354 
FXUS63 KMPX 230001
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
701 PM CDT Sun Aug 22 2021

.UPDATE...
Issued at 631 PM CDT Sun Aug 22 2021

Updated to include 00z aviation discussion below.

&&

.SHORT TERM...(This evening through Monday night)
Issued at 222 PM CDT Sun Aug 22 2021

Mostly sunny skies were evident on satellite imagery this afternoon, 
with some increase in high clouds across the west. Upstream 
convection was occurring along the leading edge of the 850 mb theta-e
gradient (MUCAPE axis) over the eastern Dakotas. This activity will 
push east through the evening, although we may continue to see 
leading edge activity fall apart as it outruns the instability (and 
wait on subsequent convection to develop and advance eastward). 
Severe weather potential looks limited, without a good overlap of 
shear and instability, although a few elevated hailers can't be 
discounted (with wind also a possibility given the large dewpoint 
depressions and potential for evaporative cooling with downdrafts). 
Expect things to transition eastward through the evening, but at this
point coverage looks to remain fairly scattered, so many locations 
will get through tonight without seeing much if any rainfall. Any 
lingering SHRA/TSRA over the south/east portion of the area early 
Monday morning should quickly move away, leaving mostly sunny 
conditions for the balance of the day. The warm frontal boundary will
start to lift northward Monday night, and as warm advection and 
elevated instability increase we should see some SHRA/TSRA develop 
over the southern portion of the area Tuesday evening and lift 
north/east overnight. Will have to see how instability and effective 
shear values pan out, but there is at least some chance for a few 
stronger elevated storms (with some hail potential) over the southern
portion of the area Monday night into early Tuesday morning.

.LONG TERM...(Tuesday through Sunday)
Issued at 222 PM CDT Sun Aug 22 2021

The key message in the long term is increasing confidence in several 
chances for showers and thunderstorms, with the potential for some 
widespread beneficial rain late in the week. 

The chances for showers and thunderstorms will be on the increase  
Tuesday with a shortwave moving through the Dakotas into Central 
Canada in the southwest flow. Thunderstorm coverage looks to increase
into the afternoon, especially north of I-94, where the best 
potential for heavier rains exist. Tuesday afternoon dewpoints will 
rise into the upper 60s and lower 70s and the atmosphere will become 
more unstable with CAPE values rising to 2000-3000 J/kg Tuesday 
afternoon/evening. Bulk shear will be sufficient for storms to 
organize and the SPC has a Marginal Risk in place for most of the 
Forecast area, but the forcing looks rather weak. We will continue to
monitor for the possibility of severe storms Tuesday 
afternoon/evening. Tuesday night the associated cold front will clear
the forecast area and cooler drier air will filter into the forecast
area from the northwest with high temperatures on Wednesday in the 
upper 70s to lower 80s with dewpoints falling into the 50s during the
day under mostly sunny skies.

Confidence is increasing in widespread beneficial rains late in the 
week. We will continue under southwest flow aloft with broad ridging 
over the southern and southeastern CONUS. As short wave energy moves 
through the flow we will have several chances for showers and 
thunderstorms. Moisture transport into the north central US looks to 
become pretty strong as well with a good fetch of Gulf moisture 
advecting north towards the CWA, with PWATs progged to increase to 
around 2 inches, the potential for heavy rains is there. The NBM has 
likely PoPs for parts of the forecast area from late Thursday into 
Saturday. Future model runs should provide better clarity on this 
system. The Climate Prediction Center has the forecast area favored 
for above average precipitation for both the 6-10 day outlook and the
8-14 day outlook which is not something we have seen much of lately.
Stay tuned...

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 631 PM CDT Sun Aug 22 2021

Tricky TAF set due to ongoing precip at 23/00z initialization and
addition convection expected late this evening into the overnight
hours. First round crossing MN currently contains showers with
embedded generic TSRA. Still, have seen some brief reductions in
visibility to 1-2SM. This band looks to push thru eastern MN and
western WI by about 03z-04z. There are more questions with the second
expected push of convection as the short-term models have varying
solutions to timing, with some as early as 04z-05z and going as late
as 09z-11z. Have included TEMPOs to account for best range of timing
at each terminal. Ceilings likely to remain in VFR range but
visibility may easily but briefly drop into MVFR to IFR range.
Conditions improve greatly during the day Monday with solid VFR
conditions and light W to NW winds.

KMSP...First round of precip to move thru the MSP area by about 03z
with potential for brief MVFR visibility. Second bout of precip looks
to come during the Monday early morning hours, between 07z-10z. At
this point, have held conditions in MVFR range but should stronger
storms develop, IFR conditions are certainly viable.

/OUTLOOK FOR KMSP/
Tue...Chance SHRA/TSRA with MVFR-IFR. Wind SE 5-10 kts.
Wed...VFR. Wind N 5-10 kts.
Thu...Chance SHRA/TSRA with MVFR. Wind E 5-10 kts becoming SE 10-15
kts.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
MN...None.
WI...None.
&&

$$

UPDATE...JPC
SHORT TERM...   
LONG TERM...CEO
AVIATION...JPC