Area Forecast Discussion
Issued by NWS Gaylord, MI

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787
FXUS63 KAPX 230134
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
934 PM EDT Sun Oct 22 2017

.UPDATE...
Issued at 927 PM EDT Sun Oct 22 2017

Cold front just about set to exit our area stage right into Lake
Huron. However, it won`t move too much further in the coming days
as low pressure develops and rides north along it. Area of light
to moderate post-frontal rain continues to pinwheel northeast
across northern Michigan. Progress has been only slowly east with
this band, and given slowing front and deep layer moisture feed,
expect this slow trend to continue. Latest hi-res progs have
focused steadier and heavier rains a bit further west than earlier
runs for later tonight and Monday, and given radar and satellite
trends, starting to think they may be onto something. Have nudged
inherited forecast partially toward this more west solution,
keeping higher pops across north central and northeast lower
Michigan through the remainder of tonight and Monday. Rainfall
totals still look really impressive through Tuesday, with some
areas of northern lower likely topping 2 inches (at least) through
this period.

&&

.NEAR TERM...(Tonight through Monday)
Issued at 352 PM EDT Sun Oct 22 2017

...Wet...

High impact weather potential...heavy rain possible near Saginaw
Bay Monday afternoon.

Cold front is just pushing into western Mack Co as well as MBL/
Frankfort. This front will slow as it crosses northern MI this
evening, and stall over Lk Huron overnight. The front stalls
thanks to a vigorous and deepening surface low moving ne along the
front. Said low will cross se lower MI Monday afternoon. Precip
trends are the main concern.

Band of moderate showers working across nw lower/eastern upper MI
presently, just ahead of the surface cold front. Weaker showers
extend westward behind the front a good ways, to around IWD and LSE.
Better precip rates with this initial batch of showers will move out
and/or fade out by mid/late evening. However, precip rates may
rebound overnight in ne lower MI, as multiple pieces of energy eject
nne-ward from the Ohio Valley, parallel to the stalling front. That
leads to some increased fgen forcing, just on the cool side of the
boundary. This won`t be especially heavy, but total nighttime
precip could reach 0.50 inches across a good portion of n central
and ne lower. Meanwhile, decreasing pops will be seen overnight w
of an ANJ-TVC line. This will be especially the case in western
Chip/Mack Cos, where partial clearing will occur late.

Min temps tonight from near 40f in western Chip/Mack to lower 50s
near Saginaw Bay.

Primary upper trof will dig into the upper MS Valley on Monday. An
initially closed 500mb low will open up but take on a negative tilt
as it ejects ahead of this digging trof, gradually moving up the
Ohio Valley. As this occurs, the associated surface low will move
nne along the stalled front (from sw IN to the Thumb area),
strengthening as it goes. Deformation and fgen forcing will amp up
substantially in portions of central and eastern lower MI. Exactly
where the band of heaviest rain sets up is still somewhat uncertain
(it`s possible the heaviest just misses us to the s and e). But rain
will continue just on the cool side of the front in n central and ne
lower MI, and will become heavier with time. Forecast precip amounts
for the 8am-8pm window will be around an inch se of an HTL-APN line,
rapidly falling off as you head further nw. Places like Frankfort/
Leland/Trout Lk will only have a very small chance of rain.

Max temps mid 50s to around 60f. Not too much in the way of wind,
with ne lower seeing a N to NNE breeze in the afternoon.

&&

.SHORT TERM...(Monday night through Wednesday)
Issued at 352 PM EDT Sun Oct 22 2017

...The Transition Begins...

High Impact Weather Potential...Heavy rain into Monday night, that
could produce flooding near Saginaw Bay. Gusty winds winds on
Tuesday and Tuesday night.

Pattern Synopsis/Forecast...The 500 mb low that is to the northwest
moves into the Upper Great Lakes Monday night and and helps to
develop the sfc low. The sfc will help to get the reinforcing shot
of cooler air to transition our warm fall to something more
seasonal. It is also expected to produce more precipitation helping
to alleviate the dry conditions. However, it does look like we could
get too much of a good thing as the 500 mb low gets a piece of
energy on the backside that allow the 500 mb low to retrograde back
into Michigan and continue the rain with heavy stripe of rain
expected from east of I-75 and into the Saginaw River Valley. This
retrogrades the sfc low as well so that gradient tightens up and we
get high winds over NW Lower. The GFS delays best gradient until
Tuesday night, while the ECMWF is faster, and holds in place into
Tuesday evening. Winds should diminish overnight as the sfc low
moves out. 850 mb temperatures fall enough that there could be some
concern for mixed rain and snow or all snow in E Upper, late Tuesday
night into Wednesday morning. Dry air then begins to move into the
region by Wednesday afternoon, and should begin to clear things out.

Primary Forecast concerns...The rain has become an issue for Monday
afternoon/night. The rain fall could be 2 to 3" or more over the 12
hours. That would be enough for the Rifle River at Sterling to go
over flood stage Tuesday night/Wednesday morning. If that happens,
it is possible that we could get some creeks and streams to go over
their banks as well. Winds on Tuesday will be the other issue as the
models haven`t brought about a consensus, but the ECMWF is holding
firm to its solution and now has the NAM12 to back it up. My guess
is that we will probably have some low wind advisory headlines
needed, at least along the lake shore.

.LONG TERM...(Wednesday night through Sunday)
Issued at 352 PM EDT Sun Oct 22 2017

Extended (Wednesday night through Sunday)...The pattern, as was
said yesterday, looks to be trying to establish a Ridge/Trough
pattern as is usually the case the last several winters. So with
several upper lows expected to move through the area, the region
will see temperatures slightly above and below normal. Wednesday
night the 500 mb trough moves out, and thing remain dry into
Thursday. The GFS disagree on the speed of the 500 mb ridge
Thursday night as the GFS pushes it straight into the Upper Great
Lakes. The ECMWF is much slower, not allowing the next system to
move into the Upper Great Lakes until late Friday. Friday night
into Sunday, both models have rain, but for different reasons, as
the timing of the 500 mb low moving through the Upper Great Lakes
is off between them by about 12 hours.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 734 PM EDT Sun Oct 22 2017

Really challenging forecast on just how far east upstream clearing
makes it later tonight and Monday. Cold front slowly crossing the
area this evening, getting set to stall out just to our southeast.
Intensifying low pressure will move north along this front,
keeping MVFR/IFR cigs and periods of light to moderate rain
across KAPN right through Monday (and likely beyond). Rain shield
will slow pivot east, perhaps clearing all western taf locations
late tonight into Monday. Definitely not sold on this idea,
especially in-light of recent guidance trends showing the low
clouds/rain shield back building west with time on Monday. Have
tentatively split the difference, leaving rain out of the
forecast later tonight and Monday, with predominately MVFR/low end
VFR conditions.


&&

.MARINE...
Issued at 352 PM EDT Sun Oct 22 2017

Gusty southerly winds will be supplanted by weaker nw winds this
afternoon/evening, as a cold front crosses the region. This front
will stall over Lk Huron late tonight, leading to relatively light
winds for much of Monday, with a n to ne breeze developing on
Huron in the afternoon. Stronger winds will develop Monday night
and Tuesday, as low pressure strengthens and moves north across
and away from Lk Huron.


&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...NONE.
LM...NONE.
LS...NONE.
&&

$$

UPDATE...MB
NEAR TERM...JZ
SHORT TERM...JL
LONG TERM...JL
AVIATION...MB
MARINE...JZ



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