Wettest Winter on Record at PDX

February 17, 2016

10pm Wednesday…

We only had one lightning strike today…near Crown Point, but at least we got a rain record out of the evening downpours!  As of 9pm it’s the wettest December-February (meteorological winter) on record at PDX.

MarkRain_WettestWinter

As you see, the records go back 78 years.  What a soaker and of course we still have another 12 days to go.  So we’ll go well beyond that record.

Speaking of rain; very good news up in the Willamette River watershed.  The reservoirs are filling right on time this year.

MarkDetroitLake_WillametteReservoirs_FillingUp

The whole system is at 26% of it’s full “summer level”.  Sounds low right?  But that’s normal because the Army Corps of Engineers keeps reservoirs low in the winter.  Then around February 1st, as peak flood season passes, they start holding back water the last part of winter and capture the spring snowmelt too.  They started a little early at Detroit Lake in mid January; in the past 30 days the level has risen 45 feet!  It took until early April last year to get to this level…big improvement.  And this year we have a bunch of snow in the Cascades so there WILL be a healthy spring melt.  BIG PICTURE:  WATER ACTIVITIES ON THESE RESERVOIRS SHOULD BE IN GOOD SHAPE THIS COMING SUMMER.

Chief Meteorologist Mark Nelsen


Thunderstorms: Could Be a Wild Afternoon

February 17, 2016

9:45am Wednesday…

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.

Capture

Highlights:

  • 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!

hrrr_cape_portland_9.png

Our RPM, which isn’t always a stellar performer, has that convective look to the cold front at 4pm:

rpm_precip

 

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