Quantitative Precipitation Forecast Discussion
NWS Weather Prediction Center College Park MD
224 PM EDT Fri Apr 20 2018


Prelim Day 1 QPF Discussion
Valid Apr 21/0000 UTC thru Apr 22/0000 UTC
Reference AWIPS Graphics under...Precip Accum - 24hr


Day 1

...Lee of the Central Rockies---Central to Southern Plains...

A much needed widespread moderate to heavy precipitation event
likely day 1 from the lee of the central Rockies---southeastward
through large portions of the Central to Southern Plains.  Strong
height falls moving east from the four corners region this
afternoon--across the central to southern Rockies evening and into
the Central to Southern Plains tonight into Saturday will help
draw increasingly anomalous pw values northward as low level
southerly to southeasterly flow strengthens across the Central to
Southern Plains.  Strong upper difluence ahead of this closed low
in this increasingly anomalous pw axis will support the likelihood
of widespread moderate to heavy totals.  There is some latitude
differences with the max precip amounts.  WPC qpf did favor the
farther south axis of the CMC GEM and hi-res ARW across southern
OK and north TX---closer to the west to east oriented frontal
boundary across north TX.  With recent dry conditions and the
overall expected progressive nature of the organized heaviest
precip---do not believe there will be any runoff issues at the
moment.  Areal average 1 to 1.5 totals depicted in the max precip
area over much of OK into north TX---with lighter totals in the 
.25-.50"+ range extending north and northwest of this into the
Central Plains and lee of the Central Rockies.

...Pacific Northwest into the Northern Rockies...

A fast moving area of strong northeast Pacific height falls will
be moving inland along the Washington---B.C.---Idaho border region
tonight/early Saturday and into southern Alberta later Saturday. 
An area of organized precip along and ahead of the associated
frontal boundary will support moderate to heavy precip totals over
the northern Washington Cascades---Olympic Range and into far
southwest B.C. and Vancouver Island.  Lighter precip totals
expected south into the Southern Washington-Oregon Cascades---west
to the coast ranges and into the Northern Rockies from far
northern ID into northwest MT.

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

The broad closed low moving into the Canadian Maritimes this
afternoon will continue to progress across New Newfoundland
tonight and over the far northwest Atlantic during Saturday.  The
persistent cyclonic flow in its wake will support scattered snow
showers from northern NY state into northern New England.  Any
precip/snow amounts are expected to be very light.


Oravec