Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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000
FXUS63 KGRR 112355
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
655 PM EST Sun Feb 11 2018

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 255 PM EST Sun Feb 11 2018

High pressure will build in tonight through Tuesday and bring fair
weather. Temperatures will undergo a moderating trend midweek with
a chance of rain showers by Wednesday night and Thursday.
Temperatures will return to near normal for this time of year by
Friday and Saturday.

&&

.SHORT TERM...(This evening through Tuesday night)
Issued at 255 PM EST Sun Feb 11 2018

We will allow the advisory to expire as scheduled at 3 pm. Radar
trends show lingering light snow is continuing to taper off.
A consensus of high res guidance indicates snow will end completely
late this afternoon.

Fcst concerns are minimal tonight through Tuesday night as high
pressure will build in and produce fair wx. A consensus of 12Z
numerical guidance is several degrees too mild with regard to
mins tonight. Given expansive snow cover across our area...
decreasing clouds (clearing line is already making its way over
Lake MI) and diminishing wind speeds min temps will fall into the
single digits above zero toward daybreak Monday. Temps should
bottom out in the lower to middle teens near Lake MI.

12Z guidance consensus time height rh progs suggest we should get
quite a bit of sun Monday. This will allow temps to reach the
lower to middle 20`s in the afternoon after a cold start to the
day.

Another cold night is fcst Monday night with mins in the single
digits above zero. High temps Tuesday will reach the mid to upper
20`s as winds become southerly. Temps Tuesday night will only drop
a few degrees given continued southerly winds and more extensive
cloud cover by then.

.LONG TERM...(Wednesday through Sunday)
Issued at 255 PM EST Sun Feb 11 2018

The weather will be significantly quieter over the next seven days
than over the previous seven days.  Temperatures will rise above
normal Wednesday only to return to below normal Friday into
Saturday. Precipitation will be sparse during this time period. We
could get rain showers with the cold front Thursday morning, any
precipitation with that event will be light at best. An ejecting
southern stream wave may interact with the colder air Friday
bringing us a mix rain and snow event but most of that looks to stay
south of Michigan at this time.

The large scale picture features the polar vortex, which has been
displaced southward into Northern Hudson Bay, will retrograde south
and west this week. This in combination with several digging Pacific
shortwaves helps to retrograde the upper trough from the east coast
to the western CONUS by the end of this week. With the upper trough
our west, that clearly leads to warmer temperatures. It also ends
the threat of lake effect snow showers due to the warmer
temperatures.

As for our next major precipitation event, as I suggested yesterday,
we have a deepening upper trough over the western Conus that will
try to come east. This will lead to a very wet system coming out of
the Gulf early in the following week. If we get rain or snow from
this will depend on how this system comes out. Both the ECMWF and
GEFS ensembles continue to show about half their members giving us
around an inch of precipitation around the 20th/21st. Colder
temperatures will then expected by the middle of the following week.
That is shown clearly by the latest run of the CFSv2.  The ECMWF
ensembles are a little slower to bring the cold air back into the
Great Lakes.

Meanwhile, as stated before this coming week should be warmer than
last week and feature mostly days with no or little precipitation.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 655 PM EST Sun Feb 11 2018

The snow has ended, but some lingering MVFR ceilings remain in the
wake of the morning snow. From KBIV to KGRR and points to the
east, ceilings around 2,000ft hang on as of 00z. By 03z, expecting
these lower ceilings to push off to the east. VFR weather will
prevail later this evening (03z-06z) in most areas.

After 06z, we are expecting some lake stratocumulus and even a few
flurries to develop for places like KMKG and KGRR. Inland TAF
sites will likely remain clear or have only scattered clouds. The
clouds along the lakeshore will continue into Monday before all
areas become VFR by mid afternoon.

&&

.HYDROLOGY...
Issued at 255 PM EST Sun Feb 11 2018

Ice jams and minor low land flooding will continue, at least for a
couple days, as cold temperatures will continue into mid week. A
flood advisory remains in effect for the Looking Glass River near
Eagle due to elevated levels of water/ice from an ice jam. River
levels in the vicinity of ice jams will continue to fluctuate by
several feet until the ice breaks free.

High temperatures above freezing Wednesday and Thursday combined
with occasional sunshine will allow some snow and ice to melt. There
is also a chance for light rain Wednesday night and Thursday. Warmer
temperatures and runoff from rain and snow will increase the
potential for the river ice to shift around. However, it does not
look significant enough to break up the larger ice jams the area is
currently experiencing.

&&

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

$$

SYNOPSIS...Laurens
SHORT TERM...Laurens
LONG TERM...WDM
AVIATION...Duke
HYDROLOGY...63



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