Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 271917
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
317 PM EDT FRI MAY 27 2016

.SHORT TERM...(Tonight and Saturday)
Issued at 317 PM EDT Fri May 27 2016

Upper level ridge axis extends thru the Great Lakes region this
afternoon. Surface pattern and surface winds remain rather weak and
ill-defined attm....but are generally from the south thanks to high
pressure anchored along the mid Atlantic states and developing low
pressure over the Plains. Temps warmed quickly this morning once the
fog dissipated...but progress has since been slowed due to a thicker
cirrus shield that lifted into the area from upstream convection...
as well as some sct/bkn altocu and cu. Temps have been rather
stagnant since...holding mainly in the mid 70s to lower 80s. No
convection has developed as of yet across our CWA...but a small area
of showers and storms is making steady progress toward the SW
portion of our area. Strengthening low level jet poking into Srn
Wisconsin attm is providing some added support and moisture
transport to ongoing convection over that region.

NAM12...RAP13 and latest HRRR all redevelop convection over our SW
CWA late this afternoon. Convection then spread N/NE thru much of
our CWA...especially across Nrn Lwr Michigan...thru the evening
hours. NAM boosts MUCAPES to around 2000 J/kg this afternoon...while
the RAP only shows around 1500 J/kg for the afternoon. Speed shear
actually diminishes later this afternoon and evening as upper level
winds weaken and low level winds strengthen as the eastern edge of
the low level jet leans into Michigan. Not quite the setup we had
yesterday afternoon. Cannot rule out an isold strong/possibly svr
storms thru evening during peak diurnal instability combined with a
weakly shear environment.

Surface low over the Plains begins to lift toward the Wrn Great
Lakes region by late evening and slowly proceeds NE to Wisconsin by
late Saturday. Deep moisture surges into Michigan ahead of this
system later tonight and Saturday. The two combined along with some
instability...diurnally enhanced Saturday afternoon...will push our
POPs to likely after 00z tonight and thru 00z on Sunday. Embedded
thunderstorms are certainly expected given MUCAPES holding around
500 J/kg tonight and then quickly increasing to near 2000 J/kg on
Saturday thanks to daytime heating/instability.

Expect another warm and muggy late May night across the
Northwoods...with overnight lows ranging from the upper 50s in Ern
Upr Michigan to the low to mid 60s across Nrn Lwr Michigan (cooler
near the lakeshores). We will see another very warm and humid day on
Saturday despite increasing chances of precip and cloud cover.
Afternoon highs will range from the upper 70s in Ern Upr Michigan to
the 80s across Nrn Lwr Michigan (cooler near the lakeshores...of
course).

.LONG TERM...(Saturday night through Friday)
Issued at 317 PM EDT Fri May 27 2016

IMPACTS: Severe thunderstorms possible Sunday afternoon/evening.
Currently in SPC marginal risk. Primary threat currently looks to be
strong winds, will see how things evolve.

PATTERN SYNOPSIS/EXPECTED EVOLUTION: Unsettled pattern continues.
Initially, there are a few areas of troughing to our west. A
negatively tilted, cutoff low over the Pacific NW, digging into ID
and western MT. Additional open waves further south over the Pacific
near the Baja California  Peninsula and over the Central Plains. The
disturbance currently in the Caribbean continues to move toward the
SE Atlantic coast, with the latest outlook from the NHC giving a 90%
chance of cyclone formation in the next 48 hours, which could be
moving inland over the weekend, with portions of Bermuda High nosing
into the Carolinas. The open wave over the Central Plains will lift
toward the Great Lakes through the weekend, helping to drive an
occluding surface low through MN/WI.  This open wave will pass over
MI Sunday, while the surface low passes to our west and north. With
strong return flow, we will remain under gradually building ridging
until the wave passes on Sunday.  Flow becomes more zonal east of
the Rockies through the day Monday, while troughing remains over the
Pacific NW and Baja California.

MAIN FORECAST CHALLENGES/CONCERNS: Severe weather threat for Sunday.

