Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 230512

Area Forecast Discussion
National Weather Service Duluth MN
1212 AM CDT Sat Sep 23 2017

.SHORT TERM...(This evening through Saturday)
Issued at 249 PM CDT Fri Sep 22 2017

Another round of showers and thunderstorms are expected tonight as
we continue to be under a very warm and unstable air mass. Not
much change from yesterday`s corresponding model runs as we remain
under southwest flow aloft due to a longwave trough over the
Intermountain West states. This flow will enhance isentropic
upglide as well, providing large-scale support for this activity.
At the sfc, an area of low pressure currently located over
northeast South Dakota will continue to advance northeastward into
north-central Minnesota by this evening. Ahead of the system, we
will continue to see southerly flow, bringing very warm and moist
air into the region. Low-level theta-e advection will become
enhanced once again tonight as a 40 to 50 kt low-level jet looks
to reintensify overnight. Pwat values will increase into the 1.5"
to 1.9" range, per the 22.12z GFS and NAM models. The NAEFS
climatological anomalies indicates these values are >99% of
climatology, so heavy rainfall will be possible with this
activity. The low pressure system will bring with it a sharp
baroclinic zone, which will act as the focal point for tonight`s
activity, which is expected to develop over north-central
Minnesota. The Storm Prediction Center has a Slight Risk of severe
weather over north-central Minnesota with these thunderstorms,
over Koochiching and Itasca counties. A Marginal Risk of severe
weather has been issued for the rest of the Northland. The main
threats will be large hail and damaging winds, with a small chance
for a tornado as well as better helicity will be in place over
the Slight Risk area.

This activity won`t be moving much as the stationary boundary
associated with the baroclinic zone moves slightly eastward, so
chances of showers and storms will continue through the day
Saturday. Much like yesterday, there are some timing and coverage
difference between the convective-allowing models, so input more
scattered showers and storms for Saturday due to the lack of
higher confidence in the areal coverage.

.LONG TERM...(Saturday night through Friday)
Issued at 249 PM CDT Fri Sep 22 2017

Not much change from the prior forecast as the blocking ridge will
be near the East Coast Saturday night and finally drift offshore by
Monday night. This allows the unseasonable long wave trof to move
from the Rockies Saturday night, to the forecast area by Tuesday. The
warm, southerly flow of Gulf of Mexico moisture will continue to
ride northward ahead of this trof. Embedded impulses in the fast
southerly flow will be difficult to time across the region, but pops
will be in place with highest potential closes to the trof and its
associated quasi-stationary surface front. Thermodynamic profiles
also suggest the best location for thunder will be along the front
through Monday evening. Not anticipating any flooding issues as
current QPF indicates the highest amounts will fall over an area
where abnormally dry to drought conditions exit. This would be over
Koochiching, Itasca and Cass counties. By Tuesday, the long wave
trof will have merged with a short wave trof that arrives Tuesday
night. The rain chances will be diminishing through Tuesday night. A
pattern change will take place Wednesday into Thursday as a
northwest flow begins to overtake the forecast area. This will bring
much cooler and drier air into the region. However, will still be
able to generate some showers with more embedded impulses crossing
the area. With less moisture, smaller pops will be in play. Temps
will be above normal at the start of the long term, and cool to near
normal Tuesday through Thursday.


.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1212 AM CDT Sat Sep 23 2017

In northeast Minnesota...VFR conditions will persist through much
of today with ceilings lowering to MVFR/IFR tonight. Isolated
showers/thunderstorms possible within the next few hours early
this morning then again during the day. South-southwest winds
today, gusty this morning then not as strong during the day around
10 knots or less. Decreasing ceilings tonight will lead to IFR or
worse conditions in some locations across northern Minnesota.

In northwest Wisconsin...VFR conditions will prevail through the
TAF period at HYR with occasional mid to high level clouds and
light south to southeast winds.


DLH  65  78  60  76 /  30  50  50  40
INL  60  63  54  64 /  50  50  80  70
BRD  64  71  60  74 /  50  60  60  50
HYR  69  84  65  83 /  10  30  30  20
ASX  67  85  62  83 /  20  30  40  20




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