Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 181455 CCA
AFDDLH

Area Forecast Discussion...CORRECTED
National Weather Service Duluth MN
955 AM CDT Sun Jun 18 2017

.UPDATE...
Issued at 704 AM CDT Sun Jun 18 2017

An updated aviation discussion is below for the 12Z TAF issuance.

&&

.SHORT TERM...(Today through Monday)
Issued at 328 AM CDT Sun Jun 18 2017

A deepening semi-vertically-stacked area of low pressure over
northeast Wisconsin and western Upper Michigan will continue lifting
and exiting to the east this morning. Rain showers associated
with the passing upper trough/low will linger over northwest
Wisconsin and parts of the Arrowhead through mid morning. There
may be a break in precipitation late this morning, leaving just
cool and breezy northwest flow. Daytime heating in this flow
pattern will trigger broken/overcast cumulus cloud coverage by
early this afternoon. Scattered light rain showers and isolated
weak storms are expected for the afternoon through early evening.
Temperatures will be nearly 10 degrees below seasonal normals,
with highs in the low to middle 60s.

The showers will dissipate this evening. Despite the cool flow
continuing tonight, with very light wind speeds, the lingering
cloud cover will help prop up the temperatures. Lows will be in
the upper 40s and low 50s.

Monday will be another cool day with breezy northwest flow.
However, it will be drier, so some areas will see some sunshine.
Very light showers are possible, mostly in the Arrowhead and
northwest Wisconsin. There is a low chance of weak storms across
the far southern forecast area. Highs will be in the middle to
upper 60s.

.LONG TERM...(Monday night through Saturday)
Issued at 328 AM CDT Sun Jun 18 2017

The beginning of the extended periods on Monday night should see
the western Great Lakes region underneath northwest flow aloft on
the western periphery of the larger scale mid level trof over
eastern Canada. There could still be a few showers or
thunderstorms around with lingering instability, but overall
increasing large scale subsidence and increasing low level ridging
should generally limit/decrease areal coverage Tuesday into
Wednesday.

By mid week, the medium range guidance still suggests that mid
level flow across the northern tier of the U.S. and southern
Canada will flatten and become more zonal as the eastern North
American trof deamplifies. As low level ridging slowly migrates to
our east, southerly return flow should gradually allow the
northern periphery of the warmth and instability axis over the
central plains to move back northward. Boundary layer moisture
content will also be increasingly aided by evapotranspiration as
the corn crop across NE/IA/srn MN is now growing in earnest.
Several weak waves moving through the flow should locally enhance
warm/moist advection over the northern plains, resulting in at
least some risk for thunderstorms.

Model guidance for the Wed thru Sat time frame is perhaps less in
agreement than it was yesterday, so exact timing and coverage of
any convection this far our is very difficult. While both the
GFS/ECM still try to bring a more significant short wave and
eventually larger-scale cyclogenesis to the northern plains and
adjacent Canadian Prairie Provinces in the Thus-Sat time frame,
the agreement on timing and placement is not very good at all.
Thus, we have not deviated much from the consensus guidance at
this time, which carries at least some risk for thunderstorms each
day during the mid to late part of the week.

&&

.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 704 AM CDT Sun Jun 18 2017

Departing surface low/trof axis will result in north/northwest
flow across the region this TAF cycle, but a rather moist boundary
layer, combined with cool temperatures aloft and at least modest
heating will likely result in the persistence/redevelopment of
scattered showers today. Sufficient instability will likely be
present for at least a few short-lived thunderstorms, but
confidence on any storms affecting specific TAF sites precludes a
specific mention with this issuance - although probability is
highest at KDLH/KHYR. Otherwise local IFR/MVFR ceiling should
slowly improve through midday, with modest gustiness developing
in northwest surface flow. Conditions are expected to improve
tonight, but some patchy fog is also expected Sunday night.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  66  49  67  49 /  50  20  20  20
INL  62  47  65  46 /  50  20  20  20
BRD  65  50  69  51 /  20  10  20  30
HYR  67  51  68  49 /  60  30  30  30
ASX  67  51  68  50 /  50  30  30  20

&&

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

$$

SHORT TERM...Grochocinski
LONG TERM...Miller
AVIATION...Miller



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