Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 231701

Area Forecast Discussion
National Weather Service Grand Rapids MI
101 PM EDT Fri Mar 23 2018


Issued at 325 AM EDT Fri Mar 23 2018

A dry forecast is expected right through the weekend with a
persistent area of high pressure situated from Ontario and Quebec
into the Great Lakes. The high will bring fair weather and
seasonable temperatures. Highs the next few days will generally be
in the lower 40s.

An area of low pressure will move through the Great Lakes region
early next week bringing moderating temperatures for Monday and
Tuesday when highs will push into the 50s. The warmer readings will
come with some rain however from Monday night into Tuesday night.
Rainfall amounts of a half inch to an inch appear possible during
this time frame.


Issued at 1110 AM EDT Fri Mar 23 2018

Tweaked max temps for this afternoon. Went a bit higher in the
west, while held temps close to the previous forecast in the east.
With winds turning NE this afternoon a cooling effect will be seen
across the eastern CWA with winds coming off of Saginaw Bay. But
NE flow is a down sloping flow for the western CWA, so bumped
temps up there.


.SHORT TERM...(Today through Sunday)
Issued at 325 AM EDT Fri Mar 23 2018

The main weather feature of note in the short term will be an area
of low pressure that will bring mixed precipitation and a swath of
snow across Illinois and Indiana tonight into Saturday. The upper
wave associated with the system will eject out of the Rockies today
and into the plains tonight and slide just southwest of our area on
Saturday. All the models keep Southwest Lower Michigan dry, so not
expecting much more than a canopy of mid clouds and possibly some
mid level virga in the far southwest corner of the forecast area.

It will be brisk on Saturday with a stiff east to northeast wind.
Expecting winds of 12 to 25 mph. A tight pressure gradient will be
found across the area between a 1040mb high near James Bay and a
1005mb low moving into the Ohio Valley.

As for the details of the forecast (all cloud related), we should be
mostly sunny today with increasing high clouds tonight, especially
across the south. Clouds across the south during the morning on
Saturday will move south out of the area during the afternoon.
Mainly clear skies are expected Saturday evening. Saturday night
into Sunday morning we may see some stratocumulus develop off of
Lake Huron in a northeast flow. Delta T`s will increase to in excess
of 10C and the NAM is indicating some moisture spreading in around
2000ft. The clouds look to mix out for Sunday afternoon.

Not much change in temperatures from what we have been seeing. Highs
the next few days will be in the low to mid 40s. Lows will remain in
the upper teens to lower 20s.

.LONG TERM...(Sunday night through Thursday)
Issued at 325 AM EDT Fri Mar 23 2018

Temps will undergo a moderating trend for the early to middle
portion of next week as southerly flow develops on the back side of
the departing ridge Monday. High temps early to mid next week should
reach the lower to middle 50`s.

The continued southerly flow will result in increasing moisture and
a chance of light warm air advection showers by Monday night. A slow
moving low pressure system will bring more widespread showers
Tuesday through Tuesday night into Wednesday. No convection is
expected at this time mainly due to weak instability.

A colder airmass will advect in behind that system late in the week
when temperatures will return to near normal for this time of year.


.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 100 PM EDT Fri Mar 23 2018

VFR conditions will continue through the next 24 hours with only
an increase in high cloudiness late in the period.

The only aviation concern will be the winds. A north wind around
10 knots will continue through the afternoon, then diminishing
early this evening. East winds will increase and become gusty shortly
after daybreak Saturday. Expect gusts to around 20 knots that will
continue beyond 18Z Sat.


Issued at 325 AM EDT Fri Mar 23 2018

Winds and waves will remain below Small Craft Advisory criteria
today and tonight. North winds today of 10-20 knots will shift to
the east late tonight increasing towards daybreak. Waves will likely
reach the 2 to 4 foot range today.

It is not out of the realm of possibilities that we may need a SCA
for winds on Saturday into Saturday night with sustained winds of 20
to 30 knots away from shore. The winds will be off the land, but
once you get out a few miles the stiff east wind will be noticeable.
The easterly winds will persist right through the weekend. Waves
this weekend with a limited fetch (east winds) will generally be in
the 1 to 3 foot range.


Issued at 1110 AM EDT Fri Mar 23 2018

Concern for elevated fire risk into the weekend. Many people will
be doing yard work, but hopefully consider conditions of low RH,
dry fuels, and strong winds that could lead to a quickly
spreading fire. We will begin to send messages on social media
today regarding this increasing threat. Will also mention this in
an updated HWO.

RH values will remain in the 25 to 35 percent range both Saturday
and Sunday. Dry fuels of dead grasses, leaves and brush from the
winter is abundant without any pcpn over the past week and a half.
Sustained winds of 15 to 25 mph from the east is expected each
day. These winds pick up around daybreak on Saturday and continue
day and night through Monday. Gustier winds will be possible
Saturday especially over the Grand River Valley as ENE winds off
of Saginaw Bay funnel through the basin. We should finally get
relief from these conditions by Monday night with a high
likelihood of rain.


Issued at 1244 PM EDT Fri Mar 23 2018

With the exception of the Portage River near Vicksburg, area
rivers and streams are holding well within their banks as
streamflow analysis reveals that river flows across the region are
mostly near to below normal. Rain continues to look likely Monday
night into Tuesday night but at this point amounts will likely
produce within bank rises on area rivers and streams, given
projections of 0.50" to 1.00" for many locations.




LONG TERM...Laurens
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