Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 210956
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
556 AM EDT Sat Apr 21 2018


.AVIATION...

VFR conditions will prevail as a surface high pressure continues to
dominate the weather conditions. Winds will remain around 5 knots or
less and variable at times with the high pressure directly overhead
this afternoon. An increase in cirrus clouds will move in today that
are associated with a low pressure drifting across the southern
plains.

.DTW THRESHOLD PROBABILITIES...

* None.

&&

.PREV DISCUSSION...
Issued at 350 AM EDT Sat Apr 21 2018

DISCUSSION...

Surface high pressure is diffuse but in full control of weather
across the Great Lakes early this morning. Radiational cooling prior
to thickening high clouds will ensure a chilly start to the day and
then the clouds will be a limiting factor for temperatures through
at least mid afternoon. These clouds are being shed by the closed
low over the central states and further supported by the entrance
region of an upper level jet max downstream of the ridge axis and
over the Great Lakes. Inherited highs in the lower to mid 50s look
good, especially as a southeast wind develops from Lake Erie into
the Detroit area mid to late afternoon. Upper 50s will be reachable
across interior sections toward the Tri Cities and possibly near 60
as high clouds thin mid to late afternoon.

Tonight the entrance region of the upper jet will migrate eastward
in a steady progressive fashion within the northern stream upper
level flow. This will allow a northern stream short wave ridge to
break over the Plains closed low and over the central Great Lakes
producing clearing sky tonight followed by full sun during Sunday.
While this occurs, there is good model agreement on the position of
the surface ridge axis becoming centered to the north of SE
Michigan. A deeper easterly low level flow will result which will
enhance the inland reach of cooling lake breeze influence. High
temperatures in the mid to upper 50s are then shaded firmly toward
the cooler end of the guidance range everywhere except interior
sections where highs are expected to reach the lower 60s. Lows
Sunday night will be influenced on the warm side by lingering
gradient wind expected to keep readings above freezing most
locations.

The surface high will be nudged farther east during Monday as the
closed low over the Plains drifts over the Tennessee Valley. The
main result in the Great Lakes will be a weaker surface pressure
gradient and lighter wind more receptive to land/lake differential
heating influence. This will allow highs to reach the mid and upper
60s over a greater portion of interior locations away from the
shorelines while subject to some increase in mid to high clouds.

Clouds will continue to increase Monday night as the now Tennessee
Valley closed low begins to open and lift toward the Ohio Valley.
This will begin a potentially more unsettled mid week period in SE
Michigan with a chance of rain Tuesday through Wednesday and
possibly into Thursday. The long range models show a complex
evolution of the upper air pattern during this time that is weakly
forced and exhibits low predictability on the location and intensity
of smaller scale features east of the Rockies. Some dependency on
the pace of renewed long wave amplification over the eastern Pacific
is also likely. The resulting model spread then seems reasonably
represented in guidance data suggesting a low chance of light rain
during the second half of next week.

MARINE...

High pressure maintaining its grip on the region through the weekend
resulting in light and variable winds and calm waves across the open
waters of Lake Huron, Lake St. Clair and western Lake Erie. Look for
light southerly winds on Monday as the surface high pressure drifts
east of Michigan. A slow moving mid level low pressure system
meandering across the southern US will lift northward into the Great
Lakes region late Tuesday into Wednesday. This will bring increasing
chances for precipitation and unsettled weather, which will continue
into the late week as a stronger trough is forecast impact the
region.

&&

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

$$

AVIATION.....AA
DISCUSSION...BT
MARINE.......AA


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