198
FXUS02 KWBC 250611
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
210 AM EDT WED OCT 25 2023
VALID 12Z SAT OCT 28 2023 - 12Z WED NOV 01 2023
...NORTH-CENTRAL ROCKIES HEAVY SNOW THREAT WITH WINTER COLD TO
OVERSPREAD THE PLAINS...
..OVERVIEW
RENEWED TROUGHING WILL ENVELOPE THE WEST THROUGH THE WEEKEND
BEFORE SHIFTING INTO PLAINS AND EVENTUALLY THE EAST NEXT WEEK.
INITIAL STRONG RIDGING OVER THE SOUTHEAST THIS WEEKEND WILL CREATE
A PRONOUNCED CONTRAST BETWEEN UNSEASONABLY WARM WEATHER OVER THE
EAST AND AN EXPANSIVE AREA OF MUCH BELOW NORMAL COLD OVER THE WEST
AND THE PLAINS. THIS PATTERN BRINGS A THREAT FOR HEAVY SNOW TO THE
NORTH-CENTRAL ROCKIES AND POSSIBLE PARTS OF THE HIGH PLAINS WITH A
MULTI-DAY PERIOD OF ENHANCED RAINFALL OVER PARTS OF THE
SOUTH-CENTRAL PLAINS TO MIDWEST SATURDAY AND SUNDAY ALONG A SLOW
MOVING FRONTAL BOUNDARY. UPPER RIDGING SHOULD BUILD OVER THE WEST
AGAIN BY MID NEXT WEEK AS THE NEXT TROUGH MOVES THROUGH THE EAST
PACIFIC TOWARDS THE WEST COAST.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
LATEST GUIDANCE, INCLUDING THE NEW 00Z RUNS, HAVE BEEN TRENDING
TOWARDS A FASTER TROUGH PROGRESSION THROUGH THE WEST WITH LESS
EMPHASIS ON SOUTHERN STREAM ENERGY OR POSSIBLE CLOSED LOW HANGING
BACK OVER THE SOUTHWEST (ALTHOUGH THE GFS DOES STILL SHOW THIS
POTENTIAL). A GENERAL MODEL BLEND SUFFICED FOR THE FIRST HALF OF
THE PERIOD, MAINTAINING GOOD CONTINUITY WITH THE PREVIOUS WPC
FORECAST. BY EARLY NEXT WEEK, A COUPLE OF POTENT SHORTWAVES MAY
DROP INTO THE NORTHERN TIER/GREAT LAKES WITH PLENTY OF LINGERING
TIMING AND STRENGTH DIFFERENCES, ESPECIALLY CONCERNING POSSIBLE
AMPLIFICATION OF THE SHORTWAVE/TROUGHING INTO THE EAST NEXT
WEDNESDAY. THE GFS IS NOTICEABLY WEAKER AND MUCH FASTER WITH
ENERGY SWINGING THROUGH WHILE THE ECMWF AND CMC SUGGEST MORE
AMPLIFICATION AND A SLOWER FRONTAL PROGRESSION THROUGH THE EAST.
OPTED TO LEAN MOSTLY TOWARDS THE ENSEMBLE MEANS (WITH MINOR ECMWF
AND CMC ADDITIONS) FOR THE WPC DAY 6 AND 7 PROGS WHICH PROVIDED A
NICE MIDDLE GROUND BETWEEN THE GFS AND ECMWF/CMC CAMPS. SOME
TIMING DIFFERENCES TOO WITH THE NEXT EAST PACIFIC TROUGH, BUT AN
ENSEMBLE MEAN BLEND SEEMED TO OFFER A GOOD STARTING POINT FOR THIS
LATE PERIOD FEATURE.
