573
FXUS02 KWBC 270724
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
224 AM EST FRI JAN 27 2023
VALID 12Z MON JAN 30 2023 - 12Z FRI FEB 03 2023
...DANGEROUSLY COLD TEMPERATURES AND WIND CHILLS ARE FORECAST
ACROSS THE NORTHERN PLAINS AND UPPER MIDWEST THROUGH EARLY NEXT
WEEK...
..OVERVIEW
A PERSISTENT CLOSED UPPER LOW ATOP THE HUDSON BAY WILL SEND A
SERIES OF SHORTWAVES INTO THE U.S., AND ITS EXTENSION OF TROUGHING
WILL LEAD TO COLDER THAN AVERAGE TEMPERATURES THAT COULD BE MOST
DANGEROUS FOR THE NORTH-CENTRAL U.S. IN PARTICULAR. MEANWHILE
RIDGING/AN UPPER HIGH OVER CUBA DURING MUCH OF NEXT WEEK SHOULD
KEEP THE SOUTHWEST WARMER THAN NORMAL. BETWEEN THESE UPPER-LEVEL
FEATURES AND TEMPERATURE REGIMES, ACTIVE WEATHER IS EXPECTED AS
SHORTWAVE ENERGY AND THE COMBINATION OF A COUPLE WAVY FRONTS ALONG
WITH PERIODS OF GULF INFLOW SUPPORT A COUPLE OF SIGNIFICANT
PRECIPITATION EVENTS EAST OF THE ROCKIES WITH RAINFALL TO THE
SOUTH/SOUTHEAST AND SOME WINTRY WEATHER IN THE COLDER AIR. SOME
LOCALLY ENHANCED RAIN AND HIGHER ELEVATION SNOW ARE POSSIBLE IN
THE SOUTHWEST AROUND MONDAY AS AN UPPER LOW/TROUGH DIGS INTO THE
MEAN TROUGH, WHILE THE WEST COAST MAY SEE INCREASING PRECIPITATION
CHANCES BY LATER NEXT WEEK.
..GUIDANCE/PREDICTABILITY ASSESSMENT
AS THE MEDIUM RANGE PERIOD BEGINS MONDAY, A FEATURE OF CONCERN
WILL BE A POSSIBLE UPPER LOW AROUND CALIFORNIA EMBEDDED WITHIN THE
MEAN POSITIVELY TILTED TROUGH. THERE HAS BEEN SOME MODEL WAFFLING
AS TO WHETHER A CLOSED LOW DEVELOPS AND THE DEGREE AT WHICH IT
STAYS PHASED WITH THE NORTHERN STREAM THROUGH TUESDAY AND BEYOND.
IN THE 12/18Z MODEL CYCLE, MOST GUIDANCE ALL INDICATED A CLOSED
LOW OTHER THAN THE UKMET. BUT THERE REMAINED SOME SIGNIFICANT
TIMING DIFFERENCES EVEN WITH MODELS THAT SHOW THE CLOSED LOW, WITH
GFS RUNS FASTER AND ECMWF AND CMC RUNS SLOWER TO MOVE IT
EASTWARD--IN FACT, SLOWER THAN MOST ENSEMBLE MEMBERS. IN THE NEWER
00Z MODEL GUIDANCE, THE UKMET DOES NOW SHOW CLOSED LOW
DEVELOPMENT, AND ECMWF AND CMC RUNS SPED UP A BIT. SO HOPEFULLY
MODELS ARE COMING TO A BETTER CONSENSUS WITH THE TRACK AND TIMING
OF THE UPPER ENERGY/LOW.
UPSTREAM, THERE CONTINUES TO BE CONSIDERABLE VARIABILITY FOR THE
OVERALL FLOW ACROSS THE PACIFIC AND IF/WHEN IT PRESSES THE
NORTHWESTERN U.S. RIDGE EASTWARD, PARTICULARLY LATER IN THE WEEK.
INDIVIDUAL MODELS VARY AS DO THE ENSEMBLE MEMBERS, WITH NO REAL
EMERGING CONSENSUS AT THIS POINT. THE ENSEMBLE MEANS WERE FAVORED
HERE.
ADDITIONALLY, THERE REMAIN SOME MODEL DIFFERENCES WITH PLACEMENT
OF FRONTAL BOUNDARIES PARTICULARLY IN THE SOUTHEASTERN U.S. WHILE
THESE ARE RELATIVELY MINOR FOR THE FORECAST LEAD TIMES, THE
LOCATIONS OF THE FRONTS WILL BE IMPORTANT FOR AXES OF ANY HEAVY
RAIN AS WELL AS TRANSITIONS TO SNOW AND/OR ICE AND THUS IMPACTFUL.
