Quantitative Precipitation Forecast
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FXUS04 KWBC 131817

Quantitative Precipitation Forecast Discussion
NWS Weather Prediction Center College Park MD
217 PM EDT Fri Apr 13 2018

Prelim Day 1 QPF Discussion
Valid Apr 14/0000 UTC thru Apr 15/0000 UTC
Reference AWIPS Graphics under...Precip Accum - 24hr

Day 1

...Lower Arkansas Valley---Lower MS Valley---Mid to Lower TN
Valley---Lower OH Valley

The strong central Plains closed low and the trailing trof into
the Southern Plains will be pushing steadily eastward day 1--with
overall good agreement with the evolution of this system.
Widespread heavy precipitation likely in the what will be an
increasingly well defined convective component pushing out of the
eastern portions of the Southern Plains into the lower MS Valley
tonight--eastward into the TN Valley-central Gulf coastal region
during the day on Saturday.  With pw values expected to rise to 2
to 2.5+ standard deviations above the mean in an axis of strong
low level south southwest flow--strong frontal convergence and
well defined upper difluence---confidence is high for the heavy
rainfall potential across these areas.  The uncertain parts of the
forecast continue to be the details with respect to the timing and
exact evolution of this convection. The latest hi res guidance is
showing a typical amount of variability run to run with how fast
this convection moves downstream.  Day 1 qpf leaned initially
toward the arw and nssl wrf runs for details at the beginning of
the day 1 period---and then more toward the href mean later in the
period when some of the timing differences become more acute
between each model cycle.  Widespread 1-2" areal average precip
values depicted across these regions with locally heavier totals
where training may occur.  At the moment---best chance of training
may be at the beginning of this day 1 time period in the 0000 utc
to 1200 utc Sat period.  In areas of training totals in the 3-5"+
range are possible.

...Central to Northern Plains---Upper MS Valley---Great Lakes into
northern NY state and northern New England...

A well defined northern precipitation max likely to the north and
northeast of the strong plains closed low in the comma
head/deformation precip band to the north and northwest of the
closed low along and north of the strong west to east frontal
boundary stretching from the Mid MS Valley into the Great Lakes.
Aside from some shorter term detail differences in the qpf---there
is good agreement in the axis of what will likely be a very broad
region of heavy precipitation oriented west to east across these
regions.  Heavy early season spring snows likely in a large
portion of the comma head/deformation precip area over northwest
KS---central to northeast NE---southeast SD into southern MN.
Heavy snows also possible on the northern edge of the overrunning
precip to the north of the strong west to east front across the
northern U.P. of MI into far northern NY state and northern New

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

A northeast Pacific cold front will be pressing slowly
southeastward day 1 toward the Pacific Northwest coast.  This will
keep a sustained period of moist southwest low level flow into the
Pacific Northwest--Northern Rockies region day 1.  There is high
confidence for heavy precip values through the Washington Cascades
west to the northern Oregon coast range into the Olympic
Range---with very good model agreement on amounts and
distributions.  Inland into the Northern Rockies---precip totals
not expected to be as heavy---with model consensus for moderate to
locally heavy totals from the Blues of northeast Oregon into
northern ID.



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