688
FXUS63 KMQT 150621
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
221 AM EDT Thu Aug 15 2024

.KEY MESSAGES...

- Wet period with showers and some thunderstorms developing
  today, continuing Friday, then ending west to east on
  Saturday.

- Generally more dry pattern for the back part of the weekend and
  beyond, though minor disturbances may bring the occasional
  shower.

&&

.SHORT TERM /THROUGH THIS AFTERNOON/...
Issued at 220 AM EDT Thu Aug 15 2024

A deepening low pressure over the Northern Plains approaches Upper
Michigan today and will bring rainfall over at least the western
half before sunset this evening. Cloud cover increases from the west
today as the low approaches. This cloud cover will help to keep
temperatures cooler over the U.P. today, mainly over the west and
central, in addition to the rainfall; expect highs to range from the
upper 60s in the interior west to around 80 in the east. With strong
equivalent temperature advection moving in this afternoon and PWATs
around 1.75 inches, we could see some heavy rain showers from time
to time late this morning over the far west through this afternoon
across the western half. These showers will be a much welcome
reprieve from the abnormally dry conditions that we`ve been seeing
over much of the western half of the U.P. the past couple of weeks;
we can only hope that this will improve soil moisture conditions
across the area. Some limited CAPE in the atmosphere could produce a
few rumbles of thunder near the state border late this afternoon.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
Issued at 253 PM EDT Wed Aug 14 2024

The weather for the remainder of the week will be driven by a 500mb
trough centered over the Dakotas by 12Z Thursday. The resulting
surface low will be around 1005mb over the Dakotas/MN border
Thursday morning, and isentropic ascent ahead of the low will bring
showers to the MI/WI state line Thursday morning per HREF guidance.
While a soaking rainfall is expected, flooding should not be a
concern given the dry pattern the past few weeks. Virtually all
of western Upper Michigan has had 50% or less of the normal
precipitation for the past 30 days, with the eastern half being
around normal to slightly below normal. HREF mean 6-hourly QPF
rates are a quarter inch to a half inch with this system.
Temperatures around 70 Thursday will lead to not much surface
instability until late, so thunder will be unlikely until the
late evening hours, and with only around 10 kt of 0-6km shear to
work with, thunderstorms will be too disorganized to be severe.
Showers continue through Friday as the center of the low
pressure passes close to the UP. PWAT values approaching 1.5
inches on Friday are up to a half inch above normal for this
time of year, so some heavy downpours are to be expected with
the stronger storms, but with cloud cover keeping temperatures
from breaking much above the lower 70s, surface instability will
be somewhat lacking and 6-hourly QPF rates will only be around
a quarter inch broadly on Friday per LREF guidance.

The last 24 hours of guidance have somewhat slowed the departure of
showers in the east as the pattern which once had three distinct
troughs over the US/Canada border will become more broad as ridging
builds over the central CONUS. While this does support slowing the
movement of the trough to the east, it will also mean a surface high
of around 1020mb will build over the Upper Great Lakes by the end of
the weekend, ushering in a more dry period. Ensembles greatly vary
on exact solutions into next week, but the general pattern of
northwesterly flow is one that is often subject to the shortwaves
that rotate around the central CONUS ridge, which means that there
will be at least some slight chances (15-25%) of precipitation in
the forecast through the middle of next week, though the impacts of
said precip chances will be lesser.

&&

.AVIATION /06Z TAFS THROUGH 06Z FRIDAY/...
Issued at 104 AM EDT Thu Aug 15 2024

Ceilings and visibilities deteriorate from VFR overnight to
MVFR/IFR Thursday as a system lifts into the Great Lakes region
and spreads rain over Upper Michigan. Rain will spread from
southwest to northeast, with KIWD likely seeing rain in the
morning hours and KCMX/KSAW by afternoon. As the rain moves in,
gusty south to southeasterly winds of 20 to 30 kts will spread
into the region.

&&

.MARINE...
Issued at 253 PM EDT Wed Aug 14 2024

Wind gusts will remain below 20 kt through Thursday morning. By
Thursday afternoon, a low pressure system will approach the Upper
Great Lakes, causing easterly and southeasterly wind gusts to around
25 kt Thursday afternoon through Friday morning. Wind gusts will
fall to around 20 kt as winds become northerly with the low pressure
passing to the south of Upper Michigan. The arrival of high pressure
by the end of the weekend will result in wind gusts below 20 kt
Saturday evening through the remainder of the forecast. During the
period of easterlies late Thursday into Friday, waves will pick up
to 4-6 feet.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.

&&

$$

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