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Area Forecast Discussion

000
FXUS63 KAPX 210422
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
1122 PM EST Mon Feb 20 2017

.UPDATE...
Issued at 927 PM EST Mon Feb 20 2017

Mid level trough axis stretches from central Canada down through 
Texas with broken segments of a S-N oriented upper jet running 
from the Gulf into Ontario. Attending surface low pressure 
analyzed over south-central Canada (ahead of the short wave) with
a cold front stretching all the way into Texas. One vorticity 
center (and entrance region of one segment of the upper jet) is 
lifting northeastward through Minnesota producing a fairly 
widespread batch of rainfall across Wisconsin/western U.P. that 
has been slowly inching it's way toward the CWA this evening. 
Second short wave and segment of the upper jet is moving into the 
western Gulf with another batch of precip impacting the lower 
Mississippi River valley. 

Rest of tonight through Tuesday morning: Northern piece of short 
wave energy will lift up through the northern lakes region, 
shearing/weakening as it does so. This will eventually push
upstream cold front and batch of rainfall into the CWA over the 
next several hours before exiting W-E Tuesday morning. Precip has
been thinning a bit over the last few hours, which certainly
raises some concern as to how much precip actually makes it
through the CWA, although guidance insists it will. But still
fairly confident that most locations will see some rainfall
through Tuesday morning.

Main forecast adjustment this evening was to slow down arrival of
precip by a few more hours particularly over the E/SE parts of the
CWA, and remove freezing rain from eastern upper Michigan. 
Surface temperatures are hovering around 32F in eastern upper
Michigan at the moment. But not so concerned about freezing rain  
as temps should inch a little warmer by the time rainfall 
actually arrives and will probably increase further once rain
begins due to frictional drag of warmer air aloft to the surface. 

Finally, removed thunder from the forecast. There is a thin axis 
of instability nosing up into the Midwest this evening with some 
lightning strikes detected on the lightning networks in Missouri.
This modest, thin instability axis will move up into lower 
Michigan late overnight/early Tuesday morning and I suppose 
thunder chances aren't zero. But chances just seem to low to worry
about for now. Actually, a better chance for some thunder may 
come Tuesday morning as pronounced dry slot and pocket of steep 
lapse rates drives W-E across the region right in behind the cold 
front. 

&&

.NEAR TERM...(Tonight and Tuesday)
Issued at 326 PM EST Mon Feb 20 2017

...Rain and Fog tonight Rain ending Tuesday...

High Impact Weather Potential...Minor river flooding following the 
rain and snow melt. Dense fog possible, but not likely with the 
rain. 

Pattern Synopsis/Forecast...Return flow is increasing as the sfc 
trough/cold front off to the west is pushing toward the Upper Great 
Lakes. Rain on MRMS is just into W Upper and W Wisconsin. It will 
continue to fight a lot of dry air ahead of it as the sfc RH is 
around 35% in the western counties of the forecast area. Dewpoints 
are creeping up with the stations in the west like CAD, MBL and FKS 
are 32 or 33F. As the moisture increases from the strong warm 
advection, will begin to see fog develop. At this point, it looks as 
if the fog will remain at 3 miles of better as the moisture 
increases, but with the rain, we may not see much restriction below 
that. 

The rain will continue through the night as the cold front 
progresses through the forecast area. It looks there could be some 
thunder with the frontal passage, as the lapse rates, and the strong 
low-level jet feeds into the system. However, it looks like the 
thunder threat is low, so have it as slight chance. The front looks 
to be through the forecast area, around 12z/Tue allowing for some 
trailing showers through about mid day. Models 
(GFS/NAM/ECMWF/NMM/ARW/SREF) all in agreement that the rain is out 
of the northern Michigan and most if not all of the Lake Huron by 
21z, and the region by 00z. 

Primary Forecast Concerns...Fog if it gets soupy, which is possible 
with these systems, but with the winds and the rain, feel that minor 
fog, with patches of denser fog are possible. However, tuesday will 
be a day to watch to see how the snow melt, and rain fall do 
anything to the rivers. The plus side is that there are large chunks 
of N Lower where the snow has melted. The rest of the region has 
about 2 to 3 inches of water equivalent, but not all of it will melt 
in 12 hours. Today, the only river that is expected to approach 
Action stage is the Manistee River near Sherman, and it has a 20% 
chance or lower of exceeding minor flooding (15Ft). So will keep an 
eye on that one and the Rifle River near Sterling for the next day 
or two.

&&

.SHORT TERM...(Tuesday night through Thursday)
Issued at 326 PM EST Mon Feb 20 2017

...Record setting warmth possible on Wednesday...

High Impact Weather Potential: Nothing from a sensible weather 
standpoint. Still monitoring river rises over the coming days.
  
