Subj : HVYRAIN: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Sat Feb 18 2023 06:53:28

FOUS30 KWBC 180653
QPFERD
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
152 AM EST Sat Feb 18 2023

Day 1
Valid 12Z Sat Feb 18 2023 - 12Z Sun Feb 19 2023

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Gallina


Day 2
Valid 12Z Sat Feb 18 2023 - 12Z Sun Feb 19 2023

....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR FAR
SOUTHEAST ARIZONA/SOUTHWEST NEW MEXICO...

A compact, highly anomalous closed low will drop southwest of Baja
California by late Saturday into Sunday with height anomalies
around 4 to 4.5 standard deviations from monthly climatological
norms.  As such, sub-tropical moisture will stream northeastward
out of the subtropical East Pacific with total PWat Values over
1.25" streaming northeastward across central Baja California
directed toward the terrain of northeast Sonora and northwest
Chihuahua, values are 2.5-3 Std Dev from mean, though total
moisture flux with IVT values of 400-500 kg/m/s forecast into the
terrain of Mexico, bleeding into far SE Arizona and far SW New
Mexico.   This high anomaly strongly suggests the potential for
intense rainfall at times, with a solid duration throughout the
day focused on the terrain which may result in localized flooding
concerns with guidance suggesting 2-3" totals through 24hrs ending
at 20.12z, particularly the 00z Hi-Res CAM solutions.

However, the angle/orientation of the moisture flux relative to
the Northwest Mexican coast and strength of downstream ridging
will determine the placement of the plume.  NAM, NAM-Conest, and
ARW2 solutions suggest greater ridging and a more northward angle
to the plume allowing for increased rainfall risk to SE AZ/SW NM,
though GFS/ECMWF and ARW/HRRR suggest axis intersecting the
terrain remains just south of the AZ/NM boarder in Mexico with
these enhanced rain areas.  This remains solid latitudinal spread,
but given the near record moisture and flux potential and desert
ground conditions, even modest rainfall totals may still pose a
low-end risk for flooding particularly if the persistence on one
or two ridges/ranges allows for those max totals near 2-3".  In
coordination with local forecast offices, have introduced a small
Marginal Risk... which may need to be further expanded northward
with subsequent model trends and increased hi-res CAM solutions.=20

Gallina/Wegman

Day 3

The Day 3 outlook will be updated by 0830Z.


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/94epoints.txt__;!!DZ3fjg!_JjNtShypyWO9-M8vC7N85TTdvCr4t2z54Q9rgfCCP0m=
Sg3XKjjQMqXGugKPNMh1WDaOHEfaUr1y0ruTdjNG5YcaE2U$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/98epoints.txt__;!!DZ3fjg!_JjNtShypyWO9-M8vC7N85TTdvCr4t2z54Q9rgfCCP0m=
Sg3XKjjQMqXGugKPNMh1WDaOHEfaUr1y0ruTdjNG3gKA_V4$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/99epoints.txt__;!!DZ3fjg!_JjNtShypyWO9-M8vC7N85TTdvCr4t2z54Q9rgfCCP0m=
Sg3XKjjQMqXGugKPNMh1WDaOHEfaUr1y0ruTdjNGFZt9oFo$=20


$$



=3D =3D =3D
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