Area Forecast Discussion
Issued by NWS Duluth, MN
Issued by NWS Duluth, 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
44
041 FXUS63 KDLH 182057 AFDDLH Area Forecast Discussion National Weather Service Duluth MN 357 PM CDT Tue Jun 18 2024 .KEY MESSAGES... - Strong to severe thunderstorms are likely to develop this afternoon and evening. Hazards include damaging winds to 70 mph, large hail up to 1.75", locally heavy rainfall possible leading to flash flooding, and a chance for a tornado or two. - Much of the Northland is under a Slight Risk (2 out of 5) for severe weather today. Storms will be beginning early this afternoon today and move east-southeast through the afternoon and evening. - Cooler temps and high pressure on Wednesday will lead to quiet conditions. Additional shower and thunderstorm chances likely later this weekend into this upcoming weekend. && .DISCUSSION... Issued at 155 PM CDT Tue Jun 18 2024 This afternoon and evening: Today is a fairly complex setup, which will be leading to a conditional threat for severe weather development this afternoon and evening. 15z surface analysis shows a stationary front located over northwestern Minnesota, which will be the main source of lift this afternoon and evening. A negatively-tilted shortwave trough will be propagating through the northern Great Plains this afternoon and evening, providing the necessary synoptic forcing to transition the stationary front into a cold front that will through the CWA. Ahead of this approaching cold front, a warm front draped across the CWA from south of Brainerd, up to the Iron Range, and then south towards the Twin Ports has been firing off scattered to widespread showers and storms in portions of northeast and north-central Minnesota. One of the most impressive ingredients with today`s severe weather threat is the high amounts of precipitable water. The 14z sounding from INL recorded a PWAT of 1.41", which comfortably places it above the 90th percentile of climatology. Dewpoints have already been rising into the low 70s across southern portions of the CWA early this afternoon. Strong southerly flow provided via a LLJ of 35-40 knots will help advect this deep moisture northward. Despite persistent cloud cover this morning, this moisture and warm air advection provided via the LLJ is expected to help destabilize the atmosphere by this afternoon across the majority of the CWA. MLCAPE by mid to late this afternoon will be building around the 1500-2500 J/kg range. Favorable 0-6km bulk shear of 35-45 knots will help provide organization to the expected convection later this afternoon. All severe weather hazards will be possible this afternoon, including damaging winds up to 70 mph, large hail up to 1.75", locally heavy rainfall leading to flooding, and a tornado or two. The tornado potential this afternoon will be contingent on the amount of discrete convection that can form before storm mode switches more linear as the storms move into northwest Wisconsin. High amounts of 0-1km SRH of 200+ m2/s2 present around and south of the Iron Range and low LCL heights continuing through the afternoon supports the potential for a tornado or two late this afternoon into early this evening. As storm mode switches to more linear this evening, which is supported by the majority of CAMs, tornado concern will transition towards possible QLCS tornados in the Arrowhead and Douglas, Burnett, and Washburn early this evening. However, this is much less of a concern compared to the discrete supercell potential late this afternoon into the early evening. One other primary concern with today into tonight`s storms is the flash flooding potential. Antecedent soil moistures are already saturated across much of the NE MN portion of the CWA, where 1-3" of rain has fallen over the past 24 hours. Additional rainfall amounts of 2-6" will be possible this afternoon into tonight as upscale growth leading to training storms occur along the warm front mainly along and north of U.S. 2 in MN. Since there has been an increasing trend in QPF in the 12z runs, the Flood Watch has been expanded to include the inland portions of Lake and Cook County. The severe weather potential is expected to decrease this evening as the storms propagate farther east into northwest Wisconsin, where instability will be decreasing and shear will be less favorable. Wednesday through Wednesday night: After the cold front sweeps through tonight into tomorrow morning, quieter weather will move in on Wednesday as high pressure builds over the region. Temperatures tomorrow will be noticeably cooler with highs in the low to mid 70s for most. Thursday through the weekend: The pattern resumes its active behavior with southwest flow bringing another large system through the region starting Thursday and Friday with a warm front before a stronger low moves through for Saturday into Sunday. Ample moisture will move into the region from the Gulf of Mexico with PWATs rising to near the top of climatology once again. Instability continues to look anemic during much of this time period with the heavy rainfall threat being more of a concern. NBM probabilities have not changed much with chances of an inch or more slightly increasing to around 60 to 80% and chances for 2 inches or more at 30 to 50%. Given the rainfall currently occurring, many areas will be primed to be mainly runoff with saturated ground and already high rivers and streams. && .AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/... Issued at 1230 PM CDT Tue Jun 18 2024 A period of severe thunderstorms is expected across most of north-central and northeast Minnesota from 20Z Tuesday to 02Z Wednesday and produces hail to the size of a ping pong ball, heavy rainfall producing visibility down to 1SM and erratic wind gusts to 35 knots. The line of strong to severe thunderstorms moves into northwest Wisconsin after 00Z into 02Z, but weakens after 03Z as it treks eastward. IFR ceilings are very likely overnight and into early Wednesday morning through 12Z. Northwest winds and clearing skies accompany the post-cold front environment tomorrow 12-18Z. && .MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/... Issued at 356 PM CDT Tue Jun 18 2024 Periods of showers and storms are expected over western Lake Superior this afternoon and evening. Strong to severe storms will be possible this afternoon and evening with wind gusts over 40 knots along with hail over 1 inch in diameter possible. A cold front will work across the western part of the lake this evening with storms expected to end following the passage of the front. Winds outside of any storms this evening ahead of the cold front will be southerly at 5 to 15 knots with gusts to 20 to 25 knots, highest near the Twin Ports. These winds will also generate waves of 2 to 5 feet along the North Shore. Small Craft Advisories remain in effect for all of the nearshore waters for today into tonight. Behind the cold front, winds will become westerly tonight into Wednesday, gradually diminishing to 15 knots or less by mid morning Wednesday. High pressure moves in Wednesday. For the open water discussion, refer to the NWS Marquette Area Forecast Discussion at weather.gov/mqt. && .DLH WATCHES/WARNINGS/ADVISORIES... MN...Flood Watch through Wednesday morning for MNZ010>012-018-019- 025-026. WI...None. MARINE...Small Craft Advisory until 1 AM CDT Wednesday for LSZ121- 144>148-150. Small Craft Advisory from 9 PM this evening to 1 AM CDT Wednesday for LSZ140>143. && $$ DISCUSSION...Unruh AVIATION...NLy MARINE...LE