649
FXUS02 KWBC 170700
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
159 AM EST WED JAN 17 2024
VALID 12Z SAT JAN 20 2024 - 12Z WED JAN 24 2024
...ANOTHER ARCTIC AIRMASS COMES INTO THE CENTRAL U.S. THIS
WEEKEND, BUT NOT AS EXTREME AS THE FIRST ONE...
...MULTIPLE ROUNDS OF POTENTIALLY HEAVY PRECIPITATION WILL AFFECT
THE WEST...
...HEAVY RAIN POTENTIAL INCREASES ACROSS THE SOUTH-CENTRAL U.S.
INTO NEXT WEEK...
..OVERVIEW
THE BROAD AND DEEP UPPER TROUGHING THAT HAS DOMINATED THE PATTERN
OVER THE LOWER 48 THIS WEEK SHOULD FINALLY GET SHUNTED EAST THIS
WEEKEND, AS AN UPPER RIDGE AXIS MOVES FROM THE INTERMOUNTAIN WEST
SATURDAY INTO THE CENTRAL U.S. SUNDAY AND TOWARD THE EAST 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. THIS WEEKEND
BEFORE 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 RECENT COLD WAVE AT MOST
LOCATIONS. THEN UPPER TROUGHING WITH MULTIPLE EMBEDDED SHORTWAVES
WILL BE ATOP THE WESTERN HALF OF THE U.S., LEADING TO MULTIPLE
ROUNDS OF PRECIPITATION IN THE WEST THIS WEEKEND INTO NEXT WEEK.
ADDITIONALLY, FOR THE EARLY PART OF NEXT WEEK, RETURN FLOW FROM
THE GULF OF MEXICO COULD LEAD TO HEAVY RAIN ACROSS THE
SOUTH-CENTRAL U.S., WITH SOME WINTRY WEATHER POSSIBLE ON THE
NORTHERN SIDE OF THE PRECIPITATION SHIELD AROUND THE GREAT LAKES
EVEN AS TEMPERATURES WARM.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL GUIDANCE CONTINUES TO SHOW GOOD AGREEMENT ON THE LARGE SCALE
PATTERN WITH EXPECTED DIFFERENCES IN SMALL SCALE FEATURES. MODELS
INDICATE AN UPPER TROUGH SHIFTING FROM THE EAST INTO THE WESTERN
ATLANTIC THIS WEEKEND WITH COLD SURFACE HIGH PRESSURE ON ITS
BACKSIDE. AN UPPER RIDGE TRACKS EASTWARD BEHIND IT, WITH ITS AXIS
OVER THE ROCKIES SATURDAY MIGRATING TO THE MISSISSIPPI VALLEY
EARLY SUNDAY AND INTO THE EAST NEXT WEEK, WHERE IT PERSISTS.
MODELS ARE QUITE AGREEABLE ON THESE FEATURES. THEN MEAN TROUGHING
IS FORECAST TO SET UP IN THE WEST DURING THE PERIOD. THERE ARE
SOME DIFFERENCES IN SHORTWAVES WITHIN THE TROUGH THIS WEEK INTO
EARLY NEXT WEEK, BUT THEY FALL 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. BY TUESDAY-WEDNESDAY
ENERGY MAY CONSOLIDATE TO DEVELOP AN UPPER LOW IN THE SOUTHWEST
POSSIBLY SPLITTING AWAY FROM THE TROUGH INTO THE SOUTHERN STREAM.
THIS WILL CONTINUE TO BE MONITORED AS THE DETAILS ARE STILL
NEBULOUS.
GIVEN THE GOOD GENERAL AGREEMENT IN THE MODEL GUIDANCE, THE WPC
FORECAST BEGAN WITH A MULTI-MODEL DETERMINISTIC BLEND AND WAS ABLE
TO MAINTAIN A BLEND OF PRIMARILY DETERMINISTIC RUNS THROUGHOUT THE
WHOLE PERIOD. DID INCORPORATE SOME GEFS AND EC ENSEMBLE MEANS
THROUGH THE LATTER HALF OF THE PERIOD TO SMOOTH OUT MODEL
DIFFERENCES BUT MAINTAIN SOME STRENGTH IN INDIVIDUAL SYSTEMS.
