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

Updated for 00z aviation discussion...
issued at 636 PM CDT Monday may 25 2015

&&

Short term...(this evening through tuesday)
issued at 406 PM CDT Monday may 25 2015

A somewhat complex weather pattern is in place this afternoon as a
broad synoptic level trough has spread itself out from essentially
The Rockies to the Great Lakes. Within this trough...there are
numerous waves sparking of showers and storms from Texas to Lake
Superior. The two that matter for US are a subtle wave moving north
out of Iowa and the shortwave/mesoscale convective vortex that is driving the thunderstorm
complex racing across Texas and Oklahoma.

Some clearing across Iowa today has allowed for instability to build
to our south...with a nice cape gradient now setup from southeast sodak
across southern Minnesota and into the La Crosse area. This cape gradient will
be the scene of scattered thunderstorms through the evening...with
activity expected to remain south of a New Ulm/Twin Cities/Chippewa
Falls line. Middle level lapse rates are quite meager and deep layer
shear is only on the order of 30 kts...so from the severe
perspective...not expecting much outside of a couple of marginally
severe cells.

Other issue for tonight will come with the potential for another
night of low stratus and fog. We currently have a boundary sprawled
out from SW Minnesota to northwest WI and this will be remaining more or less
stalled out overnight. This will result in a baggy pressure gradient
across the area...with plenty of moisture still in place...so expect
stratus and fog to fill back in overnight. Gfslamp has had dense fog
forecast for tonight all day from NE Minnesota into northwest WI...so brought in a
fog mention for tonight in the NE parts of the mpx County Warning Area...but this
could just as easily end up being low stratus.

For tomorrow...the shortwave currently near the Texas/OK border will be
heading into Wisconsin by the afternoon. This should bring another
shield of rain up into WI during the late morning and afternoon.
This is a pretty strong mesoscale convective vortex based on spin you can see on satellite
and regional radar loops...so like the idea of the European model (ecmwf) that a
pretty healthy burst of rain comes up into WI tomorrow
afternoon...just went along with the wpc idea that that band will be
a bit farther east than what the European model (ecmwf) has. As a result...trimmed
probability of precipitation across most of Minnesota tomorrow...with likely probability of precipitation confined to western
WI.

Long term...(tuesday night through monday)
issued at 406 PM CDT Monday may 25 2015

Left over showers and thunderstorms from Tuesday will be pushing
east of our WI counties Tuesday evening. Dry weather is then
forecast through Wednesday night as weak ridging builds in place.
A pocket of warm air aloft will slide southeast from the northern
rockies into the upper Midwest Wednesday ahead of the next front
sinking south to the U.S./Canadian border. 925 mb temperatures rise into
the low to middle 20s c...signaling highs in the low to middle 80s. This
agrees very well with the raw 2m temperatures off of the
NAM/GFS/ECMWF/Gem and the met/mav/Euro MOS products. Thus...raised
highs into the middle 80s most places...though kept them slightly
cooler over WI and far southern Minnesota where mixing isn/T quite as
deep...925 mb temperatures are coolest...and there are neutral height
changes.

The warm temperatures will continue Thursday...although they may be
slightly cooler due to clouds and an increasing threat for showers
and thunderstorms with an approaching trough. Maintained highest
probability of precipitation across western Minnesota Thursday afternoon...expanding eastward
Thursday night. The front will sag across the County Warning Area Friday with the
highest probability of precipitation confined to southern Minnesota/western WI. Lapse rates are
poor and winds are generally less than 35 knots below 350 mb...so not
expect much...if any severe weather at this time. There could be some
locally heavy rain with precipitable water values nearing 1.5 inches and mbe
velocities less than 15 knots. That will be the main threat.

Another cool spell arrives for the weekend as a 1030 mb high
drifts east across the upper Midwest and Great Lakes. May see lows
in the upper 30s again Saturday night in spots.

&&

Aviation...(for the 00z tafs through 00z Tuesday evening)
issued at 636 PM CDT Monday may 25 2015

Scaled back on the IFR/LIFR conditions. Skies have cleared this
afternoon...and feel the guidance is a little slow to catch up.
With that being said...the last few runs are more optimistic that
conditions will stay MVFR overnight. The northern sites (kaxn kstc
krnk) have more low level moisture...and with the surface boundary
overhead are in a more favorable position for fog development
later tonight.

Kmsp...
this evenings rain should stay south of kmsp. Could see some
stratus redevelop later tonight...but given the afternoon clearing
and mixing think feel that the probability of IFR/LIFR conditions
has decreased. Winds will be light and variable overnight and
early Tuesday morning before a consistent northerly component
develops.

/Outlook for kmsp/
Wednesday...VFR. Winds west 5-10 kts.
Thursday...VFR. Chance p.M. -Shra/-tsra. Winds southeast at 5-10 kts.
Friday...MVFR in shwrs/tsms. IFR possible. Winds SW 5-10 kts becoming
north 10-15 kts.

&&

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

$$

Short term...mpg
long term...borghoff
aviation...jrb

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