Area Forecast Discussion
Issued by NWS Duluth, MN

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000
FXUS63 KDLH 231755
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
1255 PM CDT THU JUN 23 2016

.SHORT TERM...(Today through Friday)
Issued at 422 AM CDT Thu Jun 23 2016

Rain continued to fall across northwest Wisconsin early this
morning due a shortwave and surface low. Water vapor showed the
wave over western Lake Superior and the surface low was centered
in west central Wisconsin. These features will continue to move
southeast today. We followed close to the short term high res
models and linger showers over northwest Wisconsin into early
afternoon. An additional weaker shortwave in the northwest flow
will impact that area as will weak low level convergence. We also
added isolated showers/storms along portions of the North Shore
area this afternoon as weak low level convergence will also be
present and some of the guidance was picking up on precip
developing there. Highs today will be in the seventies. Off lake
winds will be possible again today, especially along the North
Shore but they will not be as strong as yesterday at the head of
Lake Superior. There may be some patchy early morning fog, mainly
over northeast Minnesota where clouds have diminished.

An upper ridge will build over the region tonight into Friday and
we went with a dry forecast then. The 00Z NAM was showing a
shortwave cresting the upper ridge Friday afternoon bringing in
showers and storms late in the day. However, much of the other
guidance were not as aggressive with the with the wave and kept
the Northland dry. The 06Z run of the NAM has even backed off.
Highs Friday will be from 78 to 83 for most areas. It will be
cooler close to the lake, especially the North Shore.

.LONG TERM...(Friday night through Wednesday)
Issued at 422 AM CDT Thu Jun 23 2016

Hot and humid this weekend with a chance for strong to severe
thunderstorms late Friday through Saturday, then temperatures
becoming more seasonable and mainly dry through the middle of next
week.

On the synoptic scale an upper low entering the northern High Plains
into southern Saskatchewan and an upper high over the Gulf Coast
will lead to very warm and moist air being advected north across the
Great Plains into the upper Midwest Friday and Saturday, setting the
stage for a hot and humid day. A warm front associated with the low
will lift northeast across northern Minnesota Friday night, with
elevated instability fed by a strong low level jet suggesting the
possibility for overnight convection. While the best placement for
this risk appears in northwest Minnesota (with SPC having pulled
their latest convective outlook slight risk area just a tad further
west), as the low level jet shifts eastward towards Saturday morning
there could be a risk for ongoing storms on the international
border...very similar to this past Sunday morning when large hail
fell across the MN/Canada border. The evolution of this convection
will be critical to determining the set-up for Saturday, but at this
point it seems the storms should exit ENE towards Thunder Bay mid-
morning Saturday.

On Saturday Minnesota and northern Wisconsin will be well within the
warm sector of the low. The upper low is expected to move east
across southern Manitoba Saturday with the resulting surface low
nearby as the low matures. A cold front will extend south from this
low across the Red River Valley/western Minnesota Saturday morning,
moving east through the day. In a very unstable environment strong
to severe thunderstorms are expected to fire in northern Minnesota
and move east across the Northland during the late afternoon and
evening hours, again somewhat similar to this past Sunday. While
there are some uncertainties with regards to the environment (see
below), most the conditions necessary for severe thunderstorms
capable of large hail and damaging winds will be present. SPC has
had this area highlighted since it was 5 days out and this morning
has continued to highlight the area with a Day 3 Slight Risk.

In regards to the type of environment in place, 850mb temps will
approach +20C at INL, which per sounding climatology would be in the
near-record territory; the GEFS mean values are around 97-99th
percentile. While this kind of warmth at low levels could lead to
concerns about not being able to break the cap, the warmest
conditions are mainly overnight Friday night into Saturday morning
when a strong low level jet may end up feeding an MCS moving east
across the international border. Surface dew point values are
expected to be in the low 70s with precipitable water values over
1.75", which is above the 99th percentile compared to climatology.
Instability aloft will be plenty for strong to severe storms - 2000+
j/kg MUCAPE per most guidance. Deep layer shear could be limited in
the afternoon depending on the speed of the upper low and the
associated stronger mid/upper level winds coming east across the
northern Plains into the upper Midwest. Both the GFS and ECMWF have
trended towards a more favorable wind field, but there still remains
concerns that the best shear could arrive after storms are expected
to fire across northern Minnesota. While it`s bit premature to
analyze such small-scale details, at this point the low level wind
field does not seem particularly favorable for tornadoes, but (1)
this can and will change and (2) the absence of an environment
favorable for strong tornadoes does not mean tornadoes are not
possible; any supercell can be capable of producing a tornado. Storm
motions along and ahead of the front would be northeasterly at 30-45
knots - again fast storm motions like last Sunday. While the wind
field seems fast enough both on the synoptic-scale features and
storm-scale-wise to preclude risk for training storms, the high
precipitable water values bring at least some concern for locally
heavy rainfall resulting in risk for flash flooding.

In summary, all modes of severe weather appear possible Saturday
afternoon into Saturday night across all of northeast/east-central
Minnesota into northwest Wisconsin, including the potential for
flash flooding.

As the low lifts to the east-northeast across northern Ontario
through the weekend, cooler air aloft will be advected in behind the
cold front resulting in cooler conditions and a chance for light
rain showers Sunday. By Monday into Tuesday high pressure will build
across the northern plains and upper Midwest resulting in clearing
skis and a return to more seasonable conditions by mid-week. A weak
mid-level disturbance bringing a chance for clouds/light rain
remains possible mid to late week but otherwise mainly sunny and
seasonable conditions expected.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1240 PM CDT Thu Jun 23 2016

High pressure will bring quiet weather to the CWA throughout the
period, with VFR conditions and mostly clear skies. Winds will
generally be light and variable.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  73  52  79  59 /  10   0   0  50
INL  78  51  82  65 /   0   0  10  60
BRD  74  54  82  65 /   0   0  10  40
HYR  72  50  83  62 /  60  10  10  30
ASX  71  51  81  60 /  60  10   0  40

&&

.DLH Watches/Warnings/Advisories...
WI...None.
MN...None.
LS...None.
&&

$$

SHORT TERM...Melde
LONG TERM...JJM
AVIATION...DAP


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