Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 301924
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
325 PM EDT Thu Mar 30 2017

LATEST UPDATE...
Synopsis/Short Term/Long Term/Marine

.SYNOPSIS...
Issued at 325 PM EDT Thu Mar 30 2017

Showers will continue tonight through most of Friday and a few
thunderstorms are possible late this afternoon and tonight mainly
south of I-96. High pressure will bring fair weather Friday night
through Saturday night before the next low pressure system brings
more showers Sunday through Monday.

&&

.SHORT TERM...(This evening through Saturday night)
Issued at 325 PM EDT Thu Mar 30 2017

A low pressure system moving through the lower Great Lakes region
will continue to bring showers tonight through Friday. There are
still isolated reports of light snow and flurries over our far
northeast fcst area but pcpn type there will change to plain rain
showers as suggested by low level critical thickness tools and
model fcst soundings.

Both 12Z nam and gfs guidance indicate that elevated instability
will develop over our southern fcst area this evening as h8 li/s
fall to around -1 to -2. Therefore there is potential for a few
thunderstorms to develop late this aftn/eve near to mainly south
of I-96. However most of the convection will stay well south of
our fcst area across IN/OH and further south where much stronger
instability will be present.

A ridge of high pressure will build in from the northwest Friday
night through Saturday and bring fair wx with seasonable
temperatures.

.LONG TERM...(Sunday through Thursday)
Issued at 325 PM EDT Thu Mar 30 2017

It seems to this forecaster that an upper level weather pattern
change may be in our near future. By the middle of this coming week
we may see a break in the Extended East Asian Jet feature. If that
does happen we may yet see the northern and southern streams
synchronize with each other just in time for our system on Thursday.
That would suggest the chance that our Thursday storm could end up
bringing measurable snow across the area (nothing big but enough to
get the ground white for a few hours). Also there seems to be a
break in the persistent East Asian Jet feature by the middle of next
week, that could help the cause of a pattern change that would
result in a more persistent eastern upper trough. This would mean
cooler but drier weather if that pattern where to take hold.

Meanwhile the split flow continues as does the active Pacific wave
train feeding storms into the western CONUS that in turn leads to a
a closed upper low over the SW CONUS that gets kicked out by the
next upstream system (Henry Rule). The next storm to reach us is
will likely be a closed upper low over the SW CONUS by tomorrow
morning. The storm to kick it out will be a 965mb low in the Gulf of
Alaska tomorrow morning. That will then track SW CONUS system east
across the southern plains during the weekend. The question is will
there be enough phasing with the northern stream to bring that
system into Michigan for later Sunday into Tuesday. The significant
precipitation from this system would likely be Monday. Any
precipitation from this system on Sunday or Tuesday would be
minimal. The ensemble mean of the GFS says yes, the operational is
leaning that way too. The ECMWF says no, it will stay south as does
the Canadian. Still the storm today got farther north than many of
the models forecast a week ago. At this point it is too questionable
to increase pops Monday so I am letting what we have ride for now.

The next system, the one on Thursday still looks good and the latest
run of the GFS is better at bringing in enough cold air behind the
system to change the rain to snow later Thursday, the ECMWF and the
Canadian lean that way too.

Beyond this storm we seem to get northern stream systems (pattern
change I wrote about in the first paragraph),  We shall see how this
all works out but I still say no really warm weather (highs in he
70s and 80s for several days like in 2012) for at least 3 weeks

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 152 PM EDT Thu Mar 30 2017

Little question IFR conditions will prevail at all of the taf
sites by late afternoon through the night as the surface low
tracks just south of South Bend Indiana. That will result in
somewhat lighter winds and allow for lower ceiling and some fog.
As for the showers and possible thunderstorms, an area of elevated
installed does move north into the southern 1/2 of the state this
afternoon. So I continued the VCTS. The greatest risk for that
would be in the I-69 area after 21z, till around 03z.


&&

.MARINE...
Issued at 325 PM EDT Thu Mar 30 2017

The small craft advisory remains in effect through tonight into
Friday. Brisk east to northeast winds to 25 to 30 kts will
gradually back to the northeast tonight and north Friday. Wave
heights will diminish to below sca criteria north of Holland
Friday but will remain up around 3 to 5 feet near to south of
Holland through Friday evening.

&&

.HYDROLOGY...
Issued at 1200 PM EDT Thu Mar 30 2017

Widespread rainfall amounts over half-an-inch have been observed
through mid-morning with the highest reported totals at just over
one inch. The heaviest rainfall has been focused in a swath between
I-96 and I-94. Amounts quickly taper off from south to north, from
Grand Rapids through central lower Michigan.

Additional convection is expected to materialize over Illinois and
Indiana this afternoon. Another wave of rainfall will move
through later today, possibly including additional heavy rain.
Some guidance leans toward some locations receiving around two
inches of rainfall when all is wrapped up late Friday.

Rivers are beginning to rise with some rising rapidly. Current
forecasts have a few sites (Eagle, Comstock Park, Holt and
Vicksburg) rising near flood stage within the next several days.
Rainfall totals this week will weigh heavily into next week`s
sensitivity to streams and rivers. Given the moist ground, recent
heavy rainfall and no end in sight for the active pattern,
flooding issues could become more numerous. Those along/near
streams and rivers are encouraged to keep up-to-date with the
latest river forecasts.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...Small Craft Advisory until 11 PM EDT Friday for LMZ848-849.

     Small Craft Advisory until 4 AM EDT Friday for LMZ844>847.

&&

$$

SYNOPSIS...Laurens
SHORT TERM...Laurens
LONG TERM...WDM
AVIATION...WDM
HYDROLOGY...JAM
MARINE...Laurens



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