Quantitative Precipitation Forecast Discussion
NWS Weather Prediction Center College Park MD
223 PM EDT Tue Apr 17 2018


Prelim Day 1 QPF Discussion
Valid Apr 18/0000 UTC thru Apr 19/0000 UTC
Reference AWIPS Graphics under...Precip Accum - 24hr


Day 1

...Northern to Central Plains---Upper MS Valley toward the lower
Great Lakes...

The next in the current series of strong areas of height falls to
move through the Rockies-Great Basin will be pushing out into the
northern to central high plains late afternoon-evening--across the
remainder of the Northern to Central Plains tonight and into the
Upper MS Valley on Wednesday.   Precipitation initially
concentrated along the north-south oriented inverted trof over
western portions of the Northern Plains early in the upcoming day
1 period will begin to concentrate farther to the southeast early
Wednesday across the lower portions of the MO River Valley into
the Upper MS Valley from northeast NE/southeast SD into northwest
IA as the height falls amplify into a closed low across these
areas.  This enhancing area of overrunning will then spread east
northeastward across the Upper MS Valley and toward the lower
Lakes Wednesday afternoon.  Snow will be the primary precip type
across these areas---with the best chance of late season heavy
snows from northeast NE...far southeast SD---across central to
northern Iowa---far northwest IL into southern WI.  For qpf
details the in house pseudo bias corrected ensemble mean was used
to mitigate any model spread the latest suite of guidance.  See
the latest QPFHSD for additional winter weather information.

...Northern NY state into northern New England...

The deep layered cyclone initially over northern New
England-southeast Canada will lift slowly northeast day 1 into the
Canadian Maritimes.  Scattered rain and snow showers possible
underneath the upper trof---with the best chances of any
measurable precip from northern NY state into northern New England.

...Northern California into the Pacific Northwest...

The third in the series of strong systems to affect the western
U.S. will push from the northeast Pacific and toward Northern
California this period.  At the moment---the timing of this system
should keep the most organized precip offshore through day 1 with
a greater inland push of precip likely across California into the
Great Basin day 2.  Subsequently for day 1---mostly light precip
amounts expected from the Washington-Oregon Cascades west to coast
range and into northern California.

Oravec