Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 240130

Area Forecast Discussion
National Weather Service Gaylord MI
930 PM EDT Mon Oct 23 2017

Issued at 914 PM EDT Mon Oct 23 2017

Large area of deformation/fgen driven rain continues to pinwheel
north across the area, as low pressure responsible for such
continues to deepen just southwest of Saginaw Bay. This deepen
process will continue, with the low eventually bottoming out near
980mbs as it slows across eastern upper Michigan by sunrise.
Attendant comma-head rains will gradually pivot more northwest
with time as trowal matures. Heaviest additional rains, exceeding
an inch in places, will focus across northwest lower Michigan and
eastern upper Michigan with time. Heaviest rains this evening
(several reports of over 2 inches) have occurred generally along
and southeast of a line extending from Cadillac to Alpena. No
reports of any significant flooding in these areas as of yet, and
as mentioned, heaviest rains will gradually pivot northwest out of
this region. River response, however, already well underway, as
noted by just released river forecast center products. River flood
warnings will be forthcoming for a few rivers shortly, with
others expected to near flood stage by later today/tonight. Plan
is to continue with inherited areal flood watch, with additional
rains perhaps resulting in some minor flooding outside the river

Winds will ramp up quickly as the low passes/deepens. Inherited
marine and land-based headlines will remain.


.NEAR TERM...(Tonight through Tuesday)
Issued at 350 PM EDT Mon Oct 23 2017

...Heavy rain and becoming windy...

High impact weather potential...heavy rain tonight, very slowly
tapering in intensity overnight into Tuesday. Windy conditions
developing, especially along nw lower MI coast.

Low pressure systems are in far ne IN and just ne of MN. The IN
low has begun to rapidly deepen, and will pivot ne, n, and nw-
ward, ending up over eastern upper MI on Tuesday. It will absorb
the other low in the process of bombing out. Rain continues across
much of northern MI, with an earlier eastward wobble to the back
edge of the rain shield now returning westward. Precip intensity
is increasing, especially in central lower MI, southern Lake MI,
and surrounding locales. Precip and wind trends are the main
concern, in what is a busy forecast.

Heaviest rain for the entire event will play out over the next 12
hours or so. Surface low lifts from IN, skirting the ne lower MI
coastline. Heaviest rain will fall just to the left of the track of
this low, where 850-700mb deformation and fgen are both maximized.
Ongoing enhancement along the outer edge of the rain shield (seen
from Chicago to near Ludington) should reform eastward as surface
low deepens more rapidly, and forcing becomes more concentrated
somewhat closer to its track. This process already appears to be
underway. Good agreement among Nam/Rap in bringing highest QPF to
an HTL-Rogers-Drummond axis, with 2.0-2.5 inches from now thru
06z. The largest contribution from warm advection ends toward or
just after then, as the low curls nw toward eastern upper.
However, the lingering trowal will maintain healthy (though not as
heavy) precip rates for quite some time; thru much of Tuesday in
nw lower/eastern upper MI. Very late tonight, and lasting into
Tuesday precip coverage will decrease in ne lower as low-level
downsloping and (for a time) subtle mid- level dry slotting take a

Flood watch will not be altered.

Winds will increase rapidly in some areas as soon as late evening,
with the bombing out low heading toward Huron. Nnw winds on
northern Lake MI into nw lower MI will be the 1st to kick in. Per
coord with GRR/LOT, potential for 45mph gusts very quickly
develops in Gd Trav region up to Emmet Co toward or just after
midnight. Wind core further intensifies and migrates sw-ward
during the overnight and into Tuesday. Threat for 45mph gusts
develops down toward MBL/Frankfort very late tonight. All this
persists into the Wed night period. Wind advisory already posted
for the nw lower MI coast. Winds will taper will eastward extent
for exposure reasons. Meanwhile, as the low hovers over eastern
upper MI, they will see widely variable winds there: gusty
southerlies by Drummond, easterlies at Whitefish Pt, nw at Curtis.

Min temps tonight 40s. Max temps Tuesday upper 40s to mid 50s,
coolest CAD area and warmest east.


.SHORT TERM...(Tuesday night through Thursday)
Issued at 350 PM EDT Mon Oct 23 2017

...Windy and rain Tuesday night/Diminishing Wednesday...

High Impact Weather Potential: Gusty winds Tuesday night.

Pattern Forecast: Progressive five wave hemispheric pattern in place
with a bit of a split flow long wave trough over central North
America.  A pair of short wave troughs were moving through the mean
trough position this over the mid Mississippi and
lower Ohio Valleys...another was digging southeast across the
northern Plains and into the Midwest along with a nearly 160kt jet
core.  Surface reflections of these features can be found in a
1006mb low over southwest Indiana (attached to a cold/stationary
front that passed through northern Michigan Sunday afternoon/
evening)...and a 1002mb low along the Minnesota/Manitoba border.

Phasing of these short wave troughs will result in a decent closed
low encompassing the Great Lakes/Midwest/Ohio Valley Tuesday and
serve to sharpen/amplify the mean trough.
Pacific pattern (driven in no small part by the remnants of Typhoon
"Lan" getting injected into the main westerlies) will drive another
digging short wave trough into the nation`s midsection during the
latter half of the week...allowing the long wave trough axis to
retrograde a bit.  Surface pattern responds to this first by
deepening the surface low over Indiana as it lifts into Michigan
tonight...and into the Straits region Tuesday morning.  This low
will then spin slowly across the region during the day Tuesday
before filling and lifting out to the northeast Wednesday.  Then a
bit of a lull heading into Thursday while the next surface low/cold
push moves into the upper Midwest.

Primary Forecast Concerns: Strong wind gusts Tuesday night.

Surface low expected to be in the eastern U.P. vicinity Tuesday
evening...probably in the neighborhood of 987-988mb.  Strongest
gradient expected around the western semicircle of the
as the low pushes east expect gusty winds to least 25-
35mph gusts with some 40+mph winds along the northwest Lower Lake
Michigan shoreline counties (and through the Straits as well).  So
Wind Advisory for these areas will be stretched through at least
into the pre-dawn hours of Wednesday...after which wind gusts will

Deep moisture will continue to wrap around this system Tuesday
night...along with low level cold air (925mb temperatures getting
down into the 0c range) which will steepen low level lapse rates and
allow for lake enhancement to add to precipitation probabilities.
Surface based freezing layers will be potential there
for some snow to mix in away from the lakes and particularly in the
higher terrain of northern Lower.

Showers will continue into Wednesday but with a diminishing trend
into Wednesday night.

.LONG TERM...(Thursday night through Monday)
Issued at 350 PM EDT Mon Oct 23 2017

Long range models agree with a developing low pressure system over
the Great Lakes region and a trailing deep long wave trough that
will provide chances of rain and snow for the forecast area through
the extended period. Snow chances will be during the overnight and
early morning hours as temperatures drop into the upper 20s to low
30s. Daytime temperatures will be in the 40s.


.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 719 PM EDT Mon Oct 23 2017

Low pressure will continue to strengthen overnight as it move
north across the area. This low will essentially become stationary
across the tip of the mitt/eastern upper Michigan on Tuesday.
Widespread MVFR/IFR cigs/vis will be the result through this taf
duration. Bands of light to moderate rain will continue this
evening across the area, with the focus for steadier rains
becoming confined to northwest lower Michigan with time. Surface
winds will become quite gusty from the west and southwest on


Issued at 350 PM EDT Mon Oct 23 2017

Low pressure deepens rapidly as it curves from IN to the ne lower
MI coastline, to eastern upper MI by Tue morning. It will stall
there on Tuesday. A variety of marine headlines are already out;
these will be looked at again over the next hour. Will give
consideration up upgrades to storms along parts of the nw lower MI
coast, as well as upgrades to gales in other waters.


MI...FLOOD WATCH through Tuesday morning for MIZ008-015>036-041-042.
     WIND ADVISORY until 3 AM EDT Wednesday for MIZ016-019>021-026.
     WIND ADVISORY from 5 AM Tuesday to 3 AM EDT Wednesday for MIZ025-
LH...GALE WARNING until 6 AM EDT Wednesday for LHZ345>349.
LM...GALE WARNING until 6 AM EDT Wednesday for LMZ323-341-342-344>346.
LS...GALE WARNING until 8 PM EDT Tuesday for LSZ321-322.


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