931
FXUS02 KWBC 020711
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
211 AM EST SUN FEB 2 2025
VALID 12Z WED FEB 05 2025 - 12Z SUN FEB 09 2025
...ANOTHER ROUND OF PRECIPITATION COULD BE HEAVY FOR CALIFORNIA
AROUND THURSDAY...
..OVERVIEW
GUIDANCE SHOWS LOW AMPLITUDE UPPER FLOW ACROSS MUCH OF THE LOWER
48 LATER THIS WEEK INTO THE WEEKEND, BUT THE OVERALL PATTERN AND
EMBEDDED FEATURES WILL STILL PRODUCE AREAS OF IMPACTFUL WEATHER.
PRECIPITATION OVER CALIFORNIA IS FORECAST TO LESSEN SOMEWHAT FOR
MIDWEEK, BUT HEAVY RAIN AND SNOW AMOUNTS COULD GET RENEWED AROUND
THURSDAY. MOISTURE FARTHER INLAND WILL SUPPORT PRECIPITATION ACROSS
THE GREAT BASIN AND ROCKIES, WITH SIGNIFICANT SNOW POSSIBLE FOR
HIGHER ELEVATIONS. FARTHER EAST, MOISTURE RETURN AND SOME DEGREE OF
FRONTAL WAVE DEVELOPMENT WILL LEAD TO INCREASING PRECIPITATION
CHANCES ACROSS THE EASTERN THIRD OF THE LOWER 48 MID TO LATE WEEK,
INCLUDING POSSIBLE WINTER WEATHER FOR PARTS OF THE MID-ATLANTIC AND
NORTHEAST. ANOTHER ROUND OF PRECIPITATION IS POSSIBLE IN SIMILAR
AREAS BY NEXT WEEKEND WITH ANOTHER LOW PRESSURE SYSTEM. THE QUASI-
ZONAL FLOW PATTERN WITH SUBTROPICAL RIDGING NEAR CUBA WILL PROMOTE
ABOVE NORMAL TEMPERATURES ACROSS A MAJORITY OF THE COUNTRY, THOUGH
A CANADIAN SURFACE HIGH NUDGING INTO THE NORTHWESTERN TO NORTH-
CENTRAL U.S. SHOULD LEAD TO BELOW NORMAL TEMPERATURES THERE WITH
COLDEST ANOMALIES INTO WEDNESDAY.
..GUIDANCE/PREDICTABILITY ASSESSMENT
FROM THE LARGE SCALE PERSPECTIVE, THE ENSEMBLE MEANS HAVE BEEN
PROVIDING A FAIRLY STEADY AND AGREEABLE FORECAST OVER RECENT DAYS--
HELPING TO ANCHOR THE FORECAST WITHIN SOME PRONOUNCED SPREAD FOR
VARIOUS SIGNIFICANT FEATURES. THE MEDIUM RANGE PERIOD STARTS WITH
AN UPPER LOW OFFSHORE OF VANCOUVER ISLAND/WASHINGTON STATE WHILE
THERE IS SOME VORTICITY SPINNING FARTHER EAST THAT PROMOTES
SHORTWAVE TROUGH DEVELOPMENT (WITHIN BROADER CYCLONIC FLOW)
WEDNESDAY-THURSDAY IN THE NORTH-CENTRAL U.S., SUPPORTING SURFACE
LOW FORMATION. THERE WAS STILL CONSIDERABLE SPREAD IN THE POSITION
AND STRENGTH OF THE SURFACE LOW BY 12Z THURSDAY SOMEWHERE IN THE
GREAT LAKES/OHIO VALLEY, INCLUDING A FARTHER SOUTH LOW TRACK FROM
GEFS/GFS RUNS. THE NEWER 00Z ECMWF/CMC RUNS ARE AT LEAST SOMEWHAT
AGREEABLE IN A POSITION OVER SOUTHERN ONTARIO 12Z THURSDAY AND
MOVING QUICKLY NORTHEASTWARD.
REGARDING THE WESTERN UPPER LOW, AT LEAST SOME OF THE OUTLIERS
LIKE OLDER CMC RUNS THAT PULLED IT WELL OFFSHORE ARE IN BETTER
AGREEMENT NOW, BUT THE EXACT SHAPE OF FLOW AROUND THE UPPER LOW AND
ENERGY PIVOTING THROUGH THE SOUTHERN SIDE ARE MORE VARIABLE FOR
MID TO LATE WEEK. MODELS ARE AT LEAST AGREEABLE THAT AN AR WILL
IMPACT CALIFORNIA ON THURSDAY-FRIDAY BUT SURFACE LOW DETAILS MOVING
FROM THE EASTERN PACIFIC INTO CALIFORNIA VARY. LATE WEEK INTO THE
WEEKEND, THIS TROUGH SHOULD PIVOT EASTWARD INTO THE WEST AND MOST
ML MODELS MATCHED UP FAIRLY WELL WITH THE ENSEMBLE MEANS AND AN
AVERAGE OF RECENT ECMWF/GFS RUNS FOR THE OVERALL UPPER TROUGH.
UPSTREAM ENERGY DROPPING DOWN FROM ALASKA COULD COMPLICATE THE
FORECAST WITH RESPECT TO SPECIFICS THOUGH. THE OVERALL SHAPE AND
POSITION OF THE TROUGH BY SATURDAY HAS DECENT SUPPORT FROM
TELECONNECTIONS RELATIVE TO THE UPSTREAM PACIFIC/ALASKA UPPER
RIDGE. THE TROUGH AXIS MOVING QUICKLY EASTWARD COULD SPIN UP
ANOTHER SURFACE LOW THIS WEEKEND OVER THE SOUTH-CENTRAL U.S. AND
QUICKLY THROUGH THE OHIO VALLEY OR SO. SIMILAR TO THE LATE WEEK
SYSTEM, THE GFS WAS MORE SUPPRESSED WITH THE DEVELOPING LOW TRACK
COMPARED TO THE ECMWF.
EARLY IN THE FORECAST PERIOD, WPC USED A BLEND OF MAINLY
DETERMINISTIC GUIDANCE, AND INCREASED THE PROPORTION OF ENSEMBLE
MEANS AS THE PERIOD PROGRESSED.
..WEATHER/HAZARDS HIGHLIGHTS
THE LONG-LASTING ATMOSPHERIC RIVER (AR) TAKING AIM AT CALIFORNIA
WILL FINALLY WEAKEN AND MOVE SOUTH BY WEDNESDAY, LEADING TO REDUCED
RAIN AMOUNTS. LIGHT TO MODERATE SHOWERS COULD LINGER OVER SOUTHERN
CALIFORNIA, BUT THESE LOOK TO STAY UNDER ANY FLOODING THRESHOLDS
EVEN FOR THE SENSITIVE BURN SCARS IN THAT REGION. THUS DO NOT HAVE
ANY RISK AREA DEPICTED IN THE DAY 4/WEDNESDAY ERO, BUT WILL
CONTINUE TO MONITOR. MEANWHILE LOWER ELEVATION RAIN/HIGHER
ELEVATION SNOW COULD REACH OREGON INTO NORTHERN CALIFORNIA
WEDNESDAY AND INCREASE IN MAGNITUDE IN CALIFORNIA ON THURSDAY AS
ANOTHER AR STRENGTHENS. THIS AR EVENT SHOULD BE SHORTER-LIVED THAN
THE NEAR TERM/SHORT RANGE AR, BUT SOME LOCALLY HEAVY RAIN AMOUNTS
ARE POSSIBLE OVER AREAS THAT WILL HAVE QUITE WET ANTECEDENT
CONDITIONS BY THAT TIME. CURRENTLY WILL START WITH A MARGINAL RISK
IN THE DAY 5/THURSDAY ERO FOR NORTHERN/CENTRAL CALIFORNIA, WITHOUT
ANY SLIGHT RISK AREA DUE TO THE FASTER MOVEMENT OF THE AR. RISK
UPGRADES ARE POSSIBLE IN FUTURE CYCLES THOUGH. PRECIPITATION LOOKS
TO PERSIST INTO FRIDAY BUT ABATE INTO SATURDAY FOR CALIFORNIA, BUT
ANOTHER ROUND OF PRECIPITATION IS POSSIBLE FOR THE PACIFIC
NORTHWEST.
SNOW WILL ALSO BE LIKELY FROM HIGHER ELEVATIONS OF THE CASCADES
AND SIERRA NEVADA ACROSS MUCH OF THE INTERMOUNTAIN WEST INTO THE
NORTHERN/CENTRAL ROCKIES. THE HEAVIEST SNOW AMOUNTS ARE LIKELY IN
HIGHER ELEVATIONS, BUT THE NORTHERN GREAT BASIN MAY SEE SNOW AS
WELL. THE THURSDAY AR MAY PRODUCE A BETTER DEFINED PERIOD OF
ENHANCED SNOWFALL IN THE SIERRA NEVADA. THE PATTERN WILL ALSO
PROMOTE STRONG WINDS ESPECIALLY ON MOUNTAIN RIDGES LIKE THE SIERRA
AND CENTRAL ROCKIES, BUT SOME GUSTY CONDITIONS MAY REACH LOWER
ELEVATIONS OF THE GREAT BASIN AND FOUR CORNERS TOO.
MEANWHILE FARTHER EAST, MOISTURE WILL BE PRESENT BY WEDNESDAY-
THURSDAY IN THE EAST-CENTRAL U.S. AS A DEVELOPING FRONTAL WAVE
SHOULD REACH THE OHIO VALLEY/GREAT LAKES BY EARLY THURSDAY. AN
EXPANDING AREA OF PRECIPITATION WILL DEVELOP, PARTICULARLY ACROSS
OR SOMEWHAT NORTH OR SOUTH OF THE OHIO VALLEY. THERE CONTINUES TO
BE SOME THREAT FOR FLOODING SOMEWHERE WITHIN THE OHIO
VALLEY/CENTRAL OR SOUTH-CENTRAL APPALACHIANS AS INSTABILITY COULD
REACH SUFFICIENTLY FAR NORTH, AND DEPENDING ON SURFACE WAVE
STRENGTH (ESPECIALLY ON THE WEAKER SIDE OF THE SPREAD) THERE COULD
BE STRONG WESTERLY FLOW AT LOW LEVELS JUST ABOVE THE SURFACE TO
PROMOTE SOME TRAINING AND TERRAIN ENHANCEMENT. HOWEVER THE WIDE
SPREAD FOR SURFACE DETAILS AND QPF PLACEMENT FAVOR HOLDING OFF WITH
ANY DAY 4/WEDNESDAY ERO RISK AREAS. THE NORTHEAST AND NORTHERN
MID-ATLANTIC HAVE POTENTIAL FOR WINTRY WEATHER ON WEDNESDAY-
THURSDAY WHERE COLD AIR HANGS ON. A TRANSITION ZONE OF SLEET AND/OR
FREEZING RAIN MAY EXIST BETWEEN THE SNOW OVER FAR NORTHERN AREAS
AND THE RAIN TO THE SOUTH. ENERGY EJECTING FROM THE WEST NEXT
SATURDAY MAY PROMOTE DEVELOPMENT OF ANOTHER WAVE OVER THE CENTRAL
U.S. WITH ASSOCIATED NORTHERN TIER SNOW AND AN EXPANDING AREA OF
RAIN OVER THE EAST-CENTRAL U.S.
COLDER THAN AVERAGE TEMPERATURES ARE FORECAST FOR NORTHWESTERN AND
NORTH-CENTRAL PARTS OF THE LOWER 48 THROUGH THE PERIOD. MONTANA TO
THE DAKOTAS WILL BE PARTICULARLY COLD, WITH ANOMALIES OF 20-35
DEGREES BELOW NORMAL AND HIGHS BARELY REACHING 0F IN SOME LOCATIONS
INTO WEDNESDAY. THESE AREAS WILL LIKELY REMAIN BELOW AVERAGE BUT
WITH SOME MODERATION LATER THIS WEEK. MEANWHILE, OTHER AREAS FROM
THE FOUR CORNERS STATES THROUGH THE EAST SHOULD SEE ABOVE TO WELL
ABOVE NORMAL TEMPERATURES DURING THE PERIOD. SOME AREAS WILL LIKELY
SEE ONE OR MORE DAYS OF MIN/MAX TEMPERATURES REACHING 20 OR MORE
DEGREES ABOVE NORMAL AND SOME DAILY RECORDS ARE LIKELY TO BE SET.
CURRENT FORECASTS SUGGEST THAT DAILY RECORDS MAY BE MOST NUMEROUS
AROUND WEDNESDAY-THURSDAY. SOME SLIGHT COOLING IS POSSIBLE INTO
FRIDAY-SATURDAY BUT TEMPERATURES SHOULD REMAIN WELL ABOVE AVERAGE
ACROSS THE SOUTHERN TIER. UPPER TROUGHING AND A COLD FRONT WILL
LIKELY FINALLY COOL THE FOUR CORNERS TO PARTS OF THE SOUTH-CENTRAL
U.S. BY NEXT SUNDAY.
TATE/RAUSCH
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 FORECAST (QPF), EXCESSIVE RAINFALL
OUTLOOK (ERO), WINTER WEATHER OUTLOOK (WWO) PROBABILITIES, HEAT
INDICES, AND KEY MESSAGES CAN BE ACCESSED FROM:
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
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=OVW
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