Area Forecast Discussion
Issued by NWS Twin Cities, MN

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761 FXUS63 KMPX 180940 AFDMPX Area Forecast Discussion National Weather Service Twin Cities/Chanhassen MN Issued by National Weather Service Duluth MN 440 AM CDT Wed Sep 18 2024 .KEY MESSAGES...
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- Active weather pattern returns, with a marginal risk (Level 1/5) for severe thunderstorms across western MN today. - Slight risk (Level 2/5) for severe weather across eastern MN/western WI Thursday. Large hail and damaging winds are the main threats, however tornado potential does exist. - Additional chance for widespread precipitation during the second half of the weekend, followed by significantly cooler air next week.
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&& .DISCUSSION...
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Issued at 438 AM CDT Wed Sep 18 2024 A transition into a more active weather pattern begins today. Currently temperatures range in the mid to upper 60s and low 70s. A few isolated showers were located over east-central MN but shouldnt amount to much over the next few hours. Low pressure over eastern Montana is progged to continue north- northeastward over the next few days into Saskatchewan and Manitoba. A stationary boundary that extends off of the occluded region of this system will be draped across southwestern MN today. This should act as the lifting mechanism for todays convective environment. Although not as strong as yesterday, a LLJ remains in place while bringing up rich Gulf moisture. Scattered showers and thunderstorms are expected to develop over western MN this afternoon along a gradient of 1400 j/kg and 25-30kts of effective shear. Todays eastern extent of thunderstorm coverage depends depend on how well the forecasted capping inversion can erode to allow for parcel lift. The Storm Prediction Center has issued a marginal risk (level 1 of 5) across the Dakotas and Western MN with primary hazards consisting of damaging wind gusts, and isolated large hail. Any developed precip will gradually dissipate and move east overnight. On Thursday, the first wave of convection has passed. Additional development is expected across central and eastern MN and western WI as the cold front proceeds from west to east. This time, the environment looks to be more conducive for severe weather thus the SPC has issued a slight (Level 2 of 5) risk of severe thunderstorms. CAPE in the mixed layer will range between 2000-3000J/kg, steep lapse rates of 7-8 deg C/km, low-level shear around 35kts which will support the threat of a few discrete supercells capable of producing large hail, damaging wind gusts, and possibly a tornado or two across eastern MN and western WI. As the afternoon/evening progress, these storms may congeal into clusters before dissipating after sunset. As we enter the weekend, Friday looks to be the driest day with mostly clear skies and temperatures near 80 degrees. Saturday into Sunday features another clipper-type wave which will bring back widespread rainfall chances that will last into early next week. As of the latest forecasted QPF from the WPC over the next several days, 1.5 to 2.0 inches are possible especially across southern MN and western WI. At the same time though, a few members of ensemble guidance advertise lesser amounts which does hinder confidence in precip totals. Now in terms of temperatures, forecast highs will decrease into the upper 60s and lows in the lower 50s by early next week. At the same time, it would behoove mentioning that the warmth isnt over just yet. Per the CPC Temperature Outlook for the rest of the month points the northern plains being likely warmer than normal.
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&& .AVIATION /06Z TAFS THROUGH 06Z THURSDAY/... Issued at 234 AM CDT Wed Sep 18 2024 Prevailing VFR conditions continue this TAF period as well as increased southerly winds. Wind gusts are expected to gain in speed after 14z this morning as a cold front approaches from the west. With this occurring, have introduced LLWS at RWF for a few hours prior to dawn. As mentioned in the previous TAF, convection is possible to develop today which is noted in the most recent CAM guidance. However, only include AXN and RWF for precip at this time until a better grasp on timing can be determined. KMSP...Continuing to watch the line of convection off to our west and how that evolves over the next few hours. Confidence is increasing for precip to reach MSP late tonight but wanted to hold off until the 12z TAF issuance. Southerly wind gusts will increase to 20-25kts by mid-morning and persist for much of the daytime hours. /OUTLOOK FOR KMSP/ THU...VFR. SHRA/TSRA likely. Wind SSW 15G25kts. FRI...VFR. Wind WNW 5-10kts. SAT...VFR. Chc SHRA/TSRA. Wind SE 5-10kts. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...None. WI...None. && $$ DISCUSSION...Dunleavy AVIATION...Dunleavy