954
FXUS02 KWBC 130710
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
209 AM EST SAT JAN 13 2024
VALID 12Z TUE JAN 16 2024 - 12Z SAT JAN 20 2024
...HAZARDOUS AND RECORD-BREAKING COLD FROM AN ARCTIC AIRMASS WILL
SPREAD ACROSS THE NORTHWEST INTO THE CENTRAL AND EAST-CENTRAL U.S.
NEXT WEEK...
...POTENTIAL FOR AN IMPACTFUL STORM SYSTEM NEAR THE EAST COAST
NEXT TUESDAY-WEDNESDAY...
..OVERVIEW
LATEST GUIDANCE MAINTAINS A DEEP AND BROAD MEAN TROUGH ALOFT OVER
MUCH OF THE LOWER 48 THROUGH MUCH OF THE WEEK, AHEAD OF THE
UPSTREAM MEAN RIDGE OVER THE EASTERN PACIFIC TRACKING INTO THE
WESTERN U.S. LATE WEEK. THIS UPPER PATTERN AND ARCTIC HIGH
PRESSURE FILTERING IN AT THE SURFACE WILL SUPPORT VERY COLD
TEMPERATURES OVER AREAS FROM THE NORTHWEST THROUGH MUCH OF THE
PLAINS/MISSISSIPPI VALLEY INTO TUESDAY, WITH NUMEROUS DAILY
RECORDS FOR COLD LOWS/DAYTIME HIGHS. BY WEDNESDAY-THURSDAY THERE
SHOULD BE SOME MODERATION AND SHIFT EAST OF THE COLD TEMPERATURES
BEFORE A RESURGENCE IN THE CENTRAL U.S. LATE WEEK (BUT NOT QUITE
AS COLD AS THE INITIAL EVENT). PRECIPITATION-WISE, MEANINGFUL SNOW
IS STILL POSSIBLE IN PARTS OF THE MID-ATLANTIC/NORTHEAST ON
TUESDAY, THOUGH WITH CONTINUED UNCERTAINTY IN AMOUNTS. THE
NORTHERN HALF OR SO OF THE WEST SHOULD ALSO SEE INCREASING
PRECIPITATION CHANCES TUESDAY AND BEYOND.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL GUIDANCE IS QUITE AGREEABLE WITH THE LARGE AND DEEP UPPER
TROUGH COVERING THE EASTERN TWO-THIRDS OF THE NATION NEXT WEEK, AS
WELL AS THE UPSTREAM RIDGE SHIFTING INTO AND ACROSS THE WESTERN
U.S. LATE WEEK. SMALLER-SCALE FEATURES SHOW MORE DIFFERENCES THAT
WILL BE IMPACTFUL FOR SENSIBLE WEATHER THOUGH. THE FIRST OF THESE
MORE UNCERTAIN FEATURES IS THE SURFACE LOW THAT COULD CREATE AN
IMPACTFUL STORM SYSTEM NEAR THE EAST COAST. THOUGH MODELS STILL
AGREE IN SHOWING SHORTWAVE ENERGY PIVOTING THROUGH THE SOUTHERN
SIDE OF THE BROAD MEAN TROUGH SERVING TO FORM THIS SURFACE LOW,
LOW PREDICTABILITY SMALL DETAIL ISSUES WITH THE SHORTWAVE MUST BE
PRODUCING SOME SURFACE LOW DIFFERENCES IN THE TRACK AFTER
CONSENSUS SHOWING AN ELONGATED AREA OF LOW PRESSURE ALONG OR JUST
OFFSHORE THE SOUTHEAST COAST EARLY TUESDAY. IN GENERAL, MOST MODEL
RUNS IN THE PAST COUPLE OF CYCLES HAVE TRENDED TOWARD A MORE
OFFSHORE SOLUTION WITH THE SURFACE LOW, WITH THE 12Z AND 00Z UKMET
THE MAIN WESTERN/INLAND EXCEPTION. CMC RUNS ARE ALSO SLIGHTLY WEST
OF THE NOW AGREEABLE GFS/ECMWF CLUSTER BUT NOT TO THE SAME
EXTREME. 12Z/18Z ENSEMBLE MEANS GENERALLY LAGGED THE LOW TRACK
MORE SLOWLY THAN THE DETERMINISTIC RUNS, SHOWING THERE IS NOT ONLY
EAST-WEST SPREAD BUT NORTH-SOUTH TOO. THE SOLUTION CONSIDERED MOST
LIKELY WAS A BLEND OF THE GFS/ECMWF/CMC AND THE GEFS AND EC
ENSEMBLE MEANS. MOST OF THE OBSERVED RUN-TO-RUN VARIABILITY IS
FAIRLY TYPICAL FOR FORECASTS A FEW DAYS OUT IN TIME BUT STILL
LEADS TO SIGNIFICANT DIFFERENCES FOR PRECIPITATION AMOUNTS (AND IN
SOME CASES, TYPE) ALONG THE EAST COAST.
