Area Forecast Discussion
Issued by NWS Grand Forks, ND
Issued by NWS Grand Forks, ND
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303 FXUS63 KFGF 032336 AFDFGF Area Forecast Discussion National Weather Service Grand Forks ND 636 PM CDT Mon Jun 3 2024 .KEY MESSAGES... - Widespread showers and thunderstorms move through the area late tonight into Tuesday afternoon. Some storms may be strong to severe, bringing hail up to 1 inch, 60 mph winds, and isolated tornadoes. - Gusty winds 40-50 mph with scattered showers and thunderstorms are anticipated Wednesday into Thursday. && .UPDATE... Issued at 635 PM CDT Mon Jun 3 2024 A few showers are moving across portions of the region, generally along and north of the International Border to the north of Devils Lake. These are not expected to have a meaningful impact to the forecast area as they continue to move to the northeast. Looking further west, showers and thunderstorms in southwestern North Dakota are expected to continue working into central and eventually eastern North Dakota heading into the late evening and overnight hours. At this time, a few strong storms cannot be ruled out after midnight for portions of the forecast area, primarily south of Highway 2. && .DISCUSSION... Issued at 213 PM CDT Mon Jun 3 2024 ...Synopsis... Water vapor satellite imagery Monday afternoon reveals large upper troughing extending from the Pacific Northwest into the Intermountain West. Moisture wrapping around the base and exit region of the trough within the moist conveyor is creating widespread convection/cloudiness into the northern High Plains. All ensemble guidance agrees this trough will strengthen notably as it migrates into the southern Prairie Provinces of Canada. Plenty of large scale forcing from embedded shortwaves, jet dynamics, and attendant fronts will drive showers and thunderstorms tonight into Tuesday within the Dakotas and northern Minnesota. Some thunderstorms are expected to be strong to severe. Relatively rich moisture content feeding into strong forcing from this trough along with sufficient instability will help bring areas of moderate to heavy rainfall between 0.5-1.5 inches. There is however some lingering uncertainty in smaller scale features like more specific orientation, location and timing of strongest forcing as well as amount of daytime heating during the day Tuesday that would influence coverage and type of favored severe hazards. This also would influence the chance for small areas of heavy rainfall, possibly up to 2-3 inches (10% chance of occurring), of which may result in localized flooding if it occurs on saturated soils currently present in some areas and/or over an urban area. As the trough strengthens in southern Canada Wednesday and Thursday, a belt of strong winds aloft will round the base of the mid/upper circulation within its dry slot. This will allow gusty winds over 40 mph across much of the region during the day Wednesday and Thursday. There is still some uncertainty in how high wind gusts will reach, with gusts to 55 mph not out of the question. Getting into mid to late this week, ensemble guidance then suggests a weather pattern that favors relatively drier conditions for our area compared to recent weeks amid northwest flow aloft. Near to slightly below average temperatures are also favored throughout the week in this pattern. ...Strong to severe storms late tonight into Tuesday... Scattered to widespread showers and thunderstorms will move out of central North Dakota into eastern North Dakota tonight around 10pm to 2am. This convection will be driven by an initial shortwave impulse and moisture within the exit region of the broader scale trough. Convection is strongly favored to be elevated in height atop the nocturnal inversion, with instability feeding into convection via a low level jet and focused warm air advection. While the overall wind shear within the cloud bearing layer is weaker (around 30 kt), it should be enough to give convection at least some chance to organize into clusters with transient mesocyclone features. The elevated nature of convection should also allow sufficient updraft depth into the hail growth zone. Both factors will allow for the hail potentially up to 1-1.5 inches within strongest and/or shielded updrafts tonight in portions of eastern North Dakota. This activity may push into the Red River Valley late tonight into Tuesday morning generally between 3am - 11am. Early morning convection will continue to push east into Minnesota after sunrise Tuesday. Most CAMs and ensemble guidance suggest some window of opportunity for increased heating and moisture increase in the boundary layer by Tuesday midday for portions of Minnesota. This would allow initially elevated convection from the early morning to become more surface based. This along with strong storm relative shear in the lowest 1 km introduces the potential for gusty winds to 60 mph and an isolated tornado risk to accompany continued hail potential. Tornado potential would be more tied to storms that can latch themselves onto a northward advecting warm front during late morning into early afternoon, currently favored to move through the Bemidji to Lake of the Woods region. There is still some uncertainty as to the degree of daytime heating in the morning to early afternoon hours that would drive the wind and tornado potential in Minnesota. Should more daytime heating occur (resulting in temperatures pushing into the mid 70s), gusty wind and tornado potential would increase. Otherwise, hail would be the favored hazard. A fast moving cold front will eventually whisk away moisture to feed storms out of our area by 3pm Tuesday, ending the threat of strong to severe storms. ...Gusty winds with showers/storms Wednesday into Thursday ... Ensemble guidance strongly agrees in a seasonably strong trough/low into Canada by Wednesday and Thursday. When compared to climatological standards, it could rival deepest troughing and/or lowest surface pressure in its region for this time of year (as offered by NAEFS). This increases confidence in a widespread increased wind field over Northern Plains. Increased winds aloft and tightened pressure gradient within the dry slot of this system increases confidence in gusty winds over the Dakotas Wednesday, and extending into Minnesota as well as the Dakotas Thursday. Efficient mixing and continued waves of cold air advection aloft within the dry slot during the day Wednesday and Thursday will help transfer winds over 40 mph, generally out of the northwest. Depending on how deep mixing gets will dictate how high winds can be transferred (which still remains in question). Winds up to 55 mph are still possible should deep mixing occur (20% chance). Most guidance also allows steepening lapse rates amid sufficient moisture to allow for daytime showers and thunderstorms. Thunderstorms may also help transfer higher winds aloft to the ground, strongest of which may push wind gusts to the 50-60 mph range. && .AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/... Issued at 635 PM CDT Mon Jun 3 2024 VFR conditions prevail this evening at all TAF sites. Look for showers and thunderstorms to work into the area during the late evening and overnight hours. MVFR CIGs and visibility are possible at all TAF sites, primarily during periods of moderate rainfall and thunderstorm activity. Current guidance brings this through the area from west to east after 06Z. MVFR conditions could persist through at least midday Tuesday. Winds become westerly following the showers and thunderstorms as a cold front pushes through the area. Wind gusts upwards of 25 knots are possible. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. && $$ UPDATE...Lynch DISCUSSION...CJ AVIATION...Lynch