Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 171651
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
1151 AM EST Fri Feb 17 2017

LATEST UPDATE...
Hydro

.SYNOPSIS...
Issued at 226 AM EST Fri Feb 17 2017

Unseasonably warm temperatures will persist well into next week with
highs commonly in the 50s, which is 15 to 20 degrees above normal
for this time of year. After a dry weekend, rain chances return
for Monday night and Tuesday.

&&

.SHORT TERM...(Today through Sunday)
Issued at 226 AM EST Fri Feb 17 2017

Main concern through the period is fog developing early Saturday
morning with increasing dewpoints streaming into the area,
particularly farther north where residual snowpack may exist. Have
introduced patchy fog in the forecast but this could overperform and
perhaps last well into the day Saturday, which could also result in
highs below the currently advertised upper 40s for the US-10 region.
As noted in the marine discussion below, there also is some concern
for fog along the immediate lakeshore during this time.

.LONG TERM...(Sunday night through Thursday)
Issued at 226 AM EST Fri Feb 17 2017

Surface and upper ridging continues to build over SW MI leading to
quiet weather Monday and well above normal temps.  Monday and
Tuesday look like the warmest days with highs in the 50s.  However
as the ridge drifts east, the rain chances will return late Monday
night into Tuesday.  Decent agreement in the models showing a cold
front should come through Tuesday afternoon which would favor most
of the rain coming Tuesday morning.

The pattern becomes more zonal and progressive late in the long
term.  This should bring another cold front through the region Wed
night.  This front should have a better push of cool air behind it.
So it should become less warm, Wed night and Thu, but still a bit
above normal.

&&

.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
Issued at 620 AM EST Fri Feb 17 2017

No changes in thinking from the previous issuance. High confidence
for VFR through 00Z this evening. As noted before, fog may develop
after 06Z over much of central and lower MI mainly north of the
terminals. However, LAN would be the most likely to see any
impacts and this could involve a brief excursion below 3SM
visibility. KGRR could similarly see some fog but is even less
likely to touch IFR visibility thresholds.


&&

.MARINE...
Issued at 226 AM EST Fri Feb 17 2017

Primary concern is potential for marine fog Saturday morning into
Saturday as more humid air streams across Lake Michigan. GLERL GLCFS
advertises the cooler nearshore water temperatures to remain in the
upper 30s - similar to forecast dewpoints - so would not rule out
some fog. Onshore flow would also impact the immediate lakeshore
with reduced visibilities.


&&

.HYDROLOGY...
Issued at 1141 AM EST Fri Feb 17 2017

Precipitation chances will remain low through Monday across the
region. Area rivers will continue to fall slowly as a result. The
precipitation event late Monday into Tuesday could cause new
rises to develop. Temperatures will remain warm enough to prevent
ice formation.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...None.
&&

$$

SYNOPSIS...TJT
SHORT TERM...TJT
LONG TERM...JK
AVIATION...TJT
HYDROLOGY...MWS
MARINE...TJT



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