Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 281523
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
1123 AM EDT Sat Mar 28 2020

.UPDATE...
Issued at 1123 AM EDT Sat Mar 28 2020

Morning composite analysis reveals a rather impressive early
spring storm system developing across the Plains/Midwest.
Pronounced short-wave impulse/closed upper low is located over
the Kansas/Nebraksa region with a strong upper jet core extending
from Texas up through the Midwest and through lower lakes with
secondary jet max across southern Ontario and Quebec. Pronounced
upper diffluent/divergence axis is readily apparent on
satellite/radar imagery across the central Midwest region.
Deepening surface low pressure is across eastern Kansas/Nebraksa
with a warm front stretching eastward through Illinois/Indiana/Ohio.

Ongoing warm advection forcing north of the front has/is
producing a corridor of widespread showers/thunder across the
lower lakes to the east coast with the heaviest rainfall thus far
confined to areas through southern Lower Michigan. Up this way,
a few bands of lighter showers have been moving through northern
Lower Michigan...tied to the aforementioned secondary upper jet
core and mid level f-gen processes. But lower level dry air has
kept rainfall amounts on the light side thus far (most ob sites
remain VFR)...particularly north of M-72...and no rainfall north
of the bridge as of yet.

Upstream, pronounced moisture surge/warm conveyor showers/storms
are quickly expanding from eastern Texas into the Midwest and will
be pressing into the state tonight.

Details: Short-wave impulse and attending surface low on track to
further deepen and occlude while lifting into the central Midwest
region today and into central Wisconsin by Sunday morning.
Associated strong warm conveyor and upper level divergence forcing
will spread widespread rainfall up into northern Michigan tonight
along with the potential for some thunderstorms to slide up
through mainly northern Lower Michigan.

But until then, per local and regional radar trends, a bit of a
lull in precip appears to be unfolding for northern Michigan.
Mid level f-gen and upper level jet forcing is forecast to weaken
across northern Michigan over the next several hours and should
continue to bring a diminishing trend in shower coverage for the
afternoon. Inherited forecast reflects that idea with only
cosmetic tweaks made by me at this point. Showers (and thunder
chances) will ramp up again from the SW later in the afternoon
and heading into the evening.

Severe weather potential tonight: Latest SPC Day One outlook
maintains a marginal risk for elevated severe storms across
roughly the southern third of the CWA, with the threat coming from
large hail. That seems reasonable given limited surface based
instability tonight but respectable 0-6KM deep layer shear in
excess of 70 knots in the presence of some elevated instability.
Damaging wind threat should remain very low.

&&

.NEAR TERM...(Today through Tonight)
Issued at 342 AM EDT Sat Mar 28 2020

...Brief periods of heavy rain and possible thunderstorms tonight...

High impact weather potential: Marginal risk for severe storms along
and south of a Manistee to Harrisville line this evening...with
large hail being the primary severe weather concern.

Pattern synopsis/forecast: Amplified mid and upper level pattern
found across the Conus at this early hour, with most prominent
feature being full tropospheric trough emerging out of the
Intermountain west. Active baroclinic axis already well estabilished
out ahead of this system, as evident by developing surface low
pressure back across the high plains, with a warm front extending
east from this low across the lower Ohio Valley. Moisture rich
environment along and south of this front as deep Gulf of Mexico
connection has resulted in dewpoints in excess of 60F and
precipitable water values up an over an inch. Deep layer jet
dynamics spreading an elevated moisture plume much further north,
interacting with northward bowing elevated portion of the warm
front...kicking off showers and isolated thunderstorms across the
lower Great Lakes into the Mid Mississippi Valley. Dry low level
environment across the northern Great Lakes keeping much of this
activity off to our south, although suppose a few light showers may
yet spread into northern lower Michigan early this morning.
Otherwise, plenty of higher level clouds spreading overhead as upper
level jet streak does the same. Combination of those increasing
clouds and development of southeast winds on backside of retreating
surface high has kept temperatures a bit on the mild side tonight,
with most areas still in the 30s.

