Scientific Forecaster Discussion
fxus63 kdtx 240402
Area forecast discussion
National Weather Service Detroit/Pontiac Michigan
1202 am EDT sun Sep 24 2017
Strong upper ridging anchored over the region will maintain
favorable aviation conditions through the period. This environment
may support patchy fog during the early morning period, particularly
at dtw/yip. Otherwise, very dry column with stability will produce
clear skies through Sunday evening.
//Dtw threshold probabilities...
issued at 349 PM EDT Sat Sep 23 2017
Another day within the impressive +590 Dam Ridge and yet another day
of approaching and exceeding record highs. Flint has already broken
the record high of 89 degrees that was set in 1936, and dtw still
has another hour or two to reach the record of 90 degrees set in
1936. From a top down perspective, there are a number of indicators
that suggests The Heart of the upper level ridge axis will now drift
through the cwa during the next 6 hours. These signs include
geopotential heights at 500mb closing off overhead this afternoon,
and the center of the 850mb anticyclonic circulation drifting across
the Detroit Metro. Main development today has been surface dewpoints
that are now somewhat deflated in the upper 50s to lower 60s, which
has kept heat indices in the 89 to 93 range. Another sign of less
boundary layer moisture has been a very muted and flat cumulus
response. Not expecting any spurious shower or thunderstorm
development today based on observational trends and forecast
soundings that show relatively deep capping in the 4-7 kft agl
layer. For minimum values tonight, started with a straight
persistence forecast but did massage some sources in that were
keeping lows in the lower to mid 60s based on cooler dewpoints.
The closed off center of the upper level ridge will roll eastward
into portions of PA and upstate New York on Sunday. Local extension of
both the 500mb and 300mb ridge axes will extend back into
southeastern Michigan both on Sunday and again Monday, so little
change in weather is expected. Main forecast narrative will continue
to be hot, with afternoon readings climbing toward and exceeding the
90 degree mark. Weather story out references record highs for the
next couple days. As for a heat headline, will refrain with heat
indices remaining in the upper 80s to low 90s and with nighttime
minimums that have fallen back into the mid 60s.
Tuesday will mark the last day of the prolonged stretch of above
normal temperatures as the upper level ridge slides east. Highs will
again reach near record high values in the upper 80s over much of Southeast
Michigan under mainly sunny skies. A major pattern shift will then
begin midweek as a wave lifting through the western Great Lakes
pulls a cold front through the region early Wednesday. The better
forcing for precipitation looks to remain north of Southeast Michigan
leaving only a slight chance for showers and thunderstorms
accompanying the frontal passage. Temperatures will then struggle to
climb through the 70s on Wednesday as cold advection commences.
Temperatures will fall to near normal values on Thursday with highs
in the upper 60s before a northern stream wave drops southeast
through the region on Friday. This wave will bring increased cloud
cover and showers along with a reinforcing shot of cooler air as
highs fall into the lower 60s.
Extended stretch of very warm and humid conditions continues through
the latter half of the weekend as the region remains under the
influence of strong upper ridging. This pattern will support light
winds - under 15 knots - and low waves during this time. These
conditions will persist into early next week. A cold front crossing
the central Great Lakes Tuesday night will bring a low chance of
shower and thunderstorm activity, along with winds shifting to the
west and increasing to around 15 knots.
Lake St Clair...none.
Michigan waters of Lake Erie...none.