Scientific Forecaster Discussion
fxus63 kmpx 242040
Area forecast discussion
National Weather Service Twin Cities/Chanhassen Minnesota
340 PM CDT Wed may 24 2017
Short term...(this evening through thursday)
issued at 335 PM CDT Wed may 24 2017
The afternoon surface analysis indicated a surface ridge centered
across Minnesota with northeast winds across eastern Minnesota,
and east/southeast winds in the west.
The main concern over the next 24 hours is whether enough
moisture will allow for some showers to develop in west
central/central Minnesota during the afternoon.
Although models have been consistently moving a frontal boundary
across the Dakotas by late Thursday afternoon, moisture depth
remain limited in the southern half of Minnesota and upper level
energy is confined to northern Minnesota where better jet energy
exists. Only weak instability may be ample enough to generate a
few showers late Thursday afternoon in west central, and central
Minnesota. Otherwise, mid level cloudiness will increase with
temperatures rising into the 60s and lower 70s. This could be one
of the warmer days in the next seven as the extended period
Long term...(thursday night through wednesday)
issued at 315 PM CDT Wed may 24 2017
Main points of discussion in the long term are the frontal passage
Friday as light precipitation is possible along the front, and for
the development of a longwave trough over central North America.
By tomorrow evening, the strong low pressure system of interest for
the long term period will be moving east across southern
Saskatchewan into southern Manitoba and the trailing cold front
draped to the south through the Dakotas. There have been timing
differences in when this front will make its way through our region
but confidence is increasing that the front will reach the Minnesota
border overnight (early Friday a.M.) And work eastward through Minnesota
during the day, and in western WI in the late afternoon to Friday
night. The GFS remains the fastest with this idea, but the suite of
available guidance at least has more tightly packed than in previous
runs. The Canadian is still much slower and is a significant
outlier in timing of the front, so leaned to a blend of
GFS/NAM/ECMWF. Showers and a few rumbles of thunder will be
possible along and ahead of the front, especially in eastern Minnesota and
western WI based during the afternoon as lapse rates steepen.
The parent upper trough with this system will slow down and
basically sit to our north in southern Canada and repeatedly send
shortwave energy down in cyclonic flow of and on through the
weekend, leading to a forecast that is littered with chances for
showers and limited chances for thunder as well as temepratures near
to below normal and northwest surface winds persisting for days.
Early next week, the upper ridge over the West Coast amplifies, so
our upper trough will follow suit and deepen while holding steady
over our area. Persistent northwest flow will continue with
temperatures looking cooler for Monday and Tuesday, and could see
diurnally driven scattered showers continuing through this period.
Aviation...(for the 18z tafs through 18z Thursday afternoon)
issued at 1215 PM CDT Wed may 24 2017
Residual boundary layer moisture from the departing storm system
across the Ohio Valley, will slowly dry things out with VFR cigs
through this evening. There remains some concerns with MVFR/IFR
cigs redeveloping once again Thursday morning as did today. As
winds veer to the east/southeast overnight, moisture will likely
increase from the departing storm system and affect west central
Wisconsin and east central Minnesota after midnight. There could
even be IFR/LIFR/fg vsby in some of the local higher terrain in
south central Minnesota. Otherwise, no other aviation concerns
with most of the precipitation holding off until after 18z
Thursday in western Minnesota.
VFR cigs will continue through sunset with an isolated shower
possible during Max heating. Otherwise, MVFR cigs could once again
redevelop Thursday morning, but confidence remains low. However,
will introduce few009 sct020 between 11-14z as moisture increases
and the typical diurnal trends of cigs lifting in the morning
occur. A northeast to east wind will prevail through the evening,
with winds becoming southeast and increasing Thursday
/Outlook for kmsp/
Fri...VFR. Isolated -shra. Wind SW 5-10 kts.
Sat...mainly VFR. Slgt chc p.M. -Shra/-tsra. Wind west 5-10 kts.
Sun...mainly VFR. Chc -shra/-tsra. Northwest 5-10 kts.