Area Forecast Discussion
Issued by NWS Gaylord, MI

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966
FXUS63 KAPX 240353
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
1153 PM EDT Sun Apr 23 2017

.UPDATE...
Issued at 1022 PM EDT Sun Apr 23 2017

Cool/dry high pressure is over central Canada (note surface temps
already dropping toward single digits over far northern ON). Low
pressure is advancing into the northern plains, with a warm front
extending across southern MN and into western/southern WI. Quite
the airmass contrast, as befits mid-spring. Return flow is
generating a long arc of cloud cover and virga from ND into
northern MI. In this forecast area, cloud cover is most prevalent
north of M-72, though a thickening cirrus shield is starting to
press into other parts of nw lower MI.

Will need to continue the earlier trend of going somewhat
cloudier. Earlier forecast already had considerable cloud cover in
eastern upper, but need to expand this further south to some
degree. Will still lower min temps in southern locales a bit,
given window for radiational cooling (CAD already down to 40f).

UPDATE Issued at 746 PM EDT Sun Apr 23 2017

Have adjusted cloud cover higher for the 1st part of the night in
many places, thanks to stratocu in the Straits, lake breeze-
forced cu near Mio, and expanding mid/high clouds in
central/northern sections.

&&

.NEAR TERM...(Tonight through Monday)
Issued at 308 PM EDT Sun Apr 23 2017

High impact weather potential: None.

Pattern synopsis and forecast:

A cold front continues it`s march southward into srn lower Michigan
this afternoon, with a corridor of deeper moisture in the cooler air
to the north continuing to shear/thin out with time. Any light
precipitation looks to have already come to an end with the only
echoes now seen being well west across western upper Michigan where
there was still a little light rain/snow. Skies were sunny
elsewhere, with the band of clouds/moisture having quite the hard
time making it south due to mixing and walking into a very dry air
mass. Temperature here were into the middle 60s, outside of coastal
areas where lake breezes have brought cooler air off the lakes
inland. Under the clouds to the north, temperatures were quite
chilly, with upper 30s and lower 40s. Large temperature range this
afternon.

The cold front will continue to sink south through tonight with sfc
high pressure sinking into the nrn Great Lakes. Believe the clouds
will continue to diminish into the evening before some elevated axis
of warm advection is projected by many data sets to produce more
clouds into the night. Maybe across eastern upper more so, but do
not see much support for nrn lower seeing mostly clear/partly sunny
skies. Forcing is minimal tonight with main LLJ and potential right
entrance region upper divergence focused well west in the north
central conus. Maybe a touch of light rain/snow across nrn portions
of Chippewa county, but wouldn`t bet much on that.

Heading into Monday, the cold front returns as a warm front into
the western Great Lakes, as a shortwave ejects into the Central
Plains, from broad upper troughing over the western conus. Winds
start to turn more SE bringing cooler air in off Lake Huron to
portions of eastern upper and NE lower. This will keep highs in the
upper 40s to middle 50s. Meanwhile, warmer air and downsloping
effects will bring upper 50s to upper 60s for much of NW lower.
Sunshine is expected to be rather abundant across nrn lower while
sunshine will be trying to come out across eastern upper into the
afternoon. Do have a couple of concerns. One, could be some
overnight stratus developing and moving into portions of far nrn
lower and eastern upper. However, just think that the low level air
mass will be able to moisten up enough. Second, will have to watch
for low humidity and a little afternoon gustiness to elevate fire
danger in portions of NW lower tomorrow.

&&

.SHORT TERM...(Monday night through Wednesday)
Issued at 308 PM EDT Sun Apr 23 2017

...More active pattern arrives midweek...

High impact weather potential: Chance of thunderstorms Wednesday and
Wednesday evening.

Pattern Forecast: The main focus through the short term forecast
period will revolve around energy currently well off the West Coast,
expected to dive across the Pac NW into the four corners region by
Tuesday. This will allow for troughing to dig across the central US
along with surface cyclogenesis lee of the Rockies as that energy
ejects northeastward toward the Great Lakes/Midwest during the
midweek timeframe. There`s certainly overall guidance agreement in a
much more active pattern by midweek, but confidence remains low with
respect to the details of thunderstorm and heavy rain potential as
the overall evolution and placement of low pressure as it treks
toward the region remains in question.

