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Quantitative Precipitation Forecast (QPF) Discussion
(Caution: Version displayed is not the latest version. - Issued 1856Z May 23, 2018)
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Abbreviations and acronyms used in this product
Geographic Boundaries -  Map 1: Color  Black/White       Map 2: Color  Black/White

Quantitative Precipitation Forecast Discussion
NWS Weather Prediction Center College Park MD
256 PM EDT Wed May 23 2018

Prelim Day 1 QPF Discussion
Valid May 24/0000 UTC thru May 25/0000 UTC
Reference AWIPS Graphics under...Precip Accum - 24hr

Day 1

...Lower MS Valley---central Gulf coast into the
Southeast/southern Mid-Atlantic,,,

Widespread scattered diurnally enhanced convection likely day 1
along and to the south of the nearly stationary frontal boundary
expected to lie from the Lower MS Valley---across the central Gulf
coastal region and into the Southeast/southern Mid-Atlantic.  With
pw values expected to remain much above average along and south of
this front---locally heavy precip totals possible---although
confidence is low with details.  One region of potential max
precip will be in the vicinity of the nearly stationary surface to
mid level circulation in the vicinity of central Georgia.  Precip
may focus near this center and then to the west southwest and
northeast along the above mentioned frontal boundary position
and/or surface trofs separate from the frontal boundary positions
emanating from this nearly stationary low. 

...Northern Rockies--- Northern Plains into the Upper MS Valley...

Height falls pushing northward Wednesday across the Northern
Rockies will move on a more east northeast track Thursday across
the Northern Plains and toward the Upper MS Valley.  The model
consensus is for the well defined comma head/deformation precip
area currently stretching from the Northern Rockies into the
Northern High Plains to weaken at the beginning of the day 1 time
period with more scattered precip near the primary height fall
center over the Northern High Plains.  At the same time---broadly
difluent upper flow downstream of these height falls will support
scattered convection from the Northern Plains into the Upper MS
Valley.  Areal average moderate precip totals depicted with
locally heavier amounts likely where convection maximizes. 

...Central to Southern High Plains...

A lee trof/dry line will extend across a large area from the
Central to Southern High Plains day 1.  The broadly difluent upper
flow expected across the Northern Plains/Upper MS Valley will also
extend southward across the Central to Southern High Plains.  This
will support widespread scattered convection---primarily during
the first 6 to 9 hours of the day 1 period tonight and then again
late Thursday afternoon.  Confidence in qpf details is low in this
flow regime with a myriad of model solutions.  The HREF mean was
used to mitigate the model to model and model run to model run
differences.  Moderate areal average amounts depicted with locally
heavier totals likely where convection maximizes.

...Northern California---portions of the Pacific
Northwest---Northern Great Basin into the Northern Rockies...

Widespread diurnally driven shower and thunderstorm activity
likely early in the upcoming day 1 time period and again late in
the period during Thursday afternoon.  PW values expected to
remain above average across these regions in the wake of the lead
area of height fall ejecting north into the Northern Rockies early
day 1 and ahead of the developing closed low off the California
coast late day 1.  Generally light to moderate totals expected
across these areas--with isolated heavier totals possible.