Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 151802
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
202 PM EDT Sun Apr 15 2018

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 328 AM EDT Sun Apr 15 2018

The early spring storm will continue into today as a slow moving
storm, centered to our south continues to slowly move east.
Significant accumulations of ice and sleet are expected this
morning before temperatures warm enough to change the freezing
rain to rain near and south of I-96. I will remain windy into this
afternoon and temperatures will remain cold through most of this
coming week. The precipitation should become all snow tonight and
continue into Tuesday morning. Accumulations will be limited.

&&

.UPDATE...
Issued at 1118 AM EDT Sun Apr 15 2018

Late morning fcst updates included extending the southern portion
of the winter storm warning which was to expire at noon until 4
pm. A polling of sfc obs/mesonets from across this area at 15Z
shows sfc temps across the vast majority of this area are still at
or below freezing in the 29 to 32 degree range.

KGRR and rgnl radar trends still show significant pcpn coming in
from the south and moderate rain extends all the way down to
northern IN. Therefore we expect several more hours of light to
moderate freezing rain with pockets of heavy fzra which will
result in very hazardous travel conditions and continued ice
accretion. Power outages will likely increase through the rest of
the day especially near to north of I-96 due to increasing weight
from the fzra.

We were able to drop Kalamazoo and Van Buren counties from the
winter wx advisory where pcpn type has transitioned to plain rain
with sfc temps now up around 33 to 34 degrees.

&&

.SHORT TERM...(Today through Tuesday)
Issued at 328 AM EDT Sun Apr 15 2018

I extended the Winter Storm Warning north of I-96 till late
afternoon as it may take that long for that area to get above
freezing. All of the models, including the hi-res models, show
two bands of heavy precipitation today, the first one comes
through mid morning, then the band on the trailing side of the
system (deformation zone) comes through late morning into mid
afternoon. I expect there will be a significant amount of
freezing rain yet over the northern sections into late afternoon
due to that issue. Winds will continue to be strong and gusty this
morning but diminish this afternoon. Due to the models (03z HRRRX
and others) show around of inch of QPF today with between between
and quarter and half inch of that falling after noon today this
will continue the hazards in northern sections.

Tonight the system finally moves east enough to pull out the warm
layer, so when the wrap around precipitation moves in it will be
cold enough for mostly snow. I expect on and off light snow over
the area into Tuesday morning.

.LONG TERM...(Tuesday night through Saturday)
Issued at 328 AM EDT Sun Apr 15 2018

We are looking at one system in the long term that could potentially
impact the area from early Wed through Thu. Otherwise, the other
noteworthy item will be a potential return to near to slightly above
average temps by next weekend.

We expect that the last effects from the current system should move
out just prior to the beginning of the long term on Tue night. The
low will move out, and we will see a short wave ridge control the
weather Tue night and maybe early Wed.

Pcpn chances will increase on Wed from West to East across the area.
A strong short wave trough will emerge from the Rockies, and close
off as it approaches the region. It will advect warmer air ahead of
it, but it will not have a direct moisture feed from the Gulf of
Mexico. The threat of pcpn will linger from Wed into Thu as we see
pcpn ahead of the developing triple point, and then from the parent
low as it translates east.

Much of the pcpn will likely be in the form of rain with this
system. Some snow will be possible on the leading edge of the pcpn
as cool enough air will still be in place and early on Wed before
diurnal heating takes place. Snow will also be possible on Thu when
the colder air moves in on the backside of the low.

Once the system moves out of the area on Thu, a decent ridge aloft
will move in, and with sfc ridging. Milder air will move in as the
low level flow will not be from cold source regions. The mild air,
and sunshine will allow temps to warm toward 60 next weekend.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 200 PM EDT Sun Apr 15 2018

Significant icing hazard continues early this afternoon with
freezing rain and sleet persisting, however the precipitation will
be diminishing from south to north over the next couple hours.

Sfc temps will be gradually rising as well, will most terminals
recovering above freezing by 20-21Z. Despite precipitation ending
or diminishing to drizzle, IFR/LIFR cigs should remain/become
widespread into tonight. Actually some fog restricting
visibilities below one mile may develop tonight, especially from
GRR to the east and south, as the sfc winds decrease to light.

Winds will increase out of the northwest to 12-22 kts and gusty by
mid morning Monday. This should blow out the fog and LIFR, but the
snow showers are expected to develop which and flight categories
should remain predominantly IFR.


&&

.MARINE...
Issued at 328 AM EDT Sun Apr 15 2018

Winds have began to decrease over the southern parts of our Near
Shore and the models show this decrease in winds will spread north
through the Near Shore by mid afternoon. So for now I expunged the
gale headlines over the southern section in favor a small craft
advisory that I ran through Monday evening. The day shift can
adjust the gale to a small craft as they see fit.


&&

.HYDROLOGY...
Issued at 200 PM EDT Sat Apr 14 2018

As precipitation continues across the region, river levels are
around normal but rising. Precipitation totals will range from over
an inch and a half to around three inches through Sunday night. This
could lead to river flooding, but at this time only the Portage
River near Vicksburg is forecast to go above flood stage. Stay
tuned, as more flood warnings may be on the way if all of the
precipitation is realized.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Winter Storm Warning until 4 PM EDT this afternoon for
     MIZ056>059-064>067.

     Winter Weather Advisory until 3 PM EDT this afternoon for MIZ073-
     074.

     Winter Storm Warning until 5 PM EDT this afternoon for
     MIZ037>040-043>046-050>052.

LM...Gale Warning until 8 PM EDT this evening for LMZ847>849.

     Small Craft Advisory until 8 PM EDT Monday for LMZ844>846.

&&

$$

UPDATE...Laurens
SYNOPSIS...WDM
SHORT TERM...WDM
LONG TERM...NJJ
AVIATION...Meade
HYDROLOGY...63
MARINE...WDM



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