Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 202011

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
311 PM CDT Wed Jun 20 2018

.SHORT TERM...(This evening through Thursday)
Issued at 310 PM CDT Wed Jun 20 2018

Main focus of the short term continues to obviously be the heavy
rainfall potential with the occluded low pressure system just to our
southwest.  The model guidance today came in with a northward shift
in the qpf bullseye which is still focused across far northern Iowa.
 However, the risk has increased for significant rainfall through
tonight along the I-90 corridor due to this northward shift.
Precipitable water values of over 1.7 inches with ample lift but
limited CAPE will lead to efficient rainfall rates. On top of that,
the very slow moving nature of this system is key as the I-90
corridor will likely see steady rain nearly all night, leading to
the potential for several inches of rain.

The guidance today was in good agreement with the placement of the
heaviest rain.  A blend of the hi-res guidance indicates a
realistic potential for 2-4" of rainfall near Martin and
Faribault counties, with localized higher amounts possible. Still
think the heavies will remain south of the Iowa state line, but
did include these two counties in a Flash Flood Watch through
tomorrow morning. This is definitely a long duration rainfall
event for far southern Minnesota. As we head into tomorrow, the
occluded system will be very slowly working east-southeast with
time and lingering showers will likely last through the day across
southern MN.

.LONG TERM...(Thursday night through Wednesday)
Issued at 310 PM CDT Wed Jun 20 2018

The upper-level low parked over the mid-Missouri valley will finally
begin to move east Thursday night, with showers coming to an end
across far-southern Minnesota. As the low departs a brief period of
high pressure moves in with dry & pleasant weather expected Friday
into Saturday afternoon.

Over the weekend, various weak perturbations in the upper level flow
will pass overhead which will provide enough support to generate at
least slight chances for scattered thunderstorms Saturday & Sunday.
The pattern looks to get more active Monday into mid-week as another
upper-level wave comes off the northern Rockies. Large scale
southerly flow from a surface high over the eastern seaboard will
allow our dewpoints to increase into the upper 60s by Wednesday.
CAPE values look to be greater than 1000-2000 J/kg & PW values
approach 1.5" so the potential for severe weather & flooding will
have to be monitored. Models differ in timing of the upper-level
wave over our area so have capped PoPs in the 50% range mid-week.

Temperatures into next week will be relatively consistent &
seasonable, with highs around 80 & overnight lows around 60.


.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1245 PM CDT Wed Jun 20 2018

A large occluding low pressure system centered over far western
Iowa/eastern Nebraska will slowly evolve eastward through the
period, mainly impacting far southern Minnesota with rain and MVFR
cigs. Of the TAF sites, MKT will likely be the only site to see
real impacts from this, with ceilings still around OVC012 and
showing little improvement. Showers are lifting north this
afternoon and will continue to approach MKT with rain expected
later today. The remainder of the TAF sites should mainly be VFR
with the edge of the low clouds and the majority of the rain
remaining just to the south. The system is a little too close for
comfort though so be aware MVFR cigs and rain will be just to our
south and a slight shift north would lead to deteriorating

KMSP...Still expect MSP to remain dry, but the latest model
guidance did shift the precip northward and it bears watching.
High confidence that this afternoon and evening will be dry and
VFR. Early tomorrow is more in question with a slight chance of
-shra. Left it out of the TAF for now as confidence in that
 occurring is low.

Fri...VFR. Wind E 5 kts.
Sat...VFR. Chc -TSRA. Wind NW 5 kts.
Sun...VFR. Wind NE 5-10 kts.


MN...Flash Flood Watch through Thursday morning for MNZ091-092.



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