Area forecast discussion
National Weather Service La Crosse WI
1214 PM CDT Friday may 24 2013
Short term...(today and tonight)
issued at 230 am CDT Friday may 24 2013
850 mb moisture transport/jet will kick off/enhance showers/isolated
storms over Minnesota/northern Iowa tonight...along and north of a surface warm
front. Corfidi vectors would take the complex southeast. Models at
odds with each other on where the more likely precipitation will
lie...generating the main mass of precipitation in slightly different
locations. This lowers forecast confidence in where to place the
higher precipitation chances. Trends seem to favor the southwest 1/2 of the
forecast area though...and will side with that.
Long term...(saturday through thursday)
issued at 230 am CDT Friday may 24 2013
An upper level ridge holds across the upper Mississippi River valley
into the early part of the new work week...slowly shifting east for
the following weekend. Trough holds west of the ridge...spitting out
pieces of upper level energy from time to time. While not an overtly
strong...blocking type pattern...its not moving very fast at
all...with little in the way of 250-300 mb jets to move it along.
And despite having the ridge over the region for the next few
days...this does not mean its going to be dry.
NAM/GFS/ECMWF all have a warm front hanging across the Central
Plains/middle Mississippi River valley through the weekend...finally
getting a push northward through the forecast area on Tuesday. 850
mb moisture transport is fairly persistent into and through the
boundary into the middle of next week. This transport will be a main
focus for shower/storm development...and where this noses into will
house the better initiation regions. Models focus their quantitative precipitation forecast on the
moisture transport - vicinity of the warm front...and can/T fault
this placement. Any mesoscale convective vortex from overnight convection will be another
consideration...although ferreting out where these may move is more
problematic farther out in the forecast period.
With the push northward on Tuesday of the warm front...warmer/seasonable
air should return...along with instability and thus better chances
for thunderstorms if convection can develop.
Overall...rain will be on the radar nearly every day through the
weekend and into the middle part of next week. That does not mean
everyday will be a wash out though...or that everyone will see rain
everyday. Rain chances will be higher to the southwest through the
weekend...gradually moving northward for the start of the new work
week.
&&
Aviation...(for the 18z tafs through 18z Saturday afternoon)
issued at 1214 PM CDT Friday may 24 2013
Focus of the forecast is on the potential for showers late tonight
into Saturday morning. Short wave trough in the Lee of The Rockies
over Wyoming is expected to top the mean ridge and slide across
the region late tonight and Saturday morning. An axis of moisture
transport is expected to develop this afternoon ahead of this wave
then Bend to the northeast and be focused into the area late
tonight. However...this will be weakening through the night and
will not be very strong by the time it becomes focused on the
local area. The forcing from the wave and the weak moisture
transport should be enough to generate some showers. Expect these
will move into both taf sites between 09z and 12z. The showers
should be light enough to not produce any visibility restriction
but could produce some MVFR ceilings as the rain saturates the low
levels of the column enough to allow the ceilings to lower. The
24.09z sref shows the better probabilities of this occurring are
west of the Mississippi River so have included this at krst. The
isentropic upglide on the 300k surface begins to weaken after 15z
Saturday but does continue for the remainder of the morning and
should be enough to keep some showers or sprinkles going through
the end of the forecast period.
&&
Arx watches/warnings/advisories...
WI...none.
Minnesota...none.
Iowa...none.
&&
$$
Short term.....Rieck
long term......rieck
aviation...04
