Quantitative Precipitation Forecast
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000
FXUS04 KWBC 171949
QPFPFD

Quantitative Precipitation Forecast Discussion
NWS Weather Prediction Center College Park MD
348 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 series of mid-level shortwaves moves through the
Rockies-Great Basin into the northern/central high plains late
this afternoon and evening engulfing the region tonight before
moving into the Upper MS Valley on Wednesday.   Precipitation
concentrated along the meridionally-oriented inverted trough over
western Northern Plains early on will shift southeast early
Wednesday across the lower portions of the MO River Valley/Upper
MS Valley as the shortwave strengthens into a mid-level closed
low.  The enhancing area of overrunning spreads east-northeast
across the Upper MS Valley toward the lower Great Lakes Wednesday
afternoon within a region of low- to mid-level frontogenesis.
Snow will be the primary precipitation type across these
areas---with the best chance of late season heavy snows from
northeast NE...far southeast SD---central to northern Iowa---far
northwest IL into southern WI.  The precipitation forecast relied
upon the in house experimental bias corrected ensemble mean and
12z ECMWF to mitigate recent model spread.  See the latest
QPFHSD/Heavy snow and icing discussion for additional winter
weather details.


...Northern NY state into northern New England...
The deep layer cyclone over northern New England-southeast Canada
lifts slowly northeast into Atlantic Canada.  Scattered rain and
snow showers possible underneath the upper trough, 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 Wednesday afternoon.  The expected timing of this
system should keep the most organized precipitation offshore until
Wednesday night when a greater inland push is likely across
California into the Great Basin.  Mostly light precipitation
amounts are expected from the terrain of western OR and WA into
northern California.  The precipitation forecast here trended
towards a 12z GFS/12z ECMWF compromise.


Roth/Oravec

$$





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