ASSOCIATED WEATHER: With the low over the plains and the combination
of the low off the coast of Florida and Bermuda High nosing into the
Carolinas, continued strong return flow will bring high PWAT values
to the region through Sunday. Currently progged values are at or
above 90% percentile. Dewpoints will remain into the 60s over the
weekend, with the passage of the weak front late Sunday helping to
knock down the dewpoints for Monday. Showers and thunderstorms will
diminish overnight Saturday, but pick up again Sunday afternoon.
There is a chance for some of the storms Sunday to become severe. As
mentioned earlier, dewpoints will push into the 60s in the strong
return flow ahead of the approaching front. There is also some upper
level support with diffluent flow ahead of the trough and possibly
some divergence in the right entrance region of a jet streak. Just
when the trough and jet streak move over can certainly enhance or
put a damper on the severe chances. Timing right now looks like they
may come a bit before peak afternoon heating, which would be less
conducive for the severe threat. The main threat with this looks to
be high winds, with dry mid-levels, low level lapse rates around 8
C/km,and DCAPE near 800 J/Kg. Bulk shear is a bit low for supercell
support, with most of the CWA under 30kts 0-6km, with little SRH as
winds remain SW through most of the column. The NAM is quite a bit
more aggressive with CAPE, putting out around 3000 J/Kg 18Z Sunday,
with the GFS closer to the 1500 -2000 J/Kg mark. Given the tendency
for the NAM to be too moist in the low levels, I think the CAPE is a
bit overdone. That said, 1000 J/Kg is still sufficient for
development especially if the upper level support comes through
later in the afternoon. With sub 10Kft WBZ heights, there could be
some hail though it will likely remain sub-severe. With the
transition to more zonal flow and lowering PWATS, things will begin
to clear up Monday.

MAYHEW

Fairly zonal upper level flow is expected to start the period Monday
night with little in the way of consequence through the day Tuesday
as weak high pressure is anchored overhead. The envelope of
solutions widens Tuesday night through the remainder of the week as
global model guidance differs significantly as to the overall
pattern and associated precip chances. Based on run-to-run
consistency, have hedged toward the 12z ECMWF/NAM/GEM, which brings
developing low pressure into the northern Plains (rather than
digging upper level energy into the intermountain west), ultimately
swinging a frontal boundary through the Great Lakes resulting in
increased precipitation/thunder chances Tuesday night through
Thursday night.

A cooling temperature trend throughout the extended is expected with
highs ranging from through the mid-upper 70s Tuesday, falling to the
upper 60s-low 70s by Friday. Overnight lows within a few degrees of
normal, generally ranging from the mid 40s to low 50s.

Gillen

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 119 PM EDT Fri May 27 2016

Scattered showers and thunderstorms will redevelop this
afternoon...initially around MBL and TVC and will then spread N/NE
to PLN and APN later this afternoon and early evening. Areal
coverage of this precip will increase thru the night and into
Saturday as an area of low pressure and associated deep moisture
lift northward into the Wrn Great Lakes region. Winds will remain
generally from the SE under 10 kts tonight...shifting to the south
on Saturday.

&&

.MARINE...
Issued at 317 PM EDT Fri May 27 2016

Winds and waves will remain below SCA criteria thru tonight thanks
to a relatively weak pressure gradient remaining overhead.
Conditions may reach SCA criteria on Saturday and again on Sunday
for locations along Lake Michigan south of Grand Traverse Light as
low level winds strengthen ahead of low pressure lifting into the
Wrn Great Lakes region. The chance of showers and storms will
steadily increase tonight ahead of that low pressure system...with
showers and storms remaining in the forecast thru the weekend.

&&

.APX Watches/Warnings/Advisories...
MI...NONE.
LH...NONE.
LM...NONE.
LS...NONE.
&&

$$

SHORT TERM...MLR
LONG TERM...Gillen/Mayhew
AVIATION...MLR
MARINE...MLR



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