Primary Forecast Concerns: Main forecast concerns/challenges revolve
around the Tuesday night through Wednesday timeframe and includes
PoPs, thunder chances, and any potential for periods of heavier
rainfall.

Weak high pressure across the area Monday evening is quickly forced
northward as low pressure develops across the plains and Monday`s
weak stalled boundary transitions into a northward progressing warm
front. Little in the way of sensible weather is expected through
Tuesday, aside from increasing southeasterly winds and temperatures
with well-above normal highs ranging from near 60 degrees north of
the bridge to the low 70s elsewhere (cooler near the lakes).

Scattered shower chances begin to increase to an extent Tuesday
night, mainly across far northwest Lower and eastern Upper, but even
more so late in the day Wednesday through Wednesday night as low
pressure is expected to move from the mid-Mississippi Valley into
the western Great Lakes. Thunder threat also increases during the
day Wednesday as a plume of a couple hundred J/kg MUCAPE is progged
to work its way across sections of northern Lower. In addition,
pwats rising to above an inch suggest the threat for periods of
heavier rain, especially Wednesday night associated with areas of
better forcing and mid-level support arriving from the southwest.

.LONG TERM...(Wednesday night through Sunday)
Issued at 308 PM EDT Sun Apr 23 2017

Extended period continues to look very active. High pressure to our
north tries to build into the region, but successive systems moving
out of the Plains will be doing their best to thwart that. A brief
push of cold air late in the week could bring a few flakes for
northern areas of the CWA. The lows affecting the area will be
bringing Gulf moisture, and could bring some more heavy rainfall to
the area. This will be dependent on where they track, and confidence
in that is low at this time. Another concern is with Wednesday
evening. As the low approaches, there is a high shear low CAPE
environment in place, with strong upper level divergence in the area
and a tight potential temperature gradient moving across the area.
Currently progged CAPE is sub 1000 J/kg, with 0-6km bulk shear 50+
kts, even higher in some areas. Certainly see a lot of these high
CAPE low shear setups do nothing, but it is worth keeping an eye
on.

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1153 PM EDT Sun Apr 23 2017

VFR.

Low pressure will lift ne into the northern plains on Monday. This
will gradually veer winds to the e and se. Some stratocu and
mid/high clouds will be seen in advance of this system tonight and
Monday, but conditions should remain VFR. LLWS may emerge toward
the extreme end of this TAF period as se winds just off the
surface increase, but will hold off including in the TAFs for now.

&&

.MARINE...
Issued at 308 PM EDT Sun Apr 23 2017

A cold front will continue to drop south of the area into tonight,
with higher pressure working into the nrn Great Lakes. Somewhat
gusty northerly winds/lake breezes will weaken while also starting
to turn more out of the east. This winds will continue to veer and
come out of the SE Monday, increasing with time in a tightening
gradient from the cold front lifting back north as a warm front.
There is some indication by more hi-res data, that advisory level
gusts develop on many nearshore waters, especially Lake Huron. Am
not totally sold on that idea due to increasing stability.
Regardless, the chance is there. Maybe some better chances at that
Monday night as there is a more substantial increase in speeds, but
stability only grows.


&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...SMALL CRAFT ADVISORY from 8 AM Monday to 8 AM EDT Tuesday for
     LHZ345-346.
     SMALL CRAFT ADVISORY from 5 AM Monday to 8 AM EDT Tuesday for
     LHZ347-348.
LM...SMALL CRAFT ADVISORY from 8 AM Monday to 8 AM EDT Tuesday for
     LMZ341-342.
LS...SMALL CRAFT ADVISORY from 8 AM Monday to 8 AM EDT Tuesday for
     LSZ322.
&&

$$

UPDATE...JZ
NEAR TERM...SMD
SHORT TERM...MJG
LONG TERM...ALM
AVIATION...JZ
MARINE...SMD



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