Area Forecast Discussion
Issued by NWS Grand Rapids, MI

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

000
FXUS63 KGRR 250227
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
927 PM EST Sat Feb 24 2018

LATEST UPDATE...
Update

.SYNOPSIS...
Issued at 325 PM EST Sat Feb 24 2018

A low pressure system will bring rain showers tonight and it will
become quite breezy overnight through Sunday afternoon. A high
pressure ridge will build in and bring fair weather Sunday through
Tuesday. The next low pressure system will bring potential for more
rain Wednesday through Thursday. Temperatures will continue to
average above to much above normal for this time of year through
most of the upcoming week.

&&

.UPDATE...
Issued at 924 PM EST Sat Feb 24 2018

Updated to take out the thunder mention. Instability looks to
remain in check tonight across the cwa. The best chance of thunder
will remain south of the cwa.

Regional radar shows the expected split in precipitation areas
moving toward the cwa. The heaviest area of rain will remain south
of the cwa and a lighter area will likely stay over Wisconsin.
Generally qpf less than a quarter inch is anticipated overnight.

&&

.SHORT TERM...(This evening through Monday night)
Issued at 325 PM EST Sat Feb 24 2018

An occluded front will bring rain showers tonight. Showers will
first develop over our sw fcst area during the early to mid
evening hour and move northeast and overspread our entire fcst
area overnight.

Most of our area will see around a quarter of an inch of rainfall
with localized higher amounts to around a third of an inch. A very
brief period of light freezing rain is possible late this evening
over our extreme nne fcst area (north of KMOP) before thermal
profiles at/near the sfc moderate to above freezing.

The potential for -fzra up there is very marginal though as even in
our northernmost fcst area sfc temps may stay just above freezing
for the most part. Any pockets of light freezing rain that do
develop would be very short lived/light with no impacts expected.
Convective potential tonight is very low since elevated instability
of any significance stays further south of lower Michigan.

Breezy conditions will develop overnight followed by windy
conditions for Sunday as winds veer to the southwest and ramp up to
15 to 30 kts. Some gusts to near 35 kts are possible Sunday
especially near the Lake Michigan shoreline.

Tranquil wx is fcst for the remainder of the short term fcst
period as a high pressure ridge takes hold of the wx pattern
Sunday night through Monday night.

.LONG TERM...(Tuesday through Saturday)
Issued at 325 PM EST Sat Feb 24 2018

It`s still several days out, but there is growing concern about the
potential for over an inch of rain from another srn stream system
next Thursday/Thursday night. This would not be good with the
current elevated river levels.

It looks like a very dynamic system which approaches as a negatively
tilted upper trough then closes off overhead or just south of
Michigan. This scenario supports a decent amount of rain over a
somewhat lengthy duration, with even the potential for a transition
to wet snow and high winds for the tail end of the event.

As the low approaches from the southwest, we see rain overspread the
region either Wednesday night or Thursday morning. Then on Thursday
the sfc system occludes and the trowal feature sets up overhead.
This is when we could begin to see some heavier rains which continue
into Thursday night. Most model/ensemble solutions are indicating
around an inch of QPF from this system with the potential for more.

The other issue is the risk of rain changing to wet snow on Thursday
night as dynamic cooling and low level cold advection takes place
while the trowal is still overhead. Winds could gust over 30 mph.

Prior to this system, expect two very mild days Tuesday and
Wednesday with highs in the 50s. Behind the system we will have
chillier weather with highs around 40, but that is still slightly
above normal.

&&

.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 626 PM EST Sat Feb 24 2018

Cigs will lower to IFR as showers move in from south to north this
evening. Cigs will begin to lift by mid morning as the rain moves
out and drir air moves in. Expecting skies to scatter by
afternoon.

We`ll see low level wind shear tonight ahead of a fronal boundary.
Better mixing toward morning will eliminate the wind shear threat.
Gusty winds are expected Sunday.


&&

.HYDROLOGY...
Issued at 325 PM EST Sat Feb 24 2018

The Grand River crest is moving through Kent County this weekend and
will move through Ottawa County early in the week. This crest will
likely stay below the levels seen in April 2013. The crest of the
Kalamazoo River is moving out of Kalamazoo and into Allegan county.
Kalamazoo / Comstock Twp river level reached record high levels,
surpassing other historic crests of 2008, 1985, and 1947.
The Thornapple River has crested at levels not seen since at least
1985. River levels in Battle Creek and Lansing were the highest seen
since 1975. Even after river levels crest, flooding will persist
along many rivers for a number of days. Flood impacts/extent in some
communities may differ compared to similar historic crests due to
recent flood mitigation projects or other development, and it will
take rigorous documentation and analysis to adjust flood
expectations for future events along the many river points that have
been affected.

Rainfall Saturday night will amount to a quarter inch and possibly
less. This will not have much impact on river levels, but could
slightly prolong the duration of flooding on some rivers. The next
precipitation event to monitor will be on Thursday. Model guidance
is suggesting the possibility for around an inch of precip (though
perhaps not all of it will be rain).

Please see the latest flood warning/advisory statements or river
hydrographs for details. Hydrographs are available by going to
weather.gov/grr and clicking on the "Rivers and Lakes" link above
the map of flood warnings.

&&

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

$$

UPDATE...04
SYNOPSIS...Laurens
SHORT TERM...Laurens
LONG TERM...Meade
AVIATION...04
HYDROLOGY...CAS



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.