Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 261457

Area Forecast Discussion
National Weather Service Grand Rapids MI
1057 AM EDT Sun Mar 26 2017


Issued at 317 AM EDT Sun Mar 26 2017

Rain will continue today and tonight as low pressure moves across
Lower Michigan. The rain will taper off Monday morning but then
another low approaches by MOnday afternoon with more wet weather.
High pressure and drier weather arrives on Tuesday.


Issued at 1057 AM EDT Sun Mar 26 2017

Not much change to the forecast needed this morning. We have more
widespread showers flowing in over the area out ahead of the
surface front that is current positioned over Central Indiana. We
expect showers to be plentiful through the early afternoon hours
before the deeper moisture departs. Then we will see more of the
convective type pcpn develop in association with the upper low
that is currently over IL.

We are not expecting much in the way of sunshine to help
destabilize the atmosphere. Some instability will be present as
some warmer air advects in and the the upper low moves overhead.
Fcst instability parameters shows we could see a few hundred j/kg
of CAPE at best, which is maybe a bit overdone given the models
are over-forecasting temps to start with this morning. The
soundings show this CAPE is a bit thin on the soundings, and wind
shear is lacking.


.SHORT TERM...(Today through Tuesday)
Issued at 317 AM EDT Sun Mar 26 2017

Kept categorical POPs much of today as southerly fetch of deep
moisture continues along with isentropic ascent north of sfc warm
front. The front lifts north by afternoon with enough instability
to bring back the chance of thunder across the southern half of
the forecast area this afternoon.

Sfc low tracks across Lower Michigan and pulls away to the
northeast tonight with some drying out by Monday morning. This is
short lives as another low ejecting out of the base the longwave
western CONUS trough quickly follows for Monday afternoon and
night. The precip shield is progged to extend into the southern
half of the forecast area as the sfc center tracks just south of
Lower Michigan.

Northerly flow and drying/sfc ridging will arrive on the back side
of the low on Tuesday with showers ending by afternoon.

.LONG TERM...(Tuesday night through Saturday)
Issued at 317 AM EDT Sun Mar 26 2017

Fair wx will finally return Tuesday night through midweek as a
Canadian high pressure ridge to the north takes hold of our wx
pattern. Temperatures will return to near normal for this time of
year by midweek as well.

A bit more uncertainty now exists in terms of the fcst for late
in the week as the operational 00Z gfs guidance solution now
suggests that the ridge would remain in control of our wx pattern
through Thursday and Friday with the low pressure system emerging
out of the southern Plains states staying well south of our region
late in the week.

Conversely the 00Z ecmwf guidance still suggests that the low
pressure system will move much further north and bring our area rain
late in the week. This notion has been supported by a consensus of
most medium range guidance the past several days and the evolution
of the upper level pattern late in the week also favors this

Therefore we see the 00z gfs as an outlier solution and we will
maintain chc pops for rain late in the week. Temps should remain
rather close to normal for this time of year late in the week into
next weekend.


.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 942 AM EDT Sun Mar 26 2017

I updated the TAFs to change the timing of rainfall at all of the
sites, adjust ceiling forecasts and add dense fog tonight.

Based on what I see on radar and is forecast by the high
resolution models, the primary band of rain assoicated with the
system will move through the TAF sites in the 15z to 21z time
frame. I adjusted the tafs to best match what I believe will be
the timing of the rain.

Will there be thunderstorms? Seems to this forecaster there is an
extensive cloud cover over the entire area and it does not seem to
me we will get much in the way of holes in the clouds. The high
resolution models and the SPC SREF agree the best instability
will stay well south of our CWA. Maybe JXN may be on the northwest
edge of significant instability from mid afternoon into early
this evening but that is questionable. So I did not put VCTS in
any of the tafs but it would seem JXN and LAN would be the most
likely TAFs to get a thunderstorm of all of our TAF sites this
afternoon and early this evening.

As for fog, well the surface low tracks trough the CWA tonight and
brings light winds over an area that is very wet and will remain
very wet. However it is questionable if the sky will clear. Also
there is still 10 to 20 knots in the boundary layer until around
09z. So there will be significant mixing till then. However after
that it would seem dense fog would be likely. I added that to most
of the taf sites.


Issued at 715 AM EDT Sun Mar 26 2017

Winds have diminished and the Small Craft advisory is cancelled.
Do not expect any waves to winds to pose a hazard to small craft
through Monday night.


Issued at 307 PM EDT Sat Mar 25 2017

Locally over one inch of rain has fallen particularly over the
eastern reaches of the Grand River, as well as the Thornapple River,
Maple River, Looking Glass River, and Sycamore Creek. Additional
rainfall through Sunday will continue to aid in boosting river
levels for these areas. Above bankfull rises are anticipated over
the next few days for Ionia, Hastings, Maple Rapids, Eagle, and
Holt. Another round of rain toward the end of the week may ensure
that these rivers remain near or above bankfull. We will continue to
monitor the trends.




LONG TERM...Laurens
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