Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 231925
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
325 PM EDT MON MAY 23 2016

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

.SYNOPSIS...
Issued at 325 PM EDT Mon May 23 2016

It will be warm and gradually become increasingly humid this week
into the holiday weekend. There is just a small chance of a
shower or thunderstorm as early as Tuesday afternoon and evening.
A better chance for scattered showers and thunderstorms will come
late in the week and into the holiday weekend.

&&

.SHORT TERM...(This evening through Wednesday night)
Issued at 325 PM EDT Mon May 23 2016

Our primary short term fcst challenge is to determine potential
for any convection Tuesday afternoon through Wednesday night. A
frontal boundary moving in from the northwest will focus
development of a few rain showers and perhaps an isolated weak
thunderstorm Tuesday afternoon through Tuesday night.

Instability tomorrow afternoon and evening looks weak and
southwest winds off cold lake waters will also keep things even
more stable closer to the Lake Michigan shoreline. So we will
maintain only low pops for a shower or isolated storm tomorrow
afternoon through tomorrow night. Many locations in our fcst area
will not receive measurable rainfall in this time frame.

There will be a slightly better chance for a few showers and
storms late Wednesday afternoon through Wednesday night in the
vicinity of a warm front. A more humid airmass will be in place by
then with dew points by then rising through the mid to upper 50`s
and into the lower 60`s. Weak instability will develop with sb cape
values reaching around 1000 j/kg.

Potential for stronger convection Wednesday is mitigated by several
factors including lack of stronger shear or stronger forcing
mechanism and lack of favorable upper dynamics. In fact weak
shortwave ridging will move overhead. Rh progs suggest potential for
a fair amount of cloud cover that would also keep instability in
check. In fact 12z ecwmf guidance keeps our area dry
Wednesday morning/aftn.

In the near term high pressure will continue to produce mostly clear
skies through this evening as suggested by rgnl ir sat trends and
12z guidance time height rh progs. Mid to high level clouds will
gradually stream in from the west very late tonight and tomorrow.

.LONG TERM...(Thursday through Monday)
Issued at 325 PM EDT Mon May 23 2016

Overall the pattern looks warm and unsettled through the period.
Deep southwest flow will be in place through the period...which will
act to keep the temperatures well above normal. With the Gulf of
Mexico open...this will support increasingly humid conditions as
well.

The GFS generates considerable Cape on Thursday with SB values well
over 3k j/kg both Thu and Fri.  However the GFS creates a cap and
shows a stronger mid level ridge.  This would act to limit the
convective risk...and focus it further west of the CWA.  The new
High Res Euro shows tries to show this as well.  Any lifting
mechanisms remain weak.  The High Res Euro shows a low level jet
across southern lower MI Fri. As a result...will keep mainly a
chance for thunderstorms going.

Models are showing better deep layer shear on Saturday along with
favorable instability.  The main reason for this is the mid level
low over the Southwest U.S. is shown to be lifting out and tracking
through the Western Great Lakes then.  If this occurs...an increased
risk for severe would exist.  The High Res Euro is now showing a
cold front pushing out of the Upper Plains and into the Western
Great Lakes on Memorial Day. This would increase the risk for storms
here in MI.  Will keep the mention of storms going over the holiday
weekend.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 130 PM EDT Mon May 23 2016

Quiet weather pattern to continue for the Taf sites for the
period. The atmosphere remains dry. Once again the wind could be
briefly variable given the very warm dry conditions in place. We
will see some changes starting to show up on Tuesday. A warm front
will be approaching from the southwest. This will lead to a mid
level deck of clouds pushing in during the day. The wind will be
on the increase for KMKG. Any shower activity is forecasted to
hold off until after 18z Tue.


&&

.MARINE...
Issued at 325 PM EDT Mon May 23 2016

The potential for areas of marine fog to develop will increase
beginning as early as Tuesday with greater potential for fog mid to
late week as a warmer and more humid airmass overruns cold Lake
Michigan waters. Winds and waves will remain below small craft
criteria through midweek and wave heights will mainly be aob 2 feet.

&&

.HYDROLOGY...
Issued at 1229 PM EDT Sun May 22 2016

South to southwest flow will develop by Tuesday, allowing for a
moisture laden airmass to park itself through the heart of the
Midwest. This will ultimately lead to an active, wetter pattern
through much of the upcoming week. Though it is not expected to be
continually raining, multiple waves/disturbances will travel from
southwest to northeast through the Great Lakes Region and provide
periods of wet weather. Some long term forecast precipitation
estimates are 2+ inches, in addition to the fact that locally
heavier rain is fairly typical in this type of setup. Despite
recent dry weather, river levels are running slightly above normal
in some locations and could return to near/above bankfull levels,
pending the actual results through next Sunday.

&&

.GRR Watches/Warnings/Advisories...
MI...None.
LM...None.
&&

$$

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


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