Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 171141
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
641 AM CDT Wed May 17 2017

.SHORT TERM...(Today through Thursday)
Issued at 352 AM CDT Wed May 17 2017

We have reached a bit of a lull as of 4AM this morning, with a
band of light to moderate rain affecting the southeast sections of
the forecast area this morning. This band should gradually
diminish over the next few hours. Synoptically, we are in between
systems. The surface low that moved through the area in the last
24 hours is now over norther Ontario, with another developing over
western Nebraska with an inverted trough extending between them.
This southern low is associated with a strong upper low, and they
are forecast to sweep towards and over us during the next 24
hours, bringing another round of showers and thunderstorms to the
forecast area. As we have been watching over the last few days,
the Precipitable water values with this system are very high,
generally ranging from 1 to 1.4 inches, according to the latest
satellite generated PW analysis. This is well above normals for
this time of year, around 200 percent of normal. This storm is
going to produce an extended period of moderate to heavy rainfall
over much of northwest Wisconsin, and areas along and east of
Interstate 35 in Minnesota and up the North Shore. Areas that have
received a lot of rainfall in the last couple days are going to be
at risk of flooding, so have expanded the flood watch we already
had out to Bayfield county. Temperatures today are going to be
cooler than yesterday, with highs in the upper 60s southeast and
mainly upper 50s to around 60 over Minnesota and the south shore
of Lake Superior, where onshore winds will make it colder. Colder
temperatures are going to settle in for tonight and Thursday as
the trough axis shifts farther east, and have lows in the mid 30s
to mid 40s tonight. Highs Thursday should only be in the mid 40s
to upper 50s, with cloud cover and some lingering rainfall to keep
conditions cool.

.LONG TERM...(Thursday night through Tuesday)
Issued at 352 AM CDT Wed May 17 2017

Upper level and surface ridging covers the forecast area Thursday
night and Friday morning. By Friday afternoon, a closed upper low
near the Four Corners region will begin to eject short wave energy
across the region. The first one Friday afternoon will encounter the
dry air that is in place from the departing ridge. However, the
GFS/ECMWF are lifting some QPF into the Brainerd Lakes and have some
small pops as the column needs to saturate a bit before any rain
reaches the ground. Model differences begin Friday night as the
ridging remains nearby initially, but the GFS/ECMWF eject more
energy from the closed low as it begins to lift northward. The GFS
is suffering from some convective/gridscale feedback and thus
generating a lot more rain, and much farther north than the ECMWF.
Used a blend for the forecast. Model differences become exceedingly
large on Saturday and Saturday night with the speed and location of
the closed low and its surface reflection, overall coverage and
amount of QPF. Used a blended approach to the forecast. A better
agreement is reached on Sunday as the upper low moves into Ontario
on the ECMWF, the GFS opens it up into a long wave trof, and
different locations for the surface low center. The ECMWF is also
colder. Maintained the blended forecast approach. The GFS
transitions back to a closed upper low over Ontario Sunday night.
The ECMWF keeps its closed low over Ontario. Both models agree on
bringing a cold front through the forecast area, with the ECMWF
still a bit cooler. Have some low pops to account for the front. On
Monday, both models bring several pieces of energy through the
region to varying degrees. Used a consensus approach to pops due to
the speed that these features will affect the region. Monday night
will bring the coldest air in awhile over the forecast area with
850mb temps near to just below zero celsius. Enough differences
prevail to keep using the blend. Tuesday has the GFS dropping a
positively tilted long wave trof over the area, while the ECMWF has
ridging beginning to build in from the west. More blending was used.
Due to a lack of data from the GEM, it was not used for this
forecast.

&&

.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 641 AM CDT Wed May 17 2017

As low pressure moves through southern Minnesota tonight and
Wisconsin on Thursday, expect MVFR or IFR ceilings through the
forecast. The exception is INL where ceilings will improve to VFR
around 05Z. Look for periods of showers at all terminals except
INL. Thunderstorms may be in the vicinity of HYR this afternoon
and again tonight. Gusty surface winds will develop this morning.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  56  38  51  34 /  50  90  30   0
INL  57  37  55  31 /  10  20   0   0
BRD  61  43  58  36 /  60  90  20   0
HYR  63  42  50  32 /  80  90  60   0
ASX  54  38  46  31 /  90  90  60   0

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
WI...Flash Flood Watch through Thursday afternoon for WIZ002>004-008-
     009.

MN...None.
LS...Small Craft Advisory from 10 AM to 4 PM CDT Thursday for LSZ121-
     146>148.

     Gale Warning from 10 PM this evening to 10 AM CDT Thursday for
     LSZ121-146>148.

     Small Craft Advisory from 10 PM this evening to 4 PM CDT
     Thursday for LSZ140>145.

&&

$$

SHORT TERM...LE
LONG TERM...GSF
AVIATION...GSF



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