676
FXUS02 KWBC 261849
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
249 PM EDT THU OCT 26 2023
VALID 12Z SUN OCT 29 2023 - 12Z THU NOV 02 2023
...ARCTIC SURGE THROUGH THE CENTRAL TO EASTERN U.S INTO NEXT WEEK
OFFERS SOME EARLY SEASON WINTRY WEATHER POTENTIAL INCLUDING A
WIDESPREAD FROST/FREEZE RISK...
..OVERVIEW
GUIDANCE STILL INDICATES THAT UPPER TROUGHING LOOKS TO BE SLIDING
THROUGH THE WEST AS THE PERIOD BEGINS ON SUNDAY, WITH SHORTWAVES
WORKING TO MAINTAIN AND RENEW THE TROUGHING AS IT MOVES THROUGH
THE MIDWEST AND EVENTUALLY INTO THE EAST NEXT WEEK. THIS ALLOWS
FOR A MUCH BELOW NORMAL AIRMASS TO SPILL INTO THE CENTRAL U.S.,
INCLUDING AS FAR SOUTH AS TEXAS AND THE GULF COAST, SLIDING TO THE
EAST WITH TIME. HEAVY RAIN LOOKS TO BE A THREAT SUNDAY ALONG A
FRONTAL BOUNDARY THROUGH THE SOUTH-CENTRAL PLAINS AND MIDWEST, BUT
CONDITIONS SHOULD OVERALL DRY OUT THEREAFTER AS SURFACE HIGH
PRESSURE ENVELOPES MUCH OF THE NATION. UPPER RIDGING SHOULD BUILD
OVER THE WEST AGAIN BY NEXT MIDWEEK AS THE NEXT TROUGH WORKS INTO
THE EAST PACIFIC/WEST COAST.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
06 UTC GFS/GEFS AND 00 UTC CANADIAN/UKMET/ECMWF/ECMWF ENSEMBLE
MEAN SOLUTIONS NOW OVERALL SEEM BETTER CLUSTERED AND GENERALLY
REASONABLE FOR SUNDAY AND MONDAY, BOLSTERING FORECAST CONFIDENCE.
A COMPOSITE BLEND ALONG WITH INPUT FROM THE 13 UTC NATIONAL BLEND
OF MODELS (NBM) AND WPC CONTINUITY SEEMS TO PROVIDE A SOLID
FORECAST BASIS. GIVEN GROWING FORECAST SPREAD LATER NEXT WEEK,
OPTED TO SWITCH PREFERENCE CLOSEST TO THE 00 UTC ECMWF ENSEMBLE
MEAN THAT OF THE ENSEMBLES BEST MATCHES WPC PRODUCT CONTINUITY,
LATEST MODEL TRENDS OVER MUCH OF THE NATION AND ADJOINING WATERS
INCLUDING SOMEWHAT MORE AMPLITUDE AND SLOWER PROGRESSION ALONG
WITH ASSOCIATED MESSAGING.
..WEATHER/HAZARDS HIGHLIGHTS
INSTABILITY AND ANOMALOUS MOISTURE ALONG A SLOW MOVING FRONT INTO
SUNDAY WILL CONTINUE TO PROVIDE FOCUS FOR 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 COMBINED WITH THE POTENTIAL FOR
ADDITIONAL RAINS OVER THE NEXT FEW DAYS LEADING INTO THE MEDIUM
RANGE FORECAST PERIOD DO SEEM TO STILL SUPPORT A SLIGHT RISK AREA
ON THE DAY 4/SUNDAY ERO ACROSS THE MID-MISSISSIPPI VALLEY, WITH A
MARGINAL RISK EXTENDING NORTHEAST AND SOUTHWESTWARD ALONG THE SPAN
OF THE FRONTAL BOUNDARY. SOME POTENTIAL FOR LINGERING SNOW ACROSS
THE CENTRAL ROCKIES AND ADJACENT HIGH PLAINS ON SUNDAY ON THE
NORTH SIDE OF THE PRECIPITATION SHIELD, WITH TRANSITION ZONE
FREEZING RAIN/SLEET JUST SOUTH OF THIS AREA. BEYOND THAT INTO NEXT
WEEK, MUCH OF THE COUNTRY SHOULD BE MAINLY DRY AS HIGH PRESSURE
DOMINATES THE CONUS. HOWEVER, THERE SHOULD BE MODEST LAKE EFFECT
RAIN/SNOW SHOWERS DOWNWIND OF THE GREAT LAKES WITH WAVY FRONTAL
SYSTEM PASSAGE. ADDITIONALLY, A GROWING BUT STILL UNCERTAIN
GUIDANCE SIGNAL FOR DOWNSTREAM COASTAL LOW DEVELOPMENT OVER THE
WESTERN ATLANTIC SEEMS TO OFFER SOME OPPORTUNITY TO WRAP ORGANIZED
PRECIPITATION BACK INTO THE NORTHEAST BY NEXT MIDWEEK THAT WITH
COLD AIR ADVANCE COULD SUPPORT A WINDOW FOR AREAS OF EARLY SEASON
SNOWS, ESPECIALLY FOR THE INTERIOR. THERE IS ALSO AN UNCERTAIN
LIFTING OF A LOW UP FROM THE CARIBBEAN TO THE SOUTHWESTERN
ATLANTIC IN SOME GUIDANCE IN ADVANCE OF THE MAIN COLD FRONT. THIS
IS BEING MONITORED BY NHC. MEANWHILE, THE APPROACH OF AN AMPLIFIED
EASTERN PACIFIC UPPER TROUGH/HEIGHT FALLS AND SURFACE SYSTEM
ENERGIES STILL OVERALL FAVORS A MODERATELY WETTER PATTERN IN ABOUT
A WEEK FOR THE NORTHWEST AND VICINITY.
MUCH BELOW NORMAL TEMPERATURES ACROSS THE WEST INTO THE
NORTHERN/CENTRAL PLAINS WILL CONTINUE TO EXPAND SOUTH AND EAST ON
SUNDAY 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.
MEANWHILE, WELL ABOVE NORMAL TEMPERATURES WILL CONTINUE SUNDAY AND
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-THURSDAY.
SIGNIFICANTLY, THERE IS A WIDESPREAD FIRST FROST/FREEZE RISK WITH
THIS POST-FRONTAL COLD SNAP NEXT WEEK, BROADLY FROM THE
SOUTH-CENTRAL PLAINS THROUGH THE NORTHEAST AS DEPICTED ON THE WPC
HAZARDS OUTLOOK.
SCHICHTEL/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
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