I’ve got an important haircut to get to (critical for this job), but I wanted to let you know we could see some exciting stuff this afternoon first. A cold front moves across our area this afternoon and along with warm southerly flow plus arriving cool air above, we could see thunderstorms pop up. Models have been showing this for almost two days but this morning I see SPC (Storm Prediction Center) has put us in a MARGINAL threat area for severe thunderstorms west of the Cascades.
- Expect warm temperatures midday/early afternoon as the south wind arrives…around 60 degrees. Both our RPM model and WRF-GFS put us up to around 65 early afternoon!
- A line of heavy showers/thundershowers develop and/or move from SW to NE across the Willamette Valley and SW Washington in the mid/late afternoon (3-6pm).
- Thunder and/or hail is possible as this line of showers moves over.
- A strong southerly wind burst may accompany the showers as well. S/SW wind gusts 30-40 mph possible. Likely just in spots where the showers are heavy.
- It’ll finally feel like winter (the stormy part) for a few hours!
We have a nice low lifted index showing up on models at 4pm, lots of CAPE too. HRRR has the CAPE up over 1000 j/kg in the Willamette Valley mid/late afternoon!
Our RPM, which isn’t always a stellar performer, has that convective look to the cold front at 4pm:
Here’s the SPC discussion:
...SUMMARY... ISOLATED THUNDERSTORMS ARE EXPECTED FROM SOUTHWEST WASHINGTON SOUTHWARD INTO CENTRAL CALIFORNIA...A FEW OF WHICH COULD PRODUCE LOCALLY DAMAGING WIND. ...SYNOPSIS... AMPLIFIED BUT PROGRESSIVE PATTERN WILL PERSIST ACROSS NOAM THROUGH THE PERIOD. DEEP LOW NOW CENTERED NEAR 42N/135W EXPECTED TO DEVOLVE INTO A STRONG...SLIGHTLY NEGATIVELY TILTED TROUGH THAT SHOULD EXTEND FROM CNTRL CA TO JUST OFF THE ORE CST BY 12Z THU AS DOWNSTREAM RIDGE ADVANCES E INTO THE PLNS. AT LWR LVLS...COLD FRONT/OCCLUSION WITH PAC SYSTEM SHOULD REACH THE ORE/NRN CA CST AROUND 21Z AND CONTINUE EWD ACROSS THE CSTL RANGES A BIT LATER WHILE WEAKENING. A SECONDARY FRONT/TROUGH LIKELY WILL APPROACH THE CST TOWARD 12Z THU. ...N PAC CST THROUGH PERIOD... MOISTURE AND DEEP SLY FLOW WILL SUBSTANTIALLY STRENGTHEN ALONG THE ORE/NRN CA CST LATER TODAY AS FRONTAL ZONE NEARS REGION. LOW TO MID-LVL LAPSE RATES LIKELY WILL REMAIN MODEST /JUDGING BY CHARACTER OF FRONTAL CLOUD BAND NOW OVER THE PACIFIC/. NEVERTHELESS...WITH PW INCREASING TO AROUND 0.75 INCH...POCKETS OF SFC HEATING...AND DEEP UPLIFT STRENGTHENING WITH THE ARRIVAL OF THE FRONT...ISOLD THUNDER MAY DEVELOP ALONG AND AHEAD OF BOUNDARY. STRONG LOW TO MID-LVL WIND FIELD MAY FOSTER DEVELOPMENT OF OCCASIONAL SMALL BOWING SEGMENTS AND SHORT-LIVED LOW-LVL ROTATION IN SHOWERS/STORMS...ESPECIALLY ALONG THE NRN CA/ORE CST...AND IN THE WILLAMETTE VLY. WEAK BUOYANCY...HOWEVER...SHOULD LIMIT INTENSITY/DURATION OF ANY ASSOCIATED SVR THREAT. WDLY SCTD TSTMS SHOULD FOLLOW FRONTAL BAND OVER A LARGER REGION FROM SW WA SWD INTO CNTRL CA THIS EVE AND TNGT...AS MID-LVL TEMPS COOL TO AOB MINUS 25C AND ONSHORE MARITIME FLOW STRENGTHENS IN WAKE OF FRONT. SMALL HAIL MAY ACCOMPANY STRONGER/LONGER-LIVED UPDRAFTS. Of course now that I've brought this to your attention, we'll probably only see a few heavy showers and nothing happens. Or...we'll see! Chief Meteorologist Mark Nelsen