Area Forecast Discussion
Issued by NWS Grand Rapids, MI

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

FXUS63 KGRR 271130

Area Forecast Discussion
National Weather Service Grand Rapids MI
730 AM EDT WED JUL 27 2016


Issued at 329 AM EDT Wed Jul 27 2016

A slow moving cold front will result in scattered thunderstorms
today, mostly north of I-96. It will be very warm with highs from
the mid 80s to near 90. A wave on the front will slow its push
south tonight and as the wave on the front moves across Lower
Michigan Thursday, it will result in more widespread showers and a
few thunderstorms. Due to the clouds and showers it will be cooler
with highs in the lower 80s. After the frontal wave moves south
and east of the area Friday skies will start to clear as Canadian
high pressure builds in behind the front. The weekend will be
partly cloudy with near normal temperatures thanks to that
Canadian high.


Issued at 549 AM EDT Wed Jul 27 2016

I added early morning thunderstorms to our NW CWA as per the
latest radar loops. These storms are on the leading edge of deeper
moisture which and be seen on water vapor loops. Moisture
transport vectors show a max along the west coast of Michigan near
TVC at 03 am that drops nearly due south to MKG by 08 am but
weakens as it does so. there is between 500 and 1000 j/kg of
elevated cape in this area. So I figure this area of showers will
drift south over the next few hours then dissipate as the sun
comes up and results in better mixing.


.SHORT TERM...(Today through Friday)
Issued at 329 AM EDT Wed Jul 27 2016

We are tracking a slow moving cold front and the associated
thunderstorms for today. the front will only reach near I-96 by
evening. Any thunderstorms will remain near and north of the
front. The front will then stall near I-96 tonight as a surface
wave tracks along the front, crossing Lower Michigan Thursday.
Areas near and north of I-94 could see a decent amount of rain
Thursday if the ECMWF 00z run is correct as it results in over
and inch of rain over a large area of our central and northern
CWA. Since the models have been back and forth on this idea I have
50 pct pops for tomorrow but this may have to increased if the
latest ECMWF is to be believed.

That system clears the area Friday bringing clearing skies and
near normal temperatures.

.LONG TERM...(Friday night through Tuesday)
Issued at 329 AM EDT Wed Jul 27 2016

Zonal flow will transition to more of an upper trough by late this
week. But that doesn`t necessarily mean that we`ll see rain. Indeed,
a sfc high over eastern Ontario and Quebec will produce a relatively
dry northeast flow Friday night through Monday which should keep
pcpn pushed south of the cwa. GFS and ECMWF show a few short waves
moving across Indiana and Ohio over the weekend, but almost all of
the pcpn is shown south of the cwa. We`ll keep a slight chance of
pcpn in south of I-94 Friday night and Saturday, but more than
likely we`re looking at dry wx through Tuesday.

Highs will mostly be above normal due to the lower dewpoints and the
ridge to the northeast. Highs in the lower 80s Saturday will climb
to the mid to upper 80s Sunday through Tuesday.


.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 730 AM EDT Wed Jul 27 2016

There is a chance of thunderstorms this afternoon, mostly near and
west of US-131 so I put VCTS for that. tonight a cold front comes
through with will bring vfr cigs to the western taf sites but
those closer to US-69, due to the flow off Lake Huron, may see
ifr/mvfr cigs toward 10z as northeast winds bring those low clouds
into the area.


Issued at 329 AM EDT Wed Jul 27 2016

No major issues seen through Saturday.


Issued at 150 PM EDT Tue Jul 26 2016

No river flooding is expected into next week. There is a chance of
rain in the forecast Wednesday into Saturday night. Total rainfall
should be under an inch. River levels are around normal for this
time of year. Even with the precipitation, no rivers should approach
flood level.


.GRR Watches/Warnings/Advisories...


MARINE...WDM is the U.S. government's official web portal to all federal, state and local government web resources and services.