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Area forecast discussion 
National Weather Service Detroit/Pontiac Michigan
635 am EDT Thursday Apr 24 2014



Aviation...

//discussion...

High pressure settling into the region will bring VFR conditions
through 00z Friday. High/middle clouds will increase and thicken
overnight and into Thursday ahead of an approaching low pressure
system. Light and variable winds overnight will become easterly
around 10 knots as the low approaches on Thursday. Rain from this
system is expected to hold off until after 06z Friday. With timing
still not certain late Thursday night will leave dtw dry late
Thursday night as a prob30 group is not warranted that far out.

//Dtw threshold threats...

* none

&&

Previous discussion...issued 342 am EDT Thursday Apr 24 2014

Short term...today and tonight

While high pressure will steadily shift to the east and southeast
today...dry low level flow southeast flow will continue to funnel
back into the area from this high pressure center into tonight. This
will slow the encroachment of rain as a complex dual-structured low
pressure system progresses into the Great Lakes/Ohio Valley. Given
consistent model trends in this regard...will back off on shower
chances...with best chance of widespread shower activity coming
after 09z tonight as the southernmost low center moves into the Ohio
Valley. This positioning will also focus the best chance of showers
over the southern County Warning Area...so will further adjust probability of precipitation with this in
mind.

Otherwise...temperatures will moderated slightly today as highs
reach the middle 50s to lower 60s from north to south across the County Warning Area.
The coolest regions will exist immediately downwind of the Great
Lakes near upper 40s/lower 50s will be norm. With increasing clouds
and winds tonight...temperatures will remain relatively mild and
range mainly in the 40-45 degree range.

Long term...Friday through Wednesday

Models continue to be slower with the connected pair of lows
traversing Michigan early Friday while also continuing to jump around with
the evolution of an expansive upper low working through the Great
Lakes for the better part of next week. Lots of room for adjustments
with the forecast in the coming days.

For Friday...the slower solution continues to play out and has been
accounted for in the forecast with the highest probability of precipitation now early Friday
vs Thursday night. The trickle down effects will be slightly cooler
temperatures on Friday that previously advertised with the additional
clouds and precipitation and with the thermal ridge already through the
area by daybreak. Dry air will quickly moves into the area in the
evening behind the low which will track through Northern Ohio. This
will produce a few dry hours before a slight chance of showers
re-enters the picture via a cold front and weak band of fgen
dropping through lower Michigan tied to the second low crossing through
northern Michigan.

A middle level ridge will build into the area for the better part of
Saturday and Sunday...amplifying as it enters the region due to a
deepening upper level trough entering the West Coast.
In addition...the southern extent of a surface ridge will build into the
area in the wake of the exiting pair of lows from Friday. Saturday
will be dry and Sunday is a bit questionable as a warm front begins
lifting into SW Michigan. Models show this as a fading band of fgen over a
dry bl resulting frmo northerly surface flow. Kept a slight chance
Sunday but could see this being a mostly dry day.

Models offer no clarity for the large cutoff middle level low that will
move over the area late Monday and hold through the week as blocking
pattern sets up. A frontal boundary will set up through the Ohio
Valley and will likely lift into the area at some point. Will likely
see several rounds of precipitation from this upper level feature and
resulting surface low. Will keep mostly chance probability of precipitation for the week and we
can resolve tighter windows as system starts taking shape. More
confidence is placed in temperatures as 500mb temperatures around -15 to
-20c and 850mb temperatures near 0c will hold over the area for much of the
coming work week. With clouds from the upper low in place as
well...will likely turn out to be a pretty dreary week.

Marine...

Light easterly flow will persist through much of today as high
pressure will yield weak gradient flow. Winds will ramp up a bit
late tonight and early Friday morning as a low pressure system
slides through the southern Great Lakes. Waves will pile up along
the shoreline but a short residence time of moderate flow looks to
circumvent the need of small crafts currently. Winds will quickly
shift to the west Friday afternoon behind a weak front...ramping up
late Friday night and veering northwesterly as a stronger cold front
moves through the Great Lakes. At this time it appears that gusts
will stay below gales and small crafts.

&&

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

&&

$$

Aviation.....Dg
short term...dg
long term....drk
marine.......drk



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