Severe Thunderstorm Warning 1, NWS Sacramento, CA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
947 AM PST TUE FEB 19 2013

.SHORT TERM DISCUSSION...

UPPER IMPULSE THAT WAS OVER 50N/135W YESTERDAY HAS DROPPED SWD TO
JUST NEAR THE SFO BAY AREA AS OF MID MORNING. SURFACE FRONT HAS ALSO
PUSHED INLAND WITH THE UP VALLEY PRESSURE GRADIENTS INCREASING TO
ALMOST 6 MBS FROM RDD TO SAC. WE DID A QUICK MORNING UPDATE TO
INCREASE THE WIND SPEEDS UNTIL FROPA THIS AFTERNOON. THE WINDS IN
THE N END OF THE VALLEY SHOULD DECREASE THIS AFTERNOON WHILE THERE
SHOULD BE WINDS PICKING UP THROUGH THE DELTA AND SRN SAC VLY.

PREFRONTAL PRECIP MAKING ITS WAY ACROSS THE VALLEY AND INTO THE
SIERNEV...DELTA AREA...AND SAC AREA AT PRESS TIME...IS FORECAST BY
THE RUC TO BECOME N-S ORIENTED OVER THE SIERNEV BY LATE AFTERNOON
AND INTO EVENING. SO SNOWFALL IS EXPECTED TO PICK UP OVER THE
SIERNEV...AND CONTINUE INTO EVENING...BEFORE BEGINNING TO DECREASE
AFTER 03Z-04Z OR SO. PRECIP WILL THEN TAPER OFF AND TURN SHOWERY
OVER THE VALLEY AND COASTAL RANGE BEHIND THE PREFRONTAL BAND. GIVEN
THIS TIMING...THE ADVISORY FOR THE SIERNEV LOOKS GOOD...WITH THE
ADVISORY FOR THE SHASTA AND COASTAL RANGE POSSIBLY EXPIRING WITH THE
AFTERNOON PACKAGE. SNOW PROFILERS AND SPOTTER REPORTS INDICATE THE
SNOW LEVEL IS ABOUT 2000 TO 2500 FT...WITH A FEW REPORTS DOWN TO
1500 FEET OVER THE COASTAL RANGE AS THE COLD MID LEVEL IMPULSE DROPS
SWD.

THE UPPER IMPULSE IS PROGGED TO DIG INTO THE BASE OF THE TROF OVER
THE WRN STATES WITH THE COLD POCKET MAINLY TRACKING ACROSS THE
COASTAL RANGE. CAN'T RULE OUT A THUNDERSTORM OR TWO...BUT LOOKING AT
THE BUFKIT FORECAST SOUNDINGS AND RAOB RECONSTRUCTION...WE NEED TO
WARM INTO THE LOW TO MID 50S TO GET SUFFICIENT CAPE OF A FEW HUNDRED
J/KG IN THE VALLEY...AND THE AIR MASS WILL BE COOLING TOO RAPIDLY
BEHIND THE FRONT. DURING THE AFTERNOON...THE SHEAR VALUES ALSO
LOOK TOO LOW FOR SEVERE WX. MANY OF THE SHOWERS THOUGH ARE LIKELY
TO CONTAIN SMALL HAIL/GRAUPEL.

MOISTURE IS LIMITED WITH THIS SYSTEM WITH VERY LOW PWS OF .40 TO .50
INCHES SO THE SHOWERS ARE QUITE SCATTERED UNDER THE IMPULSE AND
SHOULD REMAIN THAT WAY TODAY. BEST CLOUD ENHANCEMENT IS OVER THE
NERN QUARTER OF THE FORECAST AREA IN THE DIFFLUENT UPPER FLOW FROM
THE LOW. THIS IS LIKELY TO SHIFT SWD AND HIT THE 80/50 CORRIDOR AND
AREAS SWD THIS AFTERNOON AND EARLY EVENING. GIVEN THE UPPER
DIFFLUENCE OF THE 500 MBS FLOW AND OROGRAPHICS...ALBEIT FOR A
LIMITED TIME...THE HEAIEST QPF WILL BE OVER THE W SLOPE SIERNEV
WHERE WIDESPREAD QPFS OF .50 INCHES...LOCAL AMOUNTS UP TO AROUND .90
INCHES...AND ISOLATED 1.0 INCHES ARE FORECAST. 6 TO 10 INHCES OF
SNOW STILL LOOKS GOOD FOR THE SIERNEV.      JHM

.PREVIOUS DISCUSSION...

