CA Under the Gun
Posted by
JAC on 1/18/2010, 7:48 am
SHORT RANGE FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
359 AM EST MON JAN 18 2010
VALID 12Z MON JAN 18 2010 - 00Z WED JAN 20 2010
CALIFORNIA WILL CONTINUE TO BE UNDER THE GUN OVER THE NEXT FEW
DAYS AS THE STRONG PACIFIC JET STREAM REMAINS FOCUSED ON THE
GOLDEN STATE. SYSTEM AFTER SYSTEM WILL BRING THEIR COLD FRONT
THROUGH THE STATE BEFORE DYING OVER THE GREAT BASIN. THIS SHOULD
KEEP THE PRECIPITATION WEST OF THE CONTINENTAL DIVIDE. HEAVY SNOW
IS LIKELY FROM THE SIERRA NEVADAS NORTHWARD TO THE SHASTAS IN
NORTHWESTERN CALIFORNIA WITH LESS IMPRESSIVE AMOUNTS FARTHER EAST
IN SOUTHERN UTAH. PLEASE CONSULT THE HPC WINTER WEATHER DISCUSSION
AND GRAPHICS FOR MORE DETAILED INFORMATION. WASHINGTON STATE WILL
NOT ESCAPE THE UNSETTLED WEATHER AS THE MAIN SURFACE LOW DRIFTS
NORTHWARD OFFSHORE.
FRACASSO
EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
155 PM EST SUN JAN 17 2010
VALID 12Z WED JAN 20 2010 - 12Z SUN JAN 24 2010
...PROLONGED STORMY CONDITIONS AND EXCESSIVE PCPN EPISODE FOR
CA/SW US ALL WEEK...
...SRN/SERN US TO EAST COAST/WRN ATLC COASTAL LOW PCPN THU/FRI...
...SIGNIFICANT CENTRAL US STORM POTENTIAL NEXT WEEKEND...
THE 00/06/12 UTC MODELS AND ENSEMBLES CONTINUE TO OFFER RUN TO RUN
DIFFERENCES WITH POTENT EMBEDDED SYSTEMS AND SIGNIFICANT SENSIBLE
WEATHER FOCUS...BUT SEEM IN REASONABLE LARGER SCALE AGREEMENT
OVERALL INTO MID-LATE WEEK AS POTENT PACIFIC ENERGIES PUNCH INTO
CA UNDERNEATH HIGHER LATITUDE ERN DEEP LAYERED CLOSED LOW.
IN THIS PATTERN...SOME ENERGY/PCPN THEN SPLITS INTO A MORE NRN
BRANCH AND LIFTS UP THE COAST AROUND THE PERIPHERY OF A NE PAC
MEAN CLOSED LOW POSITION AS DOWNSTREAM RIDGE AMPLITUDE CENTERED
OVER SOUTH-CENTRAL CANADA LEADS TO FURTHER DOWNSTREAM MEAN
TROUGHING/COOLING THROUGH THE NERN US. MEANWHILE...LEAD SRN STREAM
SYSTEM/LOW DEVELOPMENT AND ASSOCIATED HEAVY PCPN POTENTIAL WITH
GULF OF MEXICO THEN ATLC INFLOW CUTS UNDERNEATH OUT THROUGH THE
SRN/SERN US THU AND WRAPPING UP OFF THE EAST COAST FRI INTO SAT.
BACK UPSTREAM...THE BULK OF PACIFIC ENERGY SLAMS INLAND WITHIN A
STRENGTHENING SRN STREAM FLOW NEXT WEEK. A STEADY DIET OF MOIST
SYSTEMS SLAM INLAND FROM CA THROUGH THE SWRN US/S-CENTRAL GREAT
BASIN/ROCKIES NEXT WEEK...EVENTUALLY LEADING TO DEEP CENTRAL US
CYCLOGENESIS/HEAVY PCPN POTENTIAL NEXT WEEKEND. HPC POINTS TO
THESE SYSTEMS AS HIGH RISK EVENTS FOR EVALUATION FOR POTENTIAL WRN
PAC TARGETED OBSERVATION FLIGHTS OUT OF JAPAN THAT OFTEN REDUCE
DOWNSTREAM MODEL ERROR...ESPECIALLY CONSIDERING CONSIDERABLE DEEP
LOW MEDIUM RANGE MODEL DIFFERENCES NOW EVIDENT ACROSS THE CENTRAL
PACIFIC.
HPC FINAL MEDIUM RANGE GUIDANCE KEEPS CLOSE CONTINUITY AND REMAIN
PRIMARILY DERIVED FROM A BLEND OF 70% 00 UTC ECMWF AND 30% 00 UTC
NAEFS ENSEMBLE MEAN WED-FRI...TRANSITIONING TO A 50-50 SPLIT NEXT
WEEKEND. HPC CONTINUITY THAT HAS LEANED MORE ON A SOLUTION
CLOSEST TO THE ECMWF INTO MID-LATE WEEK DOES NOT HAVE HIGH
CONFIDENCE WITH SMALLER SCALE DETAILS...AND AS SUCH SHOULD BENEFIT
FROM INFUSION OF ENSEMBLE MEAN GUIDANCE. THE NAEFS BIAS CORRECTED
COMBINATION OF GFS AND CANADIAN ENSEMBLE MEMBERS SEEMS A BETTER
MATCH TO BLEND WITH THE 00 UTC ECMWF THAN FLATTER 00 UTC ECMWF
ENSEMBLES. PREFER EVEN A LARGER NAEFS ENSEMBLE DOSE INTO NEXT
WEEKEND. THIS IS ESPECIALLY AS AT LEAST A SOMEWHAT MORE AMPLIFIED
THAN 00 UTC ECMWF SRN STREAM FLOW FROM THE PACIFIC INTO THE US
SEEMS PRUDENT CONSIDERING LATEST WATER VAPOR AND BLENDED TPW
LOOPS...A TREND NOW BETTER SUPPORTED BY THE 12 UTC ECMWF. A GOOD
BIT OF WINTRY PRECIPITATION IS IN STORE FOR THE NATION...FROM THE
WEST WHERE THE PACIFIC JET WILL CONTINUE TO RUSH INLAND...TO THE
PLAINS AND NORTHEAST WHERE THE NORTHERN STREAM WILL SUPPLY ENOUGH
COLD AIR.
CISCO/SCHICHTEL
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