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000
FXUS63 KMQT 161348
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
948 AM EDT Tue Apr 16 2024

.KEY MESSAGES...

- Elevated fire weather conditions today as warm, dry, and windy
  conditions overspread much of the UP, with the driest and
  windiest area being along the MI/WI state line.
- A low pressure tracks through the Upper Great Lakes during the
  midweek, causing widespread rain showers Tuesday night and
  Wednesday. Gusty east winds could reach up to advisory criteria
  (45 mph) over the Keweenaw and eastern counties of the U.P.
- Chances of precipitation remain possible (~15-40%) into
  late week, though uncertainty exists on timing and intensity.

&&

.UPDATE...
Issued at 947 AM EDT Tue Apr 16 2024

Minor adjustments to the forecast this morning. High cloud cover has
already overspread most of the UP, while dewpoints remain higher
than expected so far. The impact that this earlier onset of
cloudiness (a cloud deck which should gradually lower through the
afternoon) will have on dewpoints into the afternoon is uncertain.
Model soundings still show a very well-mixed environment at lower
levels, but these were under clearer conditions. Meanwhile, winds
have come in slightly under-forecast for this morning, so those have
been dropped before better mixing and stronger winds aloft develop
this afternoon.

&&

.SHORT TERM /THROUGH THIS AFTERNOON/...
Issued at 509 AM EDT Tue Apr 16 2024

RAP analysis shows a 990mb surface low over Nebraska while to the
northeast is a 1027mb Hudson High. As the low pushes northeast and
the high sags south, the pressure gradient builds, causing breezy
conditions today. HREF wind gusts, while they do have the tendency
to overperform, show an ensemble mean of 35 mph this afternoon on
the western half of the UP, with a 25th-75th percentile range of 30-
40 mph. Enhancing the wind gusts today in addition to the surface
pressure gradient will be mixing of winds from aloft to the surface.
00Z GEFS mean 850mb winds are anywhere from 30-45 mph by the evening
hours, so if a deep and well mixed boundary layer develops, the
potential for even higher winds exists. This mixing will also bring
quite dry air to the surface. With mainly clear skies in the east
half and partly to mostly cloudy skies in the west, today`s high
temperatures will be warmer than normal. Low dew point air mixing
to the surface and higher than normal temperatures is a pretty
good recipe for low RHs. HREF probabilities of RHs falling to
below 25 percent is 40% for virtually all of the UP except the
Keweenaw Peninsula. With a Hudson High being a typical lookout
pattern, elected to go lower with RHs in the upper teens and
lower 20s for much of the UP today. This prompted a SPS for
elevated fire weather concerns. HREF PoPs over the UP are
sub-10% before 00Z, so relief from fire weather conditions will
have to wait until tonight.

&&

.LONG TERM /TONIGHT THROUGH MONDAY/...
Issued at 501 AM EDT Tue Apr 16 2024

Beginning tonight, mainly after sunset, categorical PoPs for
rain will spread w-e across the cwa supported by increasing
upper diffluence and deep layer q-vector convergence ahead of
the approaching Plains low and the categorical PoPs will
continue into Wednesday as the low moves into Wisconsin.
Confidence is high in some spots getting a decent soaking of
rain with this system as a stream of moisture off the Gulf of
Mexico with PWATs in excess of an inch surge into the Upper
Great Lakes. These PWAT values are above the 90th percentile of
Green Bay`s climatology and should support storm total QPF
ranging from 0.5" to 2". This soaking rainfall should help
alleviate fire weather concerns moving through the rest of the
week. Another thing the PWATs and mid-level RH plots highlight
is a dry slot following the initial round of showers lifting
north. CAMs indicate that this would result in a brief break in
the steady showers over the western UP late Tuesday night into
Wednesday morning and in the east late Wed morning into early
Wed afternoon, before the second wave of showers moves in later
Wed afternoon and evening. Elevated CAPE of up to 500 j/kg could
support isolated thunderstorms south central and southeast on
Wednesday.

Strong easterly winds and gusts will also be a concern later tonight
into Wednesday as the pressure gradient increases and a 60+ kt low
level jet translates east across the area. EPS probability guidance
indicates a 80-100% probability of wind gusts exceeding 40 mph later
tonight into Wed afternoon across the Keweenaw and the eastern
counties of Alger, Schoolcraft and Luce counties. Given that fcst
soundings also support the higher wind gusts with a good chance of
45 mph gusts possible at times, decided to issue a Wind Advisory
across Northern Houghton-Keweenaw and also Alger, Luce and
Schoolcraft counties from 06Z-21Z Wed. Widespread gusts across the
rest of the CWA are forecast between the 25 to 35 mph range during
this period.