..WEATHER/HAZARDS HIGHLIGHTS
INSTABILITY AND ANOMALOUS MOISTURE ALONG A SLOW MOVING FRONT THIS
WEEKEND WILL PROVIDE FOCUS FOR A MULTI-DAY PERIOD OF HEAVY
RAINFALL FROM PARTS OF THE SOUTH-CENTRAL PLAINS INTO THE
MIDWEST/OHIO VALLEY WITH POTENTIAL FOR REPEAT/TRAINING OF STORMS.
SOME LINGERING UNCERTAINTY ON EXACTLY WHERE THE HEAVIEST TOTALS
SET UP, AND DRY ANTECEDENT CONDITIONS COULD LIMIT A WIDESPREAD
FLASH FLOOD THREAT, BUT LATEST MODEL QPF AMOUNTS DO SUPPORT A
SLIGHT RISK AREA ON BOTH THE DAYS 4 AND 5 EROS ACROSS THE
MID-MISSISSIPPI VALLEY, WITH A MARGINAL RISK EXTENDING NORTHEAST
AND SOUTHWESTWARD ALONG THE SPAN OF THE FRONTAL BOUNDARY.
POTENTIAL EXISTS FOR SOME SNOW IN THE NORTHERN PERIPHERY OF THE
PRECIPITATION SHIELD, BUT SPECIFICS REMAIN VERY UNCERTAIN AND
REQUIRE MONITORING. HOWEVER, THERE IS A GROWING SIGNAL SUPPORTING
A THREAT FOR HEAVY SNOW IN THIS PATTERN FOR THE NORTH-CENTRAL
ROCKIES AND INTO THE LESS UNCERTAIN ADJACENT PLAINS INTO SATURDAY
THAT REMAINS DENOTED IN THE WPC WINTER WEATHER OUTLOOK. BY NEXT
WEEK, MUCH OF THE COUNTRY SHOULD BE DRY AS HIGH PRESSURE DOMINATES
THE CONUS WITH ONLY SOME LAKE EFFECT SHOWERS DOWNWIND OF THE GREAT
LAKES.
MUCH BELOW NORMAL TEMPERATURES ACROSS THE WEST INTO THE
NORTHERN/CENTRAL PLAINS ON SATURDAY WILL EXPAND SOUTH AND EASTWARD
BRINGING THE FIRST REAL COLD SNAP OF THE SEASON TO MANY ACROSS THE
CENTRAL U.S., INCLUDING AS FAR SOUTH AS THE SOUTHERN PLAINS/TEXAS
AND COINCIDING WITH OUTDOOR HALLOWEEN FESTIVITIES NEXT TUESDAY.
DAYTIME HIGHS 20-30 DEGREES BELOW NORMAL ARE LIKELY WITH A FEW
DAILY RECORDS POSSIBLE WITHIN THIS COLD AIR MASS. THE CLIMATE
PREDICTION CENTER (CPC) SHOWS AN EXTENSION OF THE COLD AIR THREAT
INTO EARLY NOVEMBER OVER THE CENTRAL STATES AS WELL. MEANWHILE,
WELL ABOVE NORMAL TEMPERATURES WILL CONTINUE INTO THIS
WEEKEND/MONDAY FOR THE SOUTHEAST/EAST UNDERNEATH A RETREATING
UPPER RIDGE. EXPECT A BROAD AREA OF HIGHS 10-20 DEGREES ABOVE
NORMAL WITH SOME MORNING LOWS 20-25 DEGREES ABOVE NORMAL. DAILY
RECORDS ARE POSSIBLE, WITH RECORD WARM LOWS LIKELY TO BE MORE
NUMEROUS THAN RECORD HIGHS. THE CHILLY CENTRAL U.S. AIRMASS SHOULD
PUSH EASTWARD WITH TIME NEXT WEEK (WITH SOME MODERATION) WITH MUCH
OF THE COUNTRY EAST OF THE ROCKIES BELOW NORMAL NEXT
TUESDAY-WEDNESDAY BEHIND THE STRONG COLD FRONT.
SANTORELLI
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
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page