Sunrise 5:42 AM   Sunset 9:04 PM Moonrise 6:22 PM   Moonset 3:24 AM

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FXUS63 KFGF 211153 AFDFGF

Area Forecast Discussion National Weather Service Grand Forks ND 653 AM CDT Tue May 21 2024

KEY MESSAGES

- Northerly winds gusting to 50 mph are expected across the southern Red River Valley this afternoon and evening. There is a 20 percent chance for gusts around 60 mph.

- Heavy rainfall may lead to localized overland flooding this afternoon into Wednesday for the Southern Red River Valley into Minnesota.

- Depending on the extent of heavy rain, river flooding could start as early as Thursday for some areas along the southern Red River basin.

UPDATE
Issued at 652 AM CDT Tue May 21 2024

The initial areas of rain associated with the approaching system is spreading into our south matching up with timing from earlier. Lighting activity is mimnimal and most reports so far for the activity alighned with our region are in the light to moderate range (again within expectations). So far forecast appears to be on track.



DISCUSSION
Issued at 416 AM CDT Tue May 21 2024

A strong Colorado low type system is developing currently over eastern Colorado with SW flow increasing deep moisture advection into the Northern Plains this morning. This system will be responsible for wind, rain, and potential excessive rain impacts today into Wednesday. As this system transitions east an active quasi-zonal pattern with additional organized mid/upper lows moving out of the Pacific NW or Canadian Prairies will remain in place over the next 7 days with additional rain events possible but lower confidence/predictability regarding impacts at this time.

Regarding Winds today: As the surface low deepens and moves north, strong gradient will support increased winds and while mix layers are deep, model mixed layer winds show maximum values in the 40- 47kt range in the southern Red River Valley this afternoon into the early evening and this is a consistent signal between current deterministic models. A little better mixing 50kt (warning impact)
winds may develop and NBM probs highlight around a 20% probability for this in the far southern Red River Valley.

Regarding rain/flooding potential: There is strong consensus for the 700 mb low track to support a prolonged period of deformation lining up from the southern Red River Valley into west central MN. Main instability axis is well to the south (MUCAPE may only be around 100- 200 J/KG at the most) and HRRR shows any signal for higher rates (1"+/hr) to the southeast. Still, forcing and instability (as it is)
will be enough for periods of light to moderate rain and occasional convective pocket of brief heavier rain to track over a lot of our area. Heaviest rain axis is more likely to linger longer in MN than in the southern RRV, and probs from NBM and HRRR support this trend.
HRRR PMM would indicate the heaviest rain axis supporting 2-4" over 6hr periods, though higher amounts are still possible especially if considering the length of the event. Adjusted FFG would require almost double those values for more than localized runoff and as rates are not favorable for actual flash flooding. Localized overland/areal type flooding would be favored (ponding/more gradual runoff). Depending on the extent of the higher totals riverine flooding is possible with a delay in responses (responses on rivers by Thursday from this rain event).

River probabilities relayed from RFC coordination on Mon day shift:

Minor Flooding: 20-40% Moderate Flooding: 10-30% Major Flooding: Less than 10%

For the Red River at Fargo (FGON8) specifically, one can add 10-30% to Minor and Moderate values, with chance for Major around 10%.

AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/
Issued at 653 AM CDT Tue May 21 2024

Aviation impacts will increase across southeast ND and northwest MN through the day as rain showers and eventually MVFR stratus overspread those regions. Northeast ND should remain VFR through the TAF period. Winds increase as this low pressure system moves through the region, with the strongest winds in southeast ND and parts of west central MN where gusts around 40kt are possible this afternoon and evening. Low level wind shear (around 50kt) will be possible at KBJI late in the TAF period.

FGF WATCHES/WARNINGS/ADVISORIES
ND...Wind Advisory from noon today to 11 PM CDT this evening for NDZ039-049-052-053.
MN...Wind Advisory from noon today to 11 PM CDT this evening for MNZ003-029-030-040.

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