Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 221144

Area Forecast Discussion
National Weather Service Marquette MI
744 AM EDT Sun Apr 22 2018

.SHORT TERM...(Today and tonight)
Issued at 436 AM EDT SUN APR 22 2018

WV imagery and RAP analysis indicated confluent mid/upper level nrn
stream flow over the nrn Great Lakes downstream from a ridge from MN
into nw Ontario. Sfc ridging also persisted across the Great Lakes
resulting in mostly clear skies and light winds.

Today, with plenty of sunshine and mixing through 850 mb temps
around 2C-3C, per fcst soundings, inland max temps will climb into
the upper 50s to lower 60s. Lake breezes will again keep temps
closer to 50 near the Great Lakes. Similar to Saturday, mixing
should also drop dewpoints through teens with min RH values to
around 15 percent.

Tonight, boundary layer winds in the 10-20kt range just above the
inversion near the sfc should maintain enough mixing to keep min
readings in the lower to mid 30s.

.LONG TERM...(Monday through Saturday)
Issued at 357 AM EDT SUN APR 22 2018

Broad upper ridging to start the week but by mid week a northwest
flow aloft will develop. Indications are this cooler northwest flow
aloft will likely persist into next weekend and on into early next
week, which includes the first day of May.

A couple sharper upper level and sfc troughs are expected to swing
across the Upper Great Lakes this week as the upper air pattern
transitions to more of a northwest flow aloft. Ahead of the first
trough on Mon, southwest sfc winds combined with H85 temps rising to
+5c should result in what will be the warmest day so far this
spring. Expect highs well into the 60s and agree with previous shift
that a 70F reading is possible, especially in downslope areas near
Lk Superior. GFS MOS for IMT picks up on the warmth with 70F now
pegged there for Mon.

Initial trough then moves through on Tue, with a stronger system
following on Thu. GFS most aggressive with both troughs in terms of
bringing precip to the area, especially on Tue when it is the only
model of the primary 00z models showing notable qpf. GEFS
ensembles not as bullish with precip on Tue and especially not on
Thu. The late Thu into Thu night system could also result in rain
changing to snow with minor snow accumulations possible,
especially over the west and north closer to Lk Superior. GFS much
more wrapped up than other models and GEFS ensembles in its
depiction with Thu-Thu night system as it shows main upper trough
closing off for at least a little while and a very sharp sfc low
down to 995mb dropping across Lk Superior and Upper Michigan
leading to lake enhancement with convergent north winds. GFS has
hinted at this over past many runs but this run is one of the
stronger solutions. No need to go that route now, but probably
looking at rain showers mixing with and changing to snow showers
Thu night into Fri morning.

Another impact from both of these troughs this week, in addition to
temps falling back below normal in their wake, will be gusty
northwest to north winds. Strongest winds, with gusts possibly over
30 mph, would occur along Lk Superior Tue night and late Thu night
into Fri especially between Marquette and Whitefish Point.

.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 740 AM EDT SUN APR 22 2018

With high pressure dominating the region, VFR conditions are
expected through the TAF period with light winds.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 436 AM EDT SUN APR 22 2018

Winds will remain less than 15 knots through most of the period. The
main exception will be later Tue into Tue night when northwest winds
increase to over 20 knots. Another period of strong wind will arrive
late Thu into Thu night with winds to around 30 knots in the wake of
a cold front moving across Lake Superior.

Issued at 357 AM EDT SUN APR 22 2018

Snowpack continues to melt steadily since late last week. Sampling
of sites across Upper Michigan shows that with the sunny and warmer
days snow depths after the storm on 15 April have fallen
significantly at inland areas (Painesdale at 53 inches on Thu is
down to 39 inches as of Sat morning while Hoist Basin at 50 inches
on Thu is down to 37 inches). Based on modeled and observed snow
water equivalent values (SWEs), think the higher terrain of
northwest U.P. could still have SWEs around 12 inches with other
higher terrain near Lake Superior 6-8 inches. Our latest SWE
taken on Sat around 8 inches was confirmed by similar values in
nearby locations in Marquette county. Shoreline areas have seen
less melting due to cooler lake modified air (Munising snow depth
has only went down 3 inches since Thu). On the flip side, some
exposed locations over the south central have lost most of their
snowpack with just a couple inches still on ground at Norway and
Escanaba reporting a zero snow depth on the shoreline of Bay of
Green Bay.

Though the melt so far has been slow for most areas, expect it to
increase through Tuesday as daytime highs reach the 60s inland
and nighttime lows stay mainly above freezing. However, dry
airmass with sub freezing dwpnts should result in a slower melting
of snow than would otherwise occur with these temps. Fortunately,
still looks like we will avoid any bigger precipitation events
the next week which would only increase runoff and flooding
potential. Cool down at the end of the week should really slow
down the melt. Overall, observed and forecast conditions don`t
suggest any significant concerns with the snow melt for the next
week. While melting will likely be relatively controlled given the
forecast, certainly could still see minor flooding at some point
down the road on the usual rivers that experience spring flooding.

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


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