Area Forecast Discussion
Issued by NWS Duluth, MN

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996
FXUS63 KDLH 240521
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
1221 AM CDT Mon Apr 24 2017

.UPDATE...
Issued at 1217 AM CDT Mon Apr 24 2017

Updated aviation section.

&&

.SHORT TERM...(This evening through Monday)
Issued at 237 PM CDT Sun Apr 23 2017

A band of rain/snow mixture will continue to move off to the
north this evening, but remain situated over the northern one-half
of our forecast area before lifting into Ontario Canada overnight.
The strongest 500 mb isentropic lift will be co-located with this
band, along with strong 850-700 mb layer warm air advection,
which will also lift to the north. There is concern for some
decent snowfall amounts over the Minnesota Arrowhead area due to
easterly on-shore flow off Lake Superior over the higher
elevations of the North Shore. The SREF snow probabilities are
progging higher confidence in snow amounts greater than one inch,
and even hinting at the potential for some higher amounts in this
area. The 850 mb warm air advection looks to be enhanced by a
south to north low-level jet, which will help to increase
convergence along the band, intensifying it. Latest model QPF
amounts appear to have increased since previous runs, so adjusted
these amounts accordingly. I did increase the QPF amounts even
more along the higher elevations of the North Shore, with the
heaviest amounts falling between midnight tonight and 7 AM CDT
Monday. Snow amounts through Monday morning will primarily range
between 1 to 2 inches across the Arrowhead, with the potential for
up to 3 inches possible over the higher elevations.

A mid-level shortwave will then ascend into the region from the
Intermountain West by mid-morning Monday and through the day. Much
better mid-level lift will be associated with this system, as
indicated by the GFS/NAM model soundings. This system should also
bring with it more moisture-laden air, thanks to the strong 850
mb jet and increased theta-e advection. The heaviest precipitation
should fall across our northern counties as this will be where
the strongest isentropic lift will coincide. Easterly winds off of
Lake Superior will continue as well, with a favorable easterly
fetch, which will not only keep temperatures cooler along the
Lake, but also should support some gusty winds along these areas.
Winds could turn more northeasterly as well, which would cause
fairly gusty winds over the Twin Ports area. Due to this
possibility, bumped up the sustained winds and gusts over these
areas. The sfc pressure gradient associated with this system will
only exacerbate the situation as it will be pretty tight. Not
expecting additional snowfall through Monday afternoon as the
thermal profile should be too warm through the 750 mb level to
support snow, so increasing chances of rain are expected.

.LONG TERM...(Monday night through Sunday)
Issued at 237 PM CDT Sun Apr 23 2017

An active weather pattern through the end of April wil lead to
numerous chances for precipitation, with a mix of rain and snow
expected through the week. Cloudy through the week with
temperatures below normal through the long term period.

On the synoptic scale a mid/upper level longwave trough deepens over
the Four Corners region through the week, with a number of mid-level
shortwave troughs ejecting into the Great Plains and Midwest. On
Monday a low associated with one of these shortwave troughs will
track northeast from the eastern Dakotas towards north of Lake
Superior. As the low approaches Monday afternoon a warm front
associated with the low lifts north across much of eastern Minnesota
into northwest Wisconsin. Elevated instability within this warm
sector may result in a few rumbles of thunder Monday evening before
the cold front move across the area from west to east. This first
low dissipates Tuesday as another, stronger low deepens over the mid-
Mississippi River Valley Tuesday, gradually lifting east towards
Lake Michigan Thursday morning. This low track will result in a
precipitation shield across much of the Northland and especially
across northwest Wisconsin. A mix of rain and snow is expected with
temperatures struggling to reach the freezing mark Wednesday,
especially near Lake Superior and across the Minnesota Arrowhead
region. This low then gradually lifts north towards eastern Ontario
Thursday night into Friday, but the colder cyclonic flow across
western Lake Superior may result in lingering precipitation into
Thursday night and continued cooler temperatures.

A weak mid-level ridge builds into the upper Midwest Friday into
Saturday resulting in a break in the precipitation for a period
Friday into early Saturday, but a broad warm front stretching from
the central Great Plains east to central Appalachia will lift north,
approaching the upper Midwest. The longwave trough in the west
finally begins to eject into the Great Plains with the resulting
surface low tracking north up the Mississippi River Valley towards
the upper Great Lakes on Sunday bringing a return for precipitation
chances late Saturday through Sunday.

While temperatures will be cold enough for snow much of the week,
snowfall amounts are generally expected to be light through the
week, with Wednesday night into Thursday having the most potential
for widespread accumulating snowfall.

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1217 AM CDT Mon Apr 24 2017

A warm front will gradually move north across the terminals in
the next 6 hours, pushing IFR/MVFR ceilings through KHIB and KINL,
having already exited out of KDLH, KBRD and KHYR. East winds may
bring IFR ceilings to KDLH...but uncertainty with this is fairly
high and have just put in a tempo group for now. On the south
side of the warm front breezy south winds of 10-15kts with gusts
to 20kts, with VFR conditions. A cold front will move into the
area from the west after 21z, keeping lower ceilings going for
KINL, and spreading them back into KHIB and KDLH before 06z.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  29  44  38  50 /  10  60  60  30
INL  29  43  33  40 /  80  80  80  20
BRD  35  60  39  50 /  10  50  50  30
HYR  36  62  47  58 /  10  30  40  60
ASX  32  60  45  56 /  10  40  40  50

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
LS...Small Craft Advisory until 10 PM CDT this evening for LSZ121-
     146>148.

     Small Craft Advisory until 4 AM CDT Tuesday for LSZ140>145.

&&

$$

UPDATE...LE
SHORT TERM...JTS
LONG TERM...JJM
AVIATION...LE



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