Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 231024

Area Forecast Discussion
National Weather Service Marquette MI
624 AM EDT Thu Mar 23 2017

.SHORT TERM...(Today and tonight)
Issued at 326 AM EDT THU MAR 23 2017

Upper air pattern consists of a 500 mb ridge over the plains and a
trough in the western U.S. this morning. There is also a shortwave
over Saskatchewan and Manitoba. The trough will move east into the
central plains on Fri with the area on the top of the upper ridge
through tonight. Weak 850-500 mb q-vector convergence moves across
the area through tonight. Deeper moisture tries to move through this
morning and then returns again tonight.

Complicated forecast with pcpn types for tonight. Looked at some
soundings and they all point to a warm layer aloft over a lower
layer of air that is around freezing. This will mean that most of
the pcpn tonight will be in a rain/freezing rain form. Right now,
not comfortable going with an advisory for freezing rain as the sfc
temperatures continue to be tricky being one or two degrees either
side of freezing. If temperatures are above freezing, there would be
no problem. Below freezing, could see up to 0.25 inch of ice. The
temperatures depend on how much we warm up today and then also
depend tonight on how much we evaporatively cool as the dry air at
the sfc will have to moisten up when pcpn starts. Will continue with
a special weather statement for now and mention the icing potential.
Will go with dry dew points into this afternoon. For this morning,
dry air continues to make a dent on the pcpn headed this way as very
little is hitting the ground in Wisconsin and eastern Minnesota.
Will still keep slight chance pops in for this morning and early
afternoon for this.

.LONG TERM...(Friday through Wednesday)
Issued at 457 AM EDT THU MAR 23 2017

Attention is definitely on Fri into Mon as primarily rain/freezing
rain chances will exist at times.

Driving weather through the weekend will be a weakening low that
will move from from CO/KS border Fri morning to IL on Sunday. FGen
out ahead of the system will be the dominant forcing mechanism Fri
into Sat, which is quite problematic given the uncertainty that
invokes in the placement of relatively narrow bands of precip.
Precip types will also be significantly in question. For Fri, may
see some freezing rain along until 8-9am but warming SFC temps will
quickly lead to only rain. By later Fri afternoon, some colder air
moves into the CWA, which may lead to a deep isothermal layer
between the sfc and 700mb that hovers right around 0C. This makes
precip types extremely challenging as pretty much anything is
possible depending on exact temperatures at the sfc and through the
mid-levels. At this point the best guess ptype is rain until Fri
evening when SFC temps begin to cool. Rain, freezing rain, and snow
are all possible late Fri into early Sat, with potential for
significant amounts snow and/or freezing rain. Also, best guess
location wise for precip late Fri into early Sat is over southern
Upper MI, but that could change. Thankfully, the temperatures are
the warmest over the south, so freezing rain would not be as bad as
if the band was farther north, which is also possible but not as
likely. Only have up to a tenth of an inch of ice over south-central
Upper MI late Fri into early Sat.

For the rest of Sat through Mon, there will be waves of lighter
precip moving through, with that expected to be rain during the day
and rain/freezing rain at night. Overall not looking at very
significant freezing rain accumulations, though.

.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 624 AM EDT THU MAR 23 2017

Mainly VFR ceilings and visibilities are expected today. A large
area of rain will move in this evening and should drop cigs to
IFR/VLIFR by late evening. Evaporative cooling should also be strong
enough for the rain to change to fzra at KSAW.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 326 AM EDT THU MAR 23 2017

Expect s winds as hi as 30 kts, with a few gale force gusts to 35
kts possible, on Thu evening over the east half of Lake Superior to
diminish on Thu night thru Fri as a flatter pres gradient dominates.
Expect ne veering e winds to increase up to 25 to perhaps 30 kts on
Fri night into Sun under the tightening pres gradient between hi
pres passing from Ontario into Quebec and lo pres in the lower Great
Lakes. The strongest winds are most likely over western Lake
Superior, where the lake topography will enhance the ene flow. As
these features weaken and exit to the e, winds by Mon will diminish.

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


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