Area forecast discussion
National Weather Service Twin Cities/Chanhassen Minnesota
1055 PM CDT Monday may 20 2013
Update...
for 06z aviation discussion below
&&
Short term...(today and tonight)
issued 258 PM CDT Monday may 20 2013
Early afternoon water vapor imagery together with rap40 500mb
heights...winds...overlaid with surface pressure showed a vertically
stacked cyclone over the Minnesota/Dakota border. A well-defined warm front
was oriented west/east from The Elbow of western Minnesota up
through Lake Superior...with a cold front extending southwest
through central Nebraska. Rotating around the upper level low was a
shortwave over southeastern Minnesota which was the driving factor
behind a few scattered showers along and north of i94. 19z Storm Prediction Center
mesoanalysis showed 500j/kg of SBCAPE in the warm sector of this
cyclone...with no cin...thus the scattered shower activity ongoing
across the region will persist into the evening hours. Could see a
stray thunderstorm as well...but the best deep layer shear will be
confined across the southeast of the County Warning Area. Therefore not anticipating
much of a threat for severe weather...especially considering the
controlled release of cape evident across the region via the
cellular convection.
Tonight the showers should decrease in coverage across the south...
with redevelopment expected again on Tuesday afternoon. The surface
low will gradually fill as it slowly meanders eastward. Bufr
forecast soundings via both the NAM and GFS show much shallower cape
profile Tuesday afternoon when compared to today...so have removed
thunder across the west and have lowered temperatures over the entire
region. In short Tuesday will be a cloudy and cool day with light
rain showers expected once again.
Long term...(tuesday night through monday)
issued at 247 PM CDT Monday may 20 2013
We will still be dealing with the effects of the slowly departing
upper low Tuesday night into Wednesday... with a continuation of
shower chances over the area... enhanced with the diurnal cycle
and passage of individual vorticity lobes across the area.
However... the trend of instability and shear being displaced east
will continue... so chances for severe weather will also be on the
downward trend through the period and be focused east of our area.
We finally look to get on the backside of the upper trough
Wednesday night... with surface ridging nosing in from the north
by Thursday. The GFS... NAM... and European model (ecmwf) are all in decent
agreement on the timing of things... so have good confidence that
we/ll finally see a completely dry day by Thursday. The surface
ridge will slide east by Friday... with warm advection starting to
setup across the area. At this point... the GFS and European model (ecmwf) start to
diverge some... but mainly with the degree to forcing and
instability along the elevated warm front... with the European model (ecmwf)
actually generating precipitation sooner and farther east than the GFS. At
this point... am inclined to go with the slower solution and keep
things dry through Friday. However... by Saturday and then through
the remainder of the forecast it looks like we/ll have chances for
rain showers/thunderstorms and rain across the area once again as low pressure sits over the
Central Plains and we see a prolonged period of warm advection and
elevated instability across the area with the primary surface warm
frontal boundary slowly lifting north toward the region.
&&
Aviation...(for the 06z tafs through 06z Tuesday night)
issued at 1057 PM CDT Monday may 20 2013
Widely scattered showers will be possible through the overnight
hours as a low pressure center moves into the area. Ceilings will
degrade to MVFR at Minnesota sites...with IFR ceilings at kaxn-kstc-krwf in
closer proximity to the low pressure center. Ceilings gradually
scatter and improve by 18z Tuesday. Scattered showers/ts will be
possible again on Tuesday. Winds will become southwest/westerly on
Tuesday at all but kaxn/kstc where northeasterly winds will
persist.
Kmsp...
after the line of showers and thunderstorms exits msp /by
08z/...slight visibility reductions in br will be possible through
sunrise. Ceilings expected to lower to around 1800 feet
overnight...and scatter out for awhile Tuesday afternoon. Southeasterly
winds prevail through the overnight hours...veer to southerly by
daybreak...and then southwest/westerly during the afternoon.
Speeds at 5-10 kts through the period.
/Outlook for kmsp/
Wednesday...VFR/MVFR ceilings with -shra likely. Winds NE at 05g10kts.
Thursday...VFR. Winds north-northeast at 10-15kts.
Friday...VFR. Winds southeast at 5-15kts.
&&
Mpx watches/warnings/advisories...
Minnesota...none.
WI...none.
&&
$$
Short term...jrb
long term...trh
aviation...ls
