Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 242224

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
624 PM EDT Sat Mar 24 2018


Maintenance of dry conditions under firm northeast flow will provide
VFR conditions under periodic thicker cirrus through the latter half
of the weekend. Low level winds will shift to E-NE on Sunday, which
may yield a very low coverage of stratus off Lake Erie midday in the
vicinity of YIP/DTW. Some lower end gustiness /aob 20 kts/ to the
winds again possible Sunday given the mixing depth.


*   Very low for cigs aob 5000 ft Sunday.


Issued at 336 PM EDT Sat Mar 24 2018



As of 335 PM EDT...Southeast Michigan continues to be influenced by
cold Canadian high pressure locked in place and ridging southward
into the region from Hudson Bay. Abundant dry air associated with
this continental high has helped keep the precipitation shield from
low pressure tracking across the mid-Mississippi River Valley well
south of the Michigan/Ohio border. The only noticeable effect from
this system has been an increasing canopy of thickening cirrus
(especially south of the I-69 corridor), which has allowed for
filtered sunshine at times. Further north across portions of the
northern Thumb and Saginaw Valley, cool and more moist northeasterly
boundary layer flow off Lake Huron has resulted in occasional
stratocu pushing into land areas.

Despite increasing high clouds and northeast flow, excellent mixing
in the boundary layer combined with enough insolation has allowed
temperatures to warm into the 40s for most areas, with the exception
being lower to mid 30s across the Thumb as cooler marine air moves
onshore. The northeast flow has been and will continue to be brisk
the rest of today, with frequent gusts of 20-30 mph possible
bringing a chill to the air for late March.

For tonight, the aforementioned low pressure system will continue
tracking well to the south and east, gradually weakening with time
as upper-level ridging amplifies noticeably in meridional extent.
The increasing sharpness of the upper ridge and the Canadian surface
high shifting slightly to the east will result in the flow slowly
veering from northeasterly to more easterly with time. A lingering
pressure gradient across the region and continued mechanical
boundary layer mixing will keep winds gusty at times through the
night, especially west of Lake Erie. Despite the winds, plenty of
dry air in place will help low temperatures fall into the lower 20s
for most areas, with upper teens from the northern Thumb
southwestward into the Flint area and glacial ridge.


The stretch of quiet and dry weather will continue through Monday as
upper-level ridging peaks across the region along with continued
influence from the Canadian surface high pressure, which will
actually strengthen to a solid mid 1040s hPa high by Monday as it
settles over northern New England. Cool easterly flow will continue
into Sunday with one more day of below normal temperatures as highs
struggle to hit the 40 degree mark.

The pattern will then begin to shift late Sunday night and into
Monday as inbound Pacific energy helps dig a deepening longwave
trough across the southwest CONUS. Pieces of embedded shortwave
energy will eject out of the longwave trough and help spawn ripples
of low pressure that will ride along a slow-moving frontal boundary
that will impact the region late Monday night and through Tuesday.

Ahead of this system though, the flow will take on an increasingly
southerly component as Gulf moisture is transported northward ahead
of the frontal boundary (PWATs increasing to around an inch by
Tuesday morning). This flow regime will allow for a moderation in
temperatures Monday toward normal values, with highs warming to near
50 degrees. Model guidance has trended a little slower with the
onset of precipitation Monday night as dry air from the Canadian
high holds on. 850 hPa temperatures surging into the 5-10 C range by
Tuesday morning will result in precipitation falling in the form of
rain. Tuesday looks to be a wet day with periods of moderate rain,
with enough elevated instability across southern areas for a few
possible rumbles of thunder as well. Dewpoints with this system will
rise well into the 40s and help to remove any remaining snow cover
across the region as temperatures warm further on Tuesday into the
lower 50s. At this time, it looks like a solid rainfall of 0.50-1.00
inches across the region, which is needed after the recent dry
spell. Frontal boundary and best moisture transport shift east
Tuesday night slowly ending rain chances from west to east.


Southwest flow regime will continue through much of the long term
period as broad longwave troughing remains in place across the
central CONUS. A series of northern stream impulses will eject out
of the longwave trough, bringing the potential for additional
precipitation chances the remainder of the work week, albeit with
low confidence in timing this far out. Column does look warm enough,
however, for rain to be the predominant p-type should precipitation
occur. Southern stream energy ejecting out of the lower Mississippi
River Valley towards the end of the work week will finally pull the
longwave troughing eastward, with confluent flow pattern aloft
setting up for the weekend.

With the southwest flow regime in place, temperatures will be near
to slightly above normal with daytime highs Wednesday and Thursday
reaching into the 50s for most areas, with lows generally in the
30s. Friday looks to be the beginning of another stretch of cooler
air filtering in across the region as temperatures fall back into
the 40s, with even colder air looking to return for the weekend to
round out the month of March.


Strong northeast flow (15 to 25 knots) will continue into tonight,
but winds gradually becoming due easterly by tomorrow. The NE fetch
will favor funneling into Saginaw Bay late this afternoon into this
evening, with gusts up around 30 knots. The exposed nearshore waters
along the Thumb will experience significant wave heights of 4 to 6
feet with maximum wave heights in excess of 10 feet at times
overnight. Increasing easterly flow tonight and into Sunday will
also lead to elevated waves for the western Lake Erie basin.

Increasing southeast to south winds early next week as a cold front
approaches. However, milder air and rain entering the Central Great
Lakes is expected to limit the top wind speeds to around 30 knots on
Tuesday over the open waters of Lake Huron.


A good soaking rain finally looks to be arriving late Monday night
through Tuesday night. Rainfall totals of half an inch to inch inch
are expected, with locally higher totals possible, especially if any
thunderstorms develop. Right now, there appears to be just a slight
chance of thunderstorms south of M-59. Regardless, flooding is not
expected, as rainfall will be occuring over a long duration and
river levels are running low.


Lake Huron...Small Craft Advisory until 2 AM EDT Monday for LHZ421-441>443.

     Small Craft Advisory until noon EDT Sunday for LHZ422.

Lake St Clair...NONE.
Michigan waters of Lake Erie...Small Craft Advisory from 9 PM this evening to 2 AM EDT Monday for




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