Area Forecast Discussion
Issued by NWS Marquette, MI

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000
FXUS63 KMQT 280936
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
436 AM EST Tue Feb 28 2017

.SHORT TERM...(This evening through Tuesday)
Issued at 234 PM EST MON FEB 27 2017

Upper air pattern consists of a 500 mb trough in the western Rockies
this morning. This trough moves to the eastern Rockies by Tue
evening. Nam shows some 850-500 mb q-vector convergence and deeper
moisture late tonight into Tue. GFS and ECMWF show about the same
thing as well. Will use a blend of the forecast models for this
forecast.

Looked at some soundings off bufkit and only place I could find
freezing rain being possible for a short time was IMT off the Nam
sounding. Looked like it was going to be mostly a rain/snow and some
sleet at times for the pcpn types and do not expect icing to be much
of a problem. Pcpn starts late tonight, but before it does the
temperatures will be rising. Snow totals will not be that much
either as most of the qpf that falls will be rain, but could still
see up to an inch of snow in the Keweenaw. Overall, did not make too
many changes to the going forecast.

.LONG TERM...(Wednesday through Monday)
Issued at 433 AM EST TUE FEB 28 2017

Shortwave entering the base of the trough over the western Conus
this morning should be crossing Neb and Iowa on Wed morning. H7-H5 q-
vector convergence with the wave along with ribbon of deeper h85-h7
moisture combine to bring chance of light snow of an inch or two to
south and east cwa to the northwest of 990-995mb sfc low crossing
central Great Lakes. Also will see chances of light snow showers
due to lake effect over north central cwa with NNE winds and
shallow moisture at least to H9 extending to temps of -11c to
-13c. Weak lake effect could persist through Wed night mostly
across north central cwa. Even though instability is marginal, all
the cloud layer within dgz could allow for very fluffy snow and
may even see some light accums Wed into Wed night for west and
ncntrl.

Weak shortwave swings through late Wed night into Thu morning within
deepening trough aloft. Lake effect may increase some where it will
already be ongoing, mainly north central cwa and also over far
west cwa where northerly winds are favorable for lake effect. Also
if the shortwave has enough lift and moisture could see period of
lgt snow or flurries for most of the cwa even away fm Lk
Superior. Behind the mid level shortwave, reinforcing sfc cold
front moves through Thu evening. H85 temps down to -15c by 00z Fri
fall further to around -20c 12z on Fri. Expect lake effect to
increase Thu evening into Fri morning for the NW wind snow belts.
Forecast soundings show inversions up to 5kft over the west and to
8kft at the end of fetch over eastern Lk Superior into eastern
Alger county and northern Luce county. Since it is getting colder,
dgz is pushed closer to the ground and possibly may be out of
cloud layer, so snowflakes may get smaller and be better at
reducing visibility instead of producing much accumulation.
Likely snow showers for sure, but probably looking at 1-3" or
2-4"/12 hr type snows in this setup, with isolated higher amounts
if there is stronger convergence which would bring dgz more into
play and lead to higher slr/s. Blsn should not become too
significant since 925mb winds only reach around 20 kts later Thu
night into Fri.

Large high pressure ridge axis crosses area Fri into Fri evening
switching winds to S/SE and ending lake effect off Lk Superior.
Though cold enough for lake effect off Lk Michigan with that low-
level flow into cntrl cwa also seems too dry in low-levels to hit
that up at this point. Ridge is followed by rising heights aloft and
gradual warm front passage late Sat into Sun. Could be some light
snow as the warm front approaches but due to stronge ridge aloft and
more of a focused shortwave tracking south of Upper Michigan, last
couple runs of the models have backed off of the chances. If there
would be some snow it would occur late Fri night through midday Sat.
Rest of weekend into early next week looks potentially active but
the pattern is muddled. Ridge aloft slides across later Sat into Sun
but ECMWF continues to hint at small precip chances developing Sun
along tighter gradient of sfc-h85 temps and as it shows shortwave
cutting beneath ridge. If this light precip would come in earlier in
the day could have fzra issues as it looks warm enough aloft but sfc
temps could still be blo freezing. Pretty low chance at this point
though and just went with chance of rain/snow this far out.

Still looks like stronger low pressure system could impact the Great
Lakes next Mon into Tue. Recent runs of GFS and ECMWF trended north
which would lead to more rain on Mon then changing over to snow by
Tue, but maybe not as heavy as it looked before as the strongest
height falls will be tracking north of Upper Lakes. Overall even
though there is general agreement a storm may be there, there is a
lot of variability seen in recent ensembles from NAEFS and the
ECMWF. One thing that was apparent is the very progressive solution
from the Canadian is not supported by majority of its own ensembles
that have stronger low back across Upper Lakes similar to GFS and
ECMWF. System that helps spin up this low is still over northern
Canada so a long ways to go before getting to the details.
&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 147 AM EST TUE FEB 28 2017

Llvl dry air under a good deal of mid/hi clds wl result in VFR
conditions at the TAF sites early this mrng. But as mixed pcpn in
advance of an aprchg upr disturbance arrives toward daybreak and
overspreads the area thru the mrng, predominant IFR conditions are
likely to develop and then prevail by the aftn. Expect gusty n winds
to arrive late in the day/evng following the cold fropa associated
with the passing disturbance. The pcpn wl diminish nw-se thru the
evng with the arrival of some mid lvl dry air behind the fropa.
&&

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 433 AM EST TUE FEB 28 2017

Light winds less than 20 kts to start the day but winds ramp up
quickly this aftn to 30-35 kts as low pressure system moves toward
western Great Lakes. As the low crosses the central and lower Great
Lakes into Wed and a high pressure ridge moves across northern
Ontario, expect NE gales 35-40 kts over much of the lake Tonight
with gales continuing over eastern sections on Wed morning. Winds
will then remain below 30 knots through the rest of the forecast
period. Heavy freezing spray is expected tonight into Wed,
especially for north central portions of the lake.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
  Gale Warning from 7 PM this evening to 1 PM EST Wednesday for
     LSZ265>267.

  Heavy Freezing Spray Warning from 1 AM to 1 PM EST Wednesday for
     LSZ263-264.

  Gale Warning from 4 PM this afternoon to 7 AM EST Wednesday for
     LSZ263-264.

Lake Michigan...
None.
&&

$$

SHORT TERM...07
LONG TERM...JLA
AVIATION...KC
MARINE...JLA


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