Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 210852

Area Forecast Discussion
National Weather Service Marquette MI
452 AM EDT SAT MAY 21 2016

.SHORT TERM...(Today and tonight)
Issued at 448 AM EDT SAT MAY 21 2016

WV imagery and RAP analysis indicated an amplified pattern with a
mid/upper level low over OR and a ridge from the western plains into
Alberta/Saskatchewan resulting in nw flow from northern Ontario to
the northern Great Lakes. A shortwave trough to the southwest of
James Bay was sliding to the southeast. At the surface, a cold front
was also pushing to the south to near Lake Superior as high pressure
builds over far nw Ontario. IR loop showed some mid/high clouds over
the southeast CWA on the northern fringe of a mid level trough over
southern lower Michigan. Otherwise, mostly clear skies prevailed.

Today, the shortwave trough and associated cold front will continue
to move southeast through northern Ontario but the pcpn chances are
expected to remain to the north and east of Lake Superior. A weak
frontal passage aided by the lake breeze off of Lake Superior will
bring increasing winds from the north this afternoon. However, the
pressure gradient will still be relatively weak allowing a lake
breeze to also develop off of Lake Michigan. Deep mixing, with 850
mb temps around 10C-12C, will support max temps into the mid and
upper 70s and bring dewpoints down into the mid and upper 30s
inland, at the lower end of guidance. With the NCEP models
persistent high bias on low level moisture level moisture, the light
convective pcpn produced by the GFS/NAM was disregarded.
Accordingly, RH values should again also drop into the 20 to 30 pct
range inland.

Saturday night, favorable radiational cooing conditions will allow
temps to drop toward the lower end of guidance with lows in the
lower 40s inland and mid to upper 40s near the Great Lakes.

.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 06Z TAFS through 06Z Saturday night)
Issued at 120 AM EDT SAT MAY 21 2016

With dry hi pres dominating the Upper Great Lakes region, expect VFR
conditions and light winds at all the TAF sites thru this mrng.
A weak trof will move into the area today, but limited moisture and
a weak pres gradient will result in continued VFR conditions and
relatively light winds. There could be some N wind gusts at SAW this
aftn following the passage of the trof, but frequent gusts in excess
of 15 kts are not likely.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 448 AM EDT SAT MAY 21 2016

A quiet late spring pattern is expected for Lake Superior for this
forecast period with high pressure over the Great Lakes region.
Winds will be mostly under 15kt each day. Southerly winds on Monday
increasing to 20 to 25 knots ahead of a trough lifting through the
Northern Plains will be the strongest winds expected during the
forecast period.

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

Lake Superior...
Lake Michigan...


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