/Issued 5:33 PM CDT, Wednesday, May 23, 2018
Isolated to Scattered strong to severe thunderstorms are expected over most of the Northland for Thursday and Thursday night — The greatest threat for severe thunderstorms is roughly west of a line from Ely to Aitkin.
Primary Severe Weather Hazards
•Hail (Quarter sized) 1.00 inch diameter
•Wind gusts to 60 mph
Slight Risk for Severe Thunderstorms means that scattered severe thunderstorms are possible. Short-lived and/or not widespread, isolated intense storms possible.
Marginal Risk for Severe Thunderstorms means that isolated severe thunderstorms are possible. Limited in duration/and or coverage and/or intensity.
***Remember that all thunderstorms produce lightning and could also produce flooding***
12z DLHWRF model
The next few images below is what the European and CAMS (Convection Allowing Models) are forecasting for late Thursday afternoon/early evening. Seems to be decent agreement in the models as they suggest that scattered convection will develop sometime Thursday afternoon or early evening generally across northern/central Minnesota, possibly as far east as northern Wisconsin. Just one model showing the bulk of the convection staying mainly north of Minnesota across Ontario Province.
12z European Computer Model from 5.23.2018 — Valid for 7 PM Thursday, May 24.
12z HRW NMMB model from 5.23.2018 — Valid for 7 PM Thursday, May 24.
12z HRW ARW model from 5.23.2018 — Valid for 7 PM Thursday.
12z HRW NSSL model from 5.23.2018 — Valid for 7 PM Thursday.
18z NAM-Nest model from 5.23.2018 — Simulated radar forecast from 1 AM Thursday morning to 1 AM Friday morning. A few rounds of scattered showers and thunderstorms on the way for the Northland beginning early Thursday morning, and lingering into Thursday night.
Weather Tidbits for Duluth, Minnesota
-Through May 23, we’ve had 10 days this month with a high temperature of at least 70 degrees. The average for May is 6 days, record is 19 days set in May of 1988. (Climate Normal Period 1875-2017)
-Through May 23, we’ve had 4 days this month with a high temperature of at least 80 degrees. The average for May is 2 days, record is 8 days set in May of 1980. (Climate Normal Period 1875-2017)
Cumulus clouds surging north across our area today as low level moisture increases while high level clouds move NW-SE across our area, all in all we had partly to mostly sunny skies in the Northland today with another warm day. Highs were in the upper 70s to lower 80s with late afternoon dew points generally in the 50s. A lake breeze has developed this afternoon with a stronger push of cool lake air noted in the Twin Ports area as of 5 PM, this lake breeze also extends up the North Shore and east along the South Shore of Lake Superior.
Partly to mostly cloudy skies through Friday with muggier conditions as dew points away from Lake Superior climb into the 60s on Thursday. Note: Dew points around 60 or a little higher are also expected near Lake Superior on Friday as southwest winds become strong enough to push the marine layer back out over Lake Superior.
Increasing amounts of instability, and the moisture surging north into our area combined with a strengthening southwesterly low level jet of 30 to 40 knots will help to generate some showers and thunderstorms that will impact parts of the Northland later tonight through Thursday morning. Heavy downpours, small hail and occasional lightning will be the main threats from this activity.
The atmosphere is expected to reload with greater instability forecast to develop Thursday afternoon with CAPE 1000-2000 j/kg in parts of the area. A warm front lifting NE out of western Minnesota could be one triggering mechanism for scattered showers and thunderstorms for Thursday and Thursday night. A lake breeze front near Lake Superior could be another area where scattered convection develops Thursday afternoon.
Still not seeing a great deal of wind shear with deep layer shear around or less than 30 knots on Thursday. Mid level winds are expected to increase a bit to around 30 to 35 knots with a low level jet of 25 to 35 knots. Mid level lapse rates don’t look overly impressive either, generally less than 7.0 c/km. So the main message here is that yes we should get some thunderstorms to develop with the amount of instability in the atmosphere and with the lift associated with the approaching warm frontal boundary, but the overall severe risk still looks limited due to the lack of wind shear, however, a few of the storms could still become severe Thursday afternoon or evening especially across north central/east central parts of Minnesota.
A cold front is forecast to pass through the area on Friday with lingering moisture and instability found near and out ahead of this front with a risk for more scattered showers and thunderstorms during the afternoon-evening hours.
Lows tonight will be in the 40s near Lake Superior with 50s and 60s elsewhere. Highs Thursday will be in the 70s and 80s, cooler near Lake Superior. Friday’s highs mainly in the 80s.
Note: Tricky temperature forecast ahead for Duluth and Superior. It does look like the marine layer will hold through Thursday so this should keep temps in the 50s below the hill in Duluth, but Friday a strong enough southwest wind is expected and this should push highs into the 80s. The lake wind could return over the weekend, and if it does expect much cooler temperatures once again in the Twin Ports.
Forecast for Duluth and Superior
.Tonight… Partly to mostly cloudy. Scattered showers and thunderstorms developing mainly after midnight. Low 50 to 55. Wind east to southeast at 10 to 15 mph.
.Thursday… Scattered showers and thunderstorms. Considerable cloudiness. High 72 to 77 but in the 50s near Lake Superior. Wind southeast at 10 to 15 mph.
.Friday… Warm and humid. Partly to mostly cloudy. Showers and thunderstorms possible later in the day. High 81 to 86. Wind southwest at 10 to 20 mph.
Normal Temperatures for May 24
Sunrise Thursday: 5:24 AM CDT
Sunset Thursday: 8:48 PM CDT