SATIMG SHOWS DEEP TROUGH DIGGING SOUTHWARD TOWARD NORCAL EARLY
THIS MORNING WITH LOTS OF COLD-AIR CUMULUS AROUND THE LOW CENTER
OFFSHORE OREGON. BLENDED PW PRODUCT INDICATES LIMITED MOISTURE
WITH THE SYSTEM WITH PW OF ONLY 0.40 TO 0.50 INCHES. SCATTERED
LIGHT SNOW SHOWERS DEVELOPED DURING THE OVERNIGHT HOURS ACROSS THE
NORTHERN SIERRA AS THE UPPER FRONT AND ITS ASSOCIATED MID/UPPER
LEVEL JET PROVIDED ENOUGH LIFT...BUT ELSEWHERE SKIES HAVE BEEN
PARTLY CLOUDY WITH SOUTHERLY BREEZES PICKING UP IN THE SACRAMENTO
VALLEY.

TIMING STILL LOOKS GOOD FOR THE MAIN FRONTAL BAND OF SHOWERS TO
MOVE INLAND ACROSS NORCAL AROUND MIDDAY. RADAR SHOWS THE BAND
MOVING ONSHORE NW CA ATTM. THE STRONG DYNAMICS AND STRONG CAA
WILL LEAD TO SOME DECENT QPF WITH HIGHER THAN NORMAL SNOW-LIQUID
RATIOS. STEEPENING LAPSE RATES WILL LEAD TO CONVECTIVE ENHANCEMENT
OF SNOWFALL OVER THE REGION INTO THIS EVENING. LATEST HI-RES NAM
CROSS-SECTIONS INDICATE SNOWFALL WILL INCREASE ALONG I-80 OVER THE
NORTHERN SIERRA THIS MORNING AND CONTINUE INTO THIS EVENING.
SNOWFALL TOTALS OF 10 TO 12 INCHES WITH LOCALLY HIGHER AMOUNTS
WILL BE POSSIBLE ABOVE ABOUT 4000 FEET WITH LIGHTER ACCUMULATIONS
EXTENDING DOWN INTO THE FOOTHILL ELEVATIONS.

POTENTIAL FOR THUNDERSTORMS IS GOOD WITH THE UPPER LOW MOVING
THROUGH THIS AFTERNOON. 500 MB TEMPS FORECAST TO BE VERY COLD...
-30C TO -35C AS THE LOW MOVES OVERHEAD AROUND 00Z WED. LACK OF
SUSTAINED SURFACE HEATING DUE TO CLOUD COVER AND WEAK SHEAR
PARAMETERS DUE TO THE LIGHTER WINDS NEAR THE UPPER LOW CENTER WILL
LIMIT SEVERE POTENTIAL TODAY. HOWEVER...IT DOES LOOK LIKE LOW-
TOPPED STORMS THAT DEVELOP WILL BE ACCOMPANIED BY COPIOUS AMOUNTS
OF SMALL HAIL.

SYSTEM DROPS QUICKLY SOUTH OF THE REGION TONIGHT WITH SHOWERS
EXPECTED TO TAPER OFF FROM THE NORTH DURING THE EVENING. SHORT-
WAVE RIDGING WEDNESDAY IS EXPECTED TO PROVIDE A MOSTLY DRY DAY FOR
NORCAL THOUGH A FEW SHOWERS WILL BE POSSIBLE ACROSS THE HIGHER
TERRAIN. ANOTHER IMPULSE (WEAKER) IS FORECAST TO DROP SOUTHWARD
ALONG THE COAST WEDNESDAY NIGHT...THOUGH THERE IS MORE UNCERTAINTY
WITH THE TRACK OF THIS FEATURE...BRINGING WITH IT A CHANCE OF
SHOWERS. RIDGING OVER THE AREA THURSDAY AND FRIDAY ARE EXPECTED TO
LEAVE MOST OF THE AREA DRY...THOUGH MOISTURE SPILLING OVER THE
RIDGE MAY BRING SOME SHOWERS TO THE NORTHERN MOUNTAINS.

.EXTENDED DISCUSSION (SATURDAY THROUGH TUESDAY)

