Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 140133
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
833 PM CDT Thu Jul 13 2017

.UPDATE...
Issued at 833 PM CDT Thu Jul 13 2017

Upper level closed low is moving farther to the east this evening.
This is allowing ridging aloft and at the surface to build into
the area. Drier air is already eroding some of the cloud cover
over the northwest corner of the forecast area. Elsewhere, the
clouds are hanging tough and it will be awhile before holes open
and additional clearing begins. The drizzle will be ending shortly
due to the drier air. Some fog is still possible after the
clearing as the wind goes light and variable. Made some minor
adjustments.

&&

.SHORT TERM...(This evening through Friday)
Issued at 315 PM CDT Thu Jul 13 2017

As of 20Z today, we continue to observe light returns on the
current radar imagery. Mainly seeing drizzle and light rain
showers falling at this time. This is all due to mid- to upper-
level shortwave trough and cyclonic flow that will eventually make
its way out of the region by this evening. There are a few lobes
of positive vorticity advection embedded within the wave,
providing the synoptic forcing. RAP and NAM model soundings
indicate a layer of low-level saturation from 950-800 mb,
providing ample moisture for these showers/drizzle. The best
chances of persistent showers and drizzle will continue to be from
the Twin Ports and locations adjacent to Lake Superior along the
North and South Shore areas. Accumulation amounts will remain on
the light side, with up to one-tenth of an inch possible. Some
clearing skies will move into our northwestern portions of the
forecast area through the afternoon and evening hours. The biggest
uncertainty for tonight will be how quickly cloud cover moves out
over the region. If clouds are able to retreat faster than
expected, then cooler temperatures will be possible for tonight. I
did reduce tonight`s lows slightly to better capture the
radiational cooling from the lack of clouds as I have cloud cover
moving out faster than what we had previously. However, some of
the model guidance did have some of these clouds lingering, which
would keep temperatures warmer tonight if this comes to fruition.
Lows tonight should be in the mid to upper 40s for most locations,
with near 50 along our south.

Mid-level ridging will amplify tonight over the Intermountain West
states as the shortwave departs to the east, which will remain in
control through the rest of the short-term period. Sfc high pressure
will build across the Northland, keeping winds light under the sfc
high pressure ridge. However, by the late afternoon, some small
chances of showers may move into Koochiching and Itasca counties as
a wing of 850-700 mb warm air advection moves in from the northwest.
Winds will become more southerly over our western counties helping
to warm temperatures up a bit. Temperatures will be their coolest
over northwest Wisconsin as this is where cloud cover will linger
over the longest. Thaler QG 850-300 mb layer omega also shows
strengthening deeper forcing as this warm air advection moves in.
There is some uncertainty if chances of precipitation would hold off
until after 00Z Saturday though. In any case, this will be the
precursor to increased chances of showers and thunderstorms that
will move in Friday night and Saturday morning. Highs will range
from the mid 70s over northwest Wisconsin to the upper 70s and near
80 over our western counties.

.LONG TERM...(Friday night through Thursday)
Issued at 315 PM CDT Thu Jul 13 2017

An upper level shortwave in northwest flow will combine with a
surface frontal boundary, as it moves southeast across the Northland
Friday night and Saturday. The front will bring a chance of showers
and thunderstorms to the Northland during the overnight hours of
Friday night and on Saturday. A few of the storms could be strong to
severe, especially over northwest Wisconsin on Saturday. High
pressure will build into the region on Saturday as well, bringing
generally dry conditions to northeast Minnesota by afternoon.
Coverage for the storms will be fairly limited, and generally along
and ahead of the frontal boundary. Upper level heights will build as
the surface high pressure builds into the area on Saturday and
Saturday night. This will result in a generally dry weekend for most
areas of the CWA. The dominant upper level ridge will flatten
considerably over the weekend and into early next week, with a
shortwave in the northern states and south central Canada
significantly flattening the upper level flow. A cold front and
upper level shortwave will bring a chance of showers and
thunderstorms to the region on Monday and Monday night, before the
front returns northward again as a warm front on Tuesday and
Wednesday. The ECMWF would support more precipitation into Wednesday
as well, but the GFS indicates a more substantial area of high
pressure across the northern Great Lakes. The ECMWF does show the
best consistency, so opted to continue POP`s on Wednesday before a
drying trend on Thursday. Highs throughout the period will range
from the 70s to middle 80s, with overnight lows ranging from the 50s
to lower 60s.

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 618 PM CDT Thu Jul 13 2017

As the closed upper low pulls off to the east tonight, this will
allow ridging to build across the region. MVFR/IFR cigs expected
through tonight with an improvement to VFR shortly after sunrise.
Some BR at DLH/HIB/HYR overnight with vsbys into the MVFR range.
This will also improve after sunrise to VFR. Dry air and a clear
sky by mid morning.


&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  49  76  58  82 /  20   0  30  20
INL  45  79  59  77 /   0  20  30  10
BRD  49  78  61  85 /  10   0  20  20
HYR  49  76  56  84 /  10   0  10  20
ASX  49  77  57  83 /  20   0  20  20

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
LS...None.
&&

$$

UPDATE...GSF
SHORT TERM...JTS
LONG TERM...DAP
AVIATION...GSF



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