Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Twin Cities/Chanhassen Minnesota
445 am CDT Thursday may 28 2015
Short term...(today and tonight)
issued at 345 am CDT Thursday may 28 2015
Today and tonight...there are two features of interest in the short
term period...one of which will stay just north of our area
today...and the other that will bring showers and thunderstorms to
southern Minnesota and western WI tonight into tomorrow.
For today...upper level ridge axis is currently progressing eastward
and was centered over the Minnesota/WI border. Across the Dakotas...a
shortwave trough was evolving slowly northeast overnight and
producing showers and thunderstorms across parts of the Dakotas.
Across western Minnesota...cloud cover was on the increase ahead of this
wave...but mainly high clouds were working into the area. This
shortwave is going to continue on its path to the northeast
today...and the convergence/forcing will be focused to our
north...so have a dry forecast for today with the exception of some
slight chance probability of precipitation in far western Minnesota. In fact...much of the area
will have a nice day as model soundings have indicated less low/middle
level cloudiness so filtered sunshine can be expected for much of
the day...especially the further east you go. As far as temperatures
go...went with a mix down from 800mb which would again yield
temperatures in the lower 80s across the area.
For tonight...our eyes are on another wave of energy near Kansas
early this morning that will turn north-northeast today and advance through Iowa
and reach southern Minnesota this evening. Frontogenetic forcing across the
area tonight looks less impressive than it previously did...but
upper level divergence still looks solid across southern Minnesota through
east central Minnesota and west central WI tonight thanks to a
strengthening jet to our north. Expect showers and thunderstorms
late tonight through the overnight hours to Blossom across much of
the area including the Twin Cities metropolitan as pv advection looks
best in that time frame. In addition...best lifted indice's will become
negative ahead of this wave so there will be some instability to
work with and that combined with precipitable water values
increasing to about 1.6" could create some heavy rainfall rates in
Long term...(friday through wednesday)
issued at 345 am CDT Thursday may 28 2015
Confidence is high that showers and some thunderstorms will be in
progress across the Twin Cities metropolitan as well as points east and
south early Friday morning as a wave lifts northeast across the
area. In the wake of this feature...it/S not clear cut on where
and how much convection will redevelop along a cool front sagging
southward through the forecast area on Friday. Various WRF solutions
including the arw...nmm and hopwrf-ts focus much of the convection
along I-90 and points southward. Even the namnest is depicting
more of far southern Minnesota and adjoining areas of WI for Friday
afternoon and evening. Therefore...the highest probability of precipitation were adjusted
a little farther to the south and east. Heavy rain is still a
concern in the convection on Friday due to precipitable water
values prognosticated to be over 1.5 inches. This is at the top of the
mpx sounding climatology for the end of may. Boosted high
temperatures a few degrees on Friday due to the anticipated break
in the convection between that in the morning and redevelopment in
The weekend is looking real spiffy as high pressure noses
southward across the upper Mississippi Valley. It will certainly
be cooler and less humid on Saturday (lower-middle 60s).
Temperatures will begin to warm on Sunday as we transition to the
backside of the high. This warming trend will persist through the
end of the long term (wed) with highs reaching the upper 70s to
lower 80s. Not too confident on the low chance probability of precipitation in the
forecast at the beginning of the week. A broad upper ridge is seen
across the northern plains and upper Mississippi Valley region.
Thickness forecasts suggest convective complexes moving eastward
across the northern High Plains and northwest Minnesota. Therefore
tailored probability of precipitation to the far west and north portions of the Minnesota County Warning Area
Monday and Tuesday. Chance probability of precipitation are in place starting Wednesday
as a cool front pushes slowly into western/northern parts of Minnesota.
Aviation...(for the 12z tafs through 12z Friday morning)
issued at 437 am CDT Thursday may 28 2015
For today...expect VFR conditions as we experience a gradual
increase in broad middle and high level cloudiness...before lower
level ceilings spread eastward after 00z tonight. Strong southerly
flow will get going during the day...with gusts commonly in the
20-30 knots range today. For tonight...forcing and moisture come
together especially from 04z and after to produce more widespread
showers and possibly thunder across the area. MVFR or IFR will be
possible in the showers and thunderstorms and we do expect ceilings to
be restricted by 12z Friday.
Kmsp...MVFR or even IFR ceilings could linger through much of Friday
morning...although most of the rainfall looks to occur in the
early morning hours.
/Outlook for kmsp/
Friday...MVFR/IFR ceilings/visibilities in shra/tsra. Winds SW 5-10 kts becoming
north-northwest at 10-20 kts.
Sat...VFR. Winds NE 10 kts.
Sun...VFR. Winds southeast 10 knots.