577
FXUS63 KFGF 211736
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
1236 PM 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 1236 PM CDT Tue May 21 2024

With the guidance of the RFC issued a few river flood watches
for the southern Red River Valley and a river flood warning for
Fargo with the expected rises in levels from the rain that is
falling today into tomorrow with crests not expected until later
this week. See MPD 296 for further details on short term rain
potential in the area. Wind is still on track to increase this
afternoon with rain overspread the Aberdeen to Fargo to
International falls line.

UPDATE
Issued at 911 AM CDT Tue May 21 2024

Only change to the forecast was expanding the wind advisory into
north central Minnesota based off the latest RAP and a strong
low level jet along the northern edge of the deformation axis
this afternoon. Set west central Minnesota segment to expire
around midnight while areas towards Lake of the Woods will see
high winds continue through the night as the pressure gradient
lingers longer in those areas. Monitoring for the need of a
short fused wind warning if these high winds aloft start making
it to the ground this afternoon.

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 minimal and most reports so far
for the activity aliened 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 HREF 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 HREF support this trend.
HREF 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 /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1236 PM CDT Tue May 21 2024

Rain will continue through the night with little spatial change
aside from a slight pivot as the low track northeast through
Minnesota. Ceilings in areas of rain area widely expect to be
VFR to MVFR though in heavier rain could dip into IFR for areas
such as Bemidji. Strong northerly winds around 2000ft will
create LLWS despite sfc winds near 20-30 kts as well. VIS
generally 3-5 miles in rain though periodically lower.

&&

.FGF WATCHES/WARNINGS/ADVISORIES...
ND...Wind Advisory until 1 AM CDT Wednesday for NDZ039-049-052-053.
MN...Wind Advisory until 1 AM CDT Wednesday for MNZ002-003-022-023-
     027>032-040.
     Wind Advisory until 7 AM CDT Wednesday for MNZ006-009-015>017-
     024.

&&

$$

UPDATE...TT
DISCUSSION...DJR
AVIATION...TT