Scientific Forecaster Discussion
fxus63 kdlh 240448
Area forecast discussion
National Weather Service Duluth Minnesota
1148 PM CDT Fri Jun 23 2017
issued at 937 PM CDT Fri Jun 23 2017
Showers continue to percolate over northeast Minnesota, east of
U.S. Highway 53. Another batch of showers was found in northwest
Wisconsin along the St. Croix River Valley. Showers were also
occurring over Western Lake Superior and trying to move inland.
This activity is in response to an upper level short wave moving
overhead. Made some pop adjustments due to this activity.
Short term...(this evening through saturday)
issued at 247 PM CDT Fri Jun 23 2017
An upper-level low will dive southeastward from southern Manitoba
tonight across the Northland. An associated mid-level shortwave
trough will accompany this upper-level low, and brush just over our
southwestern counties Saturday morning. The bulk of the positive
vorticity advection will stay to the south and west with this wave.
However, chances of precipitation will be highest over the
international border region due to a stronger corridor of isentropic
upglide as the mid-level trough passes to the south. Mid-level winds
will be westerly towards the mid-level trough, which should ride
upward over the isobaric surfaces, causing this isentropic lift.
Analysis of the rap model also indicates a corridor of 950-800 mb
layer fgen along this band of lift. By Saturday afternoon, showers
and some thunderstorms will expand as the atmosphere becomes more
unstable. Values of MUCAPE vary quite a bit between the guidance, so
confidence in chances of thunderstorms will be low, but cannot rule
them out entirely. Will maintain slight chances of thunderstorms
through Saturday afternoon for most of the region. Severe weather is
not expected, but the strongest storms could be capable of
occasional cloud-to-ground lightning and small hail as 500 mb level
temperatures drop into the 20 to 25 degree below zero range.
Low temperatures tonight will once again be cool as we remain in
this northwesterly, cyclonic flow, as lows approach the upper 40s
and lower 50s across the area, which are just slightly cooler than
seasonal normal. Same story for Saturday with the high temperatures,
as highs remain cooler than normal, with values ranging from the
upper 50s across the Iron Range, and into the lower to mid 60s over
Long term...(saturday night through friday)
issued at 247 PM CDT Fri Jun 23 2017
A couple more shortwaves will impact the region Saturday night into
Sunday night in northwest flow aloft then a brief dry period will
occur before chances for showers and storms return mid through late
A chance for showers and a few thunderstorms will continue into
Saturday evening then another shortwave will dive south into
northern Minnesota late Saturday night. The showers may diminish for
a time Saturday night but will then increase again Saturday night
into Sunday with the wave. The best chance for rain will be on
Sunday and we have showers likely over parts of northeast Minnesota
into northern Wisconsin. A few thunderstorms will also be possible.
Temperatures will remain cool with highs Sunday from the upper
fifties to middle sixties.
A western ridge will slowly move east Sunday through Monday and
bring a dry period starting Monday and continuing into Tuesday. The
upper ridge will be over the region Tuesday with a southerly low
level flow developing. High Monday will be warmer and be from the
upper sixties to around seventy, then warm into the seventies on
Tuesday for most areas.
An area of low pressure will bring the chance for showers and storms
to the region Tuesday night into Wednesday. There are some timing
and track differences between the GFS/ECMWF/Canadian but they all
have the low affecting the Northland. Increasing
moisture/temperature along with stronger lift from this system may
lead to strong or severe storms Tuesday night into Wednesday
Differences among the models start to amplify mid into late in the
week. The GFS develops a very strong low Thursday into Friday and is
slow moving it through with it lingering into Saturday night. The
Canadian and European model (ecmwf) are in better agreement with a weaker wave aloft
and therefore surface low. The models have all been struggling
during this time period and each has shown considerable differences
from run to run. We have periodic chances for showers/storms
Thursday/Friday for now.
Aviation...(for the 06z tafs through 06z Saturday night)
issued at 1148 PM CDT Fri Jun 23 2017
Upper level short waves will rotate over the terminals through the
forecast. This will produce periodic pockets of showers from the
start of the forecast until near sunset Saturday. Mainly VFR is
expected. However, MVFR cigs in the vicinity of showers is
anticipated. Gusty surface winds are forecast to develop by 15z.
Preliminary point temps/pops...
dlh 50 61 49 61 / 30 30 30 60
inl 49 60 48 61 / 40 60 50 60
brd 48 61 49 64 / 0 50 20 20
hyr 51 64 48 62 / 40 50 20 50
asx 51 63 49 63 / 50 30 20 60