Ejecting western trough will continue to deepen as it takes on an
increasingly negative tilt, eventually closing off as it pivots
across the Corn Belt this evening, reaching vicinity central
Wisconsin by Sunday morning. Surface low pressure will respond as it
should in such a favorably forced environment, steadily deepening as
it becomes increasingly centered under its mid level parent tonight.
Deep layer warm, moist advection out ahead of this system will
spread increasing shower chances north into our area today and
tonight, some of which may be accompanied by thunder as elevated
instability plume spreads north in the process.

Primary forecast concerns/challenges: Addressing temporal and
spatial resolution of showers through tonight. Thunder chances and
the low end potential for isolated severe storms will also need to
be addressed.

Details: Wet period of weather definitely expected, especially as we
into tonight. Shower coverage/organization remains a bit of a
challenge today as best moisture intercept and strongest forcing
remains to our south (along and north of surface based warm front)
and to our southwest (strongest forcing ahead of primary wave). In
addition, dry low level easterly flow will only intensify with time,
especially the further north one goes. Guidance derived soundings
bear this out, with only sporadic periods of sufficient deep layer
saturation. So, definitely not expecting a washout through much of
today, and very likely much of the period and most of the area will
remain largely dry. Forcing ramps up in earnest by later this
afternoon and evening with approach of that deepening shortwave
trough. Strong southerly winds ahead of this system will spread deep
moisture rapidly north into our area. Expect more intense and
organized bands of showers to develop along intense northward
surging theta-e gradient, spreading southwest to northeast across
northern Michigan later today into this evening. May even hear a few
rumbles of thunder this evening across northern lower Michigan as
elevated instability plume of several hundred joules/kg spreads
north. Brief periods of heavy rain will be possible, but transient
nature of showers should prevent any significant hydro impacts
(other than ponding on area roadways). Mid level dry slot punching
northeast brings an end to the more organized shower activity to our
southwest areas by Sunday morning.

As for severe potential: Latest SPC Day One Convective Outlook still
places areas south of a line extending from Manistee to Harrisville
in a marginal risk for severe storms this evening, with isolated
large hail being the primary concern. Perusal of all hi-res guidance
progs and simple pattern recognition of initial warm front placement
concurs, with no surface based instability to interact with an
increasingly favorable backed low level wind environment. Corridor
of enhanced mid level lapse rates juxtaposed with surge of elevated
instability plume may bring a few large hailers to our far southern
areas. Given marginal nature of instability, definitely not entirely
sold on this potential. Will continue to monitor, utilizing our
hazardous weather products and graphics to convey this isolated
severe storm potential.

&&

.SHORT TERM...(Sunday through Monday)
Issued at 342 AM EDT Sat Mar 28 2020

...A Warm Rain, then Turning Cooler ...

High Impact Weather Potential...As temperatures cool night into
Monday morning, there could be a mix of rain and snow or all snow,
especially in the highlands. Possibly making a slippery morning
commute.

Pattern Synopsis/Forecast...The models have the sfc low and the 500
mb lows roughly in the same place 12z/Sun. The tracks are similar,
and the ECMWF seems a bit faster as 500 mb lows are about 100 miles
apart. However, one notable difference is that the warm air is more
entrained into the GFS solution than the ECMWF. This will help with
keeping things warmer in general. If it wasn`t for all the rain,
that it looks to be a decent day, at least initially, to be outside.
However, after 00z/Mon, as the back side of the sfc low moves into N
lower, the colder air begins to drop into the region. With the
cooler air aloft, and the sfc temperature dropping to around
freezing, the rain will probably mix with snow at the lower
elevations, and may change to snow in the higher elevations (areas
around Gaylord). Monday morning, the temperatures are expected to
warm into the mid 30s by 14z/Mon taking the precipitation back
toward all rain, before ending by the afternoon. High pressure
builds in overnight as things dry out.

