Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 290001

Area Forecast Discussion
National Weather Service Grand Rapids MI
701 PM EST Mon Nov 28 2016


Issued at 333 PM EST Mon Nov 28 2016

A deep low pressure system remains anchored over the Northern
Plains, and southerly flow will advect in plenty of moisture this
evening and overnight. Widespread rain and gusty winds are
expected this evening and overnight. Gusty winds to around 40 mph
could result in scattered power outages. Dry air moves in on
Tuesday and should allow for a good deal of sunshine. Highs on
Tuesday will be in the mid to upper 50s. Colder and showery
weather is expected from mid to late week.


.SHORT TERM...(This evening through Wednesday night)
Issued at 333 PM EST Mon Nov 28 2016

Widespread rain and gusty winds are expected this evening and
overnight. Some stronger wind gusts to around 40-45 mph could result
in scattered power outages.

An area of rain was pushing north into Michigan from Illinois and
Indiana this afternoon. This rain was on the nose of stronger low-
level Theta-E advection. Rain will continue to overspread the area
from south to north this afternoon and evening. Precipitable water
will increase to around 1.00 inch this evening. The DTX sounding
climatology indicates normal PW is around 0.40 inches. Storm total
rainfall amounts of 0.50-1.00 inches are expected.

Potential vorticity maxima was generally co-located with a dry slot
on water vapor imagery in Oklahoma pushing into Missouri and
Arkansas. The PV max will swing northeast around the deep, parent
cyclone to northern Indiana around 06z. Excellent upper level
support will be in place tonight, as Michigan will be positioned in
the exit region of the subtropical jet. Strong upper divergence and
the significant mid-level wave will promote low-level cyclogenesis.
A ~60 kt southerly LLJ will push in this afternoon and evening.
Stability weakens overnight as colder air advects in aloft. MLCAPE
around 100-200 J/kg after 03z or so could allow for
convective/showery activity. Will feature a slight chance for
thunder over the southern half of the area. Any heavier shower or
storm would increase the likelihood of seeing 40+ kt gusts and
scattered power outages at the ground.

The dry slot overspreads the area on Tuesday, and West Michigan
could see a fair amount of sun. This will allow high temperatures to
rise into the mid to upper 50s, at least 15 degrees above normal.
Rain chances will return Tuesday night-Wednesday night as another
mid-level wave swings in and the upper low moves overhead.
Precipitation should get a boost from Lake Michigan Wednesday night.

.LONG TERM...(Thursday through Monday)
Issued at 333 PM EST Mon Nov 28 2016

Forecast concerns deal with weak troughing over the Great Lakes
early in the period and then the evolution of a potential snow storm
late in the weekend.

The models are in pretty good agreement showing a weakening upper
trough over the Great Lakes Thursday and Thursday night. Short waves
rotating through the flow may produce a few rain/snow showers during
this time frame. Temperatures are marginal for snow with the best
potential during the night.

The ecmwf has a very interesting solution late in the weekend that
so far isn`t supported by the gfs. Both models show a large storm
moving onshore the west coast Thursday and digging toward the
southern Rockies by Friday. The models diverge at that point with
the gfs cutting off the low over the Gulf of California and the
ecmwf continuing across the country as a high amplitude wave. The
ecmwf subsequently develops a sfc low in Texas and then moves it
toward western Ohio late in the weekend. The gfs on the other hand
only moves the northern portion of the trough eastward through the
Great Lakes on Sunday. The gfs would give us an inch or so of rain,
perhaps mixed with snow. The ecmwf however would perhaps result in a
significant snow storm given the track of the low. This is certainly
situation we`ll watch closely.


.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 700 PM EST Mon Nov 28 2016

Some heavy rain and IFR conditions will prevail this evening with
conditions improving after midnight as the heavier rains move
north. There could be a brief thunderstorm with wing gusts over
40 knots between 06Z and 12Z, with the highest chance across
southern Lower Michigan from AZO to JXN. The chance of this was
deemed too low to include in the forecast for now.

Winds will generally be southeast around 15 knots with gusts near
25 knots this evening then go south and southwest after midnight.


Issued at 333 PM EST Mon Nov 28 2016

The Small Craft Advisory has been extended through 7 pm Tuesday.
Southerly winds to around 30 knots and waves of 4-8 feet will make
conditions on Lake Michigan dangerous for smaller craft.


Issued at 333 PM EST Mon Nov 28 2016

Basin average amounts look to be an additional 0.50" to 0.75", with
the highest toward the western reaches of the Muskegon, Grand, and
Kalamazoo River basins. River responses to this rainfall will come in
the form of mainly within bank rises, but a few sites where a Flood
Advisory has been issued should go above bankfull after the rain
ends. No significant flooding is expected with this event. Looking
ahead, lake effect precipitation for the middle and latter portions
of the week should not have a noticeable impact on river levels.


LM...Small Craft Advisory until 7 PM EST Tuesday for LMZ844>849.



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