..WEATHER/HAZARDS HIGHLIGHTS
THE WEST COAST STATES CAN EXPECT ROUNDS OF PRECIPITATION THIS
WEEKEND INTO EARLY NEXT WEEK. MULTIPLE DAYS OF RAIN AND PERIODS OF
RAIN RATES OVER HALF AN INCH PER HOUR ARE POSSIBLE AS INSTABILITY
MAY SNEAK ONSHORE, ALONG WITH GOOD DYNAMICAL SUPPORT FOR HEAVY
RAIN FROM STRONG SHORTWAVES ALOFT. THESE COULD CAUSE FLOODING
CONCERNS ESPECIALLY INTO SUNDAY-SUNDAY NIGHT. ROUNDS OF
PRECIPITATION SHOULD CONTINUE INTO EARLY NEXT WEEK FROM THE WEST
COAST AND EXPAND FARTHER 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 HAVE SOME
POSSIBLY PERSISTENT FREEZING RAIN THIS WEEKEND.
INCREASING MOISTURE AHEAD OF THE WESTERN U.S. TROUGHING WILL START
TO SPREAD RAIN TO THE SOUTHERN PLAINS ON SUNDAY. RAIN TOTALS ARE
FORECAST TO QUICKLY RAMP UP ON MONDAY AND TUESDAY FOR PARTS OF THE
SOUTHERN PLAINS INTO THE LOWER MISSISSIPPI VALLEY, AND THESE HEAVY
TOTALS COULD PRODUCE FLASH FLOODING CONCERNS, THOUGH BEYOND THE
EXCESSIVE RAINFALL OUTLOOK PERIOD. THE PRECIPITATION SHIELD
GRADUALLY SPREADING NORTHEASTWARD ON MONDAY AND TUESDAY COULD
SPREAD SOME WINTRY WEATHER ON ITS NORTHERN SIDE. THE GREAT LAKES
VICINITY IS MOST LIKELY TO SEE WINTRY WEATHER OUT OF THIS
PRECIPITATION, BUT FREEZING RAIN OR MIXED PRECIPITATION CANNOT BE
RULED OUT FARTHER SOUTH, BUT WITH LOW CONFIDENCE IN THE DETAILS.
ELSEWHERE, THE EAST WILL GENERALLY BE DRY THROUGH THE PERIOD AFTER
SOME LINGERING LAKE EFFECT SNOW INTO SATURDAY.
ARCTIC HIGH PRESSURE WILL PROVIDE A REINFORCING SURGE OF COLD AIR
THAT SHOULD BE WELL INTO THE CENTRAL AND EASTERN U.S. BY SATURDAY.
TEMPERATURES 15-30 DEGREES BELOW NORMAL WILL BE WIDESPREAD ON
SATURDAY. THE HIGHEST POTENTIAL FOR HAZARDOUS COLD AND DANGEROUS
WIND CHILLS WILL BE ACROSS THE NORTH-CENTRAL PLAINS INTO PARTS OF
THE UPPER MIDWEST. LOCALIZED ANOMALIES MORE THAN 30F BELOW NORMAL
ARE POSSIBLE RIGHT UNDERNEATH THE HIGH IN THE NORTH-CENTRAL
PLAINS/MISSISSIPPI VALLEY, WITH LOW TEMPERATURES NEAR OR BELOW
-20F POSSIBLY SETTING RECORDS. AT LEAST WINDS SHOULD BE WEAK RIGHT
IN THE VICINITY OF THE HIGH TO LIMIT WIND CHILLS. OVERALL THIS
COLD EPISODE WILL STILL BE NOTABLE EVEN IF NOT QUITE AS EXTREME AS
THE CURRENT/RECENT COLD EVENT FOR MOST AREAS. TEMPERATURES SHOULD
STILL BE CHILLY ON SUNDAY BUT STARTING TO MODERATE TOWARD NORMAL.
THEN TEMPERATURES LOOK TO CONTINUE TO WARM MONDAY-WEDNESDAY AS THE
SURFACE HIGH SHIFTS INTO THE ATLANTIC AND THE UPPER RIDGE ALLOWS
FOR MORE SOUTHERLY FLOW. BY MIDWEEK THE EASTERN HALF OF THE
COUNTRY HAS ABOVE NORMAL TEMPERATURES FORECAST, AROUND 15-30F
ABOVE AVERAGE FOR LOWS AND 10-20F ABOVE FOR HIGHS. FROM THE
ROCKIES WESTWARD, NEAR NORMAL TEMPERATURES FOR HIGHS AND LOW
TEMPERATURES AROUND 10-15F ABOVE NORMAL ARE EXPECTED.
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
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