Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 251919
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
319 PM EDT Tue Apr 25 2017

.DISCUSSION...

Upper level pv filament exiting east of the central Great Lakes this
afternoon, taking morning light showers/sprinkles over the Thumb
Region with it, along with the clouds. Developing afternoon sunshine
has or will allow temperatures to climb to around 70 degrees across
most locations once again.

Active pattern/upper level energy over the Rockies of North America,
leading to two distant mid level circulations around Tomorrow, one
over Minnesota, with second wave/shortwave trough coming out of the
southern Plains, becoming absorbed by stronger northern stream
system, with the negative tilted trough axis lifting through
southeast Michigan on Thursday.

Warming low/mid levels is the weather story Tonight into Tomorrow,
which should serve as a good CAP, as average 850-700 mb temps rise
into the lower teens early Wednesday afternoon. 925 mb temps rising
between 19-21 C supports highs around 80 degrees as warm front
reaches at least Saginaw Bay. If warm front gets hung up over Tri-
Cities region, enhanced low level convergence/forcing could be
enough to overcome the weakening cap late in the day. If activity
does materialize by early evening, 1000-850 MB Capes around 1000
J/kg with 0-6 km bulk shear up around 50 knots would support a
marginal risk of severe storms as narrow moisture plume (PW values
around 1.5 inches) reaches the doorstep of the CWA late in the day.
Even better 0-6 KM bulk shear on Thursday, in the 60-70 knot range,
but MLcapes expected to reside mainly below 1000 J/kg as showers and
thunderstorms likely develop by early afternoon. Even so, with 50
knots at 850 mb, it will not take much to produce wind gusts up to
60 mph, and marginal risk of severe storms (last nights day 3
outlook) looks valid. If the front is even a bit slower, a better
risk of strong to severe storms can be expected. Even without
thunderstorms, should be a pretty good wind pop behind the front
late in the day, with 6 hr rise/fall pressure couplet around 15 MB,
with local probabilistic SREF weighted guidance indicating wind gusts
in the 35 to 40 mph range. Low level cold advection looks good, as
850 mb temps crash at or slightly below zero toward early evening
before leveling off Thursday Night.

High pressure over the region on Friday will bring drier and cooler
conditions with highs in the 60s. Shower chances return to the
forecast late Friday as a warm frontal boundary becomes stationary
south of Michigan. The weekend will feature a wet forecast as low
pressure developing over the Southern Plains on Saturday moves
northeastward towards the Great Lakes. The better chance for showers
on Saturday will remain south along the Ohio border closer to the
stationary frontal boundary as highs remain in the mid 50s across
the Saginaw Valley and Thumb to low 60s near the Ohio border. As low
pressure approaches the region, the frontal boundary will lift
northward across Lower Michigan on Sunday with highs warming into
the 60s to near 70 while rain and thunderstorms remain likely
throughout the day into Sunday night. Cold frontal passage looks to
occur on Monday as low pressure slowly exits the Great Lakes region
keeping shower chances in the forecast. Following the frontal
passage, a cooler air mass filters into the region for early next
week with highs returning to the mid 50s to low 60s.

&&

.MARINE...

A long duration of moderate southeasterly flow will exist through
Thursday with a gradually veering to the south by the end of that
time frame. This flow will exist within modest pressure gradient
between high pressure to the east and low pressure lifting into the
Mid Mississippi Valley. Expect sustained wind of 15 to 20 knots over
Lake Huron.

While higher gusts will likely occur, rather stable low levels
within this warming southerly flow will limit the highest gusts to
around 25 knots on Wednesday and 25-30 knots on Thursday as the low
pressure and attending cold front encroach on the area. Winds will
turn southwesterly in the wake of this system from late Thursday into
Thursday night with scattered showers or storms also accompanying
the cold front.

&&

.HYDROLOGY...

Low pressure will track into northern lower Michigan on Thursday and
drag a trailing cold front west to east from the region. Scattered
showers and thunderstorms can be expected with this front. While the
rainfall is not expected to be widespread, locally heavy downpours
may bring one quarter to one half an inch of rain to some locations.
With the basin average rainfall expected to remain low, there are no
concerns for flooding at this time.

&&

.PREV DISCUSSION...
Issued at 126 PM EDT Tue Apr 25 2017

AVIATION...

Cloud deck in the 5-9kft range is quickly eroding/shifting northeast
early this afternoon, so only bkn cigs will be from diurnal cumulus
development with bases in the 3-4kft range. Even this coverage will
remain scattered for the most part. Otherwise, VFR conditions will
prevail for the forecast with a chance of 5-6sm br late tonight.
Winds will remain southeast, but veer close to due south Wednesday,
becoming rather gusty in the 17z-19z time frame. There is an off
chance of a shra/tsra as KMBS as a warm front lifts quickly north
through the area, but not enough likelihood to mention at this time
as better organized activity appears to hold off to the west and
northwest.

//DTW THRESHOLD PROBABILITIES...

* None.


&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...NONE.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
&&

$$

DISCUSSION...SF/JD
MARINE.......DG
HYDROLOGY....DG
AVIATION.....DG


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