Area Forecast Discussion
Issued by NWS Grand Forks, ND
Issued by NWS Grand Forks, ND
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815 FXUS63 KFGF 150452 AFDFGF Area Forecast Discussion National Weather Service Grand Forks ND 1152 PM CDT Tue May 14 2024 .KEY MESSAGES... - On and off showers through at least the next week. - Thunderstorm chances increasing over the next few days. A low probability scenario exists which would include a few strong thunderstorms on Friday. && UPDATE Issued at 1005 PM CDT Tue May 14 2024 The activity that developed in central ND just west of our CWA has greatly diminished as it moved in o the Devils Lake Basin (just a few sprinkles/light showers). There is more activity (including some lightning activity) farther southwest, but this is not in line to move into our area and may face the same fate as the activity farther north due to the more dry/subsident air mass locally in our area. The more organized rain chances are still on track to arrive by midway Wednesday. I made some adjustments to delay higher PoPs (measurable chances) to the north, holding higher chances in place to the southwest until Wednesday morning. The decrease in instability near our west on RAP analysis lowers confidence in any lightning activity into our area. UPDATE Issued at 637 PM CDT Tue May 14 2024 Activity on radar continue to be mainly associated with sprinkles (non measurable rain) or virga, due to a dry 8-10 KFT dry layer below this mid level CU deck. HRRR still shows a signal for scattered showers/iso-T developing to the west this evening near the surface trough axis/instabilty gradient and spreading east towards the Devils Lake Basin before weakening/falling apart. There are a few showers within a CU field along that axis but no lightning activity. If it did occur impacts would be limited to just lightning activity as much more stable air is in place this evening. && .DISCUSSION... Issued at 230 PM CDT Tue May 14 2024 ...Synopsis... Water vapor imagery indicates zonal flow aloft with several upstream shortwaves meandering toward the region. Ensemble guidance in good agreement with the general zonal flow pattern, but differ with timing, strength, and location of individual shortwaves. All in all anticipate on and off showers through at least the next week with possibly a stronger thunderstorm. Through the next week, the 25-75 percentile range for rainfall amounts across the majority of the forecast area is 0.50-1.50 inches. ...On and Off Showers... Water vapor indicates immediate subsidence through the late afternoon behind the departing wave, but many more waves approaching. HRRR indicates a few storms initiating across north central ND this afternoon moving into the Devils Lake basin this evening. This scenario seems plausible given the current plume of instabilty ahead of the surface convergence/low pressure. Any storms that do develop would quickly dissipate this evening as they depart from the instability. Next wave of concern is currently across Idaho, with another lead wave across southwest South Dakota. Ensemble guidance in good agreement indicating these features will slowly propagate through the region on Wednesday, with rain chance increasing especially Wednesday afternoon and into the evening. Beyond Wednesday, timing and location of waves uncertain. ...Severe Storm Potential... There is a stronger wave that will be approaching from the northwest by Friday, and ensemble guidance shows many different scenarios with how this system will develop across southern Canada. Location of this feature by Friday into Saturday will be important, as stronger and further west would lead to increased moisture return along with warmer temperatures and greater instability, with the potential for strong to severe storms. In fact, the CU machine learning indicates a low chance for severe storms Friday and Saturday. Of course, a weaker and further east system would not allow for moisture return or warmer temperatures thus limiting instabilty. At this point each scenario has an equal chance of happening. && .AVIATION /06Z TAFS THROUGH 06Z THURSDAY/... Issued at 1152 PM CDT Tue May 14 2024 VFR conditions should continue during the early TAF period across eastern ND and northwest MN, with a few light showers at KDVL. MVFR stratus arrives by 12Z at KDVL and eventually MVFR (possible IFR) overspreads the region Wednesday as a low pressure system is bringing a period of rain to all TAF sites through Wednesday afternoon/evening. Winds will tend to vary from the east to southeast 8-13kt, becoming more light and variable near the low center Wednesday then shift to the north- northwest 8-11kt at KDVL Wednesday evening as the low shifts east. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. && $$ UPDATE...DJR DISCUSSION...TG AVIATION...DJR