Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Twin Cities/Chanhassen Minnesota
349 PM CDT sun Jul 5 2015
Short term...(this evening through monday)
issued at 349 PM CDT sun Jul 5 2015
The short term concerns continue to be the severe weather threat
and heavy rain threat overnight into Monday.
Latest available cold front dropping into east central South
Dakota and lifts northeast ahead of dissipating northwest Minnesota mesoscale convective system.
Expect a broken line of convection to develop along the boundary
as it sags slowly into the west and northern County Warning Area this
evening...similar to most hires/cam solutions. Severe weather
remains as activity moves into the area...with the main threat
being strong wind gusts because high dcape generated ahead of the
boundary into west central Minnesota. As greater shear works into
the region as the upper trough translates a bit farther east...we
could see a hail threat as well. Later in the evening...the upper
trough moves into the region and the weak South Dakota surface
wave moves northeast along the frontal boundary. Strong low level
jet/impressive moisture transport and high precipitable water values all paint a
heavy rain picture developing along this front. At the
moment...have basin average around 2 inches along a line from near
Dawson...St cloud and Mora. As wave approaches... expect mesoscale convective system to
develop and move over the area...with enhanced lift/frontogenesis
near the boundary. Flash flooding a threat late tonight...close to
wpc slight risk depiction.
The trough exits to the east Monday morning...with the 12z models
and especially the European model (ecmwf) a bit slower with overall movement. Will
continue to trail probability of precipitation off to the west in the morning...and
exiting to the east late afternoon.
Long term...(monday night through sunday)
issued at 349 PM CDT sun Jul 5 2015
High pressure will build into the upper Midwest Monday night
and remain near the Great Lakes through Wednesday. Cooler and
much drier air will accompany the high with none probability of precipitation. The high
will drift overhead Tuesday night. Clear skies...calm winds...and
dew points in the 40s will allow temperatures to follow suit in most
places. Record lows at eau and msp are 46 and 51 respectively and
forecast lows are within 3 or 4 degrees of these. Should also see
areas of fog...particularly east where it will be coolest and
crossover temperatures should be reached.
By middle to late week the flow will become more zonal as a ridge
builds over the plains. Northwest flow across eastern and southern
Canada will steer short waves east southeast across the northern
Continental U.S.. depending where they go will determine how warm we get or
how wet we get. GFS is more bullish in bringing the ridge
northward and advertises 90s or 100s across much of the area by
next weekend. European model (ecmwf) is more reserved with the ridge and keeps the
storm track overhead...although this is a northern shift from
previous runs. Did raise highs a few degrees late week/next
weekend closer to MOS and kept probability of precipitation in the chance category as this
pattern remains favorable for numerous convective complexes
nearby. Interestingly...for the past couple weeks the cfs hinted
at a warmer and wetter pattern toward middle July which appears to be
Aviation...(for the 18z tafs through 18z Monday afternoon)
issued at 102 PM CDT sun Jul 5 2015
Redevelopment of thunderstorms is expected late this afternoon
over the northern and western areas as the front moves into that
region. Not too much change in timing with the best threat of
thunder moving into east central Minnesota after 04z and then into
Wisconsin after 06z or so. Severe threat greatest over northwest
area...with mainly moderate/heavy rain threat developing after
06z. Expect IFR ceilings/visibilities with stronger storms and then more
widespread IFR developing late along/behind the cold front. Expect
activity to end over the west into Monday morning...and across
western Wisconsin early afternoon. Gusty south winds ahead of the
front...becoming north/northwest with frontal passage.
Kmsp...isolated rain showers/thunderstorms and rain possible late afternoon and
evening...mainly north metropolitan. Timing of widespread thunderstorms and rain during
the overnight hours and early Monday morning ... lingering
thunder and rain showers into middle morning with MVFR or lower ceilings likely.
/Outlook for kmsp/
Monday night...VFR. Winds northwest 10-15 kts.
Tuesday...VFR. Winds north-northwest 5-10 kts.
Wednesday...VFR. Winds S 5-10 kts.