011
FXUS02 KWBC 301857
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
156 PM EST MON JAN 30 2023
VALID 12Z THU FEB 2 2023 - 12Z MON FEB 6 2023
...HEAVY RAIN COULD CAUSE FLASH FLOODING IN THE LOWER MISSISSIPPI
VALLEY TO SOUTHEAST THURSDAY...
...DANGEROUSLY COLD TEMPERATURES AND WIND CHILLS ARE FORECAST
ACROSS THE NORTH-CENTRAL U.S. LATE WEEK SPREADING INTO THE
NORTHEAST FOR THE WEEKEND...
19Z UPDATE: THE LATEST 12Z MODEL GUIDANCE SUITE MAINTAINS ABOVE
AVERAGE AGREEMENT THROUGH THIS FORECAST PERIOD ON THE SYNOPTIC
SCALE. IT IS WORTH NOTING THAT THE GFS/GEFS IS A BIT MORE
PROGRESSIVE WITH THE SHORTWAVE CROSSING THE SOUTH-CENTRAL U.S.
LATE IN THE WEEK. THE NEXT SHORTWAVE CROSSING THE ROCKIES
SATURDAY AND THEN THE PLAINS BY EARLY SUNDAY IS DEPICTED MORE
STRONGLY WITH THE CMC, WHICH SUPPORTS A CLOSED LOW SOLUTION OVER
THE SOUTHERN PLAINS, AND IS SLOWER ONCE IT REACHES THE EASTERN
U.S. EARLY NEXT WEEK. THE THIRD IN A SERIES OF DISTURBANCES IS
ALSO DEPICTED WELL BY THE GUIDANCE, ALTHOUGH THE GFS IS A LITTLE
SLOWER. MORE SUBSTANTIAL DIFFERENCES BECOME APPARENT ACROSS THE
NORTHEAST PACIFIC GOING INTO MONDAY AND BEYOND. THE WPC
FRONTS/PRESSURES FORECAST WAS PRIMARILY BASED ON A
MULTI-DETERMINISTIC BLEND THROUGH SATURDAY, AND THEN UP TO 40% OF
THE ENSEMBLE MEANS WAS INCORPORATED BY MONDAY. THE SLIGHT RISK
AREA FOR EXCESSIVE RAINFALL ON DAY 4 HAS BEEN MAINTAINED WITH ONLY
MINOR REVISIONS. THE PREVIOUS FORECAST DISCUSSION IS APPENDED
BELOW FOR REFERENCE. /HAMRICK
-------------------------
..OVERVIEW
THE OVERALL UPPER-LEVEL PATTERN DURING THE MEDIUM RANGE PERIOD
LOOKS TO BE FAIRLY WAVY AND PROGRESSIVE, WITH NORTHERN STREAM
TROUGHING EXTENDING FROM A PERSISTENT HUDSON BAY CLOSED LOW
SHIFTING FROM THE MIDWEST/GREAT LAKES INTO THE NORTHEAST LATE THIS
WEEK PRODUCING SIGNIFICANTLY COLD TEMPERATURES AND WIND CHILLS.
MEANWHILE AN INITIALLY SOUTHERN STREAM UPPER TROUGH WILL SHIFT
FROM THE SOUTHERN PLAINS ACROSS THE SOUTHEAST AS IT PHASES BACK
WITH THE NORTHERN STREAM, AND IS EXPECTED TO PROVIDE SUPPORT FOR
HEAVY RAINFALL POTENTIALLY CAUSING FLASH FLOODING FROM THE LOWER
MISSISSIPPI VALLEY INTO THE SOUTHEAST THROUGH THURSDAY. MEANWHILE,
RIDGING OVER THE WEST AS THE PERIOD BEGINS WILL GIVE WAY TO A
COUPLE OF ROUNDS OF TROUGHING COMING IN FROM THE PACIFIC AND LEAD
TO A WETTER PATTERN FOR THE WEST, BUT NOTHING TOO EXTREME THERE.
..GUIDANCE/PREDICTABILITY ASSESSMENT
AS THE PERIOD BEGINS THURSDAY, MODEL GUIDANCE IS IN GOOD AGREEMENT
FOR THE OVERALL PATTERN, INCLUDING THE NORTHERN AND SOUTHERN
STREAM TROUGHS IN THE CENTRAL U.S. TRACKING EAST AND PHASING
THROUGH LATE WEEK. THE 12Z UKMET WAS A BIT ON THE SLOWER SIDE OF
THE REST OF THE WELL CLUSTERED GUIDANCE. FARTHER WEST, THERE
REMAINED SOME SPREAD IN 12/18Z MODEL CYCLE WITH THE TIMING OF
TROUGHING COMING IN FROM THE PACIFIC BY AROUND FRIDAY, WITH THE
ECMWF AND UKMET SLOWER WHILE THE CMC CLUSTERS BETTER WITH THE
FASTER GFS RUNS. A MIDDLE GROUND IN BETWEEN THESE SEEMED MOST
LIKELY, AS THE ECMWF AND UKMET APPEARED TO BE TOO SLOW COMPARED TO
THE TROUGH AXES IN THE ENSEMBLE MEANS. THE 12Z ECMWF STAYS SLOW
WHILE THE 12Z UKMET SEEMED TO FLATTEN THIS TROUGH TOO FAST BY DAY
5 WHILE OTHER GUIDANCE TRACKS THE TROUGH GOING ALL THE WAY INTO
THE CENTRAL AND EASTERN U.S.--WHICH THE 12Z CMC WAS PERHAPS TOO
DEEP WITH THE TROUGH COMPARED TO THE ENSEMBLE MEMBERS ONCE IT
REACHES THE EAST BY SUNDAY. GIVEN THE MINOR TO MODERATE UKMET
ISSUES, THE EARLY PART OF THE WPC FORECAST BLEND WAS BASED ON A
BLEND OF THE 12/18Z GFS AND 12Z ECMWF AND CMC. THE PATTERN ON THE
LARGE SCALE WITH THESE TROUGHS AND A NEXT TROUGH COMING INTO THE
WEST EARLY NEXT WEEK ARE ALL REASONABLY AGREEABLE GIVEN THE
FORECAST LEAD TIME, BUT TRANSITIONED THE BLEND TO INCLUDE THE GEFS
AND EC ENSEMBLE MEANS TO MINIMIZE ANY SMALL SCALE DIFFERENCES IN
THE INDIVIDUAL MODELS. GOOD CONTINUITY WAS MAINTAINED WITH THE
PREVIOUS FORECAST, AND THE INCOMING 00Z MODELS SEEM TO BE
CONSISTENT AS WELL.
