Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 181750
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
1250 PM EST Thu Jan 18 2018

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 247 AM EST Thu Jan 18 2018

Fair weather with moderating temperatures will continue into the
weekend before low pressure brings some rain on Sunday into
Monday. The low passes by Monday night with colder air wrapping in
for Tuesday along with some snow by Tuesday into Wednesday.

&&

.UPDATE...
Issued at 1029 AM EST Thu Jan 18 2018

We have updated the forecast this morning to account for the
latest trends in the low cloud cover. This involved expanding the
amount of low cloud cover a bit as shallow colder air (925 mb
around -7C) coming over the lake is sufficient for developing
lake stratocumulus. The models trend this cloud cover to lift to
the North a bit today, and then redevelop to the South tonight.

&&

.SHORT TERM...(Today through Saturday)
Issued at 247 AM EST Thu Jan 18 2018

No significant weather in the near term as temperatures continue
to moderate in general warm advection pattern. Expect precip to
hold off through Saturday afternoon but clouds should be on the
increase as moisture streams up from the south in advance of low
tracking west of Lower Michigan.

.LONG TERM...(Saturday night through Wednesday)
Issued at 247 AM EST Thu Jan 18 2018

Strong southerly flow warm air advection out ahead of the Plains
states low pressure system will result in much above normal
temperatures Saturday night through Sunday into Monday. Some light
mixed pcpn may develop as early as Saturday night in an area of
isentropic upglide north of the warm front.

The best chance for pcpn will come Sunday night and Monday and
thermal profiles will have moderated sufficiently enough by then for
pcpn to fall in the form of plain rain across most of our fcst area.
Some fog may develop due to the high boundary layer moisture and
melting snow pack.

Temperatures will return to near to perhaps even slightly below
normal by the middle of next week as cold air advection occurs on
the back side of that departing system. We also expect some snow
showers Tuesday with decent wrap around moisture on the back side of
the system. An upper level system may bring more snow showers for
midweek although a sfc high pressure ridge will mitigate the snow
shower potential by Wednesday considerably.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1250 PM EST Thu Jan 18 2018

Low clouds (ceilings in the 1500 ft range) have overspread most of
our I-96 SW MI TAF sites as of 1730z. Skies were either clear or
nearly so for our I-94 taf sites however. The skies should clear
from SW to NE early to mid afternoon so that by 22z all taf sites
will be either be clear or mostly clear. The low clouds will
redevelop after midnight so that all sites should have low MVFR
ceilings by 7 am. These clouds, like today, should mix out from
south to north by late morning.

There will be low level wind shear early tonight but after 06z
winds decrease some so I only included it in the TAFs between 22z
and 04z.


&&

.HYDROLOGY...
Issued at 318 PM EST Wed Jan 17 2018

Slight improvement has been noted on the Muskegon River in Mecosta
County. Water levels have receded by approximately 6 to 12 inches.
Resulting impacts are relatively similar to when they were first
reported Monday evening. Residents along the river are not out of
the woods yet, but recent decline in levels signals enough that
volume of water is making it under the ice to allow conditions to
slowly improve.

The combination of warmer temperatures and precipitation over the
weekend into early next week continues to be a concern. Guidance is
rather persistent in pushing near/above 40 degree temperatures into
Lower Michigan Friday through Monday. NOHRSC (National Operational
Hydrologic Remote Sensing) estimates show aerial averages of around
0.50" liquid equivalent in the current snowpack with highest amounts
distributed south and east of Grand Rapids. Precipitation totals are
forecast to be 0.50" over Southern Lower Michigan to more than 1.00"
over West-Central Lower Michigan through early next week.

Flood potential could increase through the weekend, especially early
next week, as temperatures and runoff impacts rivers.

&&

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

$$

UPDATE...NJJ
SYNOPSIS...Ostuno
SHORT TERM...Ostuno
LONG TERM...Laurens
AVIATION...WDM
HYDROLOGY...JAM



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