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Area Forecast Discussion
Issued by NWS Twin Cities, MN
Issued by NWS Twin Cities, MN
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194 FXUS63 KMPX 251726 AFDMPX Area Forecast Discussion National Weather Service Twin Cities/Chanhassen MN 1226 PM CDT Tue Jun 25 2024 .KEY MESSAGES... - Scattered showers are expected tonight, but precip amounts will be light and no severe weather is expected. - Next periods of unsettled weather will be Thursday night into Friday and again Monday into Tuesday next week. && .DISCUSSION... Issued at 319 AM CDT Tue Jun 25 2024 Eventually we got an MCS to form in the extreme instability environment we had on Monday, but it got going over northwest WI and made its way to Green Bay overnight, only impacting the WI portion of our area to the north of I-94. Early this morning, surface analysis shows a surface low near the southwest tail of the MCS that developed. There are a couple of surface frontal boundaries. The main cold front extends southwest from the low back into central Iowa. This has the wind shift over to the northwest, but the drop in dewpoints is an east/west boundary that was back across central MN at 3am. This secondary boundary will continue to sag south through the day and by the afternoon will meet up with the cold front north of I-80 in Iowa. This means that through the morning, our instability will be dropping appreciably. Although we`ll have some lingering instability in south central MN, the redevelopment of thunderstorms this afternoon will be well south of the MPX area. Instead, we`re waiting on the shortwave currently over southern Alberta for our next chance of rain. This will come through central & southern MN tonight and most of the CAMs show some scattered showers associated with it. Although we`ll have this forcing, by then, our moisture will be considerably lower and instability almost non existent. So no severe weather is anticipated and rainfall amounts will be light (less than a quarter of an inch). We get high pressure and dry weather for Wednesday, but will get on the backside of the high on Thursday, with moisture quickly starting to return north ahead of the next shortwave that will pass along the international border Thursday night. The trend in the highest QPF being north and south of the MPX noted in the last couple of AFDs continued with the 00z models overnight. We`re seeing higher QPF with the better forcing up along the international border, with another bullseye near the IA/MO border associated with the higher moisture. Still, we`ll have favorable diffluent flow aloft move through with the trough Thursday night, with widespread showers and storms expected, but the forcing with this system continues to favor any heavy rain issues being isolated at best. By then, all but the lower MN and MS rivers will be on a downward trend and it doesn`t look like the rainfall associated with this system will be heavy enough to reverse those trends. Next weekend still looks spectacular with dry weather and highs in the 70s and lows in the 50s, but with the seasonably strong zonal flow still in place, we won`t have to wait long for our next chance of precip. That comes early next week. Guidance shows a shortwave taking on a more negative tilt as it moves through the upper MS Valley Monday night, so the resultant system will likely be a bit stronger than what we see at the end of the week. We`re still a ways out, but at this point the system early next week would be something to keep an eye on from the severe weather and heavy rain perspective. The flow will still be progressive though, so this system does not look like it will linger into the 4th of July holiday. && .AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/... Issued at 1215 PM CDT Tue Jun 25 2024 There are two main question regarding the TAF period, with the first being how to handle the isolated weak showers present at the start of the period. For now, most of it has remained virga thus kept all the sites dry, however MKT/RWF have the best chance for a brief period of -SHRA which will likely be too weak to impact visibility. The second question is regarding a secondary wave arriving roughly 10z through 18z Wednesday, and how this wave will impact both CIGS and -SHRA potential. Kept all TAF locations dry for now, however brief MVFR or low VFR conditions are possible with a bit of increased forcing for low level clouds. As we see more CAM agreement in subsequent TAF issuance, we will hone in on whether or not to keep things dry. KMSP...As mentioned above, the main consideration for the 18z TAF period is whether or not to introduce SCT/BKN035 clouds from about 13-18z tomorrow, and also whether or not those clouds would include -SHRA. Omitted both for now due to disparity in model guidance, however we could be adding in either or both as we get closer with some better consensus. /OUTLOOK FOR KMSP/ THU...VFR, MVFR/SHRA late. Wind SE 5-10kts. FRI...VFR/MVFR, chc -TSRA. Wind SE 10-15kts. SAT...VFR. Wind NW 10-15kts. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...None. WI...None. && $$ DISCUSSION...MPG AVIATION...TDH