← Previous May 30, 2023 6:12 AM

FXUS63 KFSD 301112

National Weather Service Sioux Falls SD
612 AM CDT Tue May 30 2023

.SHORT TERM...(Today and Tonight)
Issued at 318 AM CDT Tue May 30 2023


1. A persistent unsettled pattern will continue through this week. 
Nearly daily chances for rain, but not everyone may see rain.

2.  Temperatures remain well above normal through the seven day 
forecast, solidifying May 2023 as one of the warmest on record. 

3. Severe weather risks also remain low, but not non-existent 
through the rest of this week. 


THIS MORNING: Convection continues to wane this morning as upper 
troughing moves to the east and the LLJ also veers back to the west. 
A weak MCV across northeastern Nebraska will begin to take a slow
track northeast into Iowa through daybreak. A few isolated 
showers may try to develop with this lobe of energy. Elsewhere, 
temperature remain well above normal, with cloud cover and 
persistent light and mixy winds keeping lows in the 60s. 

TODAY:  Broad mid-lvl subsidence should move in this morning, behind 
the departing trough.  Temperatures will quickly jump this morning 
given the warm start and developing southwesterly winds.  Highs by 
late afternoon likely rise into the upper 80s to even 90s in a few 
areas.   Soundings across the area show a minimally capped 
environment by 4pm, with upwards of 1500 J/KG MLCAPE. However 
there appears to be little in the way of focal points for 
convection to actually develop near. This could certainly be more
of a mesoscale or heating of the day convective development 
situation. Nevertheless, if a storm could form, hail would be the 
most logical risk with a lower chance for brief gusty winds. Will
keep PoPs only in the isolated coverage category. 

TONIGHT:  While uncertainty remains high, another subtle wave is 
likely to eject out of the Rockies later this evening.  This wave 
may enhance the LLJ just enough to provide enough convergence near 
the 800 mb layer to force elevated convection near the Missouri 
River Valley after 10pm. Again, soundings show modest elevated 
instability within the southern half of of the CWA but minimal 
effective shear, so would not rule out marginally severe hail in a 
few storms. Like we've seen over the past 24 hours, rainfall amounts 
will be scattered, but there would be support for very localized 1-
1.5" totals. This convection may try to drift northeast after 
midnight, and it's unknown if there would be a MCV to develop 
that could sustain activity further northeast. 

.LONG TERM...(Wednesday through Monday)
Issued at 318 AM CDT Tue May 30 2023

WEDNESDAY:  A very uncertain forecast is expected for Wednesday. 
Considerable uncertainty remains on what happens with any overnight 
convection.   A few models are suggesting a stronger MCV tracks out 
of Nebraska and into western Minnesota by the afternoon, in which 
case you could see some afternoon redevelopment should the 
atmosphere have enough time to destabilize. Mid-lvl lapse rates 
are still not all that significant, and effective shear remains 
less than 20 knots, so feel the severe weather risk remains low. 
Highs again rise well into the 80s, but if sufficient mid-lvl 
cloud cover remains from overnight convection, could see highs 
lower a bit. 

THURSDAY-SATURDAY: Little has changed in the overall thought process 
for the end of the week.  While the region remains in a rather 
loosely stabilized environment each afternoon,  the greatest 
synoptic lift or focus for convection remains situated in areas 
west and southwest of the James River valley. Further east, 
increasing mid-lvl heights and less focus for convection should 
really limit the overall development of any diurnal thunderstorm 
activity. Have tried to follow more of an ECMWF/GEM forecast as 
opposed to the GFS which is likely overdeveloping diurnal 
convection. Overall activity will be scattered, with not everyone 
seeing rain, despite the continuing PoP. Highs remain well above 
normal and into the 80s. 

SUNDAY-MONDAY:  A mid-lvl vorticity maxima takes a rather unusually 
track through the broad mid-lvl ridge late in the weekend and early 
next week.  Tracking from western Ontario southwest through the 
Great Lakes on Sunday, this system could provide renewed forcing for 
scattered thunderstorms late Sunday and again Monday as a cold front 
moves in from the northeast.  There remains a great deal of 
uncertainty  with the weekend forecast, and I wouldn't cancel any 
plans yet based on the low PoPs that are likely to continue.


.AVIATION...(For the 12Z TAFS through 12Z Wednesday Morning)
Issued at 610 AM CDT Tue May 30 2023

Very scattered high base showers persist this morning, but will
gradually dissipate. Most of Tuesday will feature VFR conditions
with variable high based clouds and occasional cirrus. Winds are
expected to remain out of the southwest through the daytime hours. 

There remains a very low risk of late afternoon convection
developing, but this continues to remain so scattered in nature to
preclude any mention in the TAF.   

Instability increases overnight, with the potential for an ACCAS
field to form late this evening and into the overnight hours. Some
scattered shower and thunderstorm activity may form overnight.