THERE HAS BEEN SOME MODEL CONVERGENCE IN ANOTHER ASPECT OF THE
PATTERN TUESDAY-WEDNESDAY, NAMELY A SHORTWAVE AND SURFACE LOW
DIVING TOWARD THE NORTHWEST. AFTER THE GEFS/GFS OVER THE PAST FEW
DAYS HAD BEEN STEADFAST IN MAINTAINING A STRONG UPPER RIDGE OVER
THE EAST PACIFIC/WEST COAST, THE MORE RECENT RUNS OF THE GFS/GEFS
STARTING WITH 12Z HAVE SHOWN AN INDICATION OF THE
SHORTWAVE/SURFACE LOW, MATCHING BETTER WITH OTHER GUIDANCE. THUS
THIS FORECAST WAS ABLE TO SHOW THAT LOW A LITTLE STRONGER AND
TREND PRECIPITATION UP COMPARED TO THE PREVIOUS FORECAST. HOWEVER
THERE ARE STILL SOME PLACEMENT AND STRENGTH DIFFERENCES WITH THIS,
INCLUDING IN THE NEWER 00Z MODELS. GENERALLY SPEAKING THIS
SHORTWAVE SHOULD GET ABSORBED INTO THE CENTRAL U.S. TROUGH DURING
THE LATTER PART OF THE WEEK, AND COULD BE A FACTOR IN AN UNCERTAIN
FRONTAL SYSTEM TRACKING THROUGH THE EAST-CENTRAL AND EASTERN U.S.
LATE WEEK WITH SOME PRECIPITATION. THE 12Z ECMWF SEEMED TO BE
AMONG THE SLOWEST SOLUTIONS WITH THIS FRONT AND ASSOCIATED LOW
PRESSURE THROUGH THE EASTERN U.S.
THE WPC FORECAST USED A BLEND OF THE ENSEMBLE MEANS AND
DETERMINISTIC MODELS EVEN FOR THE EARLY PART OF THE FORECAST
PERIOD GIVEN THE PREFERENCE FOR AN INTERMEDIATE/ENSEMBLE MEAN
SOLUTION FOR THE WESTERN ATLANTIC LOW. INCREASED THE PROPORTION OF
THE ENSEMBLE MEANS TO OVER HALF BY DAYS 6-7 AMID INCREASING
UNCERTAINTY.
..WEATHER/HAZARDS HIGHLIGHTS
VERY COLD AIR ORIGINALLY STEMMING FROM THE ARCTIC WILL BE ATOP THE
NORTHERN GREAT BASIN AND ROCKIES AND SOUTHEASTWARD THROUGH THE
CENTRAL U.S. ON TUESDAY, THOUGH STARTING TO MODERATE A BIT FROM
THE SHORT RANGE PERIOD. STILL, WIDESPREAD TEMPERATURES OF 20 TO 40
DEGREES BELOW NORMAL ARE FORECAST, WITH LOW TEMPERATURES IN THE
-10 TO -20 RANGE ACROSS THE NORTHERN HALF OF THE PLAINS AND INTO
THE UPPER MIDWEST, AND LOCALLY EVEN COLDER IN HIGHER ELEVATIONS OF
THE ROCKIES. HIGH TEMPERATURES AT LEAST LOOK TO BE ABOVE 0F IN
MOST AREAS BY TUESDAY. ANY WIND CHILLS WOULD BE EVEN COLDER AND
THUS MORE DANGEROUS. THE COLD AIR DIVING FARTHER SOUTH INTO THE
SOUTHERN HALF OF THE PLAINS AND MISSISSIPPI VALLEY WILL NOT BE AS
COLD IN TERMS OF ABSOLUTE TEMPERATURES, BUT TEMPERATURE ANOMALIES
OF 20 TO 40 DEGREES BELOW AVERAGE ARE LIKELY TO SET WIDESPREAD
RECORDS ACROSS THE SOUTH INTO TUESDAY. BY WEDNESDAY, TEMPERATURES
FINALLY LOOK TO MODERATE IN THE ROCKIES TO HIGH PLAINS, THOUGH
CHILLY TEMPERATURES (ALBEIT IN MODERATED FORM) WILL SHIFT INTO THE
EASTERN HALF OF THE COUNTRY BEFORE WARMING CLOSER TO NORMAL ON
THURSDAY. SOME REINFORCING COLD AIR MAY REACH THE NORTHERN PLAINS
BY THURSDAY AND EXPAND TO INCLUDE MOST AREAS BETWEEN THE ROCKIES
AND APPALACHIANS FRIDAY AND FARTHER EAST BY SATURDAY. EXPECT LESS
EXTREME TEMPERATURE ANOMALIES THAN THOSE FORECAST EARLIER IN THE
PERIOD, BUT FRIDAY AND SATURDAY MAY STILL SEE TEMPERATURES 10-25F
BELOW NORMAL.