Primary Forecast Concerns...If the ground cools back enough, and
probably will, there could be slipper spots if the snow falls in the
interior of N Lower, and some places in E Upper.

Winds have been a concern as of late. As the low tracks from
Wisconsin, to N Lake Michigan, the pressure gradient slackens, so
the winds are expected to diminish. The latest models are similar
enough, that there will be lighter winds than we had in the previous
forecast, but that will quickly change, once the sfc low moves
across the region. Then the gradient tightens increasing the winds,
and the gust potential. That would seem to be some time just after
21z/Sun on the west side of the state, and about 04z/Mon on the
east. If the lows track to the north a bit morning, there could be
some higher winds in our SE counties ahead of this system, but most
of the evidence is pointing to a day of 10-15 mph with gusts to 25
mph, with a brief pause as the sfc low moves through the region.

.LONG TERM...(Monday night through Friday)
Issued at 342 AM EDT Sat Mar 28 2020

High Impact Weather Potential...Thunder Thursday? Snow or a mix
Thursday night into Friday.

Extended (Tuesday through Friday)...Tuesday and Wednesday, the
pattern is relatively zonal, especially on the ECMWF. The GFS is a
little more amplified as it pushes a northern branch feature into
the N Plains aimed at the Upper Great Lakes. The ECMWF has this
feature, but it is slower and more shallow with the jet pointed into
the Upper Great Lakes. So the overall idea would be that Tuesday and
Wednesday would be mainly dry, with the GFS suggesting that
Wednesday night would be wet as the system moves into the region.
Thursday, will be wet, no matter the model that you use. The
question will be, based on this is will there be thunder as the
ECMWF suggests. However, once the cold front moves through, then it
will cool off, and the model soundings suggest snow or a mix will be
possible as we go into Friday. The models continue their differences
with the ECMWF more northerly idea, would put us into a drier idea,
but with the 850 mb temperatures there would be lake cloudiness. The
GFS would continue the chance for showers as the 500 mb low would
move slowly off the Atlantic seaboard before drying, maybe, Saturday
night.

If the ECMWF is right then the blends showing highs around normal
(lower to mid 40s) for Tuesday through Friday is probably on track.
If the GFS is right then we are going to be a little below normal
(upper 30s to lower 40s at the least) Thursday and Friday.

&&

.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
Issued at 640 AM EDT Sat Mar 28 2020

Conditions to slowly deteriorate across the taf sites heading
through today and tonight as deep low pressure pushes toward the
region. Cigs with steadily lower to MVFR today to IFR tonight. More
widespread showers arriving later today, and especially tonight...
with brief periods of heavy rain possible. May even see an
isolated thunderstorm or two this evening. East to southeast winds
will become increasingly gusty through the period.


&&

.MARINE...
Issued at 342 AM EDT Sat Mar 28 2020

Increasingly gusty east winds expected today as low pressure
organizes to our southwest. Winds steadily veer tonight, becoming
southwesterly on Sunday as low pressure pushes across the northern
Lakes. Winds become northwest and remain gusty Sunday night into
Monday morning as low pressure departs. Small craft advisories are
likely much of this period on most nearshore waters. Still possible
to see a few isolated gale gusts on portions of northern Lake
Michigan Sunday, especially south of the Sleeping Bear Dunes.
Showers will overspread the area, especially later today into
tonight. May even hear a few claps of thunder this evening, with any
stronger storms potentially bringing brief periods of erratic
winds, some hail, and heavy rain.


&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...SMALL CRAFT ADVISORY from 5 PM this afternoon to noon EDT Sunday
     for LHZ345>349.
LM...SMALL CRAFT ADVISORY from 5 PM this afternoon to noon EDT Sunday
     for LMZ323-341-342-344>346.
LS...SMALL CRAFT ADVISORY from 11 PM this evening to noon EDT Sunday
     for LSZ321-322.
&&

$$

UPDATE...BA
NEAR TERM...MB
SHORT TERM...JL
LONG TERM...JL
AVIATION...MSB
MARINE...MB


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