessive runoff. Signal is still there for many locations to see above 0.25"+ rainfall over the next 24hr, with swaths over 1". It is a low probability, but it is worth monitoring the track/depth of the mid level low Thursday. Stratus may persist and any dry slot may fill in, however if there is clearing the high vorticity environment in place may support funnels or conditionally landspout/weak tornado potential (particularly near surface low/boundaries. As this is highly dependent on clearing an mesoscale/smaller scale evolution the probabilities are low and ultimately funnels would be favored over landspouts in the most likely scenario. Smoke potential Friday: As the mid/upper low transitions east RAP/Canadian smoke models are showing a dense plume of wildfire smoke that is currently bottled up over northern Canada advecting south into our region. This is far enough out in time, however dense the smoke will be an any potential air quality impacts are uncertain, however the signal in near surface smoke fields is there and it is worth monitoring, especially if part of a sensitive group health-wise. && .AVIATION /06Z TAFS THROUGH 06Z FRIDAY/... Issued at 1156 PM CDT Wed Aug 14 2024 Rain and some thunderstorms in the KFAR area continue, with VFR to IFR conditions. Those sites that are still VFR should see a decrease in category as the night goes on as rain continues and we get more stratus and even some fog possibly filling in around the KDVL area. For now kept lowest vis around 1SM as not a classic ground fog situation but could see some lowered vis. Rain and VCSH will continue for most of the night, with a bit of a break possible during the day tomorrow before more showers reform. While some improvement in ceilings is not out of the question, clouds look like they will hang around for much of the day and some MVFR to IFR ceilings will be possible by the end of the period. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. && $$ UPDATE...JR DISCUSSION...DJR AVIATION...JR