Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
FXUS63 KDTX 170827
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
327 AM EST Fri Feb 17 2017
Split flow across the CONUS features an upper low across Texas and a
building mid level ridge across the upper Ms Valley/wrn Great Lakes.
This mid level ridge will expand across Lower Mi today, while the
upper low over Texas drifts to Oklahoma. A band of mid level clouds
currently extends across the ern half of Se Mi, associated with the
mid level frontal boundary. This mid level front and its associated
cloud cover will slide east of the area today, although there will
be an abundance of high clouds across the area. The sfc warm front
will nudge into SW Lower Mi. It will struggle to make inroads into
Se Mi given the southeast winds off the lakes at the sfc. This will
establish a decent thermal gradient across the area this afternoon,
with temps pushing 50 near the Ohio border, while temps hold in the
30s across the thumb region.
The mid level ridge will dampen as it pushes east of Lower Mi
tonight as a mid level short wave impulse races from ND across Lake
Superior. This will result in a tightening of the low level westerly
gradient, leading to a core of strong winds above the shallow stable
layer across srn Lower Mi. This will drive the sfc warm front across
the forecast area, with 925mb temps forecast to rise to a record
+12C overnight. This warm air advection will support rising temps
during the overnight. Although sfc dewpoints are forecast to
approach 40, low level mixing should hinder fog and low cloud
development. Confluent mid level flow will hold across Lower Mi Sat
and Saturday night amidst a quasi zonal northern stream, while a
weakening upper low meanders across the deep south. Daytime heating
on Sat will mix into the warm air above the shallow stable layer,
leading to mild and breezy conditions. High temps may actually break
60 over much of the forecast area. This will likely tie or break
record highs for the 18th. For Detroit 62 (1976); Flint 56 (2011);
Saginaw 53 (1981).
Deepening of an upper trough over ern Canada Sat night into Sunday
will force the low level thermal gradient slightly southward. This
will support a little lower high temps compared to Saturday
(although temps will still be a good 15 to 20 degrees above late Feb
norms). Conditions will remain dry, although there may be a little
more mid and high level clouds compared to Saturday.
Very mild conditions will prevail through the duration of the
forecast period as longer wavelength troughing off the west coast
keeps mid level heights rather high across the ern US. The next
chance for rain will be Tues associated with a mid level wave
forecast to eject out of the southern rockies. Otherwise, temps are
expected to hold 10 to 20 degrees above average. Intervals of
southeast flow may however hold temps a little cooler across the
thumb region at times.
Moderate south flow will veer to southwesterly as a weak cold front
translates across the waters tonight. Westerly flow persists,
eventually becoming light northerly as high pressure builds in from
the west by the end of the weekend. Wind gusts below 25 kts over
most areas throughout this time.
Issued at 1153 PM EST Thu Feb 16 2017
Favorable late February aviation conditions will be in place for
the rest of tonight through Friday night. VFR in mixed mid and high
clouds/mostly above 5000 ft will be accompanied by light southeast
wind during the night. Similar conditions will then continue through
the day as low pressure over the Plains sends the surface warm front
into the Great Lakes. Based on observations along the front during
the evening, expect VFR will continue as the boundary enters Lower
Michigan during the afternoon and as the warm sector of the
system moves in Friday night.
//DTW THRESHOLD PROBABILITIES...
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
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