Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 171818

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
118 PM EST Sat Feb 17 2018


Pockets of SCT to BKN MVFR CIGS for the early part of this afternoon
with the main plume of moisture bringing overcast high clouds. More
defined MVFR cloud deck will arrive later this afternoon as some
moisture continues to be brought northward under good southwesterly
flow. As of now, obs show the more widespread MVFR CIGS across
WI/IL/IN. A cold front will be moving through tonight and bring with
it a chance of flurries to light snow showers between 01-06Z.
Moisture and forcing is still lacking somewhat, so do not expect
much accumulation north of a dusting with these snow showers. Winds
will veer slightly more westerly overnight before returning to
southerly by tomorrow morning as skies begin to clear.

For DTW...Scattered clouds below 5000 ft remain across the area with
a more pronounced cloud deck below 5000 ft arriving later this
afternoon and early evening. Snow showers will accompany a front
sweeping through along with the lower ceilings. A few hours between
01-06Z will carry snow showers with potential for a minor reduction
in visibility.


* Medium for ceilings aob 5000ft through the afternoon. High for

* High for ptype as snow this evening.


Issued at 258 AM EST Sat Feb 17 2018


A weak shortwave will cross the area quickly this evening with a
brief period of light snow showers or flurries possible. At this
time, it appears snowfall accumulations will be insignificant (a
dusting or less in most locations). Another shortwave within the sub-
tropical jet stream is still forecast to remain well south of the
area during this time frame, focusing heavier/more widespread rain
over the Tennessee Valley.

Once this shortwave races off to the east coast, upper ridging will
begin to build across the eastern CONUS as a large upper trough digs
into the western CONUS. This pattern shift is expected to lead to a
period of very mild and wet weather from very late Sunday night on
through Monday into Tuesday/Tuesday night (and perhaps into parts of

While the weather will remain dry through Sunday, the building ridge
will already lead to moderating temperatures with highs reaching the
40s in many locations during the afternoon. Several shortwaves will
then eject northeast into the area from the expanding upper trough
to the west and provide numerous waves of rain during the first half
of next week.

The first of these will bring precipitation to the area very late
Sunday night into Monday. Most (or all) of this precipitation will
fall in the form of rain as temperatures climb steadily into the mid
30s by the time this moisture arrives over the area in the 09z-15z
time frame Monday morning. While models are rather inconsistent in
the exact placement of best FGEN forcing (and hence, heavier bands
of rainfall), all agree in a very good chance of rainfall with an
increasing chance into Monday afternoon/night. Local rainfall
amounts with this first impulse could very well top half an inch in
some locations.

Additional shortwave energy then lifts into the region Tuesday into
Tuesday night. The upper trough/ridge configuration still suggests
the surface low pressure system associated with this system will
lift into the central Great Lakes just to the west of Southeast
Lower Michigan. This puts the area well within the warm sector and
anticipate temperatures will remain in the 40s and 50s across most
of the area Monday night with highs climbing into the 50s and 60s on

It is during this period that the best chance of heavy rain and
embedded thunderstorms will exist with local rainfall amounts of an
additional inch quite possible. All told, some areas may receive 2+
inches of rain from Monday into Tuesday evening. While significant
flooding is not anticipated, the combination of this widespread
rainfall and continued snow melt will certainly lead to some minor
issues across the area. In addition, the mild temperatures will
increase the probability of ice on area streams/rivers breaking up
to some degree, potentially exacerbating local flooding concerns.

The aforementioned upper trough over the west will then flatten
somewhat and expand east across northern NOAM. While the period of
heavy precipitation will likely shift east of the area Tuesday
night, additional rain (and possibly snow) will linger into
Wednesday this upper level feature expands across the region.

Overall, temperatures will settle back into the 30s/40s during the
last half of the week after the very mild period from Monday into
Tuesday evening. Some moderation will be possible into next weekend
as the next shot of precipitation shift back east/northeast into the


Southwesterly winds will increase into the afternoon hours as the
gradient tightens in advance of an approaching cold front. Wind
gusts will peak around 30 knots through the early evening with
higher gust potential being tempered by extensive ice cover. Winds
will veer to the west-northwest in the wake of the cold front
Saturday night but will quickly flip back to the south on Sunday as
a warm front lifts up through the Great Lakes. Winds will again
approach 30 knots Sunday evening.


There is high probability of a substantial warming trend Monday into
Tuesday, resulting in a complete melt off of all snow cover across
Southeast Michigan. This warming will occur as a result of strong
southerly flow ahead of a slow moving front. In addition, periods of
rain are expected along this front, beginning Monday and possibly
persisting into Wednesday. Forecast confidence on how quickly this
system moves east of the region and where the axis of heaviest rain
will fall still carries a good deal of uncertainty. There is however
a chance that total rainfall amounts from Monday into Tuesday night
will reach two inches in some locations. While the complete melt of
snow will not be enough to support flooding, the potential rainfall
with the snow melt will lead to a chance for significant rises on
area rivers and streams. The mild weather will also lead to some
break up of ice on area rivers and streams perhaps exacerbating
issues in some locales.


Record high temperatures will be possible across much of southeast
Michigan Tuesday. Here is a look at record high temperatures for
Tuesday, February 20th:

Detroit                63 (set in 2016)
Flint                  61 (set in 1930)
Saginaw/Tri-Cities     62 (set in 1930)


Lake Huron...NONE.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.



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