Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 291109
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
709 AM EDT Mon May 29 2017


.AVIATION...

Dry air has infiltrated the region resulting in little to no cloud
fraction this morning. Only exception are some patches of midcloud
altostratus that has been filling in at times. One patch is exiting
the Thumb, while another is making a run for far southeastern
Michigan. Fairly inconsequential, but will have to be accounted for
today. Otherwise, static westerly flow around southern periphery of
Ontario closed low will lead to breezy gradient winds over the
terminals. High confidence in exceeding 20 knots, moderate
confidence in reaching and exceeding 25 knots. Antecedent ground
moisture from precipitation yesterday will help in a diurnal cumulus
response today, although dry nature of airmass overhead will lead to
very high mixing heights with cloud bases at 6.0 to 7,0 kft agl. Low
chance for showers today. Best potential now appears set for the
southern taf sites with as a 700-600mb moisture axis under favorable
deformation lifts into the area. Have accounted for the
precipitation mention with a Prob30 group.

//DTW THRESHOLD PROBABILITIES...

* None.

&&

.PREV DISCUSSION...
Issued at 335 AM EDT Mon May 29 2017

DISCUSSION...

Upper low centered just north of Lake Superior will broaden with the
addition of upper energy dropping through Central Canada and the
Northern Plains. This system will encompass the Great Lakes through
early Wednesday as it slowly wobbles east across Ontario.

Upper shortwave pivoting around the low center will swing across
Lower Michigan today, with a narrow ribbon of theta-e advection
streaming into Michigan ahead of it. Lapse rates will steepen with
daytime heating, and as upper cold pool associated with the low
slides in overhead. This looks to generate 500-1000 J/kg of SBCAPE
by afternoon, providing a chance for showers and thunderstorms.
Expecting just a scattered coverage with forecast soundings showing
saturation only between 800-600mb, and a boost from a strengthening
jet streak rounding the base of the upper low.

Breezy conditions will develop by this afternoon as southwesterly
gradient tightens between low pressure over Ontario and high
pressure over the Gulf States and Tennessee Valley. Gusts look to
reach between 25 and 30 knots by afternoon as the mixed layer
deepens and winds aloft strengthen slightly. Well-mixed boundary
layer and H925 temps rising to between 16-18C should boost max
temperatures into the mid 70s to near 80.

Chances for showers, or even a thunderstorm, tomorrow and Wednesday
look lower compared today as moist layer looks fairly shallow. Will
retain very low pops however as weak shortwaves look to continue
streaming over the area from around the upper low to our north. Cold
air advection will make for cooler temperatures, with max temps
reaching the mid 60s to near 70. Breezy conditions will also
continue as surface features remain fairly stagnant. Upper low will
finally lift out of the area Wednesday night, with high pressure
providing dry weather into Thursday.

Quite a bit of uncertainty then as we head into the end of the week
as an upper ridge builds through the Plains and into Central Canada,
and a strong upper low drops through Ontario and Quebec. Medium-
range models are still struggling with where to place the larger
features, making it difficult to pinpoint where an active frontal
zone will set up from late Thursday into the weekend. Model
solutions currently range from southern Michigan to the Southern
Ohio Valley. Latest GFS/Euro support better chance for
showers/tstorms on Friday, with at least some of the weekend under
high pressure as the frontal zone sinks to our south.

MARINE...

West to southwest winds will increase today as an upper level low
pressure system settles into the central Great lakes. Wind gusts
look to increase to around 20 knots for much of the marine areas.
The exception is over Saginaw Bay where a small craft advisory has
been issued for this morning through Tuesday evening as winds will
likely reach and exceed 25 knots This upper level low pressure
system is expected to become a persistent feature this week, possibly
reorganizing again late this week and upcoming weekend.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...Small Craft Advisory until 10 PM EDT Tuesday for LHZ421-422.

Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
&&

$$

AVIATION.....CB
DISCUSSION...HLO
MARINE.......CB


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