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Area forecast discussion 
National Weather Service Detroit/Pontiac Michigan
704 PM EDT Thursday Apr 17 2014



Aviation...

//discussion...

Dry low level environment will maintain a VFR ceiling through
this taf period. Middle level moisture does increase with time through
tonight as a cold front gradually eases across the region. Possible
brief MVFR visibility as a few light showers accompany this front during
the early to middle morning hours. A modest pre-frontal southeast to
south wind shifts to northwest with the frontal passage.

//Dtw threshold threats...

* medium confidence in a period of ceilings below 5kft middle-late
Friday morning.

&&

Previous discussion...issued 330 PM EDT Thursday Apr 17 2014

Short term... today and tonight

A baroclinic zone associated with a weak low lifting across Lake
Superior today is draped across the Midwest extending from near
Chicago through the Southern Plains. Although presently inactive
along much of its length, a band of showers associated with
developing fgen has begun to take shape near the Kansas/OK border. This
is also occurring ahead of a weak upper disturbance over the Texas
pandhandle. Although said disturbance is shown by the model guidance
to shear out over the Midwest this evening, a stronger wave near the
Gulf Coast is forecast to lift into the southern states by Friday
morning. This, in concert with height falls associated with the
trough rotating across the northern Great Lakes will be sufficient
to elicit a noteworthy jet response over the Ohio Valley. The
beginnings of this response are already evident over the lower MS
valley. This jet will further excite fgen along the frontal zone and
will be favorably positioned for Southeast Michigan to experience
added divergent flow aloft within the left exit region. 300 mb planviews
of ageostrophic wind actually show left exit forcing to be fairly
expansive and organized. Given these expectations, the forecast
remains in good shape. Likely probability of precipitation are still in place from the
Saginaw Valley and points eastward with showers expected to develop
into the area from the southeast as the upper jet lifts north and
intensifies. Clouds and a modest increase in low-level moisture will
maintain lows in the low to middle 40s.

Long term...Friday through next Thursday

Cold front and associated rain showers will exit the area from west
to east early on Friday as the surface low lifts up through eastern
Ontario and western Quebec. Models are all in agreement with a
secondary cold front then dropping down from the north during the
evening and overnight as a strong dome of Canadian high pressure
becomes centered over Ontario. This high should keep the weather
quiet from late Friday through early Sunday. Temperatures will be
the trickiest part of the forecast for the end of the week as
middle-April sunshine combats cold air advection behind the cold
fronts. Maximum temperatures in the 50s still look appropriate for
tomorrow...with a slight cool down into the upper 40s to middle 50s on
Saturday with high pressure limiting mixing and with easterly flow
off the cold Great Lakes.

Next low pressure system lifting up through Ontario will then send a
warm front northward across lower Michigan Saturday night. This will
allow temperatures to bottom out around midnight (mid 30s-near 40) before
slowly rising through the remainder of the night. Maximum temperatures will
then warm to above normal Sunday as h850 temperatures rise to an average of
+6c...supporting surface temperatures in the 60s. Occluded front associated
with the low looks to drop into northern lower Michigan on Sunday.
Moisture axis (pw of 0.75 inches) and low-level jet look to meet up
with the front at this time...but moisture and lift look positioned
too far north to affect most of the area on Sunday...perhaps just
brushing Bay/Midland/Huron counties with rain showers late.

Frontal boundary and elongated low pressure trough will cross the
area for Sunday night. The narrow frontal zone and surrounding dry
air will keep showers spotty. Cold air advection is on tap for next
week with temperatures just below the average beginning Tuesday and dry
conditions.

Marine...

A weakening low pressure system will track across Michigan and to
north of Lake Huron tonight. This will pull a cold front across the
area late tonight and early Friday...generating some rain showers.
Easterly winds will continue to gust to around 25 knots over Lake
Huron this evening...then become fairly light overnight as the low
crosses overhead. Strong high pressure will then build over the
central Great Lakes Friday night and Saturday...keeping conditions
fairly dry and calm. Southerly winds will pick up for the second
half of the weekend...remaining under 20 knots for most areas...as
another low pressure system approaches.

&&

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

&&

$$

Aviation.....Mr
short term...jvc
long term....hlo/de
marine.......hlo

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