Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 211940

Area Forecast Discussion
National Weather Service Marquette MI
340 PM EDT SAT MAY 21 2016

.SHORT TERM...(This evening through Sunday)
Issued at 339 PM EDT SAT MAY 21 2016

A decaying sfc trough sagging southward across Upper MI this
afternoon is creating enhanced convergence across the south half of
the CWA. A few radar echoes are surpassing 30dBz as low as 3kft, so
even though the sfc layer is very dry, a few sprinkles may reach the
ground through this evening.

Upper ridging building across the Upper MS Valley and sfc ridging
drifting eastward across Upper MI will bring clear skies with a few
passing high clouds and afternoon inland cumulus through Sunday.
H8/H9 temps a degree or two Celsius higher on Sunday will favor sfc
temps in the upper 70s to low 80 away from the immediate shores,
where widespread lake breeze development is expected.

The light winds will limit daytime boundary layer mixing to some
extent, but min RH values will still fall well into the 20s inland.
Some upper 10s cannot be ruled out across the interior east where
dry NE flow tonight ahead of the surface ridge leaves behind very
dry low-levels. Overall, with winds remaining light away from any
lake breeze boundary, Sunday will be another day of drying ahead of
the expected increased fire potential on Monday.

.LONG TERM...(Sunday through Friday)
Issued at 337 AM EDT SAT MAY 21 2016

Change in pattern on the way as the upper ridge moves through the
region on Sunday. This will keep dry conditions Sun and Mon when
winds will be on the increase as the pressure gradient tightens.
With that pattern change, rain chances increase Mon night through
next week. With the inability to find significant chances of strong
to severe thunderstorms with shortwaves/convection next week, loaded
primarily with consensus guidance Mon night through Fri and focused
on critical wildfire potential Sun and especially Mon.

A couple things to understand with the fire weather forecast. First,
With recent lack of rain and very dry diurnal conditions, fire fuels
have reached critical levels. Second, models have been significantly
too high with min dew points over the last couple of weeks. Bias
correction is helping with this issue, with the BC GEM
deterministic, BC ECMWF MOS, and BC EKD MOS products verifying best
during the afternoons over the past 7, 15, and even 30 days. Still
will try to improve over those models by blending Td output with
adiabatically mixed dew points based on hourly forecast sfc T and
low level moisture data from models. This methodology worked quite
well when used last week.

For Sun: High temps will be from the mid 70s interior E to the mid
80s interior W and min RH values of 20-30%. Cooler temps and higher
RH along the Great Lakes shores. Winds will generally be 10-15 mph
with gusts 15-20 mph.

For Mon: Fire Weather Watch continues given similar high temps to
Sun, min RH values of 25-30% and SW winds generally 15-20 mph
gusting to 20-30 mph. Some models suggested lower RH over the
interior E. See potential so included some of that idea in the
forecast, but not certain enough to go as low as a couple of the
models were showing. Shortwave energy passing nw of the CWA should
bring showers and thunderstorms into the far W late in the day.
Unfortunately, while much of the area should see rain Mon night into
Tue, can not guarantee that all areas will see rain. Thankfully, the
changing pattern will allow for greater moisture and better chances
for rain after Mon.

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 142 PM EDT SAT MAY 21 2016

Other than some passing mid-level clouds, expect clear conditions
through the period. Generally northerly winds this afternoon will
become light tonight before becoming southerly late Sunday morning.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 339 PM EDT SAT MAY 21 2016

High pressure over the Upper Great Lakes will keep winds under 15
knots through Sunday afternoon. Southerly winds of up to 25 knots
are then expected Sunday night through Monday night as a low
pressure trough approaches from the west. The trough will stall over
the Upper Great Lakes Tuesday through Thursday, bringing winds
generally under 15 knots.

Upper Michigan...
  Fire Weather Watch from Monday morning through Monday evening
     for MIZ001>015-084-085.

Lake Superior...
Lake Michigan...


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