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Area forecast discussion 
National Weather Service Grand Rapids Michigan
743 PM EDT Tuesday Sep 30 2014

Latest update...
aviation

Synopsis...
issued at 325 PM EDT Tuesday Sep 30 2014

The weather will remain quiet tonight and Wednesday. We will see
more sunshine Wednesday which will boost temperatures into the middle
and upper 60s. However we will be entering a wet period starting
late Wednesday night into Thursday and lasting through Saturday. A
soaking rain appears likely with some areas seeing up to two inches
of rainfall.

After a warmer day on Thursday...with highs from 70 to 75...we will
cool down for the weekend with highs only in the 50s. We should see
temperatures warm by Tuesday with highs reaching around 60.

&&

Short term...(this evening through Thursday night)
issued at 325 PM EDT Tuesday Sep 30 2014

Quiet weather for the next 24 hours. We will hang on to the clouds
through much of the night as the low levels remain moist. However
with upper ridging moving in clearing will start by middle morning
Wednesday from the SW...and by middle afternoon over the NE County Warning Area. This
clearing is slightly delayed so temperatures may struggle a bit. I trimmed
maximum temperatures slightly...but still feel middle and upper 60s will be
achieved.

Then we will enter a wet period...over the western County Warning Area late
Wednesday night...and advancing to the eastern County Warning Area by Thursday.
Deep southwest flow will set up over the Great Lakes as ridging is
seen over the eastern Seaboard...with upper troughing over the
plains. A surface cold front will only slowly progress east across
the upper Midwest into the western Great Lakes from Wednesday night into
Thursday night. Upper divergence from the right entrance region of the
upper jet sets up over lower Michigan Thursday afternoon and is
maintained through Thursday night when the bulk of the rain is
expected. Increased probability of precipitation for Thursday night and also bumped mins up
given the strong southerly flow and cloud cover.

With the deep SW flow Gulf moisture will become abundant as
precipitable water values spike toward 1.75 inches Thursday
evening. With the slow nature of the system the northwest County Warning Area appears most
likely to see the heaviest rains...which could approach two inches
by Friday morning. The severe weather threat appears low at this
point due to weak instability...and the fact that the best upper
dynamics does not come in until Thursday night. 45 knots of wind is
prognosticated over SW Michigan at 2k feet Thursday night...which a stronger
storm could mix down...making for isolated strong wind gusts.

Long term...(friday through tuesday)
issued at 325 PM EDT Tuesday Sep 30 2014

The coldest weather we have seen since the middle of may should move
into the area Friday. The chilly air appears to persist through the
weekend into early next week before the system finally moves out of
the area and another warm up starts. Lake effect rain showers
should continue through the weekend.

The models have come together now on how this will play out. All of
them now show a closed upper low over the Great Lakes Saturday into
Sunday. However as it lifts out Saturday night another shortwave
follows it...which keeps southwest lower Michigan in the cold
unstable air into early Tuesday.

850 mb temperatures fall into the -1c to -3c range by Friday night
then continuing into Monday night. Given the mostly westerly winds
through the period....Little Question Lake effect rain showers will
continue into Monday. Water spouts may be an issue too.

&&

Aviation...(for the 00z tafs through 00z Wednesday evening)
issued at 743 PM EDT Tuesday Sep 30 2014

Ceilings will be around 2000 feet above ground level this evening with north to
northeast winds below 10 knots. Model guidance shows IFR and LIFR
conditions developing late tonight but this would only be possible
if stratus clouds break up and allow dense fog or low stratus to
form. Will include a period of IFR from 11z to 14z in the forecast
to account for this...but confidence is not great that this will
happen. Expect MVFR and perhaps VFR for later Wednesday morning
and afternoon with southeast winds at or below 10 knots.

&&

Marine...
issued at 325 PM EDT Tuesday Sep 30 2014

Will allow the Small Craft Advisory to expire north of South Haven
and also cancel the area north of Pentwater. Buoy data shows waves
have diminished to 3-4 feet offshore of Ludington as winds are
slowly pivoting to the NE. Port Sheldon and South Haven buoys are
down to 2-3 feet....while Bridgeman still shows 4-5 feet. Will
allow the Small Craft Advisory south of South Haven to expire at 8 PM as winds
continue to diminish and turn more NE.

Another period of higher winds and waves is expected by Thursday
morning north of Grand Haven as south winds increase. This will
likely extend into Thursday night and expand across all the
nearshore waters as southerly winds are expected to continue to
increase.



&&

Hydrology...
issued at 325 PM EDT Tuesday Sep 30 2014

The rain from late Wednesday night into Friday is expected to be
heavy...but since it will fall over a long period of time...Hydro
issues are not expected. Much of the County Warning Area should see between one and
two inches of rain. One possible scenario would be drains clogged
with leaves may result in ponding of water.

&&

GRR watches/warnings/advisories...
Michigan...none.
Lm...Small Craft Advisory until 8 PM EDT this evening for lmz844.

&&

$$

Synopsis...jk
short term...jk
long term...wdm
aviation...ostuno
hydrology...jk
marine...jk

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