565
FXUS02 KWBC 030700
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
200 AM EST FRI JAN 3 2025
VALID 12Z MON JAN 06 2025 - 12Z FRI JAN 10 2025
...ARCTIC BLAST/WINTER STORM TO BRING HEAVY SNOW AND HAZARDOUS ICE
FROM THE CENTRAL PLAINS TO THE MID-ATLANTIC...
..OVERVIEW
A HIGHLY FAVORABLE GUIDANCE SIGNAL REMAINS IN PLACE IN SUPPORT OF
THE DEVELOPMENT OF A WINTER STORM BY SUNDAY FROM THE CENTRAL
PLAINS TO MID-MISSISSIPPI AND OHIO/TENNESSEE VALLEYS THROUGH THE
APPALACHIANS AND THE MID-ATLANTIC, LASTING INTO THE MED-RANGE
PERIOD MONDAY FOR EASTERN AREAS. HEAVY SNOW IS LIKELY, ALONG WITH
SIGNIFICANT SLEET AND A WAVY TRANSITIONAL ZONE OF ICE/FREEZING
RAIN FROM THE MID-SOUTH TO THE SOUTH-CENTRAL APPALACHIANS/MID-
ATLANTIC. ON THE SOUTHERN SIDE, HEAVY RAIN AND THUNDERSTORMS ARE
LIKELY OVER PARTS OF THE LOWER MISSISSIPPI AND TENNESSEE VALLEYS
AND SOUTHEAST. THE WEATHER IS FORECAST TO QUIET DOWN IN TERMS OF
PRECIPITATION AFTER THIS SYSTEM, ASIDE FROM PERIODIC GREAT LAKE
EFFECT SNOW ENHANCEMENT WITH REINFORCEMENT OF ARCTIC FLOW AND AREAS
OF MAINLY LIGHT PRECIPITATION IN THE WESTERN AND CENTRAL U.S., BUT
MUCH COLDER THAN AVERAGE TEMPERATURES ARE LIKELY TO PERSIST
THROUGH THE WEEK IN MOST AREAS EAST OF THE ROCKIES. THERE IS ALSO
AN UNCERTAIN SIGNAL FOR FAR SOUTH-CENTRAL U.S. RAIN/WINTER
PRECIPITATION DEVELOPMENT INTO LATER NEXT WEEK TO MONITOR GIVEN
SEPARATED SOUTHERN STREAM FLOW SYSTEM EJECTION POTENTIAL.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL AND ENSEMBLE FORECAST SPREAD CONTINUES TO SLOWLY IMPROVE FOR
MED-RANGE TIME SCALES OVER THE PAST FEW GUIDANCE CYCLES, INCLUDING
FOR THE LATEST 00 UTC CYCLE. LARGER SCALE FLOW EVOLUTION NOW SEEMS
MORE COMMONLY SHARED BY MOST GUIDANCE WELL INTO NEXT WEEK IN A
PATTERN WITH SEEMINGLY ABOVE NORMAL PREDICTABILITY, BUT CONTINUED
LOCAL SYSTEM AND FOCUS ISSUES STILL LINGER INTO SHORTER RANGE TIME
SCALES. HOWEVER, A FORECAST PLAN UTILIZING A COMPOSITE MODEL AND
ENSEMBLE SOLUTION ALONG WITH THE NATIONAL BLEND OF MODELS SEEMS TO
PROVIDE A MORE CONSISTENT AND REASONABLE FORECAST BASIS THAT ALONG
WITH TARGETED MANUAL ADJUSTMENTS HIGHLIGHTS THE MAIN THREAT IMPACTS
AND MESSAGING. THIS SOLUTION MAINTAINS GOOD WPC PRODUCT CONTINUITY.
..WEATHER/HAZARDS HIGHLIGHTS
IT VERY MUCH REMAINS THE CASE THAT THE UPCOMING SHORT TO MED-RANGE
RANGE WINTER PATTERN FROM THE WEEKEND INTO EARLY NEXT WEEK WILL BE
ESPECIALLY IMPACTFUL FOR A BROAD SWATH OF THE CENTRAL TO EASTERN
U.S.. AN UPPER TROUGH IN THE CENTRAL U.S. SUNDAY WILL PRODUCE A
CONSOLIDATING SURFACE LOW IN THE SOUTHERN PLAINS. PRECIPITATION IS
EXPECTED TO PUSH ACROSS THE EASTERN HALF OF THE U.S. WITH THIS LOW
AND GOOD DYNAMICAL SUPPORT ALOFT. COLD AIR IN PLACE WILL FAVOR
WIDESPREAD HEAVY SNOW THAT WILL BE HEAVY ACROSS AREAS FROM THE
CENTRAL PLAINS, MID-MISSISSIPPI VALLEY, AND OHIO VALLEY SUNDAY.
