289
FXUS02 KWBC 071902
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
202 PM EST TUE JAN 7 2025
VALID 12Z FRI JAN 10 2025 - 12Z TUE JAN 14 2025
...HAZARDOUS COLD AND SNOW/ICE FORECAST TO IMPACT PARTS OF THE
SOUTHERN U.S. LATE WEEK INTO THE WEEKEND...
...ANOTHER ARCTIC BLAST FORECAST FOR THE NORTHERN PLAINS AND UPPER
MIDWEST EARLY NEXT WEEK...
..OVERVIEW
WINTER IS IN FULL SWING AND WILL CONTINUE TO PUT ON A SHOW IN THE
MEDIUM RANGE PERIOD. LATE THIS WEEK INTO THE WEEKEND, A LOW
PRESSURE SYSTEM MOVING UP FROM THE GULF WILL INTERACT WITH THE
ARCTIC AIR MASS SPILLING SOUTH ACROSS THE CENTRAL AND EASTERN U.S.
AND BRING WINTRY WEATHER TO PORTIONS OF THE SOUTHERN U.S.. HEAVY
SNOW, SLEET, AND FREEZING RAIN WILL LIKELY CREATE HAZARDOUS
CONDITIONS FROM THE SOUTHERN PLAINS THROUGH THE MISSISSIPPI VALLEY
TO THE MID-ATLANTIC. WINTRY WEATHER IS ALSO EXPECTED IN THE PACIFIC
NORTHWEST AS A FRONTAL SYSTEM MOVES ONSHORE ON FRIDAY. THIS SYSTEM
WILL PUSH ACROSS THE ROCKIES AND PLAINS THIS WEEKEND AND MOVE
OFFSHORE INTO THE ATLANTIC EARLY NEXT WEEK WHILE HIGH PRESSURE
RIDGING BUILDS OVER THE WEST COAST. BY SUNDAY, ANOTHER BLAST OF
ARCTIC AIR IS FORECAST TO SPILL INTO THE NORTHERN PLAINS AND UPPER
MIDWEST AS A COLD FRONT DROPS SOUTH ACROSS THE CENTRAL U.S.,
CREATING HAZARDOUS COLD TEMPERATURES EARLY NEXT WEEK.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL AND ENSEMBLE FORECAST SPREAD CONTINUES TO DECREASE, WITH
HIGHER AGREEMENT AND RUN-TO-RUN CONSISTENCY. THERE ARE STILL SOME
DIFFERENCES IN THE FINER SCALE DETAILS, WHICH COULD AFFECT THE
SENSIBLE WEATHER AND IMPACTS ASSOCIATED WITH THE LATE WEEK WINTER
STORM, BUT THIS IS TYPICAL AT THIS TIME RANGE AND WILL LIKELY BE
RESOLVED ONCE THE EVENT MOVES INTO THE SHORT RANGE PERIOD. THERE IS
A BIT MORE MODEL SPREAD CONCERNING WEAKER FEATURES EARLY NEXT
WEEK, BUT THE AFFECT ON SENSIBLE WEATHER SHOULD BE MINIMAL SINCE NO
STRONG STORM SYSTEMS ARE ANTICIPATED.
FOR WPC'S AFTERNOON FORECAST, A GENERAL BLEND OF THE AVAILABLE
DETERMINISTIC AND ENSEMBLE GUIDANCE SEEMED TO PRODUCE A GOOD
FORECAST REPRESENTATIVE OF EXPECTED IMPACTS FROM THE WINTER STORM.
LATER IN THE PERIOD, HIGHER EMPHASIS WAS PLACED ON ENSEMBLE
GUIDANCE TO SMOOTH OUT DIFFERENCES IN THE DETERMINISTIC MODELS.
..WEATHER/HAZARDS HIGHLIGHTS
ANOMALOUS MOISTURE WILL FOCUS OVER THE LOWER MISSISSIPPI VALLEY
AND CENTRAL GULF COAST ON FRIDAY WHILE A LOW PRESSURE SYSTEM
STRENGTHENS IN THE NORTHERN GULF OF MEXICO. HEAVY RAIN ALONG THE
COAST COULD RESULT IN LOCALIZED FLOODING, ESPECIALLY IN URBAN AND
POOR DRAINAGE AREAS, AND THERE WILL BE A MARGINAL RISK OF EXCESSIVE
RAINFALL ON FRIDAY (DAY 4 EXCESSIVE RAINFALL OUTLOOK).
AS THE GULF SYSTEM PROGRESSES, MOISTURE WILL SPREAD NORTH WHILE
ARCTIC AIR SURGES SOUTH, RESULTING IN HAZARDOUS WINTRY
PRECIPITATION ACROSS THE SOUTHERN PLAINS ON THURSDAY, AND ACROSS
THE MISSISSIPPI AND TENNESSEE VALLEYS, CENTRAL AND SOUTHERN
APPALACHIANS, AND INTERIOR SOUTHEAST ON FRIDAY. THIS SYSTEM WILL
LIKELY PRODUCE A LARGE SWATCH OF HEAVY SNOW, SLEET, AND FREEZING
RAIN, CREATING HAZARDOUS TRAVEL CONDITIONS FOR MANY. ON SATURDAY,
THE SYSTEM WILL BE PUSHING OFFSHORE OF THE CAROLINAS, AND COULD
PRODUCE LIGHT WINTRY PRECIPITATION FOR THE COASTAL MID-ATLANTIC AND
NORTHEAST. IF THE LOW SLOWS DOWN, HEAVIER PRECIPITATION COULD BE
POSSIBLE, BUT LATEST TRENDS ARE FAVORING A FASTER PROGRESSION WITH
MINIMAL IMPACTS.
IN THE WEST, WIDESPREAD LIGHT TO MODERATE PRECIPITATION (LOW
ELEVATION RAIN AND MOUNTAIN SNOW) WILL ACCOMPANY THE FRONTAL SYSTEM
MOVING ONSHORE ON FRIDAY, MAINLY IN THE PACIFIC NORTHWEST.
PRECIPITATION WILL SPREAD ACROSS THE INTERMOUNTAIN WEST AND ROCKIES
TO THE NORTHERN PLAINS ON SATURDAY, THEN TO THE GREAT LAKES ON
SUNDAY. THIS SYSTEM IS FORECAST TO WEAKEN AS IT PUSHES EAST, AND
PRECIPITATION CHANCES WILL BE LOW EARLY NEXT WEEK.
THIS WEATHER PATTERN WILL FAVOR THE CONTINUATION OF WELL BELOW
NORMAL TEMPERATURES FOR MOST OF THE NATION. HAZARDOUS COLD IS
EXPECTED ACROSS THE SOUTHERN U.S. WITH THE WINTER STORM BRINGING
TEMPERATURE ANOMALIES OF 10-20 DEGREES BELOW NORMAL. TEMPERATURES
WILL MODERATE SLIGHTLY THIS WEEKEND, BUT REMAIN BELOW NORMAL, THEN
ANOTHER ARCTIC BLAST IS SET TO MOVE INTO THE NORTHERN PLAINS AND
UPPER MIDWEST EARLY NEXT WEEK. THIS SURGE OF ARCTIC AIR WILL DROP
TEMPERATURES 10-15 DEGREES BELOW NORMAL, WITH HIGHS IN THE SINGLE
DIGITS AND TEENS AND LOWS BELOW ZERO.
DOLAN
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 (QPF), EXCESSIVE RAINFALL
OUTLOOK (ERO), WINTER WEATHER OUTLOOK (WWO) PROBABILITIES, HEAT
INDICES, AND KEY MESSAGES CAN BE ACCESSED FROM:
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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