Pattern Synopsis/Forecast: Unrelenting warmth set to continue for at 
least a few more days as much modified Pacific air dominates much of 
the northern Conus. Not an overly active stretch of weather through 
the short term, although a fast moving and amplifying wave looks to 
bring a bout of showers to northern areas Wednesday night. This 
system will also send a more bonafide cold front through the region 
Thursday, starting the step-down process to more typical late 
February weather for these parts.

Primary forecast concerns: Just how warm to go Wednesday and 
addressing the rain chances late Wednesday and Wednesday night.

Details: A mild and dry Tuesday night sets the stage for possible 
record warmth on Wednesday. Morning sunshine and deepening southwest 
flow ahead of fast moving shortwave should only help the cause, as 
will a nearly complete loss of the snow pack for much of northern 
lower Michigan. Weak warm front looks to take shape during the day 
across far northern lower Michigan/the Straits, placing much of the 
area south of the big bridge squarely in the warm sector. Guidance 
progs show this well, with much of northern lower well into the 50s, 
and the southeast half of the area making a run at 60 degrees. This 
will suffice for now, although as cool as guidance numbers have been 
compared to reality during this warm stretch, would not be at all 
surprised if some areas were several degrees warmer. Taking a quick 
look at record temperatures for the date suggests nearly all records 
are in jeopardy of falling, with Houghton Lake (64 degrees back in 
1930) having the best chance to survive. That warmth continues right 
into the first half of Wednesday night as southwest flow further 
intensifies with approach and passage of that amplifying shortwave 
trough. Per trends, best forcing and focus for moisture convergence 
looks to remain across Lake Superior and points further north. 
Proximity of system does support at least some low end shower 
chances across the north later Wednesday into Wednesday night. 
Moisture and forcing starved cold front crosses the area overnight 
into Thursday morning. While post-frontal northwest to north winds 
do usher in a progressively cooler and drier airmass Thursday, real 
cold air will still be locked up well to our north. So, while it 
will definitely be cooler on Thursday, with highs largely in the 
40s, these are still 10 or more degrees above normal for the date.

As for those river rises, much of the snowpack will be largely gone 
by Tuesday night and Wednesday, with the exception being across the 
snow belts of eastern upper Michigan and the interior highlands of 
northern lower. Combination of warm temperatures and increasing 
dewpoints will do a number on this existing snow, and would not be 
at all surprised if nearly all of northern lower is essentially snow-
free by Thursday morning. Rivers will of course respond to this 
runoff, but lack of any significant rain during this period should 
keep rivers within their banks. Of course, this will continue to be 
monitored in the coming days.

.LONG TERM...(Thursday night through Monday)
Issued at 326 PM EST Mon Feb 20 2017

High Impact Weather Potential: A system moving through Fri/Sat will 
bring a wintry mix for much of northern Lower. Areas that remain all 
snow, which right now look to be mostly north of the Straits, could 
pick up a few inches of accumulating snow.

Low pressure moving out of the Plains will move into the region over 
the weekend. Strong H5 cutoff low will continue to strengthen the 
low as it enters the Great Lakes. Good return flow with an open Gulf 
will give the system plenty of moisture to work with, but it looks 
like a good portion of the precip will fall as rain or perhaps a 
rain/snow mix especially across northern Lower. Lake effect will 
linger through Saturday as a brief shot of cold air pushes south. 
This push of cold air will return temperatures to more seasonable 
readings through the weekend, though the will still be a touch above 
normal.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1122 PM EST Mon Feb 20 2017

VFR conditions continue to hold on across northern lower Michigan
for the time being, with gradually thickening and lowering 
cloud cover. Upstream, surface low pressure is over south- 
central Canada with a cold front stretching down through the 
central plains and an elongated axis of rainfall ahead the front 
stretching from the western lakes to the Gulf.

Rainfall will slowly spread W-E into the region overnight and 
persist through Tuesday morning. VFR conditions now will
deteriorate to IFR conditions at all terminal sites through 
Tuesday morning. Slow improvement Tuesday afternoon as the rain
comes to an end and wedge of dry air spreads into the region. All
sites should return to VFR by late day or early Tuesday evening. 

&&

.MARINE...
Issued at 326 PM EST Mon Feb 20 2017

Tonight through Tuesday...Small craft advisories were issued this 
morning, as the winds were expected to increase through the day. 
Offshore winds along the Lakes are beginning to hit small craft 
criteria, and are expected to continue into tonight. However, once 
the cold front moves through the region Tuesday morning, the 
gradient relaxes and the winds will diminish through the day. Winds 
on Tuesday night increase a bit, but are expected to be below small 
craft criteria, and Wednesday looks like light winds through the 
day. 

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...SMALL CRAFT ADVISORY until 7 AM EST Tuesday for LHZ345>349.
LM...SMALL CRAFT ADVISORY until 7 AM EST Tuesday for LMZ323-341-342-
     344>346.
LS...NONE.
&&

$$

UPDATE...TBA
NEAR TERM...JSL
SHORT TERM...MSB
LONG TERM...ALM
AVIATION...TBA
MARINE...JSL