Area Forecast Discussion
Issued by NWS Twin Cities, MN
Issued by NWS Twin Cities, MN
Versions:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
391 FXUS63 KMPX 281133 AFDMPX Area Forecast Discussion National Weather Service Twin Cities/Chanhassen MN 633 AM CDT Sun Apr 28 2024 .KEY MESSAGES... - Cool and rainy to close the weekend. Another half inch to inch of rain expected, with the highest amounts in western Minnesota. - Showers & thunderstorms return on Tuesday, with a few strong to severe storms possible. - Unsettled pattern to swing another chance for rain Thursday into Friday. Temperatures will remain seasonal through the work week. && .DISCUSSION... Issued at 305 AM CDT Sun Apr 28 2024 All is quiet across the region early this morning, with temperatures holding steady in the mid 40s to low 50s due to light northeast winds and a cloudy skies. A well defined upper trough is driving widespread convection for locations across the central and southern Plains, as well as portions of the Midwest. Strong surface low pressure located in central Nebraska will continue to lift northeast towards southern Minnesota today, which will bring a broad region of ascent and a expansive precipitation shield into the Upper Midwest. The surface low continues to track slower than guidance had advertised over the last few days, such that the arrival time of higher PoPs has once again featured a slight delay. Also of note, high temperatures were knocked down for this afternoon and Monday, due to the expected cloudy, cool, and rainy weather conditions. Early morning ACARS data from MSP reveals a stratus layer around 3kft, with notable mid-level dry air just above. This dry layer will have to saturate before rain can begin and forecast soundings show this occurring around mid-morning, likely in the form of scattered showers. Greater coverage of rain (and higher rainfall rates) will arrive this afternoon as the surface low draws near. The surface low is forecast to occlude over southern Minnesota, with a deformation axis setting up across western Minnesota. Not much change in expected QPF, with a half inch to inch forecast for most of the area, however the aforementioned deformation axis may result in locally higher rainfall amounts (closer to 1.5") across western Minnesota. We won`t rule out an isolated rumble of thunder here or there, however the risk for strong thunderstorms appears low. A Marginal Risk remains in place across southern Minnesota where the best chance for an isolated strong storm or two will be possible, owing to a few hundred joules of MUCAPE per the 00z HREF. The heaviest rain will end before midnight, however some showers may linger through the first part of Monday. Cooler flow out of the northwest in tandem with cloudy skies will work to keep highs in the mid 40s to low 50s Monday afternoon. Our attention then turns to Tuesday, where warmer temepratures and strong to severe thunderstorm chances make a return to the forecast. A thermal ridge will move over the region heading into Tuesday morning, with warm advection forecast to increase out of the southwest in response. Highs are forecast to surge into the 60s and low 70s for highs Tuesday afternoon. The eastward advance of the thermal ridge will be driven by a potent shortwave trough that is progged to dig through the Upper Midwest Tuesday afternoon and evening. The shortwave trough will become negatively tilted by Tuesday afternoon, which will increase lift and promote the development of rain and thunderstorms across much of the area. The environment appears conditionally supportive of strong thunderstorms across southern Minnesota, given up to 500 J/kg of MLCAPE, ~40+ knots of 0-6km bulk shear, and veering in the low-level hodograph captured on forecast soundings. Limiting factors for a more extensive severe weather threat will be poor moisture return (Guidance says you`ll have to go to central/southern Iowa to find 60s dew points!) and stable lapse rates aloft (6.0-6.5 deg/km). SPC`s new Day 3 outlook highlights much of southern Minnesota in a Marginal Risk for severe weather. The latest PoPs from the NBM highlight a 70-80% chance for precipitation across western Minnesota by midday, followed by an eastward push of the likely PoPs through Minnesota and western Wisconsin by the evening hours. Sure, the recent pattern has been active, but why stop now? It seems Mother Nature would tend to agree. Another shortwave will rotate through the northern CONUS Thursday, which will bring the reintroduction of PoPs for those living in Minnesota and western Wisconsin. Temperatures will remain mild ahead of the approach of Thursday`s shortwave (60s/low 70s), however the passage of this system will knock highs back down into the 50s to close the work week and open next weekend. The unsettled extended period will feature yet another chance for rain showers this weekend, before a more defined upper-trough comes ashore in the Pacific Northwest and "kicks" the current revolving door of weather systems every 2-3 days off to the east. While the first weekend of May appears to trending cooler, there is some hope for a revival of warmer Spring air heading into the second week of the month. && .AVIATION /12Z TAFS THROUGH 12Z MONDAY/... Issued at 620 AM CDT Sun Apr 28 2024 Only change really made to the going TAFs was to delay the start of rain by an hour or two. Otherwise our TAFs looked to cover expected trends well with our MVFR cigs giving way to IFR cigs as steadier rain arrives this afternoon. Low cigs will continue through tonight with the surface low moving through MN. Right near the center of the low, we may see IFR vis in -DZ as well, but we have time to try and pin any of that down. Kept TS out of the TAFs, some TS activity is possible this evening as the surface low moves up into southern MN, but those chances look low enough to keep TS out of the TAFs for now. KMSP...Surface low tonight looks to take a very similar path just to the west of MSP as we saw with the low pressure on Friday night. The HRRR keeps pushing the -RA start time back and now doesn`t have it breaking out at MSP until 20z. Think we`ll see some showery activity though prior to the steady rain arriving, so only pushed the start time for mentioning precip back an hour. /OUTLOOK FOR KMSP/ MON...MVFR/-SHRA early, then VFR. Wind WSW 15G25 kts. TUE...VFR. MVFR/-TSRA likely aftn/evng. Wind SE 10-15G30 kts. WED...VFR. SW 5-10 kts. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...None. WI...None. && $$ DISCUSSION...Strus AVIATION...MPG