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Area forecast discussion 
National Weather Service Des Moines Iowa
1232 PM CDT Thursday Jul 24 2014

Short term /today/...
issued at 326 am CDT Thursday Jul 24 2014

Today...surface high over the region will slowly shift further
east to southeast and allow for an area of low pressure make its
way across the Dakotas and Nebraska today. Some weak Theta-E
advection and forcing between 700-500mb associated with a subtle
500mb shortwave riding the northwest flow ahead of the surface
low. This system may spawn a few thunderstorms over the northwest
portions of the forecast area by the afternoon. However...have low
confidence with much precipitation as the surface ridge remains fairly
stubborn in moving east and there is still quite a bit of dry air
in place over Iowa. Hence...cut back on probability of precipitation through 18z and
confined them to the northwest to north central.

With the drier forecast...leaned toward warmer high temperatures
today due to the less cloud cover/precipitation as well as the addition
of weak southerly flow developing this afternoon.

Long term /tonight through Wednesday/...
issued at 326 am CDT Thursday Jul 24 2014

Water vapor imagery shows the wave...across the West Coast
beginning to round the upper level impact our area
tonight and early Friday morning. Similar solutions once again
this model package for tonights expected convective event that
should take place generally along and east of Highway 169...with
the best lift and convergence into the upper level boundary east
of Interstate 35. Trends have been similar...with some differences
on timing...GFS/Gem still slightly slower than NAM/12z Euro
which again focus most of the thunderstorms/potential mesoscale convective system over the
east/northeast late tonight and early Friday. Newest 00z Euro is
also slightly will delay the onset northwest and
extend the exit east by about 3 to 6 hours. Overall it would
appear that the event will still peak between 09z and 15z
east/northeast as strong warm air advection and moisture are
forced into developing h850/h700 frontal zone along the leading
edge of a thermal cap at h700 late tonight. GFS continues to show
precipitable water values nearing 1.5 to 2.0 inches by 12z Friday
from north central through northeast Iowa with sufficient warm
cloud depths for efficient rainfall. Soundings again tonight
indicate that elevated convection will peak between 09z and just
around sunrise over northeast sections. Still expect that any
severe threats should be limited to hail and perhaps some
wind...though there is a significant inversion that must be
overcome for any downward wind momentum to reach the surface. Overall
rainfall amounts will generally be in the half to 1 inch range
with some higher totals possible...all ending by midday Friday.
This will make for a soggy start to Friday morning over the
northeast/east. Once the convection moves east with the wave and
expected surface low tracking into the north central Iowa by Friday
afternoon...a h700 warm layer will build across Iowa and bring
rather warm/hot temperatures back into the region for Friday
afternoon. With ample sunshine...highs will quickly build back
into the lower to middle 90s south with upper 80s across the
northwest. Slight cooler readings in the lower 80s will hold on
northeast with leftover clouds exiting the region. Despite MUCAPE
in the 4500 to 5500 j/kg range Friday afternoon...strong cap aloft
likely to mute any additional convection. Along with the
heat...southern sections likely to be back to 100f to 105f heat
indices by late afternoon as well. We will stay in the warm sector
Friday night and Saturday with humid lows in the 70s and highs in
the middle to upper 80s Saturday. As the front sags south again
Saturday afternoon/evening...some convection may fire along it
over the south third of the forecast area through Saturday
evening. We are outlooked for slight risk...but with only weak surface
convergence and cap aloft...storms will be rather conditional
through the afternoon. Otherwise cooler and less humid weather
will return will by Sunday. Little change from yesterday with
regards to the extended. H500 low over Hudson Bay will phase with
approaching h500 northern stream system by Sunday. This will allow
upper level trough to amplify and expand south across the eastern
Continental U.S.. this will keep our area in a prolonged northwest flow
pattern lasting through the extended period with highs in the 70s
and lows in the 50s to lower 60s and little organized


issued at 1228 PM CDT Thursday Jul 24 2014

Low pressure system will begin to affect sites near 00z...with
precipitation chances especially at northern sites
kfod/kmcw/Kalo. Have included only vc mention at this time due to
uncertainties in timing and location of thunderstorms and rain or
rain showers...however...kmcw/Kalo may see thunderstorms and rain...especially after 06z.
Winds will increase through the period...becoming strong and gusty
after 12z. Overall...conditions will remain VFR through periods of
MVFR or lower visibilities and ceilings will be possible within
thunderstorms and rain.


Dmx watches/warnings/advisories...



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

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