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Area forecast discussion 
National Weather Service Des Moines Iowa
628 am CDT sun may 24 2015

Short term /today/...
issued at 325 am CDT sun may 24 2015

Well defined mesoscale convective vortex moving into east central Kansas at 06z with attendant
rain shield expanding northeast toward Iowa. Moderate to heavy
rainfall already occurring to our south at this time. Over the past
24 hours...h850 ridge axis over the East Coast has moved little
with strong southerly flow setting up at h850...moisture channel
directed right at eastern Texas...nearly due north to eastern
Nebraska/Iowa. Currently rainfall efficiency quite high over
eastern Kansas where one hour rates are approaching two thirds of an
inch in the heaviest showers. For today...expecting the mesoscale convective vortex to
move north with the first wave of rainfall progressing through the
forecast area by 18z... weakening slightly as it moves northeast
with time. Have raised quantitative precipitation forecast amounts through 12z this morning...and
pushed amounts higher over the east half through 18z with less
expected west of i35. By late afternoon the second wave...a
deepening surface low over eastern Kansas again will lift northeast toward
Iowa. This will bring yet another push of moisture tomorrow night.
Precipitable water today already increases to 1.70 inches by 12z
through Interstate 80...and about 1.5 inches for the remainder of
the day over the southeast half of the forecast area. Today...even
with lack of much instability... should see rainfall totals in the
range of two thirds to 1.5 inches by afternoon...with a few
locations nearing two inches. This will set the stage for flooding
potential overnight Sunday night. More information in the Hydro
discussion below. Highs today will be held in check with low
clouds and rain expected most of the morning... across the
northeast through middle afternoon and some redevelopment in the
south by late afternoon. With a few hours break in the
rainfall...some locations will likely break the 70 degree mark but
many areas will remain in the upper 60s. South southeast winds
will continue at 10 to 15 miles per hour.

Long term /tonight through Saturday/...
issued at 325 am CDT sun may 24 2015

Little has changed for the initial forecast period...with main
concerns on precipitation chances for the remainder of the Holiday weekend.
Large upper trough to remain in the west through much of the
period...with shortwave energy ejecting northeastward through the
region. First stronger shortwave trough to lift through the region
tonight...with the associated surface reflection tracking from southeast NE
into SC Minnesota tonight into Monday morning. With a continued push of
moisture northward from the Gulf and warm air advection/Theta-E advection expect
widespread precipitation across the County Warning Area tonight. Precipitable waters in the 1.5
inch range with deep warm cloud depths...therefore expect efficient
rainfall production. Instability will be only have
isolated thunder and therefore the flash flood threat will be
diminished some but still possible given decent rain expected today
as well. As the upper low lifts northward into Minnesota
Monday...expect a dry period or if any lingering showers expect
widely scattered coverage mainly by late Monday morning into the
early afternoon hours. Warm air advection to continue with a weak baroclinic zone
pushing northward into the County Warning Area by late Monday afternoon into Monday
night. Another impulse to eject northeastward through the area...may
set off some thunderstorms Monday night across the southern two-
thirds of the County Warning Area. Again this period could bring potential for heavy
rainfall especially given the greater instability present.
Continued chances for thunderstorms into Tuesday and Tuesday night
as a cold front slowly sags southward across the County Warning Area. This should
give way to a mostly dry Wednesday with an area of surface high
pressure over the region and weak upper level shortwave ridging in

Southwest flow pattern continues into the end of the week...with a
stronger cold front expected to drop through the state toward next
weekend. Long range models then build a stronger area of high
pressure into the state for early the following week. Therefore
expect an active wet pattern through much of the upcoming
week...with a trend toward quieter weather after next weekend.
Temperatures to be near average...maybe slightly cooler than average
through the upcoming week.


issued at 622 am CDT sun may 24 2015

Challenges today include ceilings...visibility and intensity of rainfall.
First mesoscale convective vortex tracking across area dropping ceilings to LIFR and visibility to
2sm at times. Lowering trends will progress north through 18z with
some improvement in conditions south areas between 15-18z as areas
of rain over Missouri shift northeast as well. By 22z another
system will track toward the region with return of IFR/LIFR
conditions after 00z south and remainder of the area before 05z.
Some uncertainty as to how tonights system will evolve...stronger
south winds may accompany areas east of the low as well. Will let
day shift refine details with 18z package. /Rev


issued at 325 am CDT sun may 24 2015

Mesoscale convective vortex tracking over the area this morning and will bring along with it
moderate rainfall through the daytime hours. H850 flow and precipitable waters
along with warm cloud depths will promote efficient rainfall today.
Totals through 12z south will approach .50 to .66 inches while
lesser but similar amounts will fall over the northeast through the
afternoon hours. Another system arriving by evening will bring
additional quarter inch amounts southwest. Totals for the day should
range from about 0.50 northwest to from the southwest to northeast.
The first round will have little overall impact to rivers though
subsequent rainfalls in the next 24 to 36 hours after 00z may cause
some Hydro issues along mainstream rivers. As the first system
departs the northeast by 20z...the second system will begin
affecting southern Iowa.

Additional chances for heavy rainfall will come Monday night into
Tuesday with thunderstorms expected across the area. At this
time...not a lot has changed with the majority of the river
outlooks expected to stay below flood stage. Again...a few
ensembles to push some of the rivers rising above flood stage with
the locations continuing to be along the Des Moines and Raccoon
river basins. No Hydro headlines are expected...but the situation
is being closely monitored through the Holiday weekend.


Dmx watches/warnings/advisories...


Short term...rev
long term...beerends

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