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Day 2 Outlook >
WPC Day 1 Excessive Rainfall Outlook
Risk of 1 to 6 hour rainfall exceeding flash flood guidance at a point
Updated: 0059 UTC Thu Dec 13, 2018
Valid: 01 UTC Dec 13, 2018 - 12 UTC Dec 13, 2018
Day 1 Excessive Rainfall Forecast
Forecast Discussion
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
758 PM EST Wed Dec 12 2018
Day 1
Valid 01Z Thu Dec 13 2018 - 12Z Thu Dec 13 2018 


...Western Washington, including western portions of the Olympic 
A strong compact shortwave will enter the Gulf of Alaska with an 
enhanced plume of increased moisture between 00z and 12z Thursday. 
Strong southwesterly LLJ with 45-55kts of 850 hPa flow will direct 
this TPW plume (~1.0") toward far northwest Washington supports 
IVT values around 500 kg/ms.  Despite virtually no instability, 
hourly totals towards 0.5" are possible in this regime, as 
supported by the latest (18Z) HREF 40 km neighborhood 
probabilities. Snow levels of 3000-4000 ft early will climb to 
5000-6000 ft by 12Z Thu with the strong, deep-layer warm/moist 
advection. As such, WPC is maintaining a Marginal Risk of 
Excessive Rainfall over portions of western WA, at elevations 
generally below 4500 ft where the pcpn is expected to change over 
to mod-heavy rainfall later tonight. See the Probabilistic Heavy 
Snow/Icing for more details on the winter weather impact.

Day 1 threat area:

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