Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 162350
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
750 PM EDT Sun Apr 16 2017

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 325 PM EDT Sun Apr 16 2017

A high pressure ridge will build in and bring fair weather tonight
through Monday night into Tuesday. The next chance for measurable
rain will come Tuesday night as a low pressure system moves east
from the upper midwest into the great lakes region. Temperatures
will continue to average above normal early this week before
returning to near normal for mid to late week.

&&

.SHORT TERM...(This evening through Tuesday night)
Issued at 325 PM EDT Sun Apr 16 2017

Short term fcst concerns are fairly minimal. Ir/vis sat trends
show a good deal of clearing off to the west/nw and extensive
clearing will develop across our fcst area tonight as the high
pressure ridge gradually builds in.

Fair wx with seasonably mild temps is anticipated for the vast
majority of our fcst area Monday. However an uppe level
disturbance may cause just a few light rain showers and sprinkles
to develop and clip our far northeastern fcst area. However most
of the showers should stay further north/ne of our area where
stronger mid level pva will occur. This notion is also supported
by latest sref pops.

Fair wx is anticipated Monday night through Tuesday afternoon. A
low pressure system over the upper midwest will move east and
bring our area a chance of rain showers Tuesday night. Isolated
storms may also develop Tuesday night over our far southern fcst
area where 12z gfs guidance suggests weak elevated instability
will develop. However 12z ecmwf/nam guidance suggests this axis of
weak elevated instability will stay south of our fcst area through
then.

.LONG TERM...(Wednesday through Sunday)
Issued at 325 PM EDT Sun Apr 16 2017

The most significant weather event in this forecast period is the
system in the Wednesday night into Thursday time frame. That has the
potential of producing heavy rain and thunderstorms (severe is
possible). Beyond that we have yet another system for that weekend
but the track of that is to questionable to pin down if will impact
us or miss Southwest Michigan to the south.

As for big picture ideas, after looking at the out going long
radiation (negative values mean thunderstorms) over the tropical
pacific has a story to tell for our overall weather pattern. Since
October of 2016 we have had the convection pinned between 170E and
120E with it being dry between 170E and 160W and 120E to 40E.  This
pattern has been amazingly persistent and shows no sign of change
even thought the eastern tropical pacific has warmed considerably in
the last month or so. What that is doing for West Michigan weather
is it has created a quasi-zonal upper air pattern that has locked
out the northern stream (for the most part) since the upper flow too
progressive. I do not expect and significant change in this over the
next few weeks. Which of course means we will continue of have an
issue with strong Pacific storm wave energy crossing the Rockies and
forming strong central plains storm systems. The only question for
us is the track of these systems.  The system moving out and the one
before that are examples of this as is the one on Wed/Thu then this
coming weekend.

The system on Wed/Thu has been rather persistent in the models for
some time now and both the GFS and ECWMF give a large part of our
CWA over an inch of rain in 24 hours from this system. This also
agrees with WPC`s day 4 and 5 forecast. There is enough inflow that
strong to severe storms are possible too. We will have to watching
this.

Temperatures will be near normal for the most part. It will be
warmest Wed and possibly Thursday depending to the exact track of
this system.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 750 PM EDT Sun Apr 16 2017

VFR weather is expected the next 24 hours. The only clouds tonight
should be high clouds with bases above 20,000ft. Winds should come
down considerably as we move past sunset. Overnight, expecting
winds less than 10 knots from the west-northwest.

On Monday mid clouds will spread in through the course of the
morning with bases around 7,000ft. Winds will be westerly on
Monday around 10 knots.

&&

.MARINE...
Issued at 325 PM EDT Sun Apr 16 2017

Minimal wave heights are anticipated tonight as west winds will
subside quickly late this afternoon and early evening. Wave
heights will remain small through Monday night due to fairly light
winds out of the west to nw Monday that will become offshore
Monday night.


&&

.HYDROLOGY...
Issued at 325 PM EDT Sun Apr 16 2017

River levels are slowly falling toward more normal levels across
Southwest Lower Michigan except for the Muskegon River basin. The
Muskegon River near Evart is now forecast to peak below flood stage
by Wednesday afternoon at 11.3 feet. All area rivers will be
susceptible to flooding from any heavy rain events in the near
future.

Weather models suggest a few possibilities for storm systems Tuesday
night into the weekend. There is low confidence in the amount of
rain to expect over the next week, but staying guarded against the
potential for additional flooding would be prudent.

&&

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

$$

SYNOPSIS...Laurens
SHORT TERM...Laurens
LONG TERM...WDM
AVIATION...Duke
HYDROLOGY...63
MARINE...Laurens



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