Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 191523
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
1023 AM CDT Wed Apr 19 2017

.UPDATE...
Issued at 1023 AM CDT Wed Apr 19 2017

Plenty of cloud cover over northwest Wisconsin and along the I35
corridor. Increased the cloud forecast over northwest Wisconsin
and along the I35 corridor. Latest satellite imagery does show
some erosion to the cloud cover along the north shore from Silver
Bay to Two Harbors. Cirrus on the increase as well from the
southwest. Delayed the start time of the rain this afternoon as
seen in the latest short term hires models and area radars. Made
other minor modifications.

&&

.SHORT TERM...(Today through Thursday)
Issued at 402 AM CDT Wed Apr 19 2017

A challenging forecast tonight into Thursday with a potential for
accumulating snowfall across portions of the Northland. Surface
temperatures will generally drive whether or not precipitation
changes over to snow, with higher elevations such as along the north
shore having a greater probability of changing over to snow. The
south shore is where uncertainty is greatest as strong northeast to
north winds will advect the relatively warmer lake air over land,
which could result in temperatures remaining just warm enough to
produce mainly rain. As we approach 14 hours of daylight and a max
solar elevation of near 55 degrees (compared to ~20 degrees at
minimum in the winter and ~66 degrees at max), a more-rain-than-snow
scenario appears more likely on a climotological basis.

On the synoptic scale the active weather pattern continues as the
west-southwest flow aloft gives way to another shortwave trough over
the central and northern Plains today, deepening as it approaches
the upper midwest due to a strengthening upper level jet over the
desert southwest ejecting into the central Plains and mid-
Mississippi River Valley towards Wednesday night. A resulting
surface low deepens tonight over the Mid-Mississippi River Valley,
tracking east towards lower Lake Michigan by Thursday morning.

Today skies will briefly clear out as drier air builds in from the
north, but winds quickly turn easterly as the low begins early
development over the central Plains and a building high pressure
drifts east across the far northern reaches of Ontario. Mostly sunny
skies to kick off the day, then increasing clouds from south to
north. A rain shield will approach from the south this afternoon
into the evening, with a thunderstorm possible south of a line from
Spooner to Hayward to Watersmeet. Otherwise a light to moderate rain
expected towards late-day, with areas north of Highway 2 likely
remaining dry through the afternoon. Highs in the mid 40s to mid
50s, warmest towards the borderland where sunshine should prevail
for much of the day.

Tonight rain spreads across much of the region, especially along and
east of I-35, up the north shore, and across all of northwest
Wisconsin. Temperatures will fall to the 30s, with east-northeast
winds ramping up, especially along the lake shore. Considerable
uncertainty remains with regards to precipitation type, with surface
temperatures likely to drive if/when a changeover to snowfall
occurs. At this point, the model consensus is leaning slightly
cooler than previous runs, continuing a trend from the day shift.
The current forecast reflects a something closer to a "worst case"
scenario with regards to snowfall amounts, but if the trend
continues snowfall could be even more widespread in coverage than
currently forecast - especially if the unusually aggressive SREF
guidance is right. Overnight precipitation types will likely go back
and forth between rain and snow across much of the Northland, with a
more steady trend to snow towards Thursday morning. There is some
concern about loss of ice aloft as the low exits and drier upper
level air advects in from the north, but in general accumulating
snowfall would occur late Wednesday night in Thursday morning.

Expect a total of 2 to 4 inches of snowfall along the north shore
and areas inland, including the higher terrain of the Twin Ports.
Strong east winds gusting to around 30 mph in the morning will
result in little snow right along the lakeshore given the relatively
warmer lake temperatures. Along the south shore up to an inch or so
is possible, especially Thursday afternoon as winds turn more
northerly and temperatures remain steady or decrease.

A tough decision regarding whether and where to issue a winter
weather advisory for the snowfall potential. Current snowfall
forecast is just scratching the low end of our advisory criteria (3-
5"), but given the uncertainty and the fact that this snowfall
forecast is quite a bit higher than the previous forecast, have
decided to hold off issuing anything just yet.

.LONG TERM...(Thursday night through Tuesday)
Issued at 402 AM CDT Wed Apr 19 2017

The low pressure system will continue to pull away from the region
Thursday night bringing an end to the precipitation for most of the
Northland overnight. Light rain or snow will linger into the evening
over far eastern Minnesota into northern Wisconsin with a light mix
continuing overnight across portions of Ashland and Iron Counties.

High pressure will then build over Minnesota and Wisconsin on Friday
leading to a dry day with highs in the fifties for most areas. An
off lake wind will keep lakeside areas cooler. The high will move
south on Saturday and a cold front will drop out of Canada into
northern Minnesota Saturday afternoon. There may be some light rain
that occurs along portions of the International Border. The ECMWF
remains faster pushing the front through with the GFS/Canadian
slower and in decent agreement. We spread chances for light rain or
snow south with the front Saturday night across much of the
Northland and expect mainly light snow accumulation. The front will
continue south and weaken on Sunday and we went with a dry forecast
for now. Highs Sunday will range from the lower to middle forties
from the Arrowhead and around Lake Superior to the lower to middle
fifties from the Brainerd Lakes region through Siren to Park Falls.

A stronger shortwave and area of low pressure will affect the
Northland as early as Sunday night with a warm front returning
north, but more so Monday into Tuesday. There remains timing
differences between the models in how fast and what track the low
will take but the result is similar in that there will be chances
for rain or snow across most of the Northland.

&&

.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 651 AM CDT Wed Apr 19 2017

A ridge of high pressure extended south into the Northland this
morning. MVFR and IFR ceilings extended from the Arrowhead
southwest through KDLH to K04W. In areas that did clear out
overnight, fog has formed in spots but will lift over the next 1
to 2 hours. The low level flow will veer through the day and will
complicate the cloud forecast today. The RAP suggests the clouds
will move back to the west through the day and we followed this
bringing MVFR ceilings back to KBRD around 18Z, keeping them at
KHYR and KDLH.

An area of low pressure will lift into Iowa by this evening then
continue into Wisconsin tonight. Rain will surge north later this
afternoon and especially tonight. As boundary layer temperatures
cool, the rain will mix with or change over to snow in spots. This
is most likely to affect the Arrowhead to the Twin Ports and in
the Iron Range.


&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  44  33  41  31 /  20 100  90  20
INL  53  35  49  31 /   0  30  40  10
BRD  53  35  48  34 /  50  90  70  10
HYR  51  36  41  31 /  50 100  90  20
ASX  45  35  40  31 /  30 100 100  40

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
LS...Gale Watch from late tonight through Thursday afternoon for
     LSZ140>147.

     Small Craft Advisory until 4 AM CDT Thursday for LSZ144>147.

     Small Craft Advisory from 4 PM this afternoon to 4 AM CDT
     Thursday for LSZ140>143.

     Small Craft Advisory from 4 PM this afternoon to 10 PM CDT
     Thursday for LSZ121-148.

&&

$$

UPDATE...GSF
SHORT TERM...JJM
LONG TERM...Melde
AVIATION...Melde



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