563
FXUS02 KWBC 242037
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
436 PM EDT TUE OCT 24 2023
VALID 12Z FRI OCT 27 2023 - 12Z TUE OCT 31 2023
...HEAVY SNOW AND WINTER COLD THREAT FOR THE NORTH-CENTRAL
ROCKIES/PLAINS...
..OVERVIEW
MEAN TROUGHING ACROSS THE WEST WILL DOMINATE THE MEDIUM RANGE
PERIOD (FRIDAY-TUESDAY) AS A COUPLE OF POTENT SHORTWAVES DROP IN
ACTING TO REINFORCE AND AMPLIFY THE TROUGH. MODELS SUGGEST SOME
SEPARATION OF STREAMS THIS WEEKEND AS SOUTHERN STREAM ENERGY DIVES
INTO THE SOUTHWEST (WITH A POSSIBLE CLOSED LOW) AND NORTHERN
STREAM ENERGY SLIDES ACROSS THE NORTHERN TIER. IN RESPONSE, UPPER
RIDGING WILL BUILD OVER THE SOUTHEAST/EAST. THIS PATTERN SHOULD
SUPPORT A MULTI-DAY PERIOD OF ENHANCED RAINFALL OVER PARTS OF THE
CENTRAL U.S., WITH PRONOUNCED CONTRAST BETWEEN UNSEASONABLY COLD
CONDITIONS OVER THE WEST/PLAINS AND VERY WARM WEATHER FARTHER
EASTWARD. THERE IS A THREAT FOR HEAVY SNOW IN THIS PATTERN FOR THE
NORTH-CENTRAL ROCKIES/PLAINS.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
06 UTC GFS/GEFS AND 00 UTC ECMWF/ECMWF ENSEMBLE MEAN SOLUTIONS
SEEM BEST CLUSTERED THROUGH MEDIUM RANGE TIME SCALES DESPITE SOME
LINGERING TIMING ISSUES. A BLEND ALONG WITH INPUT FROM THE 13 UTC
NATIONAL BLEND OF MODELS (NBM) SEEMS TO PROVIDE A SOLID FORECAST
BASIS. HOWEVER, OPTED TO LEAN BLEND WEIGHTING TOWARD THE
ECMWF/ECMWF ENSEMBLE MEAN AND THE NBM TO BETTER MATCH WPC PRODUCT
CONTINUITY (FRONTAL PROGRESSIONS) AND MESSAGING ALONG WITH LATEST
GUIDANCE TRENDS. THERE HAS BEEN A GUIDANCE TREND TOWARD SLIGHTLY
MORE AMPIFIED FLOW INTO LONGER TIME FRAMES, ALBEIT IN A PERIOD
WITH GROWING FORECAST SPREAD THAT SUGGESTS A LOWERING OF
PREDICTABILITY FROM ABOVE NORMAL LEVELS LATER WEEK BACK TOWARD
AVERAGE LEVELS INTO NEXT WEEK. LATEST GUIDANCE FROM THE 12 UTC
CYCLE STILL SEEMS REASONABLY IN LINE, ESPECIALLY INTO THE WEEKEND.
..WEATHER/HAZARDS HIGHLIGHTS
INSTABILITY AND ANOMALOUS MOISTURE WILL CONTINUE TO FUEL AT LEAST
MODERATE RAINFALL ALONG A WAVY FRONT NEAR THE SOUTHERN PLAINS AND
A SMALL MARGINAL RISK WAS CONTINUED ON