Quantitative Precipitation Forecast Discussion
NWS Weather Prediction Center College Park MD
232 PM EDT Tue May 08 2018


Prelim Day 1 QPF Discussion
Valid May 09/0000 UTC thru May 10/0000 UTC
Reference AWIPS Graphics under...Precip Accum - 24hr


Day 1

...Eastern portions of the Northern Plains---Lower MO Valley into
the Upper MS Valley...

Convection is developing in southwest MN and northwest IA along an
area identified by the recent RAP analyses and forecasts as
frontogenetical. Coverage of showers/storms is expected to
continue increasing this afternoon and evening as the region of
well defined upper difluence in advance of the upper trough in an
axis of pw values of 1.2-1.4 inches and lifted indices of -2 to -4
in Iowa this evening.  Showers/embedded storms are expected to
continue in the coupled upper divergence/lower convergence maxima
across IA,southern MN, southwest WI, northwest IL and into
northeast MO.  Widespread moderate to heavy precip totals likely
across these areas along with potential for isolated runoff issues
where convection briefly trains.   Shower and storms redevelop in
the low level axis of inflow and instability Wed in WI and IL
across Lake MI to lower MI.  Manual QPF blended continuity with
the global/Canadian regional GEM and high res ARW/ ARW2/ NMMB
models.


...Pacific Northwest to the Northern Rockies...

The closed low off the Pacific Northwest coast will be moving
northeastward to the west of Vancouver Island by the end of the
period.  Organized precipitation along the associated frontal
boundary will begin to affect the coastal Pacific Northwest
Tuesday afternoon---moving farther inland through the Pacific
Northwest Tuesday night-early Wednesday and toward the far
northern Rockies by the end of the day 1 period.  Model consensus
is for widespread moderate precipitation totals from the
Washington-Oregon Cascades--west to the coast ranges and over the
Blues of northeast Oregon and far southeast Washington---with the
day 1 WPC qpf close to the multi-model consensus.


Petersen