Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 240833
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
433 AM EDT Tue Apr 24 2018

.SHORT TERM...(This evening through Tuesday)
Issued at 239 PM EDT MON APR 23 2018

The area remains under the influence of ridging originating from a
high pressure system centered on the Eastern Seaboard.  Temperatures
this afternoon have climbed into the mid to upper 60s across much of
the area save along the Lake Michigan shore line where temperatures
remain in the lower 50s. Dew points are also (finally) starting to
increase somewhat this afternoon as snow melts, especially across
the west. Generally clear skies are being observed across the
area except for a few high clouds across the north central and
east.

Clouds will increase overnight across the west owing to an
approaching cold front associated with a low pressure system
currently located in central Ontario. Clouds along the comma head of
a low pressure system in the Tennessee River Valley will also
stream northward overnight toward the eastern U.P., leaving perhaps
an area of "lesser" cloud cover over the central overnight. All
said, low temperatures overnight are expected to be warmer than the
last and primarily above freezing leading to continued snow melt.
Light winds will prevail.

The aforementioned cold front will sweep through Upper Michigan
Tuesday morning leading to a shift in winds from southwesterly to
northwesterly. Winds may gust to 15 to 25 mph or so along the
leading edge of the front. Forecast soundings indicate low-level
dry air holding tight which will limit any precipitation to
drizzle at best. Indeed, we are thankful for our continued snow
pack to limit the potential for fire weather in the short term.
Clouds are expected to gradually abate from west to east tomorrow
afternoon and evening.

.LONG TERM...(Wednesday through Monday)
Issued at 432 AM EDT TUE APR 24 2018

Roller coaster for temperatures is expected into next week. Coldest
day will be on Fri behind cold front that moves through Thu night.
Warmest days will be Sun and Mon as upper level troughing that moves
overhead Fri-Sat is replaced by sharp ridging and very warm temps
aloft. Though could see some light rain showers changing to rain and
snow showers Thu night into Fri, heavier rain and maybe some
thunderstorms will not affect the area until next week.

Upper troughing that brings cold front through today will be heading
east of Upper Michigan daybreak Wed. High pressure builds in
bringing dry conditions. NW gradient winds result in highs on Wed
staying near 40F near Lk Superior central and east. Away from
lake moderation off Lk Superior, expect temps to push well into
the 50s toward the Wisconsin state line. High sliding east of
Upper Michigan Wed night into Thu will lead to brief warming
again. Highs on Thu ahead of approaching cold front should reach
60F over most of central and east away from Lk Michigan. Readings
could rise well into the mid to upper 60s south central. Cold
front sweeps through Thu night and should be exiting eastern Upper
Michigan daybreak Fri. Strongest forcing with the front should
stay north of Lk Superior. GFS and GEFS indicate likely showers
with total qpf to a 0.25 inch. Other models show lighter qpf with
most areas seeing brief push of showers dropping maybe 0.10 inch
of qpf. Enough cold air as front exits that precip could end as a
little light snow with minimal accumulations. As mentioned
previously, N to NW winds may get gusty in wake of the front.
Could see gusts near Lk Superior east of Marqeuette exceeding 30
mph Thu night. Winds may also get gusty on northern Lk Michigan
behind the cold front. May be looking at marine small craft
advisories for both areas due to the winds and building waves.

Trend the models have now latched onto compared to last couple
days output is secondary more compact and focused shortwave
trough crossing Upper Michigan on Fri in clipper fashion from
northwest to southeast. Current forecast only has slight chances,
but these certainly may need to be increased as the week goes on.
Ptype should stay mainly rain with adequate sfc-H85 warm layer
present as the system works through. Cold air lingers into Sat
then a significant warm up is still in store starting Sun aftn.
Temps on Sun could reach the 60s to near 70F west with climbing
temps aloft and sfc SW gradient winds. Warm up is further magnified
on Mon with strong sfc flow sfc-H85 and H85 temps rising up to
+13c. Deep mixing with this warm air aloft will result in max
temps possibly cracking the 80F mark for the first time this
spring through current forecast is close by in the mid to upper
70s. Coolest temps will be near Lk Michigan as is typical for
Spring warm ups with SW winds. Currently model dwpnts indicate
upper 30s to mid 40s which seems pretty reasonable. And then
there is the matter of a possible rain event with the ECMWF
hinting at thunderstorms with total qpf by 12z Wed over 1 inch.
GFS not as bullish, but based on GEFS probabilities, could see at
least a half inch of qpf starting late Tue. Main impact of the
warm temps and rain will be on ongoing snow melt and runoff into
area rivers. Will be something to keep eye on for sure.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 136 AM EDT TUE APR 24 2018

The region is undergoing a pattern change, allowing for a frontal
passage to come through on Tuesday, along with lower-level clouds
associated with the front. While there is a slight chance for some
showers to develop along the front, there isn`t enough confidence
that these will come to fruition at the terminals for this TAF
issuance. Should higher confidence exist in subsequent TAF issuances
as that time gets closer, could add mention at that point. Light and
variable to calm winds will persist through the overnight hours with
an increase in the winds during the day on Tuesday as the front
approaches, becoming northerly behind the front.
&&

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 239 PM EDT MON APR 23 2018

Winds across the west will remain at 15-25 knots through this
evening and weaken toward midnight.  An uptick in winds to 20-30
knots is expected across the far west toward sunrise (along the
Minnesota Arrowhead).  Elsewhere, southwesterly winds will shift to
northwesterly toward sunrise and gust 15-25 knots as a cold front
sweeps through the area. As with typical spring cold frontal
passages, winds near the surface of Lake Superior are expected to
be calm while winds near the top of shipping vessels can be quite
gusty due to the cold marine layer. Tuesday night through early
Thursday, winds are expected to remain below 20 knots across all
of Lake Superior. Winds will then pick up to 20 to 30 knots
Thursday night with the passage of a secondary cold front.
&&

.HYDROLOGY...
Issued at 432 AM EDT TUE APR 24 2018

Snowpack continues to melt steadily but runoff/rises on rivers has
been manageable to this point. The melt thus far has been gradual
with most locations losing 2-4 inches of their snowpack each of the
last few days. Some of the big winners from the last storm are
down around 20 inches compared to max snow depths from a week ago.
Now, though the snow depth is going down steadily, the liquid
water in the snowpack (SWE) is only slowly decreasing as evident
by our SWE last couple days (steady around 7.4 inches) and recent
modeled SWE per NOHRSC. Snowmelt should slow in the next 24-48
hours as temps cool, especially at night with below freezing temps
expected. No change in limited heavy precip chances through the
weekend. Still could be some light precip under one-quarter inch
late Thu into Thu night. Starting to look like we will have to
keep eye on conditions by early next week as there are indications
we could be in store for a significant warm up accompanied by
more low-level moisture/higher dwpnts than we have seen recently.
There could even be appreciable rainfall and possible thunder
just by middle of next week. If these conditions do develop and
snowpack left still has a decent SWE lingering, we could see minor
flooding on the usual rivers that experience spring flooding, so
we will continue to monitor.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&

$$

SHORT TERM...Borchardt
LONG TERM...JLA
AVIATION...lg
MARINE...Borchardt
HYDROLOGY...JLA



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