Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 271916

Area Forecast Discussion
National Weather Service Grand Rapids MI
314 PM EDT Thu Oct 27 2016

Synopsis/Short Term/Long Term/Marine

Issued at 314 PM EDT Thu Oct 27 2016

High pressure will continue to build in and bring fair weather
tonight through Friday. A low pressure system will bring scattered
light rain showers Saturday into Saturday night. Another ridge of
high pressure will bring fair weather again for Sunday into early
next week. Temperatures will average above to much above normal
Friday through the weekend into early next week.


.SHORT TERM...(This evening through Saturday night)
Issued at 314 PM EDT Thu Oct 27 2016

Primary short term fcst concerns involve determining probabilities
for showers and convection Saturday through Saturday night.

High pressure will continue to build in tonight and bring fair and
seasonably cool wx. Some breaks in the cloud cover will develop
overnight. It will be partly sunny and seasonably mild Friday as
southerly winds help to boost high temperatures into the upper
50`s to lower 60`s.

An isolated light rain shower or sprinkle may develop during the
early morning hours Saturday over our northern fcst area as the
next low pressure system approaches from the northwest.

This system will bring scattered light rain showers to most of
our fcst area Saturday and Saturday night as moisture ramps up
significantly and precipitable water values reach around 1.25 to
1.5 inches.

I have also introduced a chance for thunderstorms to the forecast
for Saturday through Saturday night mainly near to south of I-96.
12z short range guidance consensus shows weak to moderate elevated
instability will develop just to the north of the sfc boundary
across this area and the llj will also provide some forcing for
convective initiation to occur.

.LONG TERM...(Sunday through Thursday)
Issued at 314 PM EDT Thu Oct 27 2016

To start the long term...mid level heights will rise steadily Sunday
into Monday as a ridge builds in from the west.  A considerable warm
up is expected as a result as the warm air advection deepens and
strengthens.  In fact the wind may lead to impacts on Monday as good
mixing combines with a 40 knot low level jet. Little in the way of
moisture will be around for precipitation and any lift remains weak.
So we will continue the theme of dry with moderating temperatures.

A mid level shortwave tracks northeast out of the central Rockies
later Monday before tracking through the western Great Lakes on
Tuesday. This system will send a weakening cold front through the
region Tuesday.  This frontal passage looks dry given the lack of
moisture. Models are in decent agreement on this scenario.

The front then lifts slowly north Tuesday night into Wednesday. This
time the front will have relatively much more moisture with it. PWAT
values climb up to around 1.5 inches...along with the arrival of
another low level jet.  Even some elevated instability is shown. As
a increased chance for rain exists Tuesday night into
Wednesday. How far north the front goes is uncertain...with
considerable differences in the models.  The GFS suppresses the
front south by Thursday and would support drying conditions.  The
new High Res Euro develops a wave on the front and keeps it over the
region...which would allow for wet weather into Thursday.  Will
feature a risk for showers into Thursday.


.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 111 PM EDT Thu Oct 27 2016

Low clouds will persist this afternoon and evening and may expand
tonight. The low level moisture will remain high this
afternoon...although some slight drying is noted in the
models...which could support a slight rise in the cloud bases.
Much of the low level moisture is coming off the lakes as the
airmass is cooler than the water temperatures.  Many areas will
start off IFR...but a trend to MVFR should develop. There is a
possibility that the clouds could scatter out this evening across
the TAF sites. If that happens...IFR and lower fog/stratus
conditions would become likely as the wind will diminish and the
low level moisture will be relatively high.

MVFR looks likely to start the day Friday...with increasing winds
from the south.


Issued at 314 PM EDT Thu Oct 27 2016

Have decided to hoist a small craft advisory from midday Friday
through midday Saturday. Wind speeds will reach 20 to 30 kts out of
the south to sw in this time frame and wave heights will build to 4
to 8 feet late tomorrow through tomorrow night. Wind speeds and wave
heights will subside Saturday afternoon.


Issued at 1043 AM EDT Thu Oct 27 2016

Rainfalls from a half inch to over an inch occurred in the past
24 hours. Rivers and streams will stay below bankfull. River
advisories for Sycamore Creek at Holt and Maple River at Maple
Rapids have been cancelled as the rain has not translated into
large river rises. Flooding is not expected.


LM...Small Craft Advisory from noon Friday to noon Saturday for



SHORT TERM...Laurens
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