Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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680
FXUS63 KGRR 282359
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
759 PM EDT Fri Jul 28 2017

LATEST UPDATE...
Aviation/Marine

.SYNOPSIS...
Issued at 327 PM EDT Fri Jul 28 2017

Lower Michigan is in store for a fine stretch of summer weather
right through this weekend and into the first portion of next week.
Temperatures will start off mild, and gradually become very warm.
Humidity levels will be on the increase. The next chance of rain
will likely wait until at least mid-week next week.

&&

.SHORT TERM...(This evening through Sunday night)
Issued at 327 PM EDT Fri Jul 28 2017

Dry weather will rule for the entire short term period that goes
through Sunday night. We will see pleasant conditions through
Saturday, then getting a bit warmer on Sunday. Humidity levels will
likely stay low through the period.

Lower Michigan will remain under control of an upper ridge that will
remain almost stationary to our NW through the period. At the sfc,
ridging to our NW today through Saturday will pump in much drier
Canadian air from the NE. The sfc ridge will drop south by Sunday,
bringing a more WNW low level flow that will advect a bit more
warmer air over the area. The dry air and subsidence will keep the
dry conditions through the weekend.

.LONG TERM...(Monday through Friday)
Issued at 327 PM EDT Fri Jul 28 2017

For the most part this period will see near normal tempeatures and
while it will remain dry Mon and Tuesday, it now seems the risk of
significant precipitation Wednesday into Thursday is increasing.

The long wave pattern features a split upper jet with then northern
branch locked up in Canada (which will keep the truly cold air near
the Arctic) and more dominant southern branch.  The longwave pattern
feature a west coast ridge and and east coast trough. Pacific storms
dig into the off shore west coast trough, the ride over the western
CONUS ridge finally digging into the east coast trough. Since
Southwest Michigan is on upstream part of the eastern trough it will
remain dry here through Tuesday.

However there is a really strong storm from Siberia heading across
the Pacific early next week that will load into the trough off the
west coast. That will deepen the west coast trough, build the
western ridge and finally dig the east coast trough. It is this
scenario that I believe will finally lead to measurable
precipitation in the I-94 to I-96 area in the Wed/Thu time frame.
Given the system creating this is now leaving Asia, timing is
questionable but I do believe the chances of more than a tenth of an
inch of rain in the Wed/Thu time frame is improving.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 759 PM EDT Fri Jul 28 2017

Confidence is high that VFR conditions will continue tonight and
Saturday. Northeast sfc winds of 10 to 20 knots will diminish to
less that 10 knots later this evening but then increase again to
10 to 20 knots Saturday afternoon.

&&

.MARINE...
Issued at 759 PM EDT Fri Jul 28 2017

Issued a Nearshore Marine Forecast update earlier as several of
the buoys reached 4 feet. These higher wave heights should be
short lived however and only last a couple more hours as winds go
offshore after dark, so did not issue a small craft advisory.

A similar scenario may develop Saturday afternoon, where winds and
waves in the nearshore zones stay below advisory criteria much of
the day then temporarily meet criteria for a few hours in the
late afternoon and early evening hours as the northerly winds bend
slightly more onshore.

&&

.HYDROLOGY...
Issued at 327 PM EDT Fri Jul 28 2017

A handful of rivers in Central Lower Michigan continue to run above
normal due to recent rainfall. The remainder of sites are near
normal and trending lower. A dry weekend and very little rainfall to
add over the course of the next week will allow above normal rivers
to fall with no change expected with current rises. No flooding is
anticipated.

&&

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

$$

SYNOPSIS...NJJ
SHORT TERM...NJJ
LONG TERM...WDM
AVIATION...Meade
HYDROLOGY...JAM
MARINE...Meade



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