After the weakening southern stream shortwave and associated sfc low
lifts northeast through Upper MI Wed night with showers ending from
west to east late Wed night, attention turns upstream to a northern
stream trough/closed low and associated sfc low over southern
Saskatchewan. This northern stream trough and associated closed low
will move east and phase with the remnants of the southern stream
shortwave on Thu after it moves northeast of the Upper Great Lakes.
The resulting sfc low north of the Upper Great Lakes in northern
Ontario will send a cold front across Upper Mi on Thursday but
available moisture is somewhat limited at this point with the
highest PWAT values ~.5 inch, highest east. Only isolated to
scattered light rain showers are expected Thu into Thu night with
the highest coverage over the eastern third of the cwa. Rain is the
expected p-type. However, as the closed low lifts east-northeast
through Ontario on Friday and then into northern Quebec on Saturday,
the mid-level trough will move across the Upper Great Lakes Friday
into early Saturday. This trough along with increasing CAA at 850
mb will lead to another round of isolated to scattered showers which
will probably be enhanced by diurnal instability during the day on
Friday. The CAA will also allow snow showers to mix in the rain
Friday into Saturday.

Additional northern stream shortwaves in a northwest flow aloft will
move over the Upper Great Lakes into early next week, with maybe
isolated showers at times, but it looks like dry weather will mostly
win out into Tuesday as sfc high pressure prevails through
much of the period.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 738 AM EDT Tue Apr 16 2024

VFR prevails at all TAF sites through this evening. Tonight, an
advancing low pressure out of the Plains will cause widespread -SHRA
with occasional SHRA possible (40%). This will gradually cause MVFR
ceilings at all sites around midnight at all TAF sites with brief
MVFR to IFR vis during periods of heavier SHRA. CMX and SAW are
likely (60+%) to see IFR ceilings by the morning hours tomorrow,
with IFR ceilings around 30% likely at IWD. As the low approaches, E
and ESE winds will be gusty, with IWD seeing gusts up to 35 kt and
CMX seeing gusts up to 45 kt. An advancing low level jet will create
a LLWS threat at all sites tonight.

&&

.MARINE...
Issued at 501 AM EDT Tue Apr 16 2024

High pressure extending southeast over the Great Lakes will keep
winds below 20 kts through much of this morning. As low pressure
begins to move out of the Central Plains today, winds quickly
increase to northeasterly gales to 40 kt in western Lake Superior
this afternoon. Easterly gales overspread the lake tonight into
Wednesday as the low passes through the Upper Great Lakes. Strongest
gales are expected over the north central and east half of the lake
up to 40-45 knots on Wednesday. Probabilities of storm force winds
remain low at this time, with probabilities of winds exceeding 47
kts staying below 20%. Winds fall below gales in the immediate wake
of the low late in the day Wednesday, though the enhanced pressure
gradient will keep westerly winds of 20-30 kt in the forecast into
the weekend. During the northeasterly gales late Tuesday, waves of
10-13 feet are possible with 8-12 feet waves on Wednesday across the
whole lake, locally up to 17 feet between Isle Royale and the tip of
the Keweenaw Peninsula. Waves fall below 6 feet early Thursday but
remain at 2-5 feet until late Saturday.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Wind Advisory from 2 AM to 5 PM EDT Wednesday for MIZ001-003-
     006-007-014-085.

Lake Superior...
  Gale Warning from 11 PM this evening to 8 PM EDT Wednesday for
     LSZ243>246-250-264>266.

  Gale Warning from 2 PM EDT /1 PM CDT/ this afternoon to 2 PM
     EDT /1 PM CDT/ Wednesday for LSZ162.

  Small Craft Advisory from 2 PM EDT /1 PM CDT/ this afternoon
     to 8 AM EDT /7 AM CDT/ Wednesday for LSZ240-241.

  Small Craft Advisory from 2 PM this afternoon to 11 PM EDT
     this evening for LSZ242>246.

  Gale Warning from 11 PM this evening to 2 PM EDT Wednesday for
     LSZ242-263.

  Small Craft Advisory from 2 PM this afternoon to 8 PM EDT
     Wednesday for LSZ247>249.

  Gale Warning from 4 AM to 8 PM EDT Wednesday for LSZ251-267.

Lake Michigan...
  Small Craft Advisory from 2 PM this afternoon to 8 PM EDT this
     evening for LMZ221-250.

  Gale Warning from 8 PM this evening to 2 PM EDT Wednesday for
     LMZ221-250.

  Small Craft Advisory from 5 PM this afternoon to 11 PM EDT
     this evening for LMZ248.

  Gale Warning from 11 PM this evening to 8 PM EDT Wednesday for
     LMZ248.

&&

$$

UPDATE...LC
SHORT TERM...GS
LONG TERM...Voss
AVIATION...GS
MARINE...Voss