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000
FXUS63 KDLH 231750
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
1250 PM CDT Tue Apr 23 2024

.KEY MESSAGES...

- A Clipper system will bring scattered to widespread rain
  showers today with isolated non-severe thunderstorms possible.
  Snow is likely to mix in with the rain for northern portions
  of the area as cold air filters in.

- Near critical fire weather conditions will be possible on
  Wednesday across much of the Northland as dry air settles over
  the region.

- Back-to-back Colorado Lows are likely to bring widespread rain
  to the Upper Midwest on Friday through this upcoming weekend.

&&

.DISCUSSION...
Issued at 402 AM CDT Tue Apr 23 2024

A 500mb shortwave trough will be propagating a low pressure center
through the upper Great Lakes region today. Conditions early this
morning have been fairly quiet with isolated showers occurring in
the Arrowhead. Patchy fog has also been observed early this morning,
especially around the Iron Range and in the Hayward area. Expect fog
to quickly dissipate shortly after sunrise as diurnal sfc heating
begins and north to northeast winds increase as the low pressure
moves through.

Rain showers will be increasing in areal coverage later this morning
into the afternoon as a band of moisture advects southward from
Ontario along the baroclinic zone of the low pressure. Expect these
showers to sweep through the CWA from north to south this morning
through the afternoon. As sub-freezing 850mb temps filter in on the
backside of the low pressure, snow will likely mix in with the rain
showers today in the Borderlands and in north-central WI.
Measurable snow accumulations are not expected, but a dusting
is still possible (30% chance).

In the spirit of Spring in the Northland, this Clipper is also very
likely to produce isolated thunderstorms late this morning into the
afternoon for southern portions of the CWA. Mid-level lapse rates
will be steep, especially in northwest WI where values of 7-8
degC/km will persist this morning through the afternoon. These lapse
rates will help contribute to the development of a few hundred J/kg
of MLCAPE around midday into the afternoon. Lift provided via a
descending cold front is very likely to produce isolated
thunderstorms today from the I-35 corridor into northwest Wisconsin.
The limiting factor for today`s strong storm potential will be weak
0-6km bulk shear only in the 10-15 kt range. Despite the weak shear,
a strong storm or two capable of producing gusty winds up to 40 mph
will still be possible due to DCAPE values reaching 200-400 J/kg.
Small hail up to pea size may also be possible today.

A period of dry weather is expected to start late this afternoon and
persist through Thursday after the Clipper system moves downstream
of the CWA. Dry conditions are likely on Wednesday as high pressure
builds over northern Ontario. Model soundings show that a descending
layer of mid-level dry air will be mixed to the sfc as a moderately
deep mixing layer develops. Critically-dry min RH values as low as
20-25% will be possible (60% chance) across a large portion of the
CWA on Wednesday. This could lead to near-critical fire weather
conditions on Wednesday depending on how fuels respond to the light
rainfall today.

Looking ahead, a deep trough is very likely to bring back-to-back
Colorado Lows to the Upper Midwest on Friday into Saturday and again
on Sunday evening into Monday. These two low pressure systems will
have the potential to bring decent amounts of rainfall as they both
tap into strong moisture advection from the Gulf of Mexico. Early
indications from the NBM show that 72-hr QPF amounts in excess of 1"
are very likely (70% chance) southwest of the Iron Range on Friday
through the weekend. There is also a low chance (20%) that rainfall
amounts of 2" or more will occur in northwest WI over the same
timeframe. Thunderstorms will be possible (30% chance) on Friday
into the weekend as these rainy Colorado Lows move through, although
it`s too early for specifics on the potential for strong to severe
storms.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1250 PM CDT Tue Apr 23 2024

A cold front remains draped over the southern part of the region
early this afternoon. Isolated showers have developed ahead of
the front from BRD to DLH and points south with some isolated CB
and lightning. The storms are also producing pea-sized hail as
well. Any storm activity looks to be clear of DLH and HYR by
19z. MVFR clouds are seen behind the front, but VFR clearing is
working to the south from the International Border. Expecting
all shower activity and MVFR ceilings to clear by this evening
with VFR conditions prevailing for the remainder of the period.
Northwest winds will gust to around 20 knots through this
evening before becoming light and variable through Wednesday
morning.

&&

.MARINE...
Issued at 402 AM CDT Tue Apr 23 2024

Northeast are expected to increase this morning as an Alberta
Clipper moves through the upper Great Lakes. A Small Craft Advisory
has been issued for all nearshore waters today due to northeast
winds of 15 to 20 knots with gusts up to 30 knots and waves building
in excess of 4 feet. While a Gale Warning was not issued for the
outer Apostle Islands and from Grand Marais to Grand Portage, brief
gales up to 35 knots will be possible late this morning into the
early afternoon.

Expect winds to decrease this evening into tonight as high pressure
begins to build. Elevated wave heights of 3-5 feet will linger a bit
longer in the outer Apostle Islands and from Oak Point to Saxon
Harbor into Wednesday morning before subsiding.

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 until 10 PM CDT this evening for LSZ121-
     140>147.
     Small Craft Advisory until 10 AM CDT Wednesday for LSZ148-150.

&&

$$

DISCUSSION...Unruh
AVIATION...BJH
MARINE...Unruh