Quantitative Precipitation Forecast
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FOUS30 KWBC 140837
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
336 AM EST Wed Feb 14 2018

VALID 12Z Wed Feb 14 2018 - 12Z Thu Feb 15 2018


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
15 ENE SRR 35 E ALM 20 SE ALM 10 N HMN 40 W SRR 45 NW SRR
30 WNW 4CR 20 N 4CR 20 S 4CR 15 ENE SRR.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
30 S OLS 10 WNW OLS 10 SSE TUS 25 N DMA 55 W SAD 40 WNW SAD
20 W SAD 10 WSW SAD SAD 15 N SAD 35 NNE SAD 70 NE SAD 60 WNW TCS
35 WNW TCS 25 SW TCS 15 N DMN 20 W DMN 35 SW SVC 55 SW SVC
55 ENE DUG 60 E DUG 60 ESE DUG 55 SE DUG 50 SE DUG.


...Southern Arizona and Southern New Mexico...

Moisture depth and magnitude will quickly increase today as the
trough off of southern California taps into a PW plume located off
Baja. The upper air pattern is set to consolidate as northern
stream height falls expand through the Great Basin, kicking the
southern California system eastward. This large scale adjustment
will tie the Baja moisture into an extensive southwesterly flow
pattern, with the mountains in southeast Arizona and southern New
Mexico likely to intercept the core of the plume characterized by
PW values 0.75 to 1.00 inches, as many as 4 standard deviations
above climatology. The California wave, as it shears and
de-amplifies, will brush across the top of this established moist
conveyor, making for a somewhat idealized rain event, essentially
acting as an atmospheric river event.

Still, the model QPFs are not exactly overwhelming, and consensus
expectations are for amounts approaching 1 inch in the valleys and
2 or more inches atop the mountain peaks, perhaps some isolated 3
inch amounts. Occurring over 12 to 18 hours, this should not
present too much of a problem, but during the height of the event
the hi-res solutions such as the NSSL WRF produce 0.75 inch
amounts in a 3-hour period, which starts to get close to flash
flood guidance. Pattern-wise, there is at least some concern that
the event could over-perform, as the models are typically not at
their best when handling features located in the data-poor region
west of Baja. Therefore, we did introduce a Marginal Risk of
excessive rainfall for southeast AZ / southwest NM and the
Sacramento mountains in southeast NM. If rain falls heavily enough
in any given basin, rapid rises in water appear possible.

Burke

$$





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