Subj : HVYRAIN: Excessive Rainfall Discussion
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Fri Dec 29 2023 00:01:49

FOUS30 KWBC 290001
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
700 PM EST Thu Dec 28 2023

Day 1
Valid 01Z Fri Dec 29 2023 - 12Z Fri Dec 29 2023


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

Taylor


Day 2
Valid 12Z Fri Dec 29 2023 - 12Z Sat Dec 30 2023

....THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FOR NORTHERN
CALIFORNIA AND SOUTHWEST OREGON...

....20Z Update...

No changes to the previous forecast issuance as guidance maintains
continuity through the time frame with regards to precip timing,
placement, and forecast QPF. NBM has remained consistent with the
axis of highest probabilities for at least 2" along the coast from
Eureka down into San Francisco, as well as around the hills of
Mount Shasta and areas northwest of Reading. Rates will be
generally maxed at 0.5-0.75"/hr, but wet antecedent conditions
along with prolonged moderate to heavy rainfall over a 6-10 hr
time frame will lead to some localized flooding concerns on the
lower end of the MRGL risk category. There is merit to the
positioning based on both the probabilistic sense, as well as the
UFVS First Guess Fields.

Kleebauer


....Previous Discussion....

An atmospheric river will ensue Friday afternoon through Saturday
morning across portions of southwest Oregon and northern
California before waning in intensity and shifting focus
southward. The latest guidance has areal averages of 1 to 3 inches
and the NBM neighborhood probability of at least 2" is fairly
robust across the northern CA coast (70+%), with the highest
totals generally between Eureka and San Francisco. The risk for
local flooding concerns will remain elevated for this part of the
country so the Marginal Risk area remains in effect for this
period.

Campbell






Day 3
Valid 12Z Sat Dec 30 2023 - 12Z Sun Dec 31 2023

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

Campbell/Kleebauer


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/94epoints.txt__;!!DZ3fjg!_pWuLDOsBFCoI6PUhub3dH2zTDql7sDsgnEZ1LsXoWih=
svtVJHPRDRIHHlexNQLEhm7VQNwQfcqUNa0cpyYFhODO_i4$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/98epoints.txt__;!!DZ3fjg!_pWuLDOsBFCoI6PUhub3dH2zTDql7sDsgnEZ1LsXoWih=
svtVJHPRDRIHHlexNQLEhm7VQNwQfcqUNa0cpyYFAHq-xkg$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/99epoints.txt__;!!DZ3fjg!_pWuLDOsBFCoI6PUhub3dH2zTDql7sDsgnEZ1LsXoWih=
svtVJHPRDRIHHlexNQLEhm7VQNwQfcqUNa0cpyYFKU4R7Iw$=20


$$



=3D =3D =3D
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