Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 221725

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
125 PM EDT Sun Apr 22 2018


Surface high pressure and strong midlevel anticyclonic gyre aloft
has very stable atmospheric conditions in place over Southeast
Michigan. Pressure gradient has setup over the state between surface
high pressure moving into the Northeast U.S. and low pressure over
the lower Mississippi River Valley. This easterly wind is forecasted
to persist throughout the taf period. Northing more than some FEW-
SCT cirrus is anticipated.


* None.


Issued at 902 AM EDT Sun Apr 22 2018


As of 900 AM EDT...Ongoing forecast in good shape with only a few
tweaks based on the latest trends in observations. High pressure in
control again today, and with abundant sunshine, expecting an
excellent spring day across southeast Michigan. High temperatures
will reach into the lower 60s for most areas, with a few mid 60s
readings not out of the question across inland areas. Closer to the
shorelines, highs will struggle to make it into the upper 40s-mid 50s
with a light easterly flow advecting a cooler marine layer across
these areas.

Issued at 347 AM EDT Sun Apr 22 2018


Surface high pressure remains in full control across the Great Lakes
and is set to provide an ideal spring day across SE Michigan.
Plentiful sunshine will help lift high temperatures into the upper
50s to lower 60s which are at normal values for the date. Interior
sections could even see readings touch mid 60s outside of the
slightly extended lake breeze reach boosted by light easterly
gradient flow. The position of the surface high, as it becomes
centered over southern Ontario during the afternoon, presents a
struggle for shoreline areas to reach 50.

The easterly gradient will strengthen slightly tonight as the closed
low moves into the mid Mississippi valley. This will be enough to
maintain a 5 to 10 knot wind and keep temperatures from reaching
full radiational cooling potential overnight. The upper level ridge
centered overhead is otherwise well positioned to hold back mid and
high clouds until closer to Monday afternoon. Lows in the mid to
upper 30s will then get a boost from a mostly sunny start to the day,
and despite increasing clouds during the afternoon, expect highs in
the mid 60s to near 70 away from the lakeshore. The potential for 70
is in play due to substantial low level thickness warming as the
surface high is nudged even farther out of the Great Lakes toward
the Atlantic coast.

The closed low will finally begin to affect Lower Michigan Monday
night as the northern fringe of its moisture field reaches the Ohio
border. The system will be in the initial stage of opening up into
the northern stream westerlies leading to weak mid level isentropic
lift and moisture transport into SE Michigan. Model soundings show
thorough saturation in the low levels after midnight in the Detroit
area spreading northward to the Tri Cities and northern Thumb
through Tuesday into Tuesday night. There is better model agreement
on the northern stream upper trough digging more aggressively into
the Great Lakes during this time and helping to draw moisture
northward. Guidance POPs reflect that with a trend more firmly into
the chance category and seem reasonable given the low overall model
QPF. If the timing and intensity of the northern stream amplification
can hold then expect the upward trend in POPs to continue for a high
POP/low QPF scenario, especially Tuesday afternoon and night.

High pressure building into the Great Lakes Wednesday into Thursday
is shown to be mostly of Pacific origin in the extended model
output. Therefore, cooler guidance temperatures in the 50s are only
slightly below normal during the second half of the week and into
next weekend. The trend in the extended 00Z NWP cycle is for renewed
upper level development over the Great Lakes around the Friday period
with GFS and CMC solutions offering another closed low right over the
Great Lakes. The ECMWF favors a more progressive open wave which is
supported by the GEFS ensemble mean and moves the system through the
region early in the weekend.


High pressure across the Great Lakes will continue to keep calm
conditions today as it gradually lifts just northeast of Lake Huron
this afternoon. The will bring light easterly winds of 10 kts or
less and calm waters across the open waters of Lake Huron, Lake St.
Clair and western lake Erie. Waves of 2 feet or less and light winds
veering out of the southeast ahead of an approaching weak low
pressure system coming from the southern US. This surface low
pressure system combined with a shortwave trough swinging through
the Great Lakes will bring increasing chances for precipitation and
unsettled weather on Tuesday and through mid-week.


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



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