..WEATHER/HAZARD HIGHLIGHTS
THE SOUTHERN STREAM UPPER TROUGH/LOW TRACKING ACROSS THE SOUTHERN
U.S. AND THE BROADER NORTHERN STREAM TROUGH WILL PROVIDE GOOD
UPPER-LEVEL SUPPORT FOR FRONTAL BOUNDARIES WITH WAVES OF LOW
PRESSURE THROUGH THE SOUTH-CENTRAL TO SOUTHEASTERN U.S., WHICH
COMBINED WITH GULF MOISTURE STREAMING IN WILL LEAD TO WIDESPREAD
PRECIPITATION. BY THURSDAY MOST OF THE PRECIPITATION LOOKS TO BE
RAIN, AND HEAVY RAIN IS FORECAST FROM PARTS OF THE LOWER
MISSISSIPPI VALLEY INTO THE SOUTHEAST AND PERHAPS THE SOUTHERN
APPALACHIANS INTO THE CAROLINAS. INSTANCES OF FLOODING ARE
POSSIBLE ESPECIALLY WHERE THERE IS SUFFICIENT INSTABILITY FOR
HIGHER RAIN RATES, AND THERE IS A SLIGHT RISK IN PLACE IN WPC'S
EXPERIMENTAL EXCESSIVE RAINFALL OUTLOOK FOR MUCH OF THE
SOUTHEASTERN U.S. THURSDAY. RAIN MAY CONTINUE INTO FRIDAY FOR THE
SOUTHEAST AND THE FLORIDA PENINSULA, WITH DRIER CONDITIONS
SATURDAY BEFORE SOME MOISTURE FROM THE ATLANTIC MAY STREAM INTO
THE EASTERN SEABOARD SUNDAY. FARTHER NORTH, LAKE EFFECT SNOW
SHOWERS ARE POSSIBLE, AND LIGHT SNOW MAY EXPAND IN COVERAGE ACROSS
THE MIDWEST/GREAT LAKES/NORTHEAST BY THE WEEKEND WITH A CLIPPER
SYSTEM. MEANWHILE IN THE WEST, INCREASING PRECIPITATION CHANCES
ARE EXPECTED LATE THIS WEEK INTO EARLY NEXT WEEK NEAR AND AHEAD OF
A COUPLE OF UPPER TROUGHS. THE PACIFIC NORTHWEST INTO NORTHERN
CALIFORNIA WILL BE THE MOST LIKELY TO GET MULTIPLE ROUNDS OF LOWER
ELEVATION RAIN AND HIGHER ELEVATION SNOW, ALONG WITH THE NORTHERN
ROCKIES. PRECIPITATION AMOUNTS WILL BE MORE TYPICAL OF A NORMAL
COOL SEASON EVENT AND NOTHING LIKE THOSE IN THE PARADE OF
ATMOSPHERIC RIVER EVENTS ABOUT A MONTH AGO.
ANOTHER ROUND OF VERY COLD CONDITIONS IS LIKELY FOR THE
NORTH-CENTRAL U.S. THURSDAY-FRIDAY UNDERNEATH COLD UPPER
TROUGHING. HIGHS IN THE SINGLE DIGITS ARE LIKELY FOR NORTH DAKOTA
INTO NORTHERN MINNESOTA WHILE BITTERLY COLD LOWS COMBINED WITH
WIND WILL PRODUCE DANGEROUS WIND CHILLS. MUCH BELOW NORMAL
TEMPERATURES THEN SHIFT INTO THE NORTHEAST BY LATE WEEK, WITH THE
POSSIBILITY OF HIGHS BELOW ZERO IN NORTHERN NEW ENGLAND BY
SATURDAY, AND BITTERLY COLD LOWS POTENTIALLY SETTING DAILY
RECORDS. ON THE OTHER HAND, THE SOUTHEAST INTO THE FLORIDA
PENINSULA SHOULD SEE ABOVE AVERAGE TEMPERATURES THURSDAY INTO
FRIDAY, AND TEMPERATURES ARE FORECAST TO WARM TO ABOVE AVERAGE
ACROSS THE CENTRAL U.S. IN PARTICULAR BY THE WEEKEND INTO EARLY
NEXT WEEK.
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, 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
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