990 
FXUS63 KFGF 240501
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
1201 AM CDT Fri Aug 24 2018

.UPDATE...
Issued at 1152 PM CDT Thu Aug 23 2018

Cancelled the severe thunderstorm watch with the activity waning
across southern ND. Scattered coverage is expected overnight
across the southern half of the CWA. Little changed need for the
overnight into the morning. 

UPDATE Issued at 954 PM CDT Thu Aug 23 2018

Main convective activity continues to be across southern ND and NE
SD. Coverage of showers and thunderstorms is expected to increase
as forcing over spreads the area with the approach of the stacked
low pressure system. Severe chances continue to diminish with the
highest rainfall potential across the southern half of the FA 
through the overnight period.

UPDATE Issued at 631 PM CDT Thu Aug 23 2018

Have issued a severe storms watch for the three southeastern most
counties in ND in effect until 1am. Primary concern will be 
elevated storms capable of hail around an inch in size and
possibly wind gusts to around 60mph. More of a spatial threat is
the potential for heavy rain or localized flooding with Pwats
between 1 and 1.5 inches and MLCAPE ranging from 1000 to 2000 J/kg
in southern ND. 18z HREF probabilities are indicating a 90 
percent chance of more than 2.00 inches in south central ND. This 
indicates the potential or signal is there for these amounts and 
will need to watch radar trends for the actual placement and or 
occurrence.

&&

.SHORT TERM...(This evening through Friday)
Issued at 311 PM CDT Thu Aug 23 2018

Precip strength and amounts will be the main challenge for the
period. 

Water vapor loop shows a fairly vigorous upper low rotating
through eastern MT, which will move into the Dakotas along the
SD/ND border overnight. The main surface low is over western SD
and is expected to move towards the southern RRV tonight. There is
decent agreement on precip moving into our southern counties
tonight, a bit slower than earlier runs. Some showers and elevated
thunderstorms have already been lifting through south central ND,
but CAMs don't really get going with stronger convection until the
22-00Z time frame to our west and into our western counties by
late evening. MU CAPE values could be around 2000 J/kg by that
point, although deep layer bulk shear will be pretty marginal at
around 25 to 30 kts. Cannot rule out some damaging winds as the
storms move into our southern counties, but think the greater
threat will be heavy rain. PWAT values are around 1.5 inches which
is high for this time of year, and CAPE is showing a more skinny
profile better for rain than classic severe weather. Southwestern
counties will have the best chances of seeing an inch or two of 
rain, with lighter amounts further north and our northern border 
not seeing much of anything.

The showers and storms will be ongoing across our southeastern
counties early tomorrow morning, but there should be a bit of a
break during the mid-day period as the overnight convection moves
east. The upper low will be progressing into MN, with the surface
low starting to wash out as it heads east. There is the potential
for convective redevelopment under the upper low tomorrow
afternoon as we get some daytime heating. The bulk of the activity
will be to our south and east by that point, but can't rule out a
few wrap around cells impacting our southeastern counties. Thus,
kept low POPs going in that area into Friday afternoon. The clouds
and precip will help keep the southern counties a bit cooler in
the 70s, with lower 80s in the north. 

.LONG TERM...(Friday night through Thursday)
Issued at 311 PM CDT Thu Aug 23 2018

Fri night-Sat: Fri night will see upper H5 low well east of the 
forecast area as short wave ridging builds overhead. the track of a 

Sat-Sun: Progressive/active pattern is expected. Track of shortwave 
on Sat places organized large scale forcing farther north, but there 
may be enough forcing to help with initiation along/ahead of cold 
front. Current fcsts of 2 to 3 KJ/Kg of CAPE and bulk shear in 
excess of 40 kts would set up a favorable scenario for supercells 
later Sat aftn into the evening. Question mark will be ability to 
overcome a cap and this will depend on the proximity of the frontal 
surface to best instability. Front should clear area early Sun 
morning but then become a quasi-stationary or warm frontal structure 
during the aftn. Another chc for tstms then comes later Sun into 
Sun night.  

Mon and beyond : Progressive pattern with a series of shortwaves 
instigating chances for periodic thunder. Best risk right now looks 
to be later Mon/Mon night with most pronounced wave. This pattern 
also supports heights falling towards mid week with below average 
(low to mid 70s) highs increasing to near average by Thu.  

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1152 PM CDT Thu Aug 23 2018

VCTS possible at FAR and TVF overnight with MVFR CIGs for the
overnight and possibly IFR at BJI. Will see a gradual improvement
tomorrow morning into the afternoon with weak mixing and winds. 


&&

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

$$

UPDATE...JK
SHORT TERM...JR
LONG TERM...WJB
AVIATION...JK