Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Des Moines Iowa
549 am CST Tuesday Mar 3 2015
Short term /today/...
issued at 403 am CST Tuesday Mar 3 2015
Two phase system to affect the area today. Surface low lifting
northeast into central Iowa...and precipitation will continue to
lift NE through southern/central Iowa...lifting north. Forcing with
this system quickly pushes east by 15z...and precipitation chances
will diminish quickly thereafter. Models continue to develop
precipitation across northern Iowa through the morning
hours...though do not have high confidence with lack of forcing and
moisture...and have trended precipitation down across the north for the
early morning. However...as upper level low across Canada pushes
east dropping frontal boundary into Iowa...this will bring the best
chances for precipitation across the north...with ongoing
precipitation near boundary in Dakotas. However...system will bring a
quick shot and given lack of moisture across the area at this time...have
continued to cut back on snowfall totals in the north.
Precipitation type remains challenging across southern Iowa...with
ongoing freezing rain and mixed precipitation across southern County Warning Area.
Temperatures will continue to warm in the south and will see a
transition back to rain. Will keep headline across the south as is
for now with Road conditions indicating ice generally along I-80 and
east of I-35 within the advisory area. However...may need to cut
back on western extent of advisory if precipitation does not develop
to the north. Across the north precipitation will be snow...winds
will increase significantly behind boundary and with new snow
accumulations expected...will likely see hazardous travel across the
north with limited visibilities. Therefore will keep northern
portion of headline as is...though with lower snowfall totals
expected impacts from blowing snow many be reduced.
Expect precipitation to diminish quickly after 18z as boundary
pushes in with strong subsidence. May have held onto precipitation
too long into the afternoon...though light precipitation may linger.
As boundary pushes through temperatures will drop quickly...and have
cut back on highs today...especially in the southeast with slightly
quicker progression of system.
Long term /tonight through Monday/...
issued at 403 am CST Tuesday Mar 3 2015
Longer term continues to see broad northwest flow across the eastern
Continental U.S. Although less amplified by later in the forecast period as
main jet axis shifts farther north. For tonight...cold Arctic
airmass will continue to push into the state with cold air Reservoir
dumping southward from Canada. Will see one final shortwave drop
southward into the Midwest late tonight into Wednesday morning with
another round of lift overnight into Thursday morning...especially in
southern Iowa. This will likely produce some middle to high
cloudiness overnight...however the dry and cold low level airmass
will prevent the threat of precipitation as the wave passes.
The thermal trough will be moving over the state on Wednesday night
with one final night of below zero readings for much of the forecast
area. Thereafter...warm advection is expected into Friday before a
minor cool down into Saturday followed closely by warming into early
next week. In general...an upward trend to much more normal
readings by next week. There will be little threat for
precipitation as main storm path is expected to be north of the
issued at 542 am CST Tuesday Mar 3 2015
Low pressure system bringing freezing rain to southern sites kotm/kdsm and
MVFR ceilings and visibilities to sites will continue to pull
east with conditions improving early in the period.
However...additional snow will be possible across the north near
18z. Winds will become northwesterly and increase behind boundary
at sites. Winds will be sustained near 15-20kts with gusts up to
30kts or higher at times...especially in the north. This may lead
to blowing snow across northern sites reducing visibilities
through 00z. Conditions will improve to VFR behind boundary
beyond 00z...though winds will remain strong and gusty.
Winter Weather Advisory until 8 am CST this morning for
Winter Weather Advisory from 9 am this morning to 9 PM CST this
evening for Black Hawk-Bremer-Butler-Cerro Gordo-Emmet-Franklin-