Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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423
FXUS63 KGRR 170425
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
1125 PM EST Sat Feb 16 2019

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 131 PM EST Sat Feb 16 2019

-Continued Cold

-Light snow Sunday Afternoon into Sunday night with an inch or
 two possible


-Snow likely late Tuesday night and Wednesday

&&

.UPDATE...
Issued at 1040 PM EST Sat Feb 16 2019

I have increased the risk of snow late Sunday afternoon into
early Sunday evening. I also increased the snow amounts to 2 to
3" in the I-69 area for that same time frame.

This is based on the consistency of NAMDNG, NAM12 and HRRR
operational runs (NAM12 since the 16th 00z which continues to show
in increased QPF farther north and west and the HRRR 30 hour run
from the 18z and 00z runs). The NAM shows a decent area of mid-
level FGEN (850 to 700 mb) in the Sunday 7 pm till Monday 1 am
time frame near and south of I-94. This is in exit region of the
upper jet and there is a decent cold conveyor belt over this area.
Also we have decent isentropic ascent over the area near and
south of I-96 from mid day Sunday into late evening Sunday. All of
this leads me to believe we could see 2-3" of snow fall from
around 3 pm till 10 pm in the I-69 area Sunday.

So, bottom line, I have higher pop and higher snowfall amounts
near and south of I-96 but the emphasis is in the I-69 area for
Sunday evening.

&&

.DISCUSSION...(This evening through next Saturday)
Issued at 131 PM EST Sat Feb 16 2019

The main challenges deal with the potential impacts from the next
couple of storm systems.

The first system arrives on Sunday. Currently the dry airmass
in place will act to slow the arrival of the snow so the morning
should be mostly dry. Around noon the moisture deepens up as the
warm air advection strengths and mid level height falls occur. A
broad area of mostly light snow should move in and basically stay
over the area through much of Sunday night. The best forcing and
lift is over the southern half of the CWA where upwards of 2
inches looks possible. North of Grand Rapids the potential for
accumulations looks rather low. Typical of minor accumulation
events...there should be some slick spots on the roads Sunday
afternoon into Sunday night and possibly for the start of Monday.

A strong and deep southwesterly mid to upper level flow pattern
sets up for the middle part of the week from TX to the Great Lakes
Region. Gulf moisture gets draw into this system. Models are in
relative agreement in showing two main areas of heavy
precipitation with this event. One to the west of MI...where the
mid level wave tracks through resulting in stronger height falls.
The second will be in the OH Valley where the moisture convergence and
lift will be maximized around the low level jet. Here in MI we
will be in the middle with what looks like another drawn out
lighter snow event. This could be a low end advisory event...with
the main period of snow expected to be from later Tuesday night
night into Wednesday evening. There is still potential for heavier
precipitation here in MI...it just does not look like the most
likely scenario at this time.

Stay tuned for next weekend as the latest model runs are trying to
wind up a stronger storm for the Great Lakes Region.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1121 PM EST Sat Feb 16 2019

A mix of VFR/MVFR conditions will continue overnight with MVFR
conditions due to lingering low clouds which are most prevalent at
our southern terminals. Conditions will become primarily MVFR at
all the terminals Sunday as low clouds expand in coverage.
Conditions will deteriorate further to mainly IFR at all the
terminals Sunday afternoon through Sunday evening due to light
snow.

&&

.HYDROLOGY...
Issued at 1231 PM EST Sat Feb 16 2019

All the rivers in our area have now recovered or are falling
substantially after the snowmelt and rain events from earlier this
month. Several of our rivers do remain near bankfull, including the
Pere Marquette (at Scottville), the Maple River (at Maple Rapids),
the Grand River (near Ionia), and the Looking Glass River (near
Eagle). However, no significant renewed rises are expected on any of
our rivers in the next week.

There continues to be a major ice jam causing ongoing flooding in
the City of Portland. Water levels there will continue to fluctuate
up and down in response to shifting and changing ice conditions.

There is another ice jam that we are monitoring near Eastmanville,
near the 68th Avenue bridge. This ice jam is currently fairly small,
and is not currently resulting in additional flooding. There are no
ice jams in the Grand Rapids area, but we are still monitoring that
potential as the water will remain high for at least several days.

The weather over the next week looks cooler than normal and mostly
dry apart from chances for snow Sunday into Monday, and again
Wednesday. Any precipitation amounts appear to be light. These below
freezing temperatures will also limit additional snowmelt and allow
the rivers to continue to fall, however the cold temperatures will
also help maintain river ice. No significant warmups are expected to
cause any appreciable melting of snow.

&&

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

$$

UPDATE...WDM
SYNOPSIS...MJS
DISCUSSION...MJS
AVIATION...Laurens
HYDROLOGY...ANH



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