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Area forecast discussion 
National Weather Service Des Moines Iowa
639 am CDT Sat Apr 19 2014

..updated aviation discussion...

Short term /today/...
issued at 333 am CDT Sat Apr 19 2014

Main forecast concern today was focused on winds and temperatures...
and probability of precipitation late this afternoon over northwest Iowa. Models have
consistently pulled back on rain chances previous runs and leaned
toward the drier NAM/GFS for probability of precipitation today. With respect to to temperatures...leaned
slightly warmer than the sref/NAM for maximum temperatures.

Ongoing warm air advection will continue to increase through the day as the
combination of pressure gradient and deep mixing will lead to a
windy day. Winds remain below criteria at this time...but would not be
surprised to see some gusts to 40 miles per hour this afternoon as mixing to
900mb to 850mb seems reasonable. Winds atop the mix layer range
around 30-35 knots. will warm and windy with highs
over the entire forecast area rising well into the 70s. Tweak maximum
temperatures up a degree or two with warm lows and strong warm air advection.

Frontal boundary stalls across far northwest Iowa and more likely in
southeast South Dakota this afternoon. Confident enough to pull back
timing and coverage of probability of precipitation for today...and have low confidence we
will see any precipitation in the state until late tonight. Bufr soundings
in northern Iowa show deep dry layer from surface to 800mb and
remain strongly capped through the afternoon hours. Plus there is
very little elevated or surface based instability through 00z
Sunday. Even though shear profiles are adequate for
convection...there is no trigger mechanism available until after 00z

Long term /tonight through Friday/...
issued at 333 am CDT Sat Apr 19 2014

Active weather pattern in store for the region through much of the
period. First challenge is timing of precipitation and coverage with
approaching plains trough. Upper level ridge tonight cuts across
Ontario southwest through Illinois south to south Texas. Weak moisture
advection at h850 beginning to creep north along the Red River valley. At
the surface...dew points to 50f up to Wichita Falls with middle 40s along
Southern Plains warm front to western Kansas. Models differ on timing of
precipitation/coverage and forcing/quantitative precipitation forecast as well. Initially it looks like the
moisture will arrive with less instability...then gradually become
more unstable Sunday. With that in mind...have reduced to isolated
thunder Sat night and scattered thunder Sunday gradually going general
thunder for Sunday night. Gem/Euro are slower and have less moisture
input/output than GFS. Tendency has been for GFS to be too fast and
though moisture will surely get here...have slowed arrival and
eastward progression while keeping expected trough across the region
by late Sat night/Sunday active across the northwest half of the
forecast area. Thus...quite a spread of conditions expected on
Easter Sunday with cooler/wetter weather north and partly sunny and
milder weather southeast through most of day and evening. Northwest
should see best lift nearer the upper level/surface trough axis with
the entire trough slowly drifting east Sunday night and Monday
when pop increases for the remainder of the area. Expected
rainfall from the Euro/Gem through Monday looks greatest across the
northwest...over areas which saw the least amount last weekend
while lesser amounts expected southeast with a general range from
25 to .75 with locally higher amounts. GFS appears to be having
some convective feedback issues with pockets of 1-2 inch rains
near a closed surface low and large stripe of totals of 2-3 inches
which dont look likely...while the Gem/Euro show mostly a weaker
trough alignment SW/NE orientation. Prefer the latter...weaker
forcing scenario. The system may linger into Monday afternoon east
with scattered showers and thunder prior to lifting out. Relatively
quiet weather returns for Tuesday with ridge of high pressure across
the region. Despite the cooler airmass...h850 temperatures will still
reach 2c northeast to 5-6c west/southwest which should support
highs near 60 northeast and in the middle 60s central and southwest.
The remainder of the week will return to active weather as a
vigorous upper level system entering the pacnw moves east late
Tuesday night and enters the plains by 00z Thursday. Ahead of the
system...h500 ridging aloft will increase thickness/h850 temperatures
with a round of warm air advection crossing the region by Wednesday
afternoon with showers and thunderstorms. Difficult forecast for
temperatures Wednesday due to possible overcast/scattered thunder for most of the
afternoon. Highs may range from the middle 50s to middle 60s depending
on the coverage. Little chance for severe initially...but as the main
wave arrives Wednesday night...strengthening wind fields from the surface
through h300 may be enough to keep convection going overnight with
a potential for some strong storms. As the system lifts northeast occludes further and forces the best instability
east into Illinois by 00z Friday...keeping the best chances for
organized severe weather mainly east of the region. Any slower evolution
and departure...however...would place a better chance for stronger
storms back in Iowa during the day Thursday and will need to
monitor this week especially with the strong wind fields through
the column. Cooler air regionwide and lingering showers will
continue north half with a brisk west-northwest wind Thursday night and
Friday resulting in highs back in the 50s over most of the area.
Uncertainty remains into the weekend as the models diverge on
solutions. While the GFS shows moisture return late in the
weekend...the Euro is spinning up another low Saturday over the
plains ahead of the main system with warm air advection thunder by
00z Sunday over our area. For now...will lean toward a drier
solution on Saturday until some confirmation of trends is
apparent. Seems more reasonable that some separation will occur
between fridays lingering occluded low and the next upstream wave.


issued at 635 am CDT Sat Apr 19 2014

Winds will be the main concern today as strong southerly flow and
deep mixing develops ahead of an area of low pressure located over
the Central Plains. Increased wind gusts this afternoon. Only taf
site with mention of any precipitation is fod at had low confidence to
mention elsewhere due to models continually delaying system to
move across the state.


Dmx watches/warnings/advisories...none.



Short term...podrazik
long term...rev