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Area forecast discussion 
National Weather Service Twin Cities/Chanhassen Minnesota
1049 PM CDT Sat may 23 2015

Update...for 00z aviation discussion below


Short term...(this evening through sunday)
issued at 431 PM CDT Sat may 23 2015

Isolated light showers and sprinkles are possible through the
evening and most of the night but little to no accumulation is
expected over the next 6 to 12 hours. of right now were
are in a relatively lull in the precipitation after an area of light
showers affected portions of southern and central Minnesota
throughout the day /with just enough to wet the ground in spots/.
As of this afternoon...the local area is under a weak surface
ridge with light winds and an overcast altostratus deck. There is
weak 850mb flow out of the south...but Minnesota/WI is largely under the
influence of neutral temperature advection at the moment. There
is...however...warming between 850-700mb across NE/Iowa late this
afternoon. This is likely the beginning of the warmer Theta-E
plume expected to spread north overnight and bring widespread rain
to the forecast area on Sunday. Between 12-14z the rap brings
between 100-150 units of 925-850mb moisture transport into south
central Minnesota. This will probably be the leading edge of widespread
showers /perhaps with embedded weak thunderstorms/. The threat for
vigorous convection tomorrow is low...because we simply struggle
to get much of any elevated instability in here tomorrow. Middle
level lapse rates do steepen across IA/NE...but locally it is
probably just going to amount to a nice persistent stratiform rain

Long term...(sunday night through saturday)
issued at 431 PM CDT Sat may 23 2015

Finally beginning to get a bit more agreement with the guidance on
how things will unfold during the long term. It will start off on a
wet note Sunday night into looking mainly dry Monday
night through Wednesday...with another round of thunderstorms coming
through Thursday...followed by a pretty strong cold front on Friday.

We will start things off with the strongest shortwave of the weekend
working north across Minnesota. The European model (ecmwf) shows this with a 50 knots low level jet coming
up to the east side of a surface low that will be tracking due north to
the west of I-35. This will bring a heavy band of rain through the
area as precipitable waters increase to over 1.5". The only model for this event
that looks to be avoided at this point is the it has
started off too far east with precipitation today and continues to
be an eastern outlier into Sunday night. GFS of the
models show an area wide precipitation event unfolding from Sunday
afternoon into Monday morning...with just about everyone looking to
get in on 0.75" to 1.25" of rain from later Sunday through Monday
morning. One thing that is lacking with this system when looking at
soundings is a result...capped thunder mention to
just a slight chance Sunday night through Monday morning as this
looks to primarily be a rain event.

For is beginning to look drier...especially into Monday
night...where probability of precipitation were cut back significantly. During the day...the
wave from Sunday night will have about a 1000mb surface low moving into
northern Minnesota. In the wake of this morning wave...a dry slot and short wave
ridging will move across the mpx area...which may pretty much cut
off the precipitation for Monday afternoon. For Monday evening...when the
trailing cold front looks to become active...said front will be off
over WI...with most of that precipitation off to the east while the
deformation precipitation on the back side of the surface low looks to largely
fall to the north/northwest of the mpx area. This was a pretty big change from
earlier model runs and therefore the previous forecast...which
pretty much had area wide likely probability of precipitation for Monday tried to
cut a middle ground between this and the previous forecast to keep
from having such a drastic change...which basically means we cut
probability of precipitation in half on Monday night...with just chance probability of precipitation left at this

For Tuesday...we will have a baggy surface pressure pattern in
place...but some lingering instability...which may help generate
some isolated to scattered diurnally driven have
maintained some 20/30 probability of precipitation for that day. Did remove any remaining
probability of precipitation though for Wednesday with all guidance now dry as shortwave
ridging moves across the area.

For Thursday...although there are timing differences between the
GFS and European model (ecmwf) with the latter being the faster of the two...both
continue to show another front working across the area with a round
of thunderstorms out ahead of this feature. Both models have been
showing this for a few have introduced some likely probability of precipitation
for Thursday afternoon and night.

To end the extended...both the GFS/European model (ecmwf) show a rather potent cold
front dropping south across the area Friday into Saturday. Looking
at the hemispheric 500 mb actually makes physical sense
to see a strong front coming through at the end of the week as both
the GFS/European model (ecmwf) show the upper air pattern taking on a decidedly -nao/-
ao pattern as high heights move over the North Pole...with
anomalously deep upper lows moving south out of the Arctic. This
pattern...even in early Summer would allow cold air to get dislodged
from the Arctic and that is what both the European model (ecmwf)/GFS show for next
weekend as a Continental polar airmass works down in the form of a
1030+ mb high with dewps back in the 20s/30s.


Aviation...(for the 06z tafs through 06z Sunday night)
issued at 1050 PM CDT Sat may 23 2015

Isolated spits of rain are possible overnight...but the main area
of precipitation will not begin to spread north across the area
until around daybreak Sunday. Said rain will expand north and east
across the area throughout the day Sunday....with ceilings and visibilities
lowering to the MVFR category. The threat for thunder still looks
minimal so have not included a mention in the tafs. Should see a
lull in the rain around 00z Monday...and then it picks up again on
Monday evening

a few passing sprinkles are possible overnight in the vcty of the
field...but the bulk of the showers /with MVFR cigs-vsbys/ should
arrive around/after 17z. MVFR conditions develop during the early
afternoon. Preicp lightens around 23z...with more of a Dr/br
scenario developing.

/Outlook for kmsp/
Monday...VFR. Scattered rain showers/thunderstorms and rain with MVFR or lower conditions. Winds S
10 kts.
Tuesday...VFR. Chance shra/-tsra. Winds SW 10 kts.
Wednesday...VFR. Winds SW 5-10 kts.


Mpx watches/warnings/advisories...


Short term...clf
long term...mpg

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