Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 141617

Area Forecast Discussion
National Weather Service Grand Rapids MI
1217 PM EDT Sat Oct 14 2017


Issued at 315 AM EDT Sat Oct 14 2017

A storm system will track northeastward through the region today
through Sunday. This system will bring several rounds of showers
and thunderstorms with heavy rain at times. Flooding will be
possible. In addition some of the storms could be severe. Strong
wind gusts are expected on Sunday as the storm pulls away.


Issued at 1217 PM EDT Sat Oct 14 2017

We have issued an update this morning, mostly to hoist a Wind
Advisory for the entire area from later tonight through Sunday.
The rest of the forecast is on track with plenty of rain expected,
and some thunderstorms, which some could become stronger later

Axis of rainfall has shifted to the srn half of the CWFA as
expected, as the front has sank to just about the state border
this morning. Ongoing moisture transport over the front has
maintained a steady stream of mostly showers with a few embedded
weaker storms.

We are expecting the rain axis to shift north this afternoon as
the next wave of showers and storms across Nrn Illinois and Iowa
will press in over the area. Instability will increase some,
however the main show still looks to be late this evening and
overnight tonight as the very strong low level jet pushes in, and
brings the best instability of a few hundred j/kg, and best
forcing/wind fields. We still expect that any convective area
tonight could bring some of the strongest winds down. The strong
shear also could cause a brief spin up along any line of storms if
any kinks in the line can develop.

Once the cold front pushes through toward daybreak, that is when
the strong synoptic winds will kick in. We are looking at the
strong mixing tapping 40-45 knots. This will equate to 55 mph
being likely around the frontal passage, and into much of Sunday.


.SHORT TERM...(Today through Monday)
Issued at 315 AM EDT Sat Oct 14 2017

Decided to go with a flood watch. Trends in the high res models
seem to support stalling the frontal boundary in my CWA with the
northward movement of the front less certain to occur. This is
because the mid to upper level winds remain fairly parallel to the
front. PWAT values are very unusual for this time of the year up
around 1.75 inches. Low lcls and thin deep cape support efficient
rainfall. Aloft diffluence is noted across the boundary into
tonight...enhancing the lift. With the boundary not moving is likely to occur. Concern for more than 4 inches
exists. Leaves may clog drains as well creating enhanced urban

Slight risk for severe weather into tonight. Impressive low level
wind fields are forecasted to develop...thus damaging winds seem
to be the main risk. Isolated Tor possible...but not much CAPE
down low.

Gusts over 40 mph look likely for Sunday. Will need to monitor the
wind advisory potential.  Will mention this in the HWO.

.LONG TERM...(Monday night through Friday)
Issued at 315 AM EDT Sat Oct 14 2017

Any lingering light pcpn Monday should end by Monday evening and
winds will become southwesterly by then. Min temps Monday night will
range from the upper 30`s over our far ne fcst area to the middle
40`s south. Frost is not anticipated given these temps and sw winds.

Fair wx will continue for mid to late week as a sfc high pressure
ridge takes hold of our wx pattern. Very persistent sw flow waa will
continue through the rest of the week and allow temps to undergo a
slow gradual moderating trend. Temperatures will average around 5 to
10 degrees above normal for this time of year from Tuesday through
Friday and high temperatures could reach the lower 70`s by late


.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
Issued at 713 AM EDT Sat Oct 14 2017

Abundant moisture will be flowing into the TAF sites into
tonight...leading to some impacts. IFR and lower conditions will
exist in the region to start the period as the front this moisture
will be lifting over does not move very much into the evening. The
atmosphere will be unstable so a risk for storms exists.

The wind will shift late tonight as cold front arrives from the
west. Powerful winds will exist along and behind the front so
gusts over 35 knots look likely.


Issued at 1217 PM EDT Sat Oct 14 2017

We upgraded the Gale Watch to a Gale Warning earlier this morning.
This is a solid gale event, with some potential of an upgrade to a
Storm Warning. The confidence is not there to issue a Storm
Warning at this time, but we will monitor the potential.


Issued at 1217 PM EDT Sat Oct 14 2017

Multiple waves of convection, some of it training, are expected to
provide the entire area with a soaking rainfall by Sunday morning.
PW values will be at or above 1.5 inches for the entire day, which
are about as high as they can get this time of year (based on DTX
sounding climatology). With elevated instability being maintained
through a thick layer of this deep atmospheric moisture, rain
production will be efficient in convection.

Mesoscale models have been consistent with providing 1 to 3 inches
of rain to the area, but have reasonable disagreement on where the
axis of heaviest rain will fall. There could be two heavy rain
swaths that end up falling, as convection this morning and afternoon
will focus south of I-96, then convection will tend to blossom north
of I-96 later this evening and tonight. Several runs of the HRRRX
have shown the potential for isolated 4 to 6 inch totals. Already
southern Van Buren and Kalamazoo counties are approaching 2.0
inches in the past 6 hours.

A flood watch has been issued through late Saturday night. River
flood advisories or warnings may be needed if heavy rain falls in
flood-prone drainage basins. With basin-average totals between 2 to
3 inches plugged into river models in the lower Kalamazoo and upper
Grand basins, several river points climb above bankfull (the usual
suspects: Holt, Eagle, Maple Rapids, Ionia, Hastings).


MI...Flood Watch through late tonight for MIZ043>046-050>052-056>059-

     Wind Advisory from 2 AM to 8 PM EDT Sunday for MIZ037>040-

LM...Gale Warning from 8 PM this evening to 8 PM EDT Sunday for



LONG TERM...Laurens
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