301
FXUS02 KWBC 061858
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
158 PM EST FRI JAN 6 2023
VALID 12Z MON JAN 9 2023 - 12Z FRI JAN 13 2023
...ADDITIONAL ATMOSPHERIC RIVERS EVENTS WITH HEAVY RAIN AND
MOUNTAIN SNOW FOR MUCH OF CALIFORNIA NEXT WEEK WITH FLOODING
EXPECTED...
19Z UPDATE: THE 12Z MODEL SUITE HAS AN EXCELLENT OVERALL
DEPICTION OF THE SYNOPTIC SCALE PATTERN, EVEN GOING INTO THE END
OF NEXT WEEK, WITH ABOVE AVERAGE FORECAST CONFIDENCE FOR THOSE
TIME SCALES. THE REGION WITH GREATEST DIFFERENCES IS ACROSS THE
GREAT LAKES AND SOUTH-CENTRAL CANADA REGARDING THE TIMING OF A
NORTHERN STREAM SHORTWAVE, AND WHETHER THIS EVENTUALLY PHASES WITH
THE MUCH STRONGER SOUTHERN STREAM SYSTEM ACROSS THE SOUTHEAST U.S.
ON FRIDAY AND BEYOND. IN TERMS OF EXCESSIVE RAINFALL POTENTIAL,
THE DAY 4 ERO HAS A SLIGHTLY LARGER MODERATE RISK AREA FOR COASTAL
CENTRAL CALIFORNIA, AND A LARGER OVERALL SLIGHT RISK AREA
SURROUNDING IT. FOR DAY 5, A SMALL SLIGHT RISK AREA WAS ADDED FOR
PORTIONS OF THE TRANSVERSE MOUNTAIN RANGES ACROSS SOUTHERN
CALIFORNIA. IN TERMS OF THE WPC FRONTS/PRESSURES, A NEARLY
DETERMINISTIC MODEL BLEND WAS USED FOR MONDAY THROUGH WEDNESDAY,
AND THEN SOME OF THE ENSEMBLE MEANS GOING INTO THE END OF THE WEEK
TO ACCOUNT FOR SOME OF THE MESOSCALE UNCERTAINTY. THE PREVIOUS
DISCUSSION IS APPENDED BELOW FOR REFERENCE. /HAMRICK
-------------------------
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE WEATHER PATTERN OVER MUCH OF THE CONTINENTAL U.S. REMAINS
QUITE ACTIVE THROUGH NEXT WEEK, WITH MULTIPLE EMBEDDED SHORTWAVES
ALOFT WITHIN RELATIVELY WELL DEFINED NORTHERN AND SOUTHERN STREAM
FLOWS. THE HIGHLIGHT CONTINUES TO BE A VERY ACTIVE EASTERN PACIFIC
WITH A COUPLE OF DEEPENED LOW PRESSURE SYSTEMS EXPECTED TO IMPACT
THE WEST COAST WITH LEAD ATMOSPHERIC RIVER MOISTURE ALLOWING FOR
BOTH SIGNIFICANT AND IMPACTFUL QPF AMOUNTS. THERE IS GOOD
AGREEMENT FOR THE FIRST SYSTEM (MONDAY-TUESDAY) BUT MORE
UNCERTAINTY IN ESPECIALLY THE TIMING OF ANOTHER SYSTEM LATER IN
THE WEEK. THESE WESTERN U.S. SHORTWAVES SHOULD PROGRESS INLAND
THROUGH THE WEEK, AMPLIFYING EAST OF THE ROCKIES AND EVENTUALLY
OFF THE SOUTHEAST COAST. GOOD ENOUGH AGREEMENT ACROSS THE BOARD
THROUGH DAY 5 TO UTILIZE A BLEND OF THE LATEST 12Z/18Z
DETERMINISTIC GUIDANCE FOR THE LATEST WPC FORECAST. GUIDANCE
CONTINUES TO TREND STRONGER/MORE AMPLIFIED FOR A SHORTWAVE ACROSS
THE SOUTH-CENTRAL U.S. LATE WEEK, WITH INCREASING QPF TRENDS
ACROSS THE DEEP SOUTH. THERE ARE SOME NOTABLE DIFFERENCES IN TRACK
THOUGH AS THE 12Z ECMWF IS FARTHER SOUTH WITH THE UPPER LOW THAN
THE GFS. THE 12Z CMC FROM JAN 5 WAS SLOWER THAN THESE PIECES OF
GUIDANCE AND THE ENSEMBLE MEANS AND WAS NOT FAVORED FOR THIS
SYSTEM, BUT DID NOTE THE 00Z CMC (AVAILABLE AFTER FORECAST
GENERATION TIME) DID COME IN QUICKER AND MORE IN LINE WITH THE
OTHER GUIDANCE. THE WPC FORECAST TRENDED TOWARDS A MAJORITY
ECENS/GEFS ENSEMBLE MEAN BLEND FOR DAYS 6 AND 7 AMIDST GROWING
FORECAST SPREAD. OVERALL, THE FORECAST REMAINED FAIRLY CONSISTENT
WITH THE PREVIOUS SHIFT.
..WEATHER/HAZARD HIGHLIGHTS
THE BIG WEATHER STORY THROUGH NEXT WEEK WILL REMAIN OUT WEST AS
YET MORE ATMOSPHERIC RIVERS TAKE AIM AT AN ALREADY OVER SATURATED
CALIFORNIA. THE WPC EXPERIMENTAL DAY 4 EXCESSIVE RAINFALL OUTLOOK
(ERO) CONTINUES A BROAD SLIGHT WITH EMBEDDED MODERATE RISKS ACROSS
MUCH OF NORTHERN AND CENTRAL CALIFORNIA ON MONDAY, WHERE RAINFALL
AMOUNTS OF SEVERAL INCHES ARE EXPECTED. MANY AREAS ARE ALREADY OR
WILL BE VERY SENSITIVE TO ADDITIONAL RAINFALL GIVEN THE AMPLE
RECENT AND SHORTER TERM FORECAST RAINFALL. SNOW LEVELS LOOK FAIRLY
HIGH WITH THIS EVENT, BUT STILL THE HIGHER TERRAIN (GENERALLY
ABOVE 8000') OF THE SIERRAS LIKELY WILL SEE SOME VERY HEAVY
SNOWFALL MEASURED IN FEET MONDAY INTO TUESDAY. AFTER THIS, THE
NEXT SYSTEM LOOKS TO IMPACT NORTHERN CALIFORNIA AGAIN BY
WEDNESDAY-THURSDAY WITH AGAIN IMPACTFUL AND POSSIBLY HEAVY
RAINFALL.
THE INITIAL SYSTEM IN CALIFORNIA SHOULD TRACK EAST DURING THE
MIDDLE OF NEXT WEEK WITH GUIDANCE CONTINUING TO FAVOR MODEST SNOW
ACCUMULATIONS OVER THE PARTS OF THE GREAT BASIN AND THE ROCKIES.
THEN, IT HAS POTENTIAL TO SPAWN MODERATE CENTRAL PLAINS
CYCLOGENESIS LATER NEXT WEEK WHERE POTENTIAL LEAD RETURN GULF
INFLOW INTO THE MS VALLEY AND VICINITY MAY OFFER AN OPPORTUNITY
FOR AN EXPANDING AREA OF LATE PERIOD RAINFALL ACROSS PORTIONS OF
THE DEEP SOUTH/TENNESSEE VALLEY. THERE REMAINS SOME SIGNAL, THOUGH
LOW CONFIDENCE STILL, FOR SNOW AND ICE POTENTIAL ON THE NORTHERN
PERIPHERY OF THE PRECIPITATION SHIELD AS THE MOISTURE FEEDS INTO A
COOLED ANTECEDENT HIGH PRESSURE AIRMASS THAT MAY DIG IN ADVANCE OF
THIS SYSTEM FRONT CANADA INTO THE NORTH-CENTRAL THROUGH EASTERN
U.S.
ELSEWHERE, A LEADING SHORT WAVE AND FRONTAL BOUNDARY THROUGH THE
SOUTHEAST SHOULD ALLOW FOR SOME LIGHT TO MODERATE RAINFALL AS IT
PASSES THROUGH. THE NORTHWEST SHOULD SEE SOME PRECIPITATION AS
WELL ASSOCIATED WITH THE VARIOUS EAST PACIFIC SYSTEMS, THOUGH NOT
NEARLY AS IMPACTFUL AS FARTHER SOUTH INTO CALIFORNIA. TEMPERATURES
ACROSS THE SOUTH-CENTRAL PLAINS TO MIDWEST/SOUTHEAST SHOULD STAY
WARM THROUGH NEXT WEEK, WITH ANOMALIES 10-15 DEGREES ABOVE NORMAL
POSSIBLE.
SANTORELLI
ADDITIONAL 3-7 DAY HAZARD INFORMATION CAN BE FOUND ON THE WPC
MEDIUM RANGE HAZARDS OUTLOOK CHART AT:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
WPC MEDIUM RANGE 500MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,
QUANTITATIVE PRECIPITATION, EXPERIMENTAL EXCESSIVE RAINFALL
OUTLOOK, WINTER WEATHER OUTLOOK PROBABILITIES AND HEAT INDICES ARE
AT:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST500_WBG.GIF
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST_WBG_CONUS.GIF
HTTPS://WWW.WPC.NCEP.NOAA.GOV/5KM_GRIDS/5KM_GRIDSBODY.HTML
HTTPS://WWW.WPC.NCEP.NOAA.GOV/QPF/DAY4-7.SHTML
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=ERO
HTTPS://WWW.WPC.NCEP.NOAA.GOV/WWD/PWPF_D47/PWPF_MEDR.PHP?DAY=4
HTTPS://WWW.WPC.NCEP.NOAA.GOV/HEAT_INDEX.SHTML
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page