Prognostic Meteorological Discussion
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000
FXUS02 KWBC 221549
PMDEPD

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1049 AM EST WED NOV 22 2017

VALID 12Z SAT NOV 25 2017 - 12Z WED NOV 29 2017

...GUIDANCE/UNCERTAINTY ASSESSMENT AND PATTERN/WEATHER THREAT
HIGHLIGHTS...

AN ACTIVE MOIST PATTERN WILL REMAIN IN PLACE FOR THE PACIFIC
NORTHWEST/NRN CA AND THE NRN INTER-MOUNTAIN WEST/ROCKIES THROUGH
THE UPCOMING WEEKEND, AS A SERIES OF ERN PACIFIC IMPULSES ALONG
MULTIPLE STREAMS LIFT INLAND FROM THE SOUTH AND WEST. THEN ON
CYBER MONDAY, A VERY PRONOUNCED AMPLIFIED UPPER TROUGH WILL FOLLOW
UP THESE FEATURES ALOFT AND SPREAD THROUGH THE WEST TO REACH THE
INTER-MOUNTAIN REGION AND FRONT RANGE OF THE ROCKIES. MEANWHILE,
THE UPPER RIDGE INITIALLY OVER THE WEST SAT MORNING, STRETCHING
FROM BAJA CA NORTH THROUGH THE INTER-MOUNTAIN WEST... WILL
GRADUALLY PRESS DOWNSTREAM FROM THE INFLUENCE OF HEIGHT FALLS
SPREADING INTO THE WEST TO REACH THE MIDDLE TO EASTERN THIRD OF
THE COUNTRY. THIS MEANS THE INITIAL AMPLIFIED COLD UPPER TROUGH
OVER EAST OF THE MS RIVER WILL SWEEP OFF THE EAST COAST, AS
HEIGHTS ATTEMPT TO REBOUND SOME.

BY NEXT TUES AND WED, THE PROGRESSING BUT AMPLIFIED UPPER TROUGH
EJECTS OUT INTO THE PLAINS/MS VALLEY BUT INCREASING SPREAD KEEPS
SOME UNCERTAINTY ON WHETHER A RATHER DEEP CYCLONE FORMS OR WHETHER
THE SYSTEM REMAINS PROGRESSIVE WITH JUST SOME LEFTOVER UPPER
DYNAMICS POSSIBLY CLOSING OFF TOWARDS NORTHERN MEXICO. THE ECMWF
IS TRENDING TOWARD A DEEPER SOLUTION, WHILE THE GFS RUNS FLIP FLOP
BACK AND FORTH. THE MEANS OF BOTH GLOBAL MODELS PRETTY MUCH
SUPPORT THE LATEST OPERATIONAL SOLUTIONS.

WPC AS A WHOLE FOLLOWED A BLEND OF THE 00Z ECMWF/EC MEAN WITH THE
00Z GFS AND 06Z GFS/GEFS MEAN, WITH THE LARGEST WEIGHT ON THE 00Z
ECMWF, THROUGH NEXT MONDAY. THEN NEXT TUES, A BLEND OF THE 00Z
ECMWF/GFS/EC MEAN WAS USED AND FINALLY NEXT WED, A BLEND MOSTLY ON
THE EC MEAN WITH SMALL PERCENTAGES OF THE 00Z ECMWF/GFS OR A TREND
TO A DEEPER AND SLOWER CYCLONE OVER THE MIDDLE TO UPPER PORTION OF
THE COUNTRY.

PRECIPITATION CHANCES FOR OVER THE WEEKEND THROUGH NEXT MONDAY
WILL SOLELY OVER THE WEST WITH THE HEAVIEST QPF ANTICIPATED FROM
COASTAL WA/OR INTO THE CASCADES AND ACROSS NORTHERN CA AND SIERRA
SPINE. ENHANCED OROGRAPHICS WILL ALSO BE LIKELY TO INCREASE QPF
AMOUNTS IN THESE LOCALES AND HELP PINPOINT THE FAVORED TERRAIN
EAST OF THE RAIN SHADOW AND THROUGH THE INTER-MOUNTAIN WEST TO THE
NORTHERN/CENTRAL ROCKIES. ALSO DURING THIS THREE DAY PERIOD OR
MAINLY MON, A STREAK OF LIGHT TO MODERATE OVERRUNNING QPF WILL BE
ANTICIPATED FROM EASTERN MT/NERN WY THROUGH THE DAKOTAS TO
NORTHERN MN. THEN NEXT TUES AND WED, THE FOCUS WILL BE ACROSS THE
UPPER MIDWEST/MS VALLEY WHERE AN AXIS OF HEAVIER QPF IS
ANTICIPATED WITH THE THREAT OF FROZEN ACCUMULATIONS, ESPECIALLY
ACROSS MN INTO WI. ALSO NEXT TUES/WED, WARM SECTOR SHOWERS/STORMS
WILL BE POSSIBLE FROM THE GULF COAST/SOUTH TO OH VALLEY/GREAT
LAKES BUT MOISTURE RETURN FROM THE GULF OF MEXICO WILL BE SOMEWHAT
LIMITED.

TEMPERATURES OVER THE 5 DAYS, THE WPC MEAN MAX TEMP ANOMALY
SUGGESTS BASICALLY AVG TO ABOVE AVG HIGHS FOR THE COUNTRY. ABOVE
AVG HIGHS WILL BE COMMON OVER MUCH OF THE WEST INTO THE PLAINS/MS
VALLEY WITH HIGHS 10 TO 20 DEG ABOVE AVG DURING THE PERIOD FROM
PARTS OF THE FOUR CORNERS REGION INTO EASTERN MT/WY AND MUCH OF
THE NORTHERN/CENTRAL PLAINS. IN FACT, A FEW RECORD HIGHS COULD BE
POSSIBLE OVER PARTS OF CA/NV INTO THE DESERT SOUTHWEST AND FOUR
CORNERS REGION SAT - MON. OVER THE EAST, HIGHS DURING THIS 5 DAY
STRETCH WILL BE NEAR AVG FOR THE MOST PART.

MUSHER

$$




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