Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus63 kdtx 182250 

Area forecast discussion
National Weather Service Detroit/Pontiac Michigan
650 PM EDT Fri Oct 18 2019


During the course of the night, there will be the development of a
light southeast flow off Lake Erie. The relatively Warm Lake temps
and potential for some nocturnal cooling inland raises the concerns
for some fog development around Metro Detroit off the lake plume
late tonight. The low level south-southeast flow will strengthen
overnight, thus enhancing mixing into the very dry air atop what
will likely be a very shallow stable layer. This should mitigate the
development of a more impactful fog layer. So for this reason, only
a brief interval of MVFR type vsby restrictions in fog will be
introduced at the Metro tafs around 12z Sat morning. Otherwise,
light winds with only high clouds above 20k ft will prevail through
the night.

Dtw threshold probabilities...

* none.


Previous discussion...
issued at 357 PM EDT Fri Oct 18 2019


Cool high pressure is in control of the weather across Southeast Michigan
today and tonight. Some fair weather cumulus over The Thumb during
early afternoon gave way to thin cirrus that still allowed sunshine a
chance add some warmth to slightly below normal highs in the mid
50s. This leads to a chilly start this evening as temperatures drop
quickly toward 40 degrees and then steady out in the mid to upper 30s
overnight. Surface high pressure sliding eastward generates a light
southeast wind that prevents temperatures from reaching full radiational
cooling potential by sunrise Saturday.

Continued development of south wind during Saturday occurs as high
pressure moves farther east to the Atlantic coast and as the next
low pressure system moves from the plains today into northern
Ontario and the Midwest states by Saturday afternoon. A slight boost
in temperatures is main result under gradually thickening high
clouds that balances afternoon highs in the lower half of the 60s.
The pressure gradient over lower Michigan is projected weaker in
model solutions compared to over the plains today which cuts into
the more aggressive temperature advection pattern observed upstream.
That being said, readings still end up above the normal values of 60
at dtw each day this weekend.

A shallow/modified Gulf moisture supply is forced through the High
Plains by high pressure over the lower Mississippi Valley and then
drawn into lower Michigan Saturday night. It appears adequate to
fuel some weak convection over the Midwest during peak heating
Saturday afternoon. The latest model solutions then remain in good
agreement with a marked weakening trend as activity moves eastward
Saturday night. The front washes out convincingly over lower
Michigan as this section becomes parallel to the upper level height
field and as the surface low moves to the northern reaches of Hudson
Bay. Fragmented to nonexistent forcing within the remnants of the
frontal zone continue supporting a dry forecast while clouds linger
into Sunday within the leftover inverted trough. The residual clouds
along with high pressure over Northern Lake Huron suggest leaning the
forecast toward the lower end of guidance offerings which still
means highs in the lower half of the 60s.

Pacific upper level jet energy remains abundant and reinforces the
long wave trough centered over The Rockies during the weekend. The
leading short wave is shown to proceed through classic Lee side
cyclogenesis during Sunday and is able to tap a better supply of
Gulf moisture Sunday night. There is good model agreement on a
strong cold front developing and moving into the Great Lakes during
peak heating Monday afternoon. The occlusion process is also slated
for this time period right about over lower Michigan which could be
a limiting factor for surface based convection while the moisture
supply adds confidence to a likely/numerous pop forecast Monday
before the dry slot surges in Monday night. Monday could also be the
last time we see 70 degrees this year if the warm sector is able to
surge into Southeast Michigan prior to occlusion.

As the low lifts up off to the northeast, Post frontal conditions on
Tuesday will bring cooler air back across the area. High
temperatures settle back down into the 50s beginning Tuesday and
last through the end of the extended forecast. The area is
forecasted to remain dry for Wednesday and Thursday before unsettled
weather makes a move back in at the end of the week.


High pressure drifting across the central Great Lakes is bringing
dry conditions through the remainder of today and through much of
the weekend. Light winds today will pick up slightly tonight and
tomorrow as an increasing southerly pressure gradient allows for
winds of 10 to 15 knots with gusts of 20 to 25 knots across central
and Northern Lake Huron. The gradient weakens on Sunday allowing
winds to decrease back to around 10 knots or less while becoming
more easterly. By Monday morning, winds ramp up out of the southeast
as a low pressure system lifts across Western Lake Superior. Winds
through the rest of Monday will bring potential for gales with gusts
at or above 30 knots over much of Lake Huron. Elevated winds above
20 knots persist into Tuesday with Post frontal flow veering to the
southwest. Conditions for Tuesday look to remain below gales at this


DTX watches/warnings/advisories...
Lake Huron...none.
Lake St Clair...none.
Michigan waters of Lake Erie...none.



National Weather Service Glossary of Abbreviations