Yesterday the cutoff low spinning off the coast of Oregon/NCalifornia contributed to the front that brought thunderstorms to WWA. Today the cutoff low has halted its southward advance and has reversed direction ... it is heading northeast into Washington tomorrow to be reabsorbed by the jet stream.
The low is packing a lot of moisture and lift ... Friday should be very wet in WWA with some areas in the central Sound and along the Cascades seeing up to an inch of rain. The GFS MOS for KSEA gives 0.25 - 0.5 inches for tomorrow. Although conditions won't be as unstable as yesterday, thunderstorms could pop up easily. GFS MOS has tstorm odds at 34%.
Prepare for some heavy rain tomorrow ... should be a nice temporary reprieve from the drought!
Thursday, August 13, 2015
Saturday, June 27, 2015
Weekend convection + 4thofJulycast
Here's the story:
* Near record highs today
* Decent chance of thunderstorms tonight and Sunday
* Very warm overnight temperatures due to daytime heat and impressive humidity!
* 4th of July is looking warm and dry!
We have a strong ridge pushing up along the west coast and an upper level low (see image below) parked off the coast of California leading to impressive warm air + moisture advection.
See current 300mb upper level image:
This pattern will support high temps in the Puget Sound and help advect monsoonal moisture into the area. Dewpoints in the 60s will give an 'east coast' feel to the air today through Sunday. Tonight and Sunday we have a good chance of thunderstorms ... lifted indices above 0 supported by unstable atmosphere in the mid-levels (todays 12z sounding at UIL below shows the conditionally unstable conditions above 800 mb ... almost dry adiabatic lapse rate from 600 - 500 mb):
Good chance of record highs today, and high humidity with dewpoints in the low 60s (see GFS MOS ensemble stats below). With increasing vorticity advection and upper level divergence as the jet streak associated with the cutoff low moves northeast, there will be plenty of support to fire off convection over WWA. Thunderstorms should be most active along Cascades, where lifting flow can fire off convection ... also lines of tstorms should fire off along lines of upper level divergence associated with the jet streak. The trough moves east Monday morning, bringing in a surge of marine air that will cool us down for Monday and Tuesday. The GFS ensemble MOS output is here:
High chance of precip (relatively) Sunday - Monday associated with the passing of the trough + convection. After a slight 'cool down' another ridge forms leading to high temps Wed - Fri. Looks like another weak surge of onshore flow + marine layer for morning of the 4th of July, then quick burnoff with warm/dry 4th of July evening!
* Near record highs today
* Decent chance of thunderstorms tonight and Sunday
* Very warm overnight temperatures due to daytime heat and impressive humidity!
* 4th of July is looking warm and dry!
We have a strong ridge pushing up along the west coast and an upper level low (see image below) parked off the coast of California leading to impressive warm air + moisture advection.
See current 300mb upper level image:
This pattern will support high temps in the Puget Sound and help advect monsoonal moisture into the area. Dewpoints in the 60s will give an 'east coast' feel to the air today through Sunday. Tonight and Sunday we have a good chance of thunderstorms ... lifted indices above 0 supported by unstable atmosphere in the mid-levels (todays 12z sounding at UIL below shows the conditionally unstable conditions above 800 mb ... almost dry adiabatic lapse rate from 600 - 500 mb):
Good chance of record highs today, and high humidity with dewpoints in the low 60s (see GFS MOS ensemble stats below). With increasing vorticity advection and upper level divergence as the jet streak associated with the cutoff low moves northeast, there will be plenty of support to fire off convection over WWA. Thunderstorms should be most active along Cascades, where lifting flow can fire off convection ... also lines of tstorms should fire off along lines of upper level divergence associated with the jet streak. The trough moves east Monday morning, bringing in a surge of marine air that will cool us down for Monday and Tuesday. The GFS ensemble MOS output is here:
High chance of precip (relatively) Sunday - Monday associated with the passing of the trough + convection. After a slight 'cool down' another ridge forms leading to high temps Wed - Fri. Looks like another weak surge of onshore flow + marine layer for morning of the 4th of July, then quick burnoff with warm/dry 4th of July evening!
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