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Area forecast discussion 
National Weather Service Grand Rapids Michigan
335 am EDT Wednesday Oct 1 2014

Latest update...
synopsis/short term/long term/Hydro/marine

issued at 335 am EDT Wednesday Oct 1 2014

The weather will be rather fall like over the course of the next
several days with swings in temperatures...breezy conditions and
soaking rains. Conditions will be rather benign today and into
tonight as a ridge of high pressure retreats from the Great Lakes
region. A cold front will approach the area from the west Thursday
and Thursday night and swing through Friday morning. Showers will
begin to increase in coverage Thursday morning and become more
widespread as we head through the day and into Thursday night. The
highest concentration of precipitation will likely come Thursday
night into Friday morning when showers and thunderstorms are
expected. Cooler and showery weather will sweep into the region for
the weekend. High temperatures will reach a peak...70s...on Thursday
in the southerly winds ahead of the cold front. Saturday behind the
front we will struggle to around 50 for maximum temperatures.


Short term...(today through friday)
issued at 335 am EDT Wednesday Oct 1 2014

Main forecast focus is on the strong Fall storm system to swing
through the area Thursday into Friday. Chances for precipitation
begin to increase late tonight as moisture begins to surge in from
the west. A solid increase in dew points at 850mb/S in noted by all
the models we will not have significant instability in place so only
expecting showers in the west late.

Better chances begin to show up on Thursday as 850mb moisture
transport begins to increase. That said...the values are not
significant. Expecting decent coverage to overspread the area
though...especially in the afternoon. Most areas should see rain
showers along with some embedded thunderstorms especially in the

By far the best moisture transport occurs Thursday night into Friday
morning. Expecting soaking rains during this time frame with rounds
of showers and storms moving through the area. Convection allowing
models show this to be the case as well...including the 4km NAM.
Severe threat still looks slim given timing which will limit
instability. Winds are strong in the lower tropopause however and we will
need to keep an eye on linear storms for wind potential. 40-50 knots
resides in the profile between 1500-4000ft.

The cold front sweeps east on Friday with cold air advection setting
in through the course of the day. We will probably fall back into
the 50s during the afternoon.

As for today...expecting a gradual erosion of the low clouds from
the south. The NAM has done very well the last couple days in regard
to the low clouds though and it keeps solid moisture in at least
through the early afternoon. The trend should be toward
improvement/clearing though.

Long term...(friday night through tuesday)
issued at 335 am EDT Wednesday Oct 1 2014

The main theme for the long term portion of the forecast continues to be
cool and unsettled conditions expected right through the period.

The pattern shift in the upper levels of the atmosphere that will
take place will be just about complete by the beginning of the long
term on Friday night. We will be seeing the long wave trough that
extends from The Rockies right on through northern British Columbia
digging southeast. A strong short wave will help drive this long wave
trough over the area and set it up as the upper air pattern becomes
quite amplified from the Pacific through the Atlantic. Strong
ridging across the eastern Pacific and western Atlantic will help keep this
pattern intact.

This long wave trough will bring a cold pool of air down from Canada
along with a wave train of short waves poised to move through the
region on northwest flow aloft. This will bring waves of rain showers to
the area at times...with some enhancement of the showers and some
pure lake effect rain showers from Lake Michigan with sufficient
over lake instability present. Timing of these features will be
problematic as expected with a pattern like this. Waterspouts remain
a distinct possibility over the lake with the trough and cold pool
aloft overhead.


Aviation...(for the 06z tafs through 06z Wednesday night)
issued at 150 am EDT Wednesday Oct 1 2014

Conditions will deteriorate a little bit through daybreak this
morning before conditions then improve through the remainder
of the period.

MVFR ceilings continue to dominate across most of the area early this
morning. Some local IFR spots are present across the east where
there is a flow off of Lake Huron. We expect conditions to remain
rather stable with little change other than maybe clouds dropping
a few hundred feet tonight. Ceilings will then lift to MVFR by middle
morning...and then clear out this afternoon as drier air moves in
and the moisture mixes out.


issued at 335 am EDT Wednesday Oct 1 2014

Fairly tame conditions out on the lake today and into tonight before
the winds begin to ramp up. We are looking at southerly winds which
may flirt with Small Craft Advisory conditions Thursday and Thursday
evening. Better chances for strong winds and high waves set up for
late Thursday night into Saturday. Small Craft Advisory conditions
during this time are likely if not gales at times. The fall season
looks to be taking shape on the Great Lakes.


issued at 335 am EDT Wednesday Oct 1 2014

Soaking rains are expected from Thursday into Friday. Amounts of
0.75 to 1.50 inches appear common. Could see some locally heavier
amounts especially across west central lower Michigan towards
Muskegon and Ludington. The good thing is river levels are low and
should be able to absorb those amounts without much issue. We will
be keeping an eye on model forecast trends though. Wpc is
forecasting amounts by Saturday morning of 2+ inches over a good
deal of western lower Michigan. Precipitable water values are still forecast to be up
around 1.7 inches which is near the 99th percentile for this time of
year. A solid surge of moisture is feeding north into the system off
the Gulf.


GRR watches/warnings/advisories...


short term...Duke
long term...njj

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