EXTENDED MODELS STILL STRUGGLE TO CAPTURE DETAILS OF THE UNSETTLED
WEATHER PATTERN IN THE EXTENDED FORECAST. ANOTHER TROUGH SYSTEM
WILL DROP INTO THE PACIFIC NORTHWEST FRIDAY NIGHT INTO SATURDAY
AND THE BASE OF THE TROUGH WILL IMPACT NORCAL. THE ECMWF MODEL
SUGGESTS A DEEPER TROUGH EXTENDING TOWARDS SOCAL WHILE THE GFS AND
GEM SHOW THE BASE OF THE TROUGH BRUSHING NORCAL THEN DEEPENING
DEEPENING OVER THE GREAT BASIN. DRIER FOR MOST OF OUR CWA BY SUNDAY
AFTERNOON THOUGH LINGERING SHOWERS ARE POSSIBLE ACROSS FAR NORCAL
AND HIGHER TERRAIN. MODELS SUGGEST ANOTHER SYSTEM IMPACTING NORCAL
EITHER ON MONDAY OR TUESDAY. AGAIN MODEL CONSISTENCY HAS BEEN POOR
SO HAVE JUST KEPT SLIGHT CHANCE OF RAIN/SNOW DURING THIS TIME FRAME.
TEMPERATURES IN THE EXTENDED WILL GENERALLY BE NEAR TO SLIGHTLY
BELOW NORMAL FOR DAYTIME HIGHS: MID 50S TO LOW 60S IN THE VALLEY AND
30S TO 40S IN THE MOUNTAINS. MINIMUM TEMPERATURES ARE EXPECTED TO BE
BELOW NORMAL WITH LOWS IN THE MID 30S TO LOW 40S IN THE VALLEY AND
TEENS TO 20S IN THE MOUNTAINS.

&&

.AVIATION...

INCOMING WEATHER SYSTEM IS NOW BRINGING VCSH TO NORCAL VALLEYS AND
SNOW TO THE MOUNTAINS. -RA WITH MVFR CIGS AND BREEZY SOUTHERLY
WINDS GUSTING UP TO 30KTS CURRENTLY IMPACTING KRDD-KRBL VICINITY
WILL SPREAD SOUTHWARD THIS MORNING REACHING THE SAC METRO AREA BY
MID-MORNING AND THE KSCK-KMOD VCNTY AFTER 18Z. VALLEY
THUNDERSTORMS ARE POSSIBLE THIS AFTERNOON AND EVENING WHICH COULD
BRING LOCALIZED STRONG GUSTS, HEAVIER RAIN AND SMALL HAIL.
GENERALLY SOUTH TO SOUTHWEST FLOW TODAY BECOMING NORTHERLY TONIGHT
WITH IMPROVING CIGS AND DRIER WEATHER AFTER THE STORM SYSTEM
PASSES. CURRENT SNOW LEVELS AROUND 2500-3500 FT AND WILL CONTINUE
TO LOWER THROUGH TOMORROW TO AROUND 1500 FT. IFR/LIFR CONDITIONS
EXPECTED TODAY IN THE MOUNTAINS WITH SN AND WIND GUSTS UP TO 30
KTS. -DVC

&&

.STO WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL 11 PM PST THIS EVENING ABOVE 2000
FEET FOR THE MOTHERLODE...NORTHEAST FOOTHILLS/SACRAMENTO
VALLEY...WEST SLOPE NORTHERN SIERRA NEVADA...WESTERN PLUMAS
COUNTY/LASSEN PARK.

WINTER WEATHER ADVISORY UNTIL 6 PM PST THIS EVENING ABOVE 2000
FEET FOR THE CLEAR LAKE/SOUTHERN LAKE COUNTY...MOUNTAINS
SOUTHWESTERN SHASTA COUNTY TO NORTHERN LAKE COUNTY...SHASTA LAKE
AREA / NORTHERN SHASTA COUNTY.

&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE SACRAMENTO CA
445 AM PST TUE FEB 19 2013

CAZ013>019-063-064-066>069-201500-
SHASTA LAKE AREA/NORTHERN SHASTA COUNTY-
BURNEY BASIN/EASTERN SHASTA COUNTY-NORTHERN SACRAMENTO VALLEY-
CENTRAL SACRAMENTO VALLEY-SOUTHERN SACRAMENTO VALLEY-
CARQUINEZ STRAIT AND DELTA-NORTHERN SAN JOAQUIN VALLEY-
MOUNTAINS SOUTHWESTERN SHASTA TO NORTHERN LAKE COUNTIES-
CLEAR LAKE/SOUTHERN LAKE COUNTY-MOTHERLODE-
EAST FOOTHILLS/NORTH SACRAMENTO VALLEY-
WESTERN PLUMAS COUNTY/LASSEN PARK-WEST SLOPE NORTHERN SIERRA NEVADA-
445 AM PST TUE FEB 19 2013

THIS HAZARDOUS WEATHER OUTLOOK IS FOR INTERIOR NORTHERN CALIFORNIA.

.DAY ONE...TODAY

A COLD LOW PRESSURE SYSTEM WILL MOVE THROUGH NORTHERN CALIFORNIA
TODAY BRINGING SHOWERS AND A FEW THUNDERSTORMS TO THE REGION.
SIGNIFICANT SNOWFALL IS LIKELY OVER THE NORTHERN MOUNTAINS AND
NORTHERN SIERRA NEVADA WITH TRAVEL DELAYS LIKELY OVER THE MOUNTAIN
PASSES BEFORE SHOWERS DIMINISH THIS EVENING.

* WINTER WEATHER ADVISORY....SEE WWUS46 KSTO - WSWSTO FOR DETAILS *

.DAYS TWO THROUGH SEVEN... WEDNESDAY THROUGH MONDAY

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS TO THEIR LOCAL NATIONAL WEATHER SERVICE OFFICE.

THE LATEST WEATHER INFORMATION IS AVAILABLE ON THE INTERNET AT
(LOWER CASE): HTTP://WWW.WRH.NOAA.GOV/STO

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE SACRAMENTO CA
149 PM PST TUE FEB 19 2013

CAZ015-016-063-066-192245-
GLENN CA-TEHAMA CA-BUTTE CA-
149 PM PST TUE FEB 19 2013

THE NATIONAL WEATHER SERVICE IN SACRAMENTO HAS ISSUED A

SIGNIFICANT WEATHER ADVISORY FOR...
  WEST CENTRAL BUTTE COUNTY IN NORTHERN CALIFORNIA
  TEHAMA COUNTY IN NORTHERN CALIFORNIA
  NORTH CENTRAL GLENN COUNTY IN NORTHERN CALIFORNIA

UNTIL 245 PM PST

AT 142 PM PST...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED
SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS DEVELOPING FROM RED
BLUFF SOUTHWARD ALONG AND BOTH WEST AND EAST OF INTERSTATE 5 FROM
PASKENTA TO LOS MOLINOS. THE CELLS ARE DEVELOPING ALONG A STRONG
CONVERGENCE LINE WHICH IS FORECAST TO MOVE SLOWLY SOUTH THIS
AFTERNOON.

SMALL HAIL IS LIKELY WITH THESE SHOWERS AND POSSIBLE THUNDERSTORMS.
THE PUBLIC REPORTED A BRIEF FUNNEL CLOUD BRIEF TORNADO TOUCHDOWN
NEAR PROBERTA AROUND 130 PM.

LOCATIONS IMPACTED INCLUDE...
   HENLEYVILLE...
   CORNING...
   RICHFIELD...
   RED BLUFF AND VINA...

SEEK SHELTER WHEN THREATENING WEATHER APPROACHES. THE CELLS WILL
STRENGTHEN AND WEAKEN RAPIDLY THIS AFTERNOON. BE PREPARED TO MOVE
QUICKLY.

LAT...LON 4032 12203 3982 12174 3961 12250 3994 12269
TIME...MOT...LOC 2141Z 236DEG 17KT 3993 12244

JHM

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Service Notice</title>
  <link rel="stylesheet" href="index.css">
</head>
<body>
  <main class="wrap">
    <section class="card" role="status" aria-live="polite">
      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
      <p id="message1">
        The site you requested is temporarily down for maintenance or an unexpected outage.
      </p>
      <p id="message2">
        Please try again in a few minutes.
      </p>
      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
      </p>
    </section>
  </main>
  <script src="index.js"></script>
</body>
</html>

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Service Notice</title>
  <link rel="stylesheet" href="index.css">
</head>
<body>
  <main class="wrap">
    <section class="card" role="status" aria-live="polite">
      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
      <p id="message1">
        The site you requested is temporarily down for maintenance or an unexpected outage.
      </p>
      <p id="message2">
        Please try again in a few minutes.
      </p>
      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
      </p>
    </section>
  </main>
  <script src="index.js"></script>
</body>
</html>

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Service Notice</title>
  <link rel="stylesheet" href="index.css">
</head>
<body>
  <main class="wrap">
    <section class="card" role="status" aria-live="polite">
      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
      <p id="message1">
        The site you requested is temporarily down for maintenance or an unexpected outage.
      </p>
      <p id="message2">
        Please try again in a few minutes.
      </p>
      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
      </p>
    </section>
  </main>
  <script src="index.js"></script>
</body>
</html>

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Service Notice</title>
  <link rel="stylesheet" href="index.css">
</head>
<body>
  <main class="wrap">
    <section class="card" role="status" aria-live="polite">
      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
      <p id="message1">
        The site you requested is temporarily down for maintenance or an unexpected outage.
      </p>
      <p id="message2">
        Please try again in a few minutes.
      </p>
      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
      </p>
    </section>
  </main>
  <script src="index.js"></script>
</body>
</html>

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Service Notice</title>
  <link rel="stylesheet" href="index.css">
</head>
<body>
  <main class="wrap">
    <section class="card" role="status" aria-live="polite">
      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
      <p id="message1">
        The site you requested is temporarily down for maintenance or an unexpected outage.
      </p>
      <p id="message2">
        Please try again in a few minutes.
      </p>
      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
      </p>
    </section>
  </main>
  <script src="index.js"></script>
</body>
</html>