Area Forecast Discussion
Issued by NWS Twin Cities, MN
Issued by NWS Twin Cities, MN
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850 FXUS63 KMPX 041757 AFDMPX Area Forecast Discussion National Weather Service Twin Cities/Chanhassen MN 1257 PM CDT Sat May 4 2024 .KEY MESSAGES... - Rain showers this morning. Rainfall amounts of a tenth to a quarter of an inch expected. - Another round of showers and thunderstorms likely Monday night into Tuesday morning. && .DISCUSSION... Issued at 334 AM CDT Sat May 4 2024 Rain showers continue to slowly spread eastwards out of western Minnesota overnight. The MCS over Nebraska has taken on a more easterly track into Iowa, meaning the trend towards heavier precipitation & possible thunderstorms over southern Minnesota no longer is expected. Most locations will see between a tenth to a quarter inch of rain as the band of showers north of the convective complex migrates east across the area. A few hours of rain is expected, with the rain ending by mid-morning across central MN, late morning/early afternoon for eastern Minnesota, & by mid-afternoon for western Wisconsin. Skies will slowly clear out after the rain, so a sunny afternoon or early evening still looks salvageable for areas east of the St. Croix River. The rain and clouds will keep temperatures cool this afternoon, generally around 60 degrees. Drier, sunny, & warm weather is expected Sunday into Monday as high pressure moves over the region. High temperatures around low 70 are likely, potentially warming into the mid to upper 70s Monday with some compressional warming possible ahead of an approaching front. Winds will be relatively light on Sunday with the high overhead, but increase through the day on Monday as the pressure gradient increases ahead of the approaching front. Southeasterly winds could gust as high as 40-50 mph late Monday afternoon & evening across western Minnesota, in response to the surface low deepening into the low 980s mb over the northern Plains. A band of showers an thunderstorms is expected to develop along the front extending ahead of this deepening surface low, with ensemble guidance showing a very high likelihood (>90%) of precipitation occurring across the entire area. Strong dynamics will be present with this system with surface winds gusting to 40-50 mph along of the front & bulk shear values of 50-60 kts. However, instability will be lacking this far north across the Dakotas & western Minnesota, further exacerbated by the fact that the model consensus brings the front & thunderstorms through the area late Monday night & overnight into Tuesday morning. The threat for damaging winds isn`t negligible given the strong background surface winds, but for now the severe threat looks to mainly develop across the central Plains & mid- Mississippi valley. Ensemble guidance generally shows rainfall amounts between 0.5-1" across the entire area, mainly owing to the forecast quick progression of the storms across the area. Amounts over an inch are still possible if the system slows somewhat between now & Monday night. In general, thunderstorms & another soaking rain look a like a sure bet Monday night. Beyond Tuesday, the upper-air pattern remains active as the upper-level low responsible for the Monday-Tuesday system stalls out, & potential becomes cutoff over the Great Lakes. A number of weak disturbances pivot around this broad area of low pressure as a result, meaning multiple chances for generally light rain through the end of the week. Model consensus in timing any of these disturbances is low so a generic broad ~30% chance for rain exists pretty much exists for Wed-Fri. Temperatures will be cooler as well with lower heights over the region, with daytime highs generally in the low 60s. The upper- level low finally exits the Great Lakes region over the weekend, with likely a return to drier & more seasonable weather. && .AVIATION /18Z TAFS THROUGH 18Z SUNDAY/... Issued at 1244 PM CDT Sat May 4 2024 Main swath of rain has shifted off to the east, thus outside of potentially a brief lingering sprinkle/shower in far eastern MN into western WI, no additional precipitation is expected this duration. Visible satellite imagery shows the stratus deck continuing to slide eastward, with it still holding east of a line from Princeton to Mankato, while points west are breaking out with fair wx cumulus clouds. One by one, TAF sites will have their ceilings erode away to VFR cumulus this afternoon, followed by clearing overnight through Sunday. Breezy NW winds at initialization will diminish this evening then go light/variable overnight through daybreak and into late Sunday morning. For much of central-eastern MN into western WI, a period of pre-dawn MVFR-worthy ground fog is looking likely at the TAF sites early Sunday morning but this should be of limited impact. KMSP...Low/MVFR stratus looks to hold on through about 20z, with VFR conditions thereafter. Skies will clear out this evening through Sunday morning while winds continue to diminish. There is a decent chance of moisture trapped under the nightly inversion being manifested as ground fog Sunday morning so have included mention of it in this TAF. /OUTLOOK FOR KMSP/ MON...VFR. MVFR/-TSRA likely late. Wind SE 20G35 kts. TUE...VFR. Chance MVFR/-TSRA. Wind SW 15G25 kts. WED...VFR. Chance MVFR/-RA. Wind 10-15kts. && .HYDROLOGY... Issued at 236 PM CDT Thu May 2 2024 The continued wet pattern for the next week will also continue to cause rising rivers over the entire HSA. Soils have started to become saturated at upper levels, so runoff is increasing with each rain event, though the onset of the growing season does help along with recovery days between rain events. All told, most tributaries and mainstem rivers will continue a slow rise for at least the next week, with some in the Minnesota and Crow river basins approaching minor flood stage by early next week (Minnesota at Morton already there). && .MPX WATCHES/WARNINGS/ADVISORIES... MN...None. WI...None. && $$ DISCUSSION... AVIATION...JPC HYDROLOGY...CCS