290
FXUS63 KFGF 191808
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
108 PM CDT Sun May 19 2024

.KEY MESSAGES...

- Isolated severe thunderstorms are possible between 8 pm and
  Midnight in far southeast North Dakota. Hail to 1.5 inches is
  the primary threat.

- The probability for greater than 1 inch of rainfall is 50%
  Tuesday into Wednesday across parts of northwest and west
  central Minnesota.

&&

.UPDATE...
Issued at 105 PM CDT Sun May 19 2024

Dry air is sill preventing much of the precipitation aloft from
reaching the ground, save some sprinkles under returns in the
20-30 dbz range.

Adjusted potential hail size for this evening`s possible isolated
severe storms to ping pong balls. This adjustment to slightly
higher hail size was based on the expectation of storms to be
elevated, with a larger portion of updrafts to be within the
hail growth zone amid sufficient shear.

Issued at 1005 AM CDT Sun May 19 2024

Dry air in the lower levels is preventing much of this morning`s
precipitation as seen on radar from reaching the ground. This
dry layer underneath mid to low level ridging will linger in
place over our area through mid afternoon before pushing
northeast away from the area. As such, reduced PoPs in the
forecast this update to match expectation of virga much of the
day. There may be some sprinkles that do make it to the ground,
with better chance (40%) of seeing intermittent light rain in
the southern Valley into west-central MN.

Still expecting the chance for deeper convection from the
central Dakotas to move east into our area, first in southeast
ND, late afternoon and evening.

Issued at 700 AM CDT Sun May 19 2024

Light returns associated with high based showers are spreading
into the southern Red River Valley matching up with earlier
trends in CAMs/guidance. There is some lightning activity in SD,
but confidence is low this more unstable air mass will make it
up this far north during the early morning hours with this
current wave. Otherwise, forecast for the rest of the day is
still on track per earlier discussion.


&&

.DISCUSSION...
Issued at 351 AM CDT Sun May 19 2024

Southwest flow is beginning to build into the central/Northern
Plains in response to building mid/upper level troughing over the
Pacific Northwest. This trough is expected to continue to amplify
and deepen southwest flow over the plains and a series of waves
ejecting through this flow (along with increase moisture advection)
will keep periodic rain/thunderstorm chances in our forecast area,
with confidence reasonably high through mid week despite some
variations with timing/evolution of some of these waves. By late
next week this trough breaks down and a more zonal/progressive flow
featuring lowered heights aloft as the northern storm track shifts
south. There is lower confidence in evolution of any waves and low
confidence in any potential impacts). Temperature trends will be
seasonably mild in the mid 60s to lower 70s the next several days,
but below average temperatures (50s/lower 60s) become favored during
the later periods.

Severe risk today: Several impulses bring scattered showers/isolated
thunderstorms during the day, with a more organized mid level
shortwave passing south of our region late this afternoon and
evening. THe norther extent of this will feature a near by
baroclinic zone where southerly flow will help increase BL Tds. Mid
level lapse rates are shown to steepen enough to support an axis of
elevated instability near our forecast area by late
afternoon/evening. Consensus is favoring better instability farther
west and southwest based on the surface pattern and with increasing
low/mid clouds resolved by all current guidance there isn`t
currently a risk for surface based parcels (elevated parcels will
support hail/wind as primary threats if there is any threat). As
current guidance shows lowered instability towards our area (around
1000 J/KG max MUCAPE) confidence is lowered in any strong/severe
storms. There is still high shear (40-60kt effective shear) and some
CAMs try to hold some organized/embedded cells together as they
approach far southeast ND during the 6pm-10pm period. 0-3km shear is
in the 30-35 kt range, so while profiles are not that supportive of
a wind risk (DCAPE less than 800 J/KG) there is still a low threat
for downburst winds if a cell takes on brief/orthogonal linear
structures (as some CAMs show).

Midweek rainfall (Tuesday-Wednesday): There is increased consensus
on a stronger negatively tilted mid level trough passage through SW
flow over our eastern forecast area, with the potential for
organized/deformation and widespread moderate to localized heavy
rainfall. Excessive rainfall isn`t expected as any higher totals
(1-3") would fall over a longer duration. Impacts to possibly
delay any planting operations are possible though across
northwest MN/west central MN as 24hr probs for at least 0.5" is
near 80% and 1"+ is 50%.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1255 PM CDT Sun May 19 2024

VFR conditions are forecast through 00Z, followed by lowering
ceilings in the MVFR to IFR categories between 00Z to 12Z. Most
likely to be impacted with IFR ceilings is KBJI between 08-18Z,
with a 20% chance of LIFR ceilings in the 08-15Z timeframe.

Virga can be anticipated this afternoon across the area before
00Z. The chance for scattered showers and thunderstorms
increases between 00Z-06Z. The chance for thunderstorms remains
low enough to omit from TAFs for now, although sites like KFAR
hold highest chance (40%) of seeing -TSRA between 03Z-05Z. Some
storms may be strong bringing lightning and hail within
southeast North Dakota within this timeframe.

Winds will be light under 12kt, shifting from the southwest to
southeast, then turning variable after 06Z.

&&

.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.

&&

$$

UPDATE...CJ/DJR
DISCUSSION...DJR
AVIATION...CJ