Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 191936
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
336 PM EDT Thu May 19 2022

.SHORT TERM...(Rest of Today)
Issued at 211 PM EDT THU MAY 19 2022

Diurnal cu has set up across the area today as weak WAA continues
into Upper MI ahead of an approaching warm front. With diurnal
heating limited over the west, temps have not warmed as much as
previously thought. Satellite imagery and local observation data
show that a lake breeze has moved in from the Great Lakes this
afternoon, dropping temps in the marine influenced air (as can be
seen with the temp trends at our office). Expect the lake breeze to
continue into the late afternoon hours, beginning to end by evening
time as the solar radiation from the sun starts to subside.

CAM models show rain showers entering into the U.P. through the WI
border late this afternoon via the warm front. While model guidance
shows abundant turning of the winds with height along the front via
a low-level jet, thunderstorm activity appears to be quite limited,
as model guidance has significantly reduced the CAPE available for
convective development late this afternoon since yesterday; guidance
shows the warm front coming in a little slower than previously
predicted, dropping even the MUCAPEs to just a couple hundred J/kg.
Therefore, severe wx does not look likely at all late this
afternoon.

.LONG TERM...(Tonight through Thursday)
Issued at 335 PM EDT THU MAY 19 2022

Longwave trough/ridge pattern over North America with the elongated
trough axis over the Northern Plains will start off the forecast
period this evening. As we progress through the weekend, trough axis
will shift into the Upper Great Lakes, followed by quasi-zonal flow
trying to establish itself across the northern tier of CONUS next
week. There`s a couple shortwaves embedded in this pattern and a
closed low looks to develop somewhere over the Central Plains or
Ohio River Valley, which will give the region a couple shots for
rain. Airmass associated with each looks to swing between above
normal early on, followed by a cooler airmass for the weekend
bringing us below or near-normal for a little while, then trending
upward to above normal again by mid-week.

Starting off tonight, precip associated with weak warm front will
continue progressing through the region, with much of the structure
and nature of the storms depending on upstream conditions. At the
moment, there doesn`t appear to be much in the form of instability,
with all but the NAM suggesting MLCAPE below 500j/kg. 0-6km shear
though looks to clock in between 50-70ish kts, so I suspect if an
elevated core is able to get going, the shear should be able to
support some strong thunderstorms capable of producing some hail or
strong winds. Weak cold front will follow by early Friday morning,
with a second wave of showers and perhaps a thunderstorm progressing
west to east late tonight into Friday morning.

As the surface low pulls northeast of the region during the day
Friday, elongated trough axis aloft will shift will slowly drift into
the forecast area. Some weak fgen signals look present along the
boundary, which may support some dinurally induced convective
activity by Saturday afternoon; however as the boundary looks
largely south and east of the area, a majority of the forecast area
may stay dry. With the boundary sticking close to the region through
mid-Sunday, some showers will be possible through the weekend, at
least until the next upstream ridge builds in Sunday afternoon.

A cooler airmass is expected to build in after the initial cold
front late tonight. Before then, 850mb temps between +10-15C will
support a warmer and muggy night tonight. This, combined with the
rain showers, will also support areas of dense fog Friday morning.
The core of the cooler air won`t enter into the area until the
weekend, so a warmer day with most in the 60s or low 70s is expected
Friday. By Saturday though, guidance suggests 850mb temps to be
between +3 (east) and -3 (west), which could result in temps topping
out in the 50s during the day and 30s, with some low 30s and frost
possible overnight. The best chance for any frost looks to be Sunday
night given the core of the cooler air aloft and partly cloudy/clear
skies being over the region and the light winds.

Beyond this, the pattern looks to shift into something very quasi-
zonal. There`s a couple shortwaves embedded within the flow pattern,
but GEFS 500mb spaghetti plot suggests some variance in the timing
and magnitudes of this shortwaves. Overall, the signals do suggest a
dry start of the week with temps near normal.
&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 117 PM EDT THU MAY 19 2022

Expect conditions to improve to VFR for a short time this afternoon
at all TAF sites as cigs rise ahead of an approaching warm front. As
the warm front comes through this evening, expect conditions to fall
to LIFR/low IFR tonight, with SHRAs and a few TSRAs moving across
the area along and behind the warm front. With moisture being socked
in over the lowest levels of the atmosphere tonight, especially at
KCMX and KSAW, we could see some FG develop over the TAF sites when
rain is not occurring; it`s possible that KCMX may get below airport
mins at times tonight into Friday morning. As a cold front comes
through the area Friday morning, expect skies to improve to VFR
behind the front.

LLWS is expected across the TAF sites tonight as a low level jet
moves through the area.
&&

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 335 PM EDT THU MAY 19 2022

Guidance continues to suggest a relatively calm forecast period.
Some exceptions could be any thunderstorm induced wind activity
tonight and early Friday and gusty southwesterly winds after the
cold front Friday morning. Post-frontal winds look largely to top
out 25-30kts given the pressure rise being decoupled from the
stronger cold air advection. Highest winds would be expected across
the western portions of Lake Superior, mainly between the Keweenaw
and Isle Royale, and any high reporting platforms like Stannard Rock
or Rock of Ages. Winds will shift to northwest by late Friday as
winds begin to lighten. I suspect there could be some lingering
gusty winds here and there given the expected pressure rises,
especially downwind of the Arrowhead, but with decreasing dinural
influence in Minnesota, I suspect the window would be short lived.
High pressure builds in slowly through the weekend and into early
next week, and winds look largely to remain below 20kts.

With rain showers and thunderstorms being expected tonight and early
Friday, the cooler lake will support fog developing. Some fog will
be dense and likely follow the wind direction during the day.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
  Dense Fog Advisory until midnight EDT tonight for LSZ244-245-
     265>267.

Lake Michigan...
None.
&&

$$

SHORT TERM...TAP
LONG TERM...JTP
AVIATION...TAP
MARINE...JTP


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