441
FXUS63 KFGF 171459
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
959 AM CDT Tue Jun 17 2025

.KEY MESSAGES...

- Active pattern keeps thunderstorm chances in the forecast
  Wednesday thru the weekend. Strong to severe storms are
  possible.

&&

.UPDATE...
Issued at 957 AM CDT Tue Jun 17 2025

Fog has diminished as mixing has intensified this morning. A few
isolated weak cumulus has developed in some locations with some
radar returns, but observations do not appear to support
rainfall so precipitation chances remain fairly low. Isolated
showers/storms may develop this afternoon with a bit stronger
instability across southeastern North Dakota, however shear
profiles are not great and forcing is nearly nonexistent so
organized severe convection is not likely.

UPDATE
Issued at 659 AM CDT Tue Jun 17 2025

Check of webcams confirmed the variable nature of the fog and in
most areas ground fog based. SPS out thru 14z looks good.
Otherwise the showers and isold thunder that was skirting the
border has dissipated. So its dry to start the day. 06z models
and latest HRRR confirm a mosty dry day across the area.

&&

.DISCUSSION...
Issued at 332 AM CDT Tue Jun 17 2025

...Synopsis...

Ground fog continues over parts of northweset and west central
Minnesota. It has been moving more out of far NW MN and
spreading south into lakes country in Otter Tail county. Updated
the SPS for areas of dense fog thru 14z. Will continue to
monitor for any advisory.

For today...overall a quiet day. We are with no real short waves
to speak of moving thru. MU CAPE does reach nhear 1500 j/kg in
far southeast ND into South Dakota, so cannot rule out something
forming but looks like any sfc boundaries or short wave
activity is to our south. There have been and still are a few
showers even a t-storm marching east thru Southern Manitoba
overnight and the south edge of a few of these are skirting the
far northern border so will have a small pop for this this
morning into early aftn. There is a short wave in central
Manitoba moving into NW Ontario north of Kenora today, so south
edge of any activity may brush far NW MN/LOW midday or early
aftn. Otherwise temps about normal for this time of year with
highs 75-80 with a northwest wind 10-15 mph.

Light winds tonight...may yield some patchy ground fog again.
But didnt include at this time as didnt want to broadbrush all
areas with patchy fog.

...Thunderstorm chances Wednesday thru the weekend with strong
to severe storms possible...

Mid thru late week into the weekend will see a prolongued period
where strong to locally severe storms are possible. Low level
moisture (dew pts) which have been low up until now will be
enough (low 60s in many areas in the aftn) combined with temps
70s to low 80s to generate daily surface CAPE values over 1000
j/kg. Wednesday will see a sfc-850 mb cold front dropping south
out of Canada and be near the International border by mid aftn.
A pocket of slightly cooler 500 mb temps also moves into
southern Saskatchewan and northwest into central ND in the aftn
Wednesday. CAPE values increase to around 1300-1800 j/kg mid
aftn to early evening. 0-6 km shear right near a southward
moving boundary will be 30-40 kts along the Intl border mid to
late aftn. Indications are sufficient shear and instability
present and no capping to generate scattered t-storms from
southern Saskatchewan thru northern ND into far NW MN mid aftn
Wednesday with this front and move southeast thru the evening.
Sufficient cooler air aloft for some hailers and 50 mph wind
gusts. A borderline severe event, and SPC does have the area in
a marginal risk for this Wed aftn/eve.

Thursday late aftn will see the max instability to our south but
also return northward into central or western ND by Thursday
evening. Thoughts are a few storms are possible Thursday late
aftn in southern fcst area but main chances will be overnight as
scattered storms move east. Southerly 850 mb jet 25 kts may help
sustain a few storms...possibly severe thru the evening into the
overnight over E ND. But set up for nocturnal severe storms is
rather weak and thus agree with marginal risk from SPC.

Friday to Sunday will see upper ridge start to build north with
warmer and more humid airmass move northeast into the area esp
Sat aftn into parts of Sunday. Scattered storms possible Friday
aftn but looks like potential for overnight clusters of t-storms
Friday night as 850 mb jet of 40 kts develops 06z-12z from
eastern SD into central MN with focus of pote ntial MCS in areas
from far SE ND thru west central into central MN.

Saturday a warm and humid day but as ridge builds so does 850 mb
temps temps and soundings suggest stronger capping developing
Saturday aftn and into parts of Sunday ahead of a cold front,
low pressure system. Models differ in timing of low pressure
moving northeast and cold front moving thru Sunday....but ahead
of front sfc CAPE values of 3000 j/kg or higher are forecast and
if capping issues can be overcome then severe storms would be an
outcome. Where this would be depends on front location at the
time. Concensus has front near the Red River with highest
t-storm threat MN late aftn/evening Sunday.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 659 AM CDT Tue Jun 17 2025

Ground fog situation will improve..esp in that 13-14z period in
MN. Otherwise today will see VFR conditions with a west-
northwest wind 8 to 15 kts and scattered mid or high clouds.
Winds go light tonight. May once again have some ground fog, but
after a day of drying out the lowest levels should not be as
last night.

&&

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

&&

$$

UPDATE...Perroux/Riddle
DISCUSSION...Riddle
AVIATION...Riddle