902
FXUS63 KDLH 142111
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
411 PM CDT Wed Aug 14 2024

.KEY MESSAGES...

- Widespread rain and thunderstorms move in late this afternoon
  and evening. Severe weather is not expected.

- Locally heavy rain is expected Thursday, especially along the
  North Shore, which could lead to elevated streamflows and
  ponding of water.

- Cooler temperatures expected Thursday, followed by a warming
  trend through the weekend.

&&

.DISCUSSION...
Issued at 410 PM CDT Wed Aug 14 2024

A period of wet weather will finish up our work week, with rain
and embedded thunder moving in tonight, continuing to spread
across the area on Thursday, then pulling out Thursday night
into Friday. This is a very fall-like system, with mainly
elevated instability. Mid level lapse rates (700-500mb) increase
to around 6.5C/km late tonight and Thursday but only across our
southern third or so of the forecast area. Surface based CAPE
builds to near our area Thursday afternoon and evening, but not
quite into the forecast area. Lift for tonight is going to be
mainly synoptically driven, with a good 850mb moisture plume and
shortwaves moving across the area ahead of a potent upper level
shortwave approaching the area. I have delayed the onset of
precipitation tonight a small amount as things do appear to be a
little slower than the models are currently depicting. Thursday
that surface based CAPE comes into play, and together with
Precipitable Water values up near an inch and three quarters, we
are looking at some fairly significant rainfall totals over
northwest Wisconsin, ranging from a half inch to nearly an inch.
Rainfall for northern MN will be slower, with totals more in
the quarter to three quarters of an inch, with one significant
exception. The strong southeast winds moving across Lake
Superior will interact with our terrain, the warmer surface
waters in the mid 60s and the instability to produce much higher
rainfall rates there, with total amounts ranging from 1 to 3
inches. We have had some upwelling cool the lake surface
temperatures immediately along the North Shore, so it will be
interesting to see if we can detect how that affects the
rainfall patterns tonight into Thursday. The clouds and rainfall
on Thursday will produce a chilly day, with high temps in the
mid 60s to low 70s, but these should rebound into the 70s for
Friday. The upper low remains in our vicinity for Friday, so
have kept chance pops going into Friday, but then they should
pull out of the area with the upper low on Saturday. Highs on
Saturday to warm back up into the 70s and low 80s. While we
currently have a dry forecast Saturday, I would not be surprised
if we need to add in some diurnally driven showers.

After Saturday, we will be in an extended period of northwest
flow aloft, with ridging to our west and troughing over the East
Coast. A ridge of high pressure at the surface should keep our
weather quiet on Sunday, but that slides to our east and we
begin getting shortwaves diving across the forecast area
beginning Monday, which brings precipitation chances back into
the area for at least the first half of the work week. This
should also bring near to above normal temperatures.

&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 1240 PM CDT Wed Aug 14 2024

Expect gradually deteriorating conditions through much of this
TAF period. Rain with some embedded thunder to move into the
terminals after 03z from the southwest, gradually overspreading
all of the terminals by 15z. Ceilings will gradually lower to
MVFR/IFR, accompanied by MVFR visibilities in -SHRA and BR. The
lowest conditions will be found at KDLH, KHIB, KBRD and KHYR.
Southeast winds less than 10 kts will gradually increase to gust
up to 20kts for the southern terminals. At this time LLWS does
not appear likely, but there are stronger winds aloft and we may
need to add it in for Thursday morning.

&&

.MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/...
Issued at 410 PM CDT Wed Aug 14 2024

East to northeast winds on the lake today will gradually
increase tonight into Thursday, before backing into the north
Thursday night into Friday and decreasing. Wind gusts and
building waves should produce hazardous conditions for Small
Craft during the day on Thursday into Thursday night before
diminishing again into Friday. With fairly high confidence in
these conditions, have gone ahead and issued a Small Craft
Advisory for Thursday into Thursday night. Waves will stay built
up with the northerly winds on Friday, but not enough to require
lingering Advisories. Winds become northwest Friday night into
Saturday and diminish to 5 to 15 knots.

For the open water discussion, refer to the NWS Marquette Area
Forecast Discussion at weather.gov/mqt.

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
MN...None.
WI...None.
MARINE...Small Craft Advisory from 1 PM Thursday to 4 AM CDT Friday for
     LSZ140-141.
     Small Craft Advisory from 10 AM Thursday to 4 AM CDT Friday
     for LSZ142-143.
     Small Craft Advisory from 10 AM to 10 PM CDT Thursday for
     LSZ146-147-150.

&&

$$

DISCUSSION...LE
AVIATION...LE
MARINE...LE