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Area forecast discussion 
National Weather Service Twin Cities/Chanhassen Minnesota
1204 am CDT Monday may 25 2015

Updated for 06z aviation discussion...
issued at 1157 PM CDT sun may 24 2015

&&

Short term...(this evening through monday)
issued at 430 PM CDT sun may 24 2015

Today has been about as much of a washout as you can get as an
isentropically forced rain shield lifts north across the area to the
north of a warm front that this afternoon was approaching I-80 down
in Iowa. Models of both the deterministic and cam variety are in
good agreement on this band slowly lifting north through the evening
before stalling out overnight from west central Minnesota over toward northwest WI
as a surface low begins to take shape over southern Minnesota as the warm front
lifts into the state. Followed the general idea of the hopwrf
members and hrrr with the probability of precipitation in bringing some low chance probability of precipitation up
through about the southern half of the area tonight as a dry period looks
to get about as far north as a Montevideo/Twin Cities/Eau Claire line.

Where a fair degree of uncertainty lies is what happens after this
band of rain lifts north late tonight and the strong shortwave
currently moving out of Texas into central OK moves toward WI. There
should be a band of moderate to heavy rain that lifts north with this
wave late tonight through Monday morning...but where it GOES is
where the uncertainty lies. The GFS and Canadian bring this band
across western WI while the NAM/European model (ecmwf) take it more toward Green Bay. The
short term models...which now end Monday morning would favor the eastern
solution being correct. If that is that case...then a dry slot will
result in a dry Memorial Day outside of the persistent rain band
across central Minnesota. The GFS/Canadian solution would have yet another
washout for folks in western WI. Hard to split the difference bet wet or
dry...so just reduced probability of precipitation into the likely category in our east
Monday morning given the uncertainty.

Other change for the short term was to remove most of the thunder
mention as we just do not see any instability develop. The lone
exception to this is for south central Minnesota Monday afternoon where
temperatures will warm to around 70...allowing for a few hundred
j/kg of cape to develop. Cams also show the trailing cold front
firing off storms in western Iowa Monday afternoon...which may start
getting near the I-90 corridor by the end of the short term period.

For temperatures...extensive cloud cover tonight will keep
temperatures pretty much steady through the night. For highs
tomorrow...with continued light rain and clouds across central Minnesota
expected...did drop highs down to just the low 60s there...while the
return of SW winds during the afternoon in southern Minnesota should allow for
temperatures to warm closer to late may normals.

Long term...(monday night through sunday)
issued at 430 PM CDT sun may 24 2015

We pick up the long term on Monday night. The short term
discussion above mentioned the threat for thunder in far southern
Minnesota Monday afternoon. There is still some question as to exactly
how far north storms will end up. There is good agreement among
the 12z and 18z guidance that the warm front will make it into
southern Minnesota tomorrow with weak to moderate elevated
instability arriving in the southern forecast area between 21z-
00z. The available cam guidance /WRF-arw...WRF-nmm...NAM nest/
supports a healthy east-west orientated line of convection
breaking out in the late afternoon somewhere near the Iowa/Minnesota in
response to building instability and the arrival of a shortwave
trough out of the Central Plains. A couple strong to severe storms
can't re ruled out at this point.

The frontal boundary is slow to clear the eastern forecast on
Tuesday...so we felt it was best to linger the chance for showers
and storms across eastern Minnesota and west central WI until building
heights kick the front to the east Tuesday night into Wednesday.
Therefore...the middle of this coming week looks dry at the
moment. Beyond Wednesday...the pattern remains active with
southwest flow and another trough making its way through Minnesota/WI
late in the week. Thursday and Friday could see a couple rounds of
showers and storms with the potential for heavy rain fall given
another slow frontal passage.

&&

Aviation...(for the 06z tafs through 06z Monday night)
issued at 1157 PM CDT sun may 24 2015

No significant changes to the prior taf. Clouds continue to be the
limiting restrictions...with IFR ceilings widespread across the state.
Pockets of drizzle will continue overnight. Hires models clear out
the precipitation by morning...so tapered off the rain in the tafs. A
surface trough will be oriented SW/NE across the region...so not
anticipating much improvement until later Monday afternoon.

Kmsp...
areas of drizzle will continue...with ceilings fluctuating around
500ft. Light easterly winds should gradually take on a southerly
component by morning...and southwesterly during the afternoon. Low
confidence in the timing of the 1700ft ceilings...but increased
confidence in a drier forecast.

/Outlook for kmsp/
Tuesday...VFR. Winds SW at 10 kts.
Wednesday...VFR. Winds SW at 5-10 kts.
Thursday...VFR with rain showers/-tsra possible. Winds southeast at 5-10 kts.

&&

Mpx watches/warnings/advisories...
Minnesota...none.
WI...none.
&&

$$

Short term...mpg
long term...clf
aviation...jrb

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