A LOW PRESSURE SYSTEM DEVELOPING ALONG A FRONT IN THE WESTERN
ATLANTIC WILL TRACK QUICKLY NORTHWARD TUESDAY INTO WEDNESDAY. SNOW
COULD SPREAD ACROSS THE MID-ATLANTIC AND NORTHEAST TO THE WEST OF
THE LOW TRACK, BUT SNOW AMOUNTS AND PLACEMENT/COVERAGE WILL BE
VERY SENSITIVE TO THIS STORM TRACK AND STRENGTH. THE GENERAL MODEL
TREND OVER THE PAST COUPLE OF CYCLES HAS BEEN FOR A FARTHER
EAST/MORE OFFSHORE LOW TRACK, LESSENING THE COVERAGE OF
PRECIPITATION FALLING FARTHER INLAND, BUT AN AREA OF 30 PERCENT OR
GREATER POTENTIAL FOR 0.25 INCH LIQUID IN THE FORM OF SNOW IS
STILL IN PLACE ACROSS EASTERN PARTS OF THE NORTHERN NORTHERN
MID-ATLANTIC COAST THROUGH NEW ENGLAND. CONTINUE TO MONITOR
FORECASTS FOR ADDITIONAL CHANGES. FARTHER SOUTH, MOISTURE MAY
FOCUS ALONG AND AHEAD OF THE FRONT THAT MOVES ACROSS FLORIDA ON
TUESDAY. THERE IS PERHAPS A NONZERO CHANCE OF HEAVY RAINFALL, BUT
DOES NOT LOOK IMPACTFUL ENOUGH FOR AN AREA IN THE EXCESSIVE
RAINFALL OUTLOOK TUESDAY. BACK TO THE NORTH, EXPECT CONTINUED
PERIODS OF LAKE EFFECT SNOW WITH PERSISTENCE OF COLD AIR AND
BREEZY CONDITIONS. THEN A FRONT AND POSSIBLE LOW PRESSURE SYSTEM
REACHING THE EAST LATE IN THE WEEK MAY PRODUCE SOME PRECIPITATION,
BUT AT THIS POINT CONFIDENCE IS VERY LOW REGARDING
COVERAGE/AMOUNTS AS WELL AS FOR WHERE THE RAIN-SNOW LINE WILL BE.
EXPECT MOISTURE TO INCREASE OVER THE NORTHWEST AROUND TUESDAY,
WITH SOMEWHAT INCREASED CONFIDENCE IN LOW PRESSURE JUST OFFSHORE
WEDNESDAY HELPING TO ENHANCE AMOUNTS. THIS EVENT WILL LIKELY SEE
SNOW CONFINED TO HIGHER ELEVATIONS THAN IN THE SHORTER TERM, BUT
AREAS WHERE EARLIER COLD AIR PERSISTS LONGER THAN FORECAST COULD
STILL PRESENT SOME LOWER ELEVATION WINTER WEATHER ISSUES.
PRECIPITATION IS LIKELY FOR THE NORTHERN HALF OR SO OF THE WEST
FOR WEDNESDAY-THURSDAY, WITH GENERALLY MORE OF A PRECIPITATION
FOCUS ALONG COASTAL AREAS INTO LATE WEEK.
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, 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