Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 251923

Area Forecast Discussion
National Weather Service Grand Rapids MI
325 PM EDT MON JUL 25 2016

Synopsis/Short Term/Long Term/Marine

Issued at 325 PM EDT Mon Jul 25 2016

High pressure will continue to build into the Great Lakes region
and produce fair weather through Tuesday. A cold front moving in
from the north will bring a small chance of a shower or storm late
Tuesday night through Wednesday. Another low pressure system will
bring a chance of showers and storms late in the week.


.SHORT TERM...(This evening through Wednesday night)
Issued at 325 PM EDT Mon Jul 25 2016

Short term fcst concerns are fairly minimal as high pressure
continues to build in to produce fair weather tonight through
Tuesday evening. There is potential for some patchy fog to develop
during the early morning hours Tuesday primarily over our northern
fcst area as winds go calm overnight.

A backdoor cold frontal boundary moving in from the north will
bring a small chance of a shower or thunderstorm very late Tuesday
night across our northern fcst area. We will maintain low pops for
a chance of a shower or storm across our area Wednesday as the
frontal boundary continues to sink south across our area.

Any convection that does develop Wednesday will be weak given
weak instability and weak forcing with the boundary. Patchy fog
may develop again Wednesday night as dew point values climb to the
middle to perhaps upper 60`s ahead of the front.

.LONG TERM...(Thursday through Monday)
Issued at 325 PM EDT Mon Jul 25 2016

Weak west-east oriented sfc frontal boundary which drops in from the
north appears to stall over the region Thursday and Friday and
should be a focus for scattered convection.

The ECMWF shows a rather potent wave of low pressure moving along
the boundary on Friday, and there is even a suggestion of heavy rain
potential within the deformation zone of this system as the trough
aloft digs and the upper low closes off.

The GFS meanwhile does not look like the ECMWF toward the end of the
week. It is much less amplified at 500 mb and shows only
weak/progressive shortwaves in the northwest flow aloft. It does not
show the Friday wave at all, and also builds the canadian sfc high
farther south which pushes the sfc boundary farther south.

The vast differences in the GFS/ECMWF model solutions toward the end
of the week leads to a low confidence fcst. If the ECMWF solution
verifies, a breezy/gloomy/showery Saturday could follow on the back
side of the departing wave.

Both models show the sfc high dominating on Sunday so perhaps a
better chance for dry/pleasant weather for the second half of the
weekend should Saturday be impacted by the ECMWF wave.


.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 145 PM EDT Mon Jul 25 2016

VFR weather is expected over the next 24 hours with the exception
of the risk of some patchy radiation fog late tonight into early
Tue morning. Continued the theme of the previous TAFS, which
advertises 3-5 mile MVFR vsbys from 09z through about 13z. Some
IFR vsbys are possible too but dew pts have been falling today so
still not confident enough to go with any IFR in the TAFs.


Issued at 325 PM EDT Mon Jul 25 2016

High pressure will result in minimal wind speeds and wave heights
through midweek with wave heights generally near to below two
feet. Patchy fog may pose a hazard to mariners toward midweek as
higher humidity levels return.


Issued at 1254 PM EDT Mon Jul 25 2016

No river flooding is expected through the week. Area wide rain of
around an inch with locally up to 3 inches (mainly near Lake
Michigan) fell this weekend. A small chance of rain is in the
forecast Wednesday through Friday. River levels have risen and are
at or above normal for this time of year. Even with the
precipitation, no rivers should approach flood level.


.GRR Watches/Warnings/Advisories...


SHORT TERM...Laurens
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