River Flood Warning 16, NWS Des Moines, IA

Area Forecast Discussion
National Weather Service Des Moines IA
121 PM CDT Wed Mar 13 2019

.UPDATE...
Issued at 121 PM CDT Wed Mar 13 2019

Have sent out an update to extend the dense fog advisory through
this evening. Have seen some improvement across the east central
portions of the forecast area and also into SW/west central Iowa.
May still need some adjustments as winds pick up and help to
dissipate the fog. However latest guidance suggests that the fog
across the far north could linger through tonight, so will be
assessing the need for a further extension of the advisory through
the afternoon hours. All other forecast elements remain on track
with the heaviest of the rain moving through the state currently.
Will continue to see flooding concerns as many have already been
observed due to poor drainage due to frozen culverts/heavy
blocking drainage routes. Also reports of ice jams in several
locations. Therefore flood watch to remain in place and many areal
flood warnings have been issued with the large swath of rain
moving across the area this afternoon.

Will continue the wind advisory as they area starting to increase
across the south and west, a bit later than expected. May still
end up with marginal wind advisory conditions.

&&

.DISCUSSION.../Today through Tuesday/
Issued at 330 AM CDT Wed Mar 13 2019

Very active weather over the next 24 to 48 hours as a negatively
tilted upper level trough ejects across the central Plains. At
the surface an impressive low pressure center tracks from
southeast Colorado and across Kansas. Deep southerly flow ahead of
the system feeds an unseasonably moist airmass into the region
today, aided by a 60+ knot low level jet. Moisture transport over
the top of a melting snowpack has led to the ongoing dense fog
across much of the cwa. The lowest visibilities persist into the
morning hours before gradually improving, but areas of fog between
1sm to 3sm may linger through much of the day. Gusty winds
develop by late morning and afternoon hours as the local pressure
gradient tightens in response to the deepening low. Wind Advisory
continues for areas generally along and south of I-80 where the
strongest gusts should reside. Our next round of rainfall is
already ongoing early this morning in a zone of increasing mid-
level convergence stretching across Nebraska into western Iowa.
Weak elevated instability has supported a few lightning strikes,
which will likely continue as the activity drifts off to the
north. Strongly diffluent flow aloft will support another round
of widespread showers and storms later this morning and afternoon.
Heavy rainfall is possible at times as pwats push toward
climatological maximums. Some concern that more robust deep
convection could generate sporadic gusts near or exceeding severe
limits as higher velocity mid-level winds are transported to the
surface. However this scenario remains highly conditional due to
limited instability. A more unstable environment that may support
a severe weather threat looks to hang closer to the low center in
KS/NE today. Dry slot punches through the cwa by late Wednesday
and brings a lull to most appreciable precip chances.

Intense upper level trough and attendant surface low become
stacked and begin to weaken as the system crosses the state
Thursday. Additional showers develop as more moisture wraps
around the south side of the low pressure center. Another push of
strong winds develop as the low moves east and forces a cold front
through the state. Highest confidence in advisory level winds
remains over western Iowa. Falling temperatures bring ptypes into
question by late Thursday afternoon and evening. Sporadic loss of
ice introduction in the models makes it difficult to discern
between freezing rain or snow. Regardless of ptype the qpf
intensity should be waning over this period and hopefully limit
the extent of any wintry impacts especially considering the gusty
wind potential. Best chance to see light snowfall accumulation is
generally across northwest and north central Iowa where some
impacts to travel are possible late Thursday.

Much anticipated dry and seasonable stretch of weather arrives
Friday as an expansive area of surface high pressure settles into
the region. River flooding issues continue into next week due to
runoff from the ongoing precip and widespread snowmelt.

&&

.AVIATION.../For the 18Z TAFS through 18Z Thursday afternoon/
Issued at 1213 PM CDT Wed Mar 13 2019

Strong low to lift out of the Rockies into the Plains. Widespread
LIFR/IFR visibility and ceilings to persist for much of period
across northern TAF locations but southern TAF locations will see
improving conditions as a dry slot lifts into the area.  Some
question as to how far north the improving cigs/vsbys will get so
confidence is low on cigs in later periods.  The low will lift into
NE Iowa by 18Z Thu with clouds/vsbys lowering again on the backside
of the low.  Precip should be light and strong winds are expected.

&&

.HYDROLOGY...
Issued at 330 AM CDT Wed Mar 13 2019

Widespread rainfall in excess of 1" is still possible today as
additional rounds of showers and storms move through central Iowa.
The heavy rainfall will combine with expected rapid snowmelt to
bring an increasing flood threat to much of the state through
Thursday. The flood threat will extend beyond mainstem rivers to
smaller basins and poor drainage areas as well. Conditions are
favorable for the continued development of ice jams, and
confidence is particularity high for ice jamming to occur in
typically favorable areas within the next 24 to 48 hours. This
includes the Des Moines River through Fort Dodge and the Raccoon
River from Van Meter to Des Moines. Please continue to pay
attention in the coming days for any flood warnings issued by the
NWS.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
Flood Watch through Thursday evening for IAZ004>007-015>017-
023>028-033>039-044>050-057>062-070>075-081>086-092>097.

Dense Fog Advisory until 7 PM CDT this evening for IAZ004>007-
015>017-023>028-033>038-044>048-057>060-070>072.

Wind Advisory until 7 PM CDT this evening for IAZ057>060-070>075-
081>086-092>097.

&&

UPDATE...Beerends
DISCUSSION...Martin
AVIATION...FAB
HYDROLOGY...Martin

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PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
830 PM CDT WED MAR 13 2019

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0600 PM     FLOOD            4 NE ARION              41.98N 95.41W
03/13/2019                   CRAWFORD           IA   EMERGENCY MNGR

            U.S. HIGHWAY 30 CLOSED FROM DENISON TO DOW
            CITY DUE TO FLOODING.

&&

AK

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
832 PM CDT WED MAR 13 2019

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0820 PM     FLOOD            2 N OTHO                42.45N 94.15W
03/13/2019                   WEBSTER            IA   EMERGENCY MNGR

            MOST GRAVEL ROADS CANNOT BE DRIVEN ON.
            SEVERAL BLACKTOP ROADS ARE COVERED IN WATER.
            LOW VSBY MAKING IT HARD TO SEE FLOODED
            ROADWAYS. THE COUNTY HAS TAKEN MOST UTILITY
            TRUCKS OF THE ROADS DUE TO FLOOD DANGERS.

&&

AK

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
836 PM CDT WED MAR 13 2019

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0835 PM     FLOOD            1 NNW WALLINGFORD       43.34N 94.80W
03/13/2019                   EMMET              IA   DEPT OF HIGHWAYS

            PORTIONS OF IA 4 ARE CLOSED DUE TO FLOODING.

&&

AK