Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 312320

Area Forecast Discussion
National Weather Service Gaylord MI
720 PM EDT TUE MAY 31 2016

.SHORT TERM...(This evening and overnight)
Issued at 245 PM EDT Tue May 31 2016

Surface ridge axis remains over the Great Lakes region this
afternoon...providing Northern Michigan with a beautifully sunny and
pleasant last day of May. Leading edge of residual mid and high
clouds from upstream convection is tending to diminish as it moves
eastward into the more stable and dry airmass over our CWA. Temps
have warmed into the 60s across Ern Upr Michigan and well into the
70s across much of Nrn Lwr Michigan. The shoreline areas of NE Lwr
Michigan are only in the 60s thanks to low level easterly flow off
pushing cooler air inland off of Lake Huron.

A look upstream shows diurnally enhanced convection increasing in
both areal coverage and intensity over the Upper Mississippi valley
thanks to building instability and moisture ahead of an approaching
cold front. Still appears both the instability axis and the 850 mb
theta e ridge ahead of this front will remain west of our CWA thru
tonight as eastward push of this whole system will remain rather
slow. Thus...tonight will feature mainly scattered to broken
residual mid/high cloud streaming eastward into the area from
upstream convection. Dry low level easterly flow will keep any low
clouds at bay. Low temps will cool mainly into the 50s tonight.

.LONG TERM...(Wednesday through Tuesday)
Issued at 245 PM EDT Tue May 31 2016

High impact weather potential: Marginal risk for severe
thunderstorms Wednesday.

Pattern synopsis/expected evolution: One energetic late May system
diving across the northern plains, itself embedded in somewhat of a
more zonal regime across central NOAM. Decently coupled upper level
jet structure and very aggressive digging mid level energy providing
the support for such a strong system. This system is in the process
of reaching maturity today, with it expected to slowly opening up as
it moves east northeast across southern Canada through mid week.
Attendant dynamics will still be rather strong as they swing across
northern Michigan Wednesday into Wednesday night, and when coupled
with a increasingly narrow, but focused moisture axis, looks to
provide the impetus to drive at least a broken band of
showers/storms across our area. Conditions look to quiet down for a
few days thereafter, with pattern amplification and additional
digging energy drumming up additional rain chances heading into the
upcoming weekend.

Primary forecast concerns/challenges: Addressing shower and
thunderstorm evolution (and intensity) Wednesday/Wednesday night.

Details: Overhead pattern set to go through some rather significant
changes Wednesday into Wednesday night, with departure of current
overhead ridge axis as upstream system advances through the region.
Focused area of deeper moisture within persistent deep southwest
flow regime out ahead of attendant cool front, allowing pwat values
to briefly surge to 1.25-1.50 inch levels. While above sounds decent
for some beneficial rains, actual collocation of dynamics and deeper
moisture is a brief one, and really focused along the frontal slope
itself (or perhaps along an upstream convectively induced pre-
frontal outflow boundary). Timing for best shower/storm threat
remains rather uncertain, and tied to what will be the primary
forcing mechanism (cold front or an initial outflow boundary). If
main forcing is tied to a pre-frontal outflow boundary, best chances
for rain occurs from late morning through the afternoon (with
perhaps some additional lighter shower development with passing cold
front during the evening). If main impetus for shower development is
tied to the cold front, then best chances for rain holds off until
the evening hours. Unfortunately, this uncertainty will continue to
result in what in all likelihood will be a several hour too long
window of high pop mention. Shower chances look to decrease rather
substantially during the overnight as surface convergence and what
instability there was is lost.

With regards to severe thunderstorm potential: Area remains solidly
within latest SPC day 2 marginal outlook, and per their verbiage,
this centers on a moderately high shear (deep layer shear pushing 40
to 50 knots) low cape (both mean layer and 0-6km cape only on the
order of a few hundred joules/kg) environment. Latest guidance
trends concur, as does backward run trajectory analysis using latest
12km Nam-Wrf. So, upshot to the above, is while yes cannot
completely rule out the chance for a few severe storms, the overall
coverage should be minimal and isolated...if it even occurs at all.

Forecast concerns Thursday turn to one of a cloud issue as post-
frontal high pressure once again brings a refreshing airmass into
the lakes. While day long deep layer drying will continue, some
evidence for a rather persistent stcu deck to hang tough most of the
day, especially for the northern half of the area. More sun than
clouds expected by Friday as high pressure centers itself across the


Low amplitude troughing will give way to height rises working into
the region ahead of a shortwave and surface low working through the
Northern Plains by late in the week. This shortwave will strengthen
into a closed low over the weekend as it moves into the Great Lakes
region, which will bring deep troughing through the Tennessee
Valley, and possibly some below normal temperatures for us Sunday
and going into mid-week. This slow moving low will result in rain
chances through the extended. Could be some rumbles of thunder
Saturday. Severe potential Saturday looks minimal right now, will
keep an eye on the SW portion of the CWA where instabilities are
likely to be more favorable with some higher dewpoint air able to
advect in ahead of the low.



.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 720 PM EDT Tue May 31 2016

VFR tonight. A touch of MVFR possible Wednesday with SHRA/TSRA.

A ridge of high pressure is starting to move east out across Lake
Huron. As it continues, southerly flow will increase, bringing
increasingly moist air to the region. Low pressure will move north
of Superior by late Wednesday, contributing to an increasing
SHRA/TSRA threat. Some SHRA may approach MBL/TVC/PLN just after
daybreak. Much better chances for precip, including thunder,
during the upcoming day. Some possibilities for MVFR cigs/vsbys,
especially at MBL.

SE winds nearly 10kt tonight, veering S on Wednesday.


Issued at 245 PM EDT Tue May 31 2016

Winds and waves will remain just below SCA criteria thru Thursday
despite the approach and passage of a cold front Wednesday into
Wednesday night. Chances of precip increasing on Wednesday ahead of
our next cold front...and will continue into Wednesday evening as
the front moves thru. Dry weather will return on Thursday as high
pressure builds back into the Wrn Great Lakes region.


.APX Watches/Warnings/Advisories...


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