THESE FRONTAL POSITIONS WILL CONTINUE TO BE REFINED GOING FORWARD.
THE WPC MODEL BLEND WAS BASED ON A CONSENSUS OF THE 12/18Z GFS AND
12Z ECMWF AND CMC RUNS EARLY IN THE PERIOD AND TRIED TO AIM FOR A
MIDDLE GROUND FORECAST FOR THE UPPER LOW FOR EXAMPLE BY BLENDING
IN SOME ENSEMBLE MEAN GUIDANCE AS WELL. AN INCREASING PROPORTION
OF ENSEMBLE MEAN GUIDANCE WAS USED LATER IN THE PERIOD AMID
INCREASING UNCERTAINTY.
..WEATHER/HAZARD HIGHLIGHTS
AS THE WORKWEEK BEGINS NEXT WEEK, THE NORTH-CENTRAL U.S. WILL
CONTINUE TO BE QUITE COLD AFTER A CHILLY WEEKEND AS WELL, AS A
STRONG COLD FRONT PRODUCES A SURGE OF ARCTIC AIR BEHIND IT. HIGHS
IN THE SINGLE DIGITS AND EVEN BELOW ZERO ARE POSSIBLE IN THE
DAKOTAS INTO MINNESOTA WHILE BITTERLY COLD LOWS COMBINED WITH WIND
WILL PRODUCE DANGEROUS WIND CHILLS. MUCH BELOW NORMAL TEMPERATURES
SHOULD EXTEND ACROSS MUCH OF THE CENTRAL U.S. THROUGH MIDWEEK
ESPECIALLY, AS WELL AS ACROSS MUCH OF THE INTERIOR WEST WITH
TEMPERATURES 15-25F BELOW NORMAL THROUGH MONDAY-TUESDAY WITH
GRADUAL MODERATION THEREAFTER. MEANWHILE THE FAR SOUTHEAST AND
FLORIDA PENINSULA SHOULD SEE THE MOST CONSISTENT ABOVE AVERAGE
TEMPERATURES WITH HIGHS 10-15F ABOVE AVERAGE AND LOWS WITH +20F
ANOMALIES.
THE EMBEDDED POSSIBLE UPPER LOW WITHIN THE TROUGH COULD PRODUCE
SOME ENHANCED PRECIPITATION ACROSS SOUTHERN CALIFORNIA CONTINUING
INTO MONDAY AND ACROSS THE SOUTHWEST MONDAY-TUESDAY. THEN THIS
FEATURE AND THE OVERALL TROUGHING AND OTHER SHORTWAVES WILL
PROVIDE SUPPORT FOR FRONTAL BOUNDARIES WITH WAVES OF LOW PRESSURE
THROUGH THE SOUTH-CENTRAL TO SOUTHEASTERN U.S., WHICH COMBINED
WITH GULF MOISTURE STREAMING IN COULD LEAD TO MULTIPLE ROUNDS OF
PRECIPITATION. ON THE SOUTHERN SIDE LOCALLY HEAVY RAIN AND
LOCALIZED FLOODING ARE POSSIBLE, ESPECIALLY AT TIMES WHEN THERE IS
SUFFICIENT INSTABILITY FOR HIGHER RAIN RATES. WITH COLDER THAN
NORMAL AIR IN PLACE ON THE NORTHERN SIDE, WINTER WEATHER COULD
ALSO BE A THREAT. THERE ARE UNCERTAIN CHANCES OF SNOW ACROSS PARTS
OF THE SOUTHERN HALF OF THE PLAINS AND MISSISSIPPI VALLEY INTO THE
OHIO/TENNESSEE VALLEYS AND THE MID-ATLANTIC AT TIMES. THIS IS ALSO
A PATTERN THAT COULD SUPPORT FREEZING RAIN WITH ICE ACCUMULATIONS
WITH THE COLD AIR IN PLACE AT THE SURFACE AND POTENTIAL FOR WARM
MOIST AIR TO FLOW OVERTOP IT. THE PLACEMENT OF HEAVIEST RAIN,
FREEZING RAIN, AND SNOW ALL REMAIN IN QUESTION GIVEN SMALL-SCALE
DETAILS LIKE THE FRONTAL POSITIONS ARE QUITE UNCERTAIN. A COUPLE
ROUNDS OF LIKELY MAINLY LIGHT SNOW ARE ALSO POSSIBLE IN THE
NORTHEAST NEXT WEEK. BY LATER NEXT WEEK, PRECIPITATION LOOKS TO
RETURN TO THE WEST COAST BUT WITH UNCERTAINTY IN THE SPECIFICS
THERE AS WELL.
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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