SNOW WILL PUSH INTO THE MID-ATLANTIC SUNDAY NIGHT INTO MONDAY. JUST
TO THE SOUTH, THERE IS A RELATIVELY BROAD TRANSITIONAL AREA THAT
WILL SEE IMPACTFUL MIXED PRECIPITATION TYPES, TRANSITIONING BETWEEN
MULTIPLE P-TYPES AND/OR SEEING SNOW AND SLEET/FREEZING RAIN.
POTENTIALLY SIGNIFICANT SLEET AND FREEZING RAIN ARE POSSIBLE ACROSS
THE OZARKS EAST TO THE TENNESSEE VALLEY AND SOUTH-CENTRAL
APPALACHIANS/MID- ATLANTIC. WPC IS ISSUING KEY MESSAGES FOR THIS
WINTER STORM. MEANWHILE FARTHER SOUTH IN THE WARM SECTOR, EXPECT
LINGERING TRAILING FRONTAL SHOWERS AND THUNDERSTORMS TO SPREAD
EASTWARD INTO AND ACROSS THE SOUTHEAST INTO MONDAY.
GREAT LAKE EFFECT SNOW WILL BECOME REJUVENATED WITH COLD AND BRISK
FLOW BEHIND THE MAIN LOW PRESSURE SYSTEM AND WITHIN LATER NEXT WEEK
COLD PATTERN AMPLITUDE. LIGHT TO MODEST PRECIPITATION INCLUDING
HIGHER ELEVATION SNOW IS EXPECTED TO SPREAD FOCUS OUT FROM THE
NORTHWEST THROUGH THE ROCKIES NEXT WEEK, AND EVENTUALLY THE
NORTHERN PLAINS WITH AN EMERGING SURFACE LOW. FARTHER SOUTH, THERE
ARE SOME CHANCES FOR PRECIPITATION FROM THE SOUTHWEST TO SOUTHERN
PLAINS AND LOWER MISSISSIPPI VALLEY DEPENDENT ON UNCERTAIN
TIMING/EJECTION OF A POTENTIALLY AMPLIFIED SOUTHERN STREAM SYSTEM.
AN EMERGING PRECIPITTAION PATTERN MAY UNFOLD INTO LATER NEXT WEEK
AND WITH THE COLD AIR IN PLACE FROM TEXAS EASTWARD, SOME AREAS
WILL NEED TO MONITOR THE ONSET OF SOME WINTRY PRECIPITATION.
COLDER THAN NORMAL TEMPERATURES ARE LIKELY ACROSS THE CENTRAL AND
EASTERN U.S. UNDERNEATH ROUNDS OF UPPER TROUGHING AND WITH COLD
SURFACE HIGH PRESSURE SYSTEMS. NOTABLE COLD IS POSSIBLE IN THE
NORTHERN TIER, WITH EVEN HIGH TEMPERATURES BARELY REACHING 0F AND
LOWS BETWEEN -10F AND -20F IN SOME AREAS. THIS SHOULD NOT BE RECORD
BREAKING, BUT THE COLD COULD STILL BE HAZARDOUS AS WIND CHILL
VALUES MAY DIP BELOW -20F TO -30F. TEMPERATURE ANOMALIES OF 10-20
DEGREES ARE ALSO LIKELY ACROSS PARTS OF THE NORTHERN/CENTRAL PLAINS
TO MIDDLE MISSISSIPPI AND OHIO VALLEYS TO APPALACHIANS INTO MUCH
OF NEXT WEEK, ESPECIALLY IF AREAS ARE SNOW COVERED AND HOLD
TEMPERATURES DOWN. MEANWHILE, INITIAL UPPER RIDGING IN THE WESTERN
U.S. WILL ALLOW FOR SLIGHTLY ABOVE NORMAL TEMPERATURES IN THE
INTERMOUNTAIN WEST, AND 10-20 DEGREES ABOVE NORMAL ANOMALIES IN THE
SOUTH-CENTRAL U.S. SUNDAY WILL COOL TO BELOW NORMAL BEHIND A COLD
FRONT BY MONDAY. THE UPPER PATTERN IN THE WEST IS UNCERTAIN BY
MIDWEEK NEXT WEEK, CAUSING TEMPERATURES TO BE IN QUESTION, BUT
THERE MAY BE A TREND TOWARD WARMING FOR PARTS OF THE WEST.
SCHICHTEL
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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