Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 210921

Area Forecast Discussion
National Weather Service Marquette MI
421 AM EST Tue Feb 21 2017

.SHORT TERM...(This evening through Tuesday)
Issued at 356 PM EST MON FEB 20 2017

Strong upper trough is pressing across northern Plains with sfc low
lifting over southern Manitoba. Strong moisture advection with pwats
over 1 inch (a whopping 300-400+ percent of normal) surging in ahead
of the sfc trough is resulting in widespread showers and a few
clusters of tsra lifting toward Upper Michigan from the central
Mississippi river valley. RAP and HRRR matching reality well and
show showers moving over western cwa through late this aftn then
spreading to central cwa this evening and into far east cwa by late
evening. Have seen isold lightning strikes every now and then with
showers over eastern IA into western WI where RAP and NAM showed
elevated MUCAPE up to 100j/kg and based on the forecast instability
this evening could see isold tsra potential this evening as showers
slide across. Given the unusually high moisture lifting in and
the elevated instability could see heavy downpours as the rain
moves through.

As shortwave lifts across Upper Great lakes and sfc trough crosses
the region, showers should shift steadily west to east across Upper
Michigan. High res guidance including the NAM, HRRR, RAP and NSSLWRF
indicate that there will be brief break with initial showers and
then there may be another push of showers move through on the sfc
trough axis. Given steeper h85-h5 lapse rates near 7c/km moving in
with surge of mid level drying think best chance of tsra could
actually occur 05z-07z Tue over west, 08z-11z Tue over cntrl and
over east cwa 11-13z Tue. Effective shear up to 50 kts with wbzero
heights lowering to 7k and 50 dbz height for 1 inch hail of lower
than 20kft suggests that if storms can form overnight, there would
be risk of hail.

On into Tue. Once showers and possible isold tsra exit eastern cwa
early in the day should see column dry out quickly from west to
east. Breezy on the Keweenaw and those stronger winds are sign of
better mixing depth that will spread over rest of cwa. As main
trough exits east, low-level winds will start out west then shift to
the southwest ahead of another weaker low pressure system sliding
over northern MN. Overall mixing to 900-875mb supports highs well
into the 50s over much of cwa expect where winds are onshore. May
even see readings top out in the low 60s for interior west and
central. For now, increased temps to near 60F to come more into line
with better perfoming guidance with recent warm spell. Any showers
with the northern MN wave should stay west of cwa through late in
the aftn.

Thus far with the warm up rivers have not responded much likely due
to gradual melt as nighttime lows have dipped near or blo freezing.
Rivers should respond tonight into Tuesday though more significantly
as mins tonight will remain above freezing and with rainfall and
melting snow tonight and since readings spike into the 50s on Tue.
Overall the rivers should see their greatest rises in the next few
days. At this time, significant hydro issues are not expected due to
lower river and stream levels, overall lower than normal amounts of
water equiavalent in the snowpack and generally quick moving
rainfall tonight with total qpf staying mainly less than 0.75 inch
in most areas. Still some unknowns though including extent of ice on
rivers. At the least with the rain and melting snow tonight could
see ponding of water in low-lying/poor drainage areas, especially if
there is any ice/snow plugging up storm drains. Will mention this
potential in HWO.

.LONG TERM...(Wednesday through Monday)
Issued at 419 AM EST TUE FEB 21 2017

Models continue to struggle with consistent handling of shortwave
energy and associated precip Wed afternoon into early Thu. Overall
best chances of a wintry mix are over the north. No significant
impacts are expected at this time

Attention then turns to a low pressure system that models continue
to show moving just SE of the CWA or along the SE edge of the CWA
Thu night into early Sat. Still plenty of time for the track,
intensity and speed to shift considerably as the upper energy is
still over AK and there will be interaction with an upper low moving
across southern Canada. At this point, the best heavy snow potential
is over the central and/or western Upper Michigan, especially in
areas favored by upslope NE/NNE winds, but these details may change
significantly. Over the southeastern CWA, better chances for mixed
precip exist. Blowing snow also appears to be an issue near Lake
Superior. Definitely bears close watching by those with weather
sensitive interests.

Beyond that system, much cooler temps and generally NW wind LES are
expected through Mon. Southerly winds Tue will change things up with
a temporary end to LES as it appears now.

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1219 AM EST TUE FEB 21 2017

A period of IFR conditions is expected overnight with rain and
abundant low level moisture moving into the area on southerly winds.
Some LIFR CIGS are also possible, mainly at CMX and SAW. After
trough passes tonight, there is uncertainty in how quickly low
clouds will clear out but expect some improvement to MVFR late as
winds veer wrly and drier air moves in. By mid morning on Tue, VFR
conditions will dominate with gusty westerly winds, especially at
the more exposed KCMX location.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 356 PM EST MON FEB 20 2017

Tighening pres gradient btwn high pres ridge shifting toward the E
Coast and an approaching low pres trof will result in SE gales of 35-
40kt thru much of tonight across the e half of Lake Superior. Gales
will end with the passage of the trof late tonight. Winds should
then stay mostly 25kt or less Tue thru Thu. Stronger winds, perhaps
gales, are expected later Fri into Sat as a low pres system tracks
ne thru the Great Lakes region. After a hiatus from winter type
conditions, should also the potential for freezing spray return
later Fri into Sat.

Upper Michigan...
Lake Superior...
Lake Michigan...


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