767
FXUS63 KFGF 171821
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
121 PM CDT Tue Sep 17 2024

.KEY MESSAGES...

- There is a level 1 out of 5 risk for severe storms Wednesday
  afternoon and evening, including the potential for supercells.

- Additional chance for showers and storms between Saturday and
  Monday, with potentially heavy rain.

&&

.UPDATE...
Issued at 112 PM CDT Tue Sep 17 2024

More cloud cover than previously expected in northwest MN, thus
increased coverage here. Lessening in coverage of clouds here
is anticipated as daytime mixing continues. Additionally, added
some slight chance PoPs this afternoon in northwest MN for the
off chance convective temperatures and subtle mesoscale forcing
helps spark a few showers. This is where capping is weakest and
convective temps are liable to be reached.

UPDATE
Issued at 1002 AM CDT Tue Sep 17 2024

Low stratus and fog lingers north of a stationary front in
northeast North Dakota, and will continue to linger into the
afternoon for some locations.

Otherwise, expecting mostly clear skies with breezy winds out
of the south and continuation of summer-like temperatures well
into the 80s, potentially touching 90 for some in the southern
Red River Valley. Very little evidence suggesting for
thunderstorms this afternoon in our area, with the exception of
near the international border where scattered showers and weak
thunderstorms may exist.

This morning`s high resolution guidance attempts at resolving
the mesoscale environment tomorrow continue to reveal potential
for supercells, of which could include tornadoes in addition to
hail and gusty winds. More details on this to follow in this
afternoon`s AFD Discussion.

UPDATE
Issued at 706 AM CDT Tue Sep 17 2024

The thunderstorms have moved out of NW MN and the narrow line
of showers and t-storms that was developing from SD into MN made
up to near Morris and is moving east and not likely to affect
our area. So updates to pops were made.

&&

.DISCUSSION...
Issued at 358 AM CDT Tue Sep 17 2024

...Synopsis...

Very complex 500 mb pattern to evolve as upper low in Nevada
moves northeast into southeast Saskatchewan by 06z Thu and then
moves northeast followed by a second 500 mb low that moves
southeast from northwest B.C. into southern Manitoba 00z Sun.
The location, track of these upper lows will play a huge role in
t-storm potential, location, timing the next several days.

...Today...

T-storms that have brought heavy rain the past 24 hours to areas
along the Manitoba/North Dakota/Minnesota border area will exit
the area, though western edge of a few storms may linger thru
the day around Lake of the Woods. Also seeing mid level
convection forming in far eastern SD into western MN and this
will track north-northeast and is likely to affect parts of the
far southeast or east areas this morning and maybe into the
aftn. Thus pop wise kept some pops in Lake of the Woods area and
also from Bemidji to Wadena region thru the day. Mostly sunny
elsewhere and warm and humid with highs in the 80s.

...Tonight into Wednesday...

Uncertain about tonight as will start to moisture associated to
the east of the upper low that is moving north well west of the
area. Some support for mid level showers and t-storms thru
tonight. Wednesday will see a band of showers and t-storms that
is behind pushed ahead of the upper low move into E ND and NW MN
during the morning or afternoon, depending on timing of low
movement and location. It is once the band of showers/t-storms
moves out that some heating will occur in an mid/upper level dry
slot, but still sfc dew pts will hold near 70 thru Wed eve. Some
potential for storms to re-fire in this moist airmass that with
temps near 80 will bring MUCAPE 1500-2500 j/kg. Sufficient 0-6
km shear as well 35+ kts in E ND so that isolated supercell
development is possible. Per SPC narrow zone of severe storms
may form given the right conditions with level 1 out of 5 risk
noted for the Red River valley for the late aftn/eve hours.

...Rest of the period...

Thursday will see the upper low move from SE Sask to central
Manitoba and a frontal system push east into Minnesota in the
aftn. Where this front is located will be key to potential
severe t-storm development in a narrow zone just ahead of this
front. At this time it would appear best chc for strong/severe
storm development is in region from Intl Falls to Brainerd.

This weekend into early next week is another headache. Models
have been differing greatly on how to handle potentially another
upper low that would lift north or northeast from the central
Plains into Minnesota. Per extended discussion from WPC low
confidence in any one solution due to varying ideas and changes
day to day from the models and ensembles. Latest idea is for now
to have pops much of the weekend into Monday, but not high as of
now and QPF from WPC on the lower end. But NBM QPF is quite high
and significantly higher than WPC so some heavy rain threat is
indeed possible in the RRV Sun-Mon. NBM has totals 1-2 inches in
a wide area.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 112 PM CDT Tue Sep 17 2024

VFR conditions are forecast at all sites this afternoon through
Wednesday morning. LLWS is forecast to develop at KGFK, KFAR,
KTVF, and KBJI, generally around 35-45kt at 020 kft. Winds will
become gusty out of the south 1-3 hours after sunrise Wednesday,
gusting between 20-30kt, and likely continuing into the day.

There is a chance for scattered showers and thunderstorms
between 03-15Z across the region, 15-18Z for Minnesota, as a
low pressure system approaches. However, confidence wasn`t high
enough in timing of potential impacts from these to include TAFs
for now. Thunderstorms are not anticipated to be severe,
although could still hold gusty erratic winds over 30kt in
addition to lightning.

KTVF still holds an AMD NOT SKED due to AWOS outage at the
site.

&&

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

&&

$$

UPDATE...CJ/Riddle
DISCUSSION...Riddle
AVIATION...CJ