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600
FXUS63 KAPX 280736
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
336 AM EDT Wed Jun 28 2017

.NEAR TERM...(Today through Tonight)
Issued at 325 AM EDT Wed Jun 28 2017

...Heavy Rain to Fall Late this Afternoon and Tonight...

High Impact Weather Potential...Marginal Risk of severe storms, and
a slight risk excessive rain of exceeding flash flood guidance.

Pattern Synopsis/Forecast...All the models start with the sfc low
coming out of the N Plains this morning, and heading into the Upper
Mississippi Valley/Upper Great Lakes by the evening. This sets up a
strong baroclinic zone/warm front with strong 850 mb LLJ (40-50 kt)
by the afternoon and begins the impetus of the heavy rain that we
have been advertising. However, the details are a little murkier
this model run as the NAM and GFS have brought the QPF bull`s south
into N Lower while the ECMWF is still in E Upper and the HiResW
models are toward the tip of the mitt. Overnight, the sfc low moves
into southern Lake Superior, with most of the rain focused along the
warm front, which looks to be north of Lake Huron in Ontario by
12z/Thu.

Primary Forecast Concerns...with the right curve of the qpf from the
NAM and GFS, the main concern is that the heavy rain could be
anywhere in the forecast area. Considering that the HiRes models and
the ECMWF are still in the same basic area as they were from the 12z
model runs, would believe that a bit more. It is interesting to note
that the 00z ECMWF shows a configuration in the QPF as the ongoing
radar out in the Plains. So if the ECMWF is right then the rain,
while heavy will be progressive and pushes out quickly enough before
we reach Flash flood guidance. Also with the WPC excessive rainfall
discussion with only a 5-10% chance of reaching FFG (slight risk)
will, at this time, hold off from issuing any flood watches.

&&

.SHORT TERM...(Thursday through Friday)
Issued at 325 AM EDT Wed Jun 28 2017

...Another round of substantial rain Friday-Friday night??...

High Impact Weather Potential...Potential for additional substantial
rainfall across a portion of northern Michigan Friday into Friday
night. Some thunderstorms also possible.

Pattern Synopsis/Forecast...Northern Michigan will briefly be in the
warm sector Thursday morning while the surface low moves across
eastern Lake Superior into Ontario. An ill-defined trailing cold
front will make little southward progress and become more zonally
oriented through the day, stretching from Drummond Island down into
Iowa. Shower chances expected to gradually diminish through the
morning into early afternoon across northern MI as drier air
encroaches from the west with the approach of a building upper
ridge. However, scattered showers may linger longer over eastern
Upper, closer to the low. Attention then shifts to Iowa where
another developing low will ride northeast along the front into
Michigan on Friday.

The 28.00Z model run has created far more questions than answers
with regard to Friday`s system, but it does look like there will be
potential for some additional widespread decent rainfall across a
portion of northern Michigan. The track of this system is the
biggest factor in question, but expect it will be somewhere through
northern Lower or eastern Upper. Dynamics and thermodynamics are
very much in question, though it appears a developing LLJ will allow
favorable moisture transport to nose into northern MI Friday
afternoon/evening with PWATs likely in excess of 1.5". Instability
will largely depend on the track of this system, but as of now it
appears there will be enough to support some thunderstorm activity.
Given the considerable uncertainties with this system, it`s
premature to speculate about potential rainfall amounts. For
instance, GEFS QPF plumes for KAPX show spread anywhere from 0.25"
to 2" Friday afternoon through Friday night. Will have to wait for
subsequent model runs later today for (hopefully) more clarity and
watch where tonight`s heaviest rainfall materializes to gauge any
potential impacts from additional rainfall Friday night.

Expect cloud cover to be more extensive across the northern part of
our forecast area on Thursday, which (along with any lingering
showers) will keep temperatures in the 60s north of the Straits.
Skies will become partly cloudy over northern Lower, where
temperatures will rise through the 70s, even flirt with 80 near
Saginaw Bay. Friday`s readings will be similar.

&&

.LONG TERM...(Friday night through Tuesday)
Issued at 325 AM EDT Wed Jun 28 2017

High impact weather potential...Minimal. A thunderstorm or two
possible on Saturday.

Longwave troughing aloft will sit over the Upper Great Lakes through
the weekend with a couple shortwaves rotating across northern
Michigan. This will allow for additional diurnal showers (and
possibly a storm or two) on Saturday, but drier air filtering into
the region Saturday night into Sunday should allow for mostly dry
conditions the latter half of the weekend...aside from perhaps a
stray shower or two. Surface high pressure and a building upper
ridge looks to provide a period of quiet weather across northern
Michigan for Monday and Independence Day, though the more active
weather will be found just to our south downstate. And to add to
that good news (for those craving more summerlike temperatures), a
subtle warming trend looks to be on tap through the first half of
the week with highs around normal.

&&

.AVIATION...(For the 06Z TAFS through 06Z Wednesday evening)
Issued at 1034 PM EDT Tue Jun 27 2017

No issues for the terminal sites tonight as diurnally driven
clouds (and spotty showers) have faded with loss of heating.
Anticipated VFR conditions through tonight and Wednesday morning.

Another system will be impacting the region later Wednesday
through Thursday with an area of low pressure deepening and
lifting through the upper Midwest into the northern lakes region
by Thursday morning. This system will bring another round of
heavier rainfall to northern Michigan...with rain spreading into
the region Wednesday afternoon and persisting through Wednesday
night. With the rain...cigs will lower to MVFR heights Wednesday
afternoon/evening. Also...there will be a risk for thunderstorms
at the terminal sites...primarily Wednesday evening.

Finally...strong low level winds develop on Wednesday with gusts
running 20 to 30 knots. LLWS will be a possibility later in the
day and Wednesday night as rainfall cools/stabilizes the boundary
layer but winds remain strong aloft.


&&

.MARINE...
Issued at 325 AM EDT Wed Jun 28 2017

Today through Thursday night...As an area of low pressure migrates
from the Northern Plains to the Upper Great Lakes tonight, the
gradient is expected to tighten up and produce small craft winds
and waves later this morning and into the night. Winds should
begin to diminish as the low moves north of the UP, and gradient
relaxes again. High pressure settles into the Upper Great Lakes
and the winds remain below small craft thresholds through Thursday
night.

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...SMALL CRAFT ADVISORY from 8 PM this evening to 8 AM EDT Thursday
     for LHZ346-347.
     SMALL CRAFT ADVISORY from 8 AM this morning to 8 AM EDT Thursday
     for LHZ348-349.
LM...SMALL CRAFT ADVISORY from 8 AM this morning to 8 AM EDT Thursday
     for LMZ323-341-342-344>346.
LS...SMALL CRAFT ADVISORY from 8 PM this evening to 8 AM EDT Thursday
     for LSZ322.
     SMALL CRAFT ADVISORY from 8 AM this morning to 8 AM EDT Thursday
     for LSZ321.
&&

$$

NEAR TERM...JSL
SHORT TERM...MEK
LONG TERM...MEK
AVIATION...TBA
MARINE...JSL