976
FXUS02 KWBC 161847
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
147 PM EST TUE JAN 16 2024
VALID 12Z FRI JAN 19 2024 - 12Z TUE JAN 23 2024
...ANOTHER ARCTIC AIRMASS COMES INTO THE CENTRAL U.S. LATE WEEK,
BUT NOT AS EXTREME AS THE FIRST ONE...
...MULTIPLE ROUNDS OF POTENTIALLY HEAVY PRECIPITATION WILL AFFECT
THE WEST...
..OVERVIEW
THE LARGE SCALE PATTERN WILL FINALLY BECOME MORE PROGRESSIVE BY
LATE WEEK INTO EARLY NEXT WEEK AS THE DEEP, BROAD UPPER TROUGH
OVER THE EASTERN U.S. SHIFTS EAST INTO THE ATLANTIC. AS THE TROUGH
SHIFTS EAST, A RIDGE WILL FOLLOW BEHIND IT, MOVING FROM THE
WESTERN TO THE CENTRAL U.S. THIS WEEKEND AND TO THE EASTERN U.S.
EARLY NEXT WEEK. NORTHWESTERLY FLOW AHEAD OF THE RIDGE WILL BRING
IN ANOTHER ARCTIC SURFACE HIGH, PRODUCING MUCH BELOW NORMAL
TEMPERATURES ACROSS THE CENTRAL AND EASTERN U.S. LATE THIS WEEK
INTO THIS WEEKEND, ESPECIALLY FRIDAY AND SATURDAY, BEFORE
GRADUALLY MODERATING. WHILE TEMPERATURES ARE FORECAST TO BE
GENERALLY BE 15-30F BELOW AVERAGE, THIS SECOND ROUND OF COLD
TEMPERATURES SHOULD BE LESS EXTREME THAN THE CURRENT COLD WAVE AT
MOST LOCATIONS. MEANWHILE, ROUNDS OF PRECIPITATION ARE EXPECTED
FOR THE WEST COAST, AND POTENTIAL LOW DEVELOPMENT ALONG A SURFACE
FRONTAL SYSTEM OR TWO COULD PRODUCE SOME WINTER WEATHER IN THE
EAST, PARTICULARLY ON FRIDAY. RETURN FLOW FROM THE GULF OF MEXICO
WILL INCREASE PRECIPITATION CHANCES ACROSS THE SOUTH-CENTRAL U.S.
FOR THE EARLY PART OF NEXT WEEK.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL GUIDANCE CONTINUES TO SHOW GOOD AGREEMENT ON THE LARGE SCALE
PATTER WITH EXPECTED DIFFERENCES IN SMALL SCALE FEATURES. AN UPPER
TROUGH WILL SHIFT OVER THE EAST EARLY IN THE PERIOD THEN INTO THE
ATLANTIC LATE THIS WEEKEND. FOLLOWING BEHIND THIS, A RIDGE WILL
SHIFT EAST ACROSS THE LOWER 48 AND SEVERAL WAVES OF
ENERGY/SHORTWAVES WILL MOVE TOWARDS THE WEST COAST. MODELS HAVE
ALSO BEEN SHOWING A TROUGH/UPPER LOW DEVELOPING NEAR OR SOUTH OF
THE SOUTHWEST U.S. MID-NEXT WEEK, WITH MOIST GULF AIR MOVING NORTH
INTO THE SOUTH-CENTRAL U.S. AHEAD OF IT. AT THE SURFACE, THIS
PATTERN WILL PRODUCE A COUPLE OF FRONTAL SYSTEMS MOVING OFF THE
EAST COAST EARLY IN THE PERIOD AND A SERIES OF FRONTAL SYSTEMS
PUSHING INTO THE WEST THROUGH THE WEEKEND. THERE ARE SOME TIMING
DIFFERENCES BETWEEN THE MODELS CONCERNING THE SHORTWAVES MARCHING
INTO THE WEST, BUT FALLS WITHIN TYPICAL SPREAD EXPECTED IN THE
MEDIUM RANGE PERIOD. THESE WILL TAKE ADDITIONAL TIME TO RESOLVE
ESPECIALLY SINCE THEY ARE TRACKING FROM THE DATA-POOR PACIFIC THAT
CAUSES MODELS TO STRUGGLE.
THE WPC AFTERNOON FORECAST WAS BASED ON A MULTI-MODEL
DETERMINISTIC BLEND EARLY IN THE FORECAST PERIOD. GRADUALLY
INCORPORATED THE GEFS AND EC ENSEMBLE MEAN GUIDANCE WHILE PHASING
OUT THE CMC (STRAYED A BIT FARTHER FROM THE GENERAL CONSENSUS THAN
OTHER GUIDANCE) AND UKMET (TIME-LIMITED) AS THE PERIOD PROGRESSED,
ENDING UP WITH AN EVEN BLEND OF THE 06Z GFS AND GEFS MEAN AND 00Z
ECMWF AND EC MEAN BY DAY 7. THIS SMOOTHED OUT MODEL DIFFERENCES
BUT MAINTAINED SOME STRENGTH IN INDIVIDUAL SYSTEMS.
..WEATHER/HAZARDS HIGHLIGHTS
THE WEST COAST STATES CAN EXPECT ROUNDS OF PRECIPITATION THROUGH
THIS WEEKEND INTO EARLY NEXT WEEK. BY LATE FRIDAY, A ROUND OF
PRECIPITATION LOOKS TO AFFECT CALIFORNIA ALONG AND AHEAD OF A
FRONTAL SYSTEM. MODELS INDICATE THAT RAIN RATES COULD BE OVER HALF
AN INCH PER HOUR AS INSTABILITY MAY SNEAK ONSHORE, ALONG WITH GOOD
DYNAMICAL SUPPORT FOR HEAVY RAIN FROM A STRONG SHORTWAVE ALOFT.
THUS THERE IS A MARGINAL RISK IN THE EXCESSIVE RAINFALL OUTLOOK
FOR PORTIONS OF NORTHERN CALIFORNIA ON FRIDAY-FRIDAY NIGHT. AS
PRECIPITATION GENERALLY EXPANDS SOUTHEASTWARD OVER THE WEEKEND, A
SIMILAR MARGINAL RISK IS IN PLACE FOR SATURDAY-SATURDAY NIGHT BUT
WITH SOME SOUTHWARD EXPANSION COMPARED TO FRIDAY'S OUTLOOK. THESE
MULTIPLE ROUNDS OF PRECIPITATION SHOULD CONTINUE INTO EARLY NEXT
WEEK FROM THE WEST COAST INTO THE INTERMOUNTAIN WEST. SOME LOCALLY
MODERATE/HEAVY TOTALS ARE POSSIBLE OVER FAVORED TERRAIN, DEPENDING
ON UPPER LEVEL AND SURFACE DETAILS THAT WILL BE BETTER RESOLVED IN
COMING DAYS. PARTS OF THE INTERIOR NORTHWEST COULD SEE CONDITIONS
FAVORABLE FOR FREEZING RAIN FOR MULTIPLE DAYS. EVENTUALLY BY EARLY
NEXT WEEK, THE PATTERN SHOULD ALLOW FOR GULF RETURN FLOW TO
PRODUCE RAIN CHANCES FOR THE SOUTH-CENTRAL U.S. ON SUNDAY. MODELS
INDICATE HEAVIER RAIN DEVELOPING IN THE SOUTH BY MONDAY WHILE THE
PRECIPITATION SHIELD EXPANDS NORTHEASTWARD MONDAY-TUESDAY, WITH
SOME POSSIBLE WINTRY WEATHER ON THE NORTHERN SIDE.
A FRONTAL SYSTEM WITH EMBEDDED LOW PRESSURE REACHING THE EAST
DURING THE LATTER PART OF THE WEEK MAY PRODUCE SOME PRECIPITATION
ACROSS THE APPALACHIANS AND PARTS OF THE EAST COAST FRIDAY. SNOW
SHOULD BE THE PRIMARY PRECIPITATION TYPE CONSIDERING THE COLD AIR
IN PLACE. THE CENTRAL APPALACHIANS WILL LIKELY SEE THE HEAVIEST
SNOW WITH UPSLOPE FLOW HELPING TO CONTRIBUTE TO AMOUNTS. FARTHER
EAST THE MOST LIKELY AXIS FOR NOTABLE SNOW LOOKS TO BE MAINLY
ACROSS THE NORTHERN MID-ATLANTIC INTO SOUTHERN PARTS OF THE
NORTHEAST, BUT AMOUNTS DO NOT LOOK TO BE TOO HEAVY. EXPECT
CONTINUED PERIODS OF LAKE EFFECT SNOW WITH PERSISTENCE OF COLD AIR
AND BREEZY CONDITIONS INTO SATURDAY. LAKE EFFECT SNOW WILL LIKELY
TAPER OFF BY SUNDAY AS SURFACE HIGH PRESSURE BUILDS INTO THE EAST.
ARCTIC HIGH PRESSURE WILL PROVIDE A REINFORCING SURGE OF COLD AIR
THAT IS FORECAST TO PUSH WELL INTO THE CENTRAL AND EAST-CENTRAL
U.S. BY FRIDAY AND INTO THE EAST ON SATURDAY. TEMPERATURES 15-30
DEGREES BELOW NORMAL SHOULD BE WIDESPREAD, WITH LOCALIZED
ANOMALIES MORE THAN 30F BELOW NORMAL, AND THIS COLD EPISODE WILL
STILL BE NOTABLE EVEN IF NOT QUITE AS EXTREME AS THE CURRENT COLD
EVENT FOR MOST AREAS. THE HIGHEST POTENTIAL FOR HAZARDOUS COLD AND
DANGEROUS WIND CHILLS WILL BE ACROSS THE NORTH-CENTRAL PLAINS INTO
PARTS OF THE UPPER MIDWEST. TEMPERATURES ARE FORECAST TO START
MODERATING TOWARDS NORMAL SUNDAY AND BECOME NEAR TO ABOVE AVERAGE
IN THE CENTRAL AND EASTERN U.S. BY MONDAY-TUESDAY AS THE SURFACE
HIGH SHIFTS INTO THE ATLANTIC AND THE UPPER RIDGE ALLOWS FOR MORE
SOUTHERLY FLOW. FROM THE ROCKIES WESTWARD, NEAR TO ABOVE NORMAL
TEMPERATURES ARE EXPECTED, WITH HIGHER ANOMALIES (GENERALLY 10-20F
ABOVE AVERAGE) FOR LOWS THAN HIGHS.
DOLAN/TATE
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, EXCESSIVE RAINFALL OUTLOOK,
WINTER WEATHER OUTLOOK PROBABILITIES, HEAT INDICES AND KEY
MESSAGES 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
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=OVW
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page