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Area forecast discussion 
National Weather Service Des Moines Iowa
1219 PM CDT Fri Oct 21 2016

..updated aviation discussion...

Short term.../today/
issued at 329 am CDT Fri Oct 21 2016

High pressure currently centered over the state with light and
variable winds and chilly temperatures. The high will slide off to
the east today with westerly flow setting up aloft and waa. May
therefore have increasing mid/high clouds through the day, and
temps a bit warmer than readings from Thursday, which should
result in mid 50s east to around 60 west. Winds to remain lighter
and variable this morning before shifting around to the south and
picking up a bit this afternoon with mixing and an increase in the
sfc pres gradient.

Long term.../tonight through Thursday/
issued at 329 am CDT Fri Oct 21 2016

Summary...quiet, and generally above normal fall conditions through
Mon. Temperatures into the 60s and low 70s Sat/sun before return of
northerly winds drops highs a few degrees. Active period returns
late Mon night through Wed with low pressure moving across the state
and likely return of thunder.

Tonight through Monday...little to no tangible change in previous
forecasts for this period. Upper trough will be well east of the
region by tonight and begin a period of upper level ridging and
northwest flow. Southerly winds will work to boost temperatures into
60s and low 70s for the weekend before weak cold front moving
through Sun afternoon, dropping highs Mon back a few degrees. Sun
continues to look a bit windy with weak short wave moving through
and high pressure on its heels, tightening pressure gradient, esp
across the north. Soundings suggest possibility of tapping into 20-
25kt gusts, so have boosted just a bit over original guidance.

Tuesday through Thursday...upper level northwest flow and ridging
begins to break down at the beginning of this window, and wave out
of the southwest US moves into the region and amplifies with
attendant surface low. Euro/GFS/Gem have all come into better
agreement in timing and magnitude last couple of runs, resulting in
growing confidence in showers/storms, as reflected in trending up
pops beginning late Mon. Initial warm air advection will produce showers ahead of
main surface low, but may struggle initially ahead of best moisture
return. Euro/GFS consistent in depiction of <500 j/kg elevated cape
within warm air advection and ahead of surface front, so have kept with thunder
mentions but have limited at isolated. Low level shear and helicity
remain supportive for severe weather considerations, however the
window for anything surface based appears very small with questions
as to whether or not warm nose ever fully dissipates and nocturnal
timing Tue night for frontal passage. Pwats continue to trend
upward, with GFS pushing close to 1.5", keeping concern for heavy
rainfall. Even with the dry period ahead of event, with no help from
vegetation/crops limiting runoff or uptake, water issues could
become a concern. System then moves out of the area Wed afternoon.


Aviation.../for the 18z tafs through 18z Saturday afternoon/
issued at 1218 PM CDT Fri Oct 21 2016

VFR conditions will prevail throughout the entire taf period.


Dmx watches/warnings/advisories...none.



Short term...beerends
long term...Curtis

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