Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 230539
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
139 AM EDT MON MAY 23 2016

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 315 PM EDT Sun May 22 2016

A ridge of high pressure will continue to dominate the weather
pattern through Monday and result in mostly clear skies. The
moderating trend of temperatures will continue the next several
days. There is a small chance of a shower or thunderstorm
beginning late Tuesday with a better chance for showers and storms
for mid to late week.

&&

.UPDATE...
Issued at 905 PM EDT Sun May 22 2016

I have lowered the low temperature forecast for tonight across
most of the area by around 5 degrees. I did that due to surface
dew points currently in the mid 30s east to mid 40s west. With
light winds and clear skies...temperatures should have little
problem falling to near lowest afternoon dew point.

&&

.SHORT TERM...(This evening through Tuesday night)
Issued at 315 PM EDT Sun May 22 2016

The primary short term fcst challenge is to determine
probabilities for showers and perhaps a few thunderstorms Tuesday
afternoon and evening.

Fair wx will continue tonight through midday Tuesday as high
pressure continues to dominate the wx pattern. 12z model guidance
consensus time height rh progs suggest skies will remain mostly
clear through Monday evening and the nam cu scheme shows zero
potential for cu tomorrow aftn with a dry airmass in the low to
mid levels of the atmosphere.

A low pressure system moving ese from the upper midwest will bring
a chance of showers and perhaps a couple of thunderstorms as early
as Tuesday afternoon and evening. The area mainly west of US-131
should stay quite stable due to the increasing sw flow off
relatively cold lake waters. However an axis of weak instability
does develop from near US-131 eastward. So we expect scattered
showers and perhaps a couple of thunderstorms to develop Tuesday
afternoon into Tuesday evening.

We will maintain mention of a small chc of showers and storms in
the fcst through Tuesday night as 12z gfs guidance shows potential
for weak elevated instability to linger through the night
particularly over our southern fcst area. Some of the other short
range guidance solutions look more stable so the overall
convective threat Tuesday night looks fairly low.

.LONG TERM...(Wednesday through Sunday)
Issued at 315 PM EDT Sun May 22 2016

The long term pattern continues to look warm and unsettled. The main
challenges deal with the timing and strength of any storms. Starting
with Wednesday...a low level jet is shown to be pushing in from the
southwest. Instability is forecasted which will likely lead to the
formation of showers and thunderstorms...especially Wednesday
evening.  Pwat values climb to up around 1.5 inches which is well
above normal. Thus some of the storms could have locally heavy
rainfall.

Increased uncertainty exist with the Thursday forecast.  The High
Res Euro supports a lull in the storms on Thursday as little in the
way of forcing is shown. The GFS winds up another low level jet with
a mid level shortwave.  The associated stronger deep layer shear
would warrant some organized convection.  Will maintain the risk for
storms with all models showing elevated pwat values and instability.
Will need to  monitor trends closely.

Another low level jet is forecasted to arrive later Friday into
Friday night.  This...combined with the instability and unseasonably
high pwat values will likely lead to another round of thunderstorms
for most locations.  Deep layer shear is also shown to increase on
Saturday as the low level jet persists...somewhat elevating the risk
for organized storms.  This increase in shear is associated with the
mid level low kicking out of the Southwest U.S. which tracks through
the western Great Lakes region on Saturday.

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 139 AM EDT Mon May 23 2016

Another forecast period in which minimal impacts to aviation
interests are expected. Skies are mainly clear, and winds have
gone light. Chance for fog is very low with the very dry air mass
is place. Only a few cumulus clouds are expected this afternoon.
Winds will generally be from the S under 10 knots. KMKG will have
another lake breeze with wind speeds a little higher there. Winds
will die down around sunset tonight with mainly clear skies.

&&

.MARINE...
Issued at 315 PM EDT Sun May 22 2016

Wave heights will remain aob two feet through early this week due to
fairly light winds with high pressure still in control of the wx
pattern. Southwest winds will increase a bit by Tuesday.


&&

.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.
&&

$$

UPDATE...WDM
SYNOPSIS...Laurens
SHORT TERM...Laurens
LONG TERM...MJS
AVIATION...NJJ
HYDROLOGY...JAM
MARINE...Laurens



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