Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 192005
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
305 PM EST Sun Feb 19 2017

.DISCUSSION...

Warm air in place and sunshine has brough another day of record high
temperatures across the region as temperatures have surged into the
upper 50s to mid 60s. At 3PM the temperature in Detroit (DTW) was
65, breaking the old record of 64 (1884). Saginaw (MBS) was 58,
breaking its old record of 57 (1930), and Flint was 57, just a few
degrees shy of its record of 59 (1994). Will handle with Record
Event Reports (RERs) and social media this evening after the diurnal
cycle has completed.

Axis of surface high pressure will slide overhead this evening,
providing dry weather and light winds. A backdoor cold front will
meanwhile slip across Lake Huron and into the Thumb this evening.
Cooler air combined with cold northerly, and then easterly, flow off
Lake Huron will allow temperatures to drop more rapidly this evening
across the Thumb, with temps expected to fall into the 30s after
about 8PM. The remainder of the area will exhibit more of a diurnal
cooling cycle. Some mid clouds will settle into the area with the
front this evening and early tonight, while high clouds also stream
in ahead of low pressure lifting through the Northern Plains. Cloud
cover will limit radiational cooling, mitigating the fog threat
(there was quite a bit under the ridge axis upstream and into the
Ohio Valley last night). Will keep mention out of forecast given
virtually no support from forecast soundings. Clouds should keep
mins in the upper 20s over the Thumb, with low to mid 30s expected
elsewhere.

Cooler airmass at the start of the day will be offset some by
renewed warm air advection late tomorrow and Monday night as surface
low pressure lifts from the Northern Plains into Manitoba/Ontario.
This will provide another day with well-above normal temperatures,
despite highs 5-10 degrees cooler than today. Increasing easterly
flow off the cold waters of the Great Lakes will have some impact on
temperatures however, as will increasing clouds, holding max temps
near the lakeshores and much of the Thumb in the 40s, while allowing
areas further inland to warm into the low and even upper 50s.

Upper trough over the Western U.S. will dampen as it lifts northeast
and across the Great Lakes Monday night into Tuesday. Nice plume of
theta-e will advect up into the area ahead of a weak cold front,
with PW values forecast to rise to over 1 inch. Combination of
moisture and (mostly) mid-level forcing will provide a good coverage
of showers. Frontal boundary looks to clear the far southeast corner
of Michigan before the onset of the diurnal cycle, keeping
thunderstorms to our southeast later in the day. Lack of strong cold
air advection on Tuesday will not drop temps, but rather expect to
see an increase (warming to mid 50s-near 60) as the inversion we
will hold onto over the next few days is weakened by cooler air
aloft and steeper lapse rates in the low-levels fueled by sunshine.

Next area of low pressure tracking across the Northern Great Lakes
Wednesday will increase southerly flow and feed more warm air into
the area. There is some uncertainty as to how high we will be able
to mix as an inversion again strengthens, but it appears much of the
area will have a solid shot at 60 degree temperatures once again,
possibly even mid 60s.

Upper level ridge will hold across the area through Wednesday, which
will allow for dry weather to continue.  A low pressure system then
skirts across the northern Great Lakes region late Wednesday into
early Thursday bringing a slight chance for rain showers.  A more
significant storm system with then sets up over the Rockies and
moves northeast across the Central Plains on Friday before moving
across the region early Saturday.  This system has the potential to
bring rain, thunderstorms and gusty winds as it moves through the
area. Temperatures will remain well above normal to end out the
upcoming week before temps drop back to more near normal for the
upcoming weekend.

&&

.MARINE...

Light northerly winds tonight to become easterly on Monday as high
pressure drifts across the area.  Winds then strengthen out of the
southeast late Monday and Monday night in advance of a cold front.
Gusts of 25 to 30 knots during the overnight period, before
diminishing on Tuesday as the gradient weakens with the frontal
passage.  A modest post-frontal southwest wind to persist through
the mid week period.

&&

.PREV DISCUSSION...
Issued at 1147 AM EST Sun Feb 19 2017

AVIATION...

Dry and stable low level environment sustained under prevailing high
pressure ensures continued clear skies across the lowest 10 kft
through the period.  The degree of drying will keep any potential
shallow fog development very limited despite the weak gradient flow.
Northwest flow into the evening to become light/variable overnight,
then light easterly on Monday.

//DTW THRESHOLD PROBABILITIES...

* None


&&

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

$$

DISCUSSION...HLO/SS
MARINE.......MR
AVIATION.....MR


You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.



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