Prognostic Meteorological Discussion
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6
000
FXUS02 KWBC 101600
PMDEPD

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1100 AM EST SAT DEC 10 2016

VALID 12Z TUE DEC 13 2016 - 12Z SAT DEC 17 2016

...PATTERN OVERVIEW AND GUIDANCE EVALUATION/PREFERENCES...

MODELS AND ESPECIALLY ENSEMBLES HAVE TENDED TO CONVERGE UPON A
SOMEWHAT BETTER CLUSTERED LARGER SCALE FLOW PATTERN EVOLUTION INTO
EARLY-MID NEXT WEEK. THIS INCLUDES AMPLIFIED MID-UPPER LEVEL
TROUGH DEVELOPMENT AND REINFORCEMENT OVER THE ERN PACIFIC...ALBIET
WITH STILL SIGNIFICANT EMBEDDED SYSTEM VARIANCE. GUIDANCE DOES
STILL OFFER MORE SUBSTANTIAL DIFFERENCES IBY LATER NEXT WEEK INTO
NEXT WEEKEND WITH THE PROGRESSION AND AMPLITUDE OF THESE ENERGIES
WORKING INLAND INTO THE WEST/SW AND OUT OVER THE MID-LOWER
LATITUDES OF THE CENTRAL AND ERN US. THE ECMWF ENSEMBLES REMAIN
MORE PROGRESSIVE IN THIS FLOW THAN GEFS AND ESPECIALLY
CANADIAN/NAEFS ENSEMBLES...BUT ALL ARE FASTER THAN CONTINUITY OVER
THE PAST FEW DAYS FOR THE MOST PART. ITS HARD TO IGNORE THE TREND
AND THE ECMWF ENSEMBLES SEEM A BIT ERRATIC OVER THE PACIFIC SO
PREFER TO HOLD ON AS MUCH LATE PERIOD CONTINUITY AS POSSIBLE BY
EMPHASIZING THE CANADIAN/NAEFS ENSMEBLES FOR THIS WPC PRODUCT
SUITE THAT OFFERS UP A QUICKER THREAT FOR SRN TIER PCPN SWATHS
INCLUDING POTENTIAL TO INCREASINGLY OVERRUN COLD SETTLED HIGH
PRESSURE TO THE NORTH. WITH THIS...GUIDANCE CONTINUITY IS BETTER
WITH AN ENERGETIC NRN STREAM OVERTOP WILL BE HIGHLIGHTED ALOFT BY
A CLOSED VORTEX SWINGING UNDERNEATH HUDSON BAY AND INTO ERN CANADA
THAT FORCES SUBSTANTIAL COLD AIR DOWN THROUGH THE NWRN US AND
N-CENTRAL INTERMOUNTAIN WEST/ROCKIES AS WELL AS FOR ALL OF THE
CENTRAL AND ERN US IN BROAD CYCLONIC FLOW ALOFT.


...WEATHER HIGHLIGHTS/THREATS...

AS STATED OVERNIGHT...ONGOING SPREAD WITH DETAILS OF ERN PAC/WRN
U.S. FLOW LOWERS CONFIDENCE IN SPECIFICS FOR LOCATION OF BEST PCPN
FOCUS AND TIMING OVER THE WEST. AT LEAST FOR THE 5-DAY PERIOD THE
BEST SIGNALS FOR HIGHEST RAIN AND INLAND/HIGHER ELEV SNOW TOTALS
STILL LIE ACROSS THE MIDDLE LATITUDES OF THE REGION WITH
PARTICULAR FOCUS ON FAVORED COASTAL/TERRAIN LOCATIONS IN NRN-CNTRL
CA AND INTO THE CNTRL ROCKIES. ACTIVITY MAY BE ENHANCED BY
INCORPORATION OF SOME LOWER LATITUDE TROPICAL MSTR. ARCTIC BNDRY
DUG/DRAPED THROUGH THE NORTHWEST AND N-CENTRAL ROCKIES/HIGH PLAINS
MAY PROVIDE ANOTHER FOCUS FOR PCPN WITH SNOWS ENHANCED BY
POST-FRONTAL UPSLOPE FLOW. EXPECT TEMPS TO RANGE UP TO 20-30F
BELOW NORMAL FOR COLDER POST-FRONTAL AREAS OVER NRN PARTS OF THE
WEST WITH PERHAPS A FEW ISOLD DAILY RECORD VALUES. ABOVE NORMAL
TEMPS OVER SRN AREAS EARLY IN THE PERIOD SHOULD TREND COOLER BY
FRI-SAT.

TO THE E OF THE ROCKIES... EXPECT THE NRN PLAINS TO REMAIN 20-30F
BELOW NORMAL.  COLD AIR SURGING SEWD TUE ONWARD MAY BRING
SIMILARLY COLD ANOMALIES INTO THE MIDWEST FOR AT LEAST A COUPLE
DAYS MID-LATE WEEK WITH SIGNIFICANT BUT LESS EXTREME DEPARTURES
FROM NORMAL ELSEWHERE.  THE SRN PLAINS ON TUE AND SOUTHEAST
THROUGH WED WILL BE THE LONE POCKETS OF WARMTH.  AS WITH THE NRN
PARTS OF THE WEST DAILY RECORD VALUES SHOULD BE FAIRLY ISOLD.
COLD FLOW ACROSS THE GRTLKS WILL LIKELY GENERATE PERIODS OF LAKE
EFFECT SNOW FOR MULTIPLE DAYS.  OVER THE REST OF THE EAST THE PCPN
FCST HAS BELOW AVG CONFIDENCE DUE TO ISSUES WITH UPSTREAM FLOW
ALOFT.  ONE PERIOD OF SOMEWHAT HIGHER POTENTIAL WILL BE TUE-WED
WITH THE FRONT STALLING OVER THE SOUTHEAST AND PSBLY WAVY ARCTIC
FRONT APPROACHING FROM THE MIDWEST.  AFTER A BRIEF LULL MSTR MAY
SPREAD ACROSS PARTS OF THE CNTRL-ERN STATES WITH LINGERING COLD
AIR AIDING OVER-RUNNING SNOW/ICE THREAT POTENTIAL.

SCHICHTEL

$$




USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.