Quantitative Precipitation Forecast Discussion
NWS Weather Prediction Center College Park MD
255 PM EDT Sun Apr 22 2018


Prelim Day 1 QPF Discussion
Valid Apr 23/0000 UTC thru Apr 24/0000 UTC
Reference AWIPS Graphics under...Precip Accum - 24hr


Day 1

...Lower Ohio Valley---TN Valley--Southern Appalachians into the
Southeast...

There are no significant model differences with the evolution of
the strong closed low moving slowly from the Lower MS Valley into
the TN Valley this period.  A stream of much above average pw
values will continue to be entrained into this
circulation---supporting widespread heavy precipitation potential
in a region of well defined upper difluence ahead of this
circulation.  There is good model qpf agreement with the overall
heavy precip distribution.  One max region expected in the comma
head/deformation precip area to the north of the closed low track
from the TN Valley to the OH Valley---with 1 to 1.5"+ areal
average totals depicted.  A more convective precip max expected
farther to the southeast from eastern Gulf coast into the
Southeast.  Max values across this region likely across the
southern Appalachians from northeast GA----the Upstate of SC into
western NC where strong southeasterly upslope flow will persist
for most of this period. Rainfall totals in excess of 5" likely
across the southern Appalachians.  While one max precip area is
likely over the southern Appalachians---another precip max
possible along the southeast coast in the vicinity of the upper
GA/SC coast where strong onshore in an axis of greater instability
extending north from FL will persist.  Here 2-3"+ totals possible.

...Northern Rockies into the northern High Plains...

Shortwave energy moving through the Pacific Northwest Sunday
afternoon expected to amplify across the Northern Rockies-northern
High Plains region Sunday.  Strengthening upper difluence and low
level upslope north northeasterly flow will support increasing
precipitation  coverage early Monday across portions of the
Northern Rockies into the northern High Plains.  Model consensus
is for moderate to heavy precip totals from far northeast ID---far
northwest to northern  WY and across the southern portions of MT. 
Early spring heavy snows likely across the northern Rockies of
northwest WY into southern MT.  See the latest QPFHSD for
additional winter weather information.

Oravec