Area Forecast Discussion
Issued by NWS Grand Forks, ND
Issued by NWS Grand Forks, ND
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851 FXUS63 KFGF 100318 AFDFGF Area Forecast Discussion National Weather Service Grand Forks ND 1018 PM CDT Tue Jul 9 2024 .KEY MESSAGES... - Isolated thunderstorms across the region through the evening. Severe storms are not expected. - Risk for heat related impacts Friday through Sunday. && .UPDATE... Issued at 1018 PM CDT Tue Jul 9 2024 Thunderstorm activity is now mainly limited to portions of southeastern North Dakota, where a few stronger storms persist this evening. The primary concerns with these storms are gusty winds up to 50 mph, up to nickel sized hail, and very heavy rain. There is a slow moving boundary that is providing the axis of development for these storms, which is very slowly moving to the south and west. Look for storms to continue to form along this boundary over the next couple hours, while gradually diminishing in strength. UPDATE Issued at 702 PM CDT Tue Jul 9 2024 Isolated showers and thunderstorms continue to form primarily from the Red River Valley and points west. Most activity thus far has been brief, with observations of heavy rain and gusty winds approaching 50 mph. Look for this to diminish gradually through the remainder of the evening as temperatures fall below convective temps and cause low level lapse rates to fall. && .DISCUSSION... Issued at 256 PM CDT Tue Jul 9 2024 ...Synopsis... Ensemble guidance in decent agreement with evolution of the larger scale pattern through the next week - depicting a building western CONUS ridge with the main storm track across Canada. The main uncertainty exists with the speed and track of individual upper waves and how they will affect the ridging. After surface ridging Wednesday into Thursday, there will be periods of instability and forcing leading to thunderstorms, but not sure how far south and/or severe risk (especially strength of deep layer bulk shear). CWASP and CSU machine learning both indicate periods of marginal severe risk this weekend into next week. ...Isolated thunderstorms this evening... Water vapor imagery indicates an upper wave approaching the region from the north, with the cu field building across the region. Radar imagery indicates showers/thunderstorms developing. Deep layer shear is weak, so most storms will effectively kill themselves. However, given steep lapse rates in a decently mixed boundary layer, wouldn`t be surprised to see stronger storms produce gusts 40-50 mph. Additionally, stronger storms may produce brief heavy downpours resulting in local amounts around 1 inch and minor flood impacts in more susceptible spots. ...Risk for heat related impacts this weekend... As the upper ridge builds across the western CONUS and gradually shifts east a much warmer and moist airmass propagates across the region, especially Friday through Sunday. NBM MaxT 25-75 percentiles range from ~90F to ~98F during this period (across the southern CWA at least), and with crops nearing peak Evapotranspiration Td each day should be ~70F. Heat index values would be >100F if the temperatures were able to reach upper 90s, but that is still a low probability outcome. At this point most likely (80% chance) heat index values each afternoon will be in the mid to upper 90s, which is below advisory criteria. However, the new NWS heat risk product (which accounts for duration of heat including both daytime and nighttime temperatures as well as if those temperatures pose an elevated risk of heat related impacts based on data from the CDC) indicates a moderate risk of heat related impacts Friday into Saturday with a major risk of heat related impacts on Sunday. www.wpc.ncep.noaa.gov/heatrisk && .AVIATION /00Z TAFS THROUGH 00Z THURSDAY/... Issued at 633 PM CDT Tue Jul 9 2024 VFR conditions prevail through the period at all TAF sites. Isolated showers and thunderstorms remain possible through around 03Z, which could include brief gusty winds. Otherwise, winds remain light and variable through Wednesday morning, then increase slightly, but generally remain less than 10 knots heading into the midday hours. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. && $$ UPDATE...Lynch DISCUSSION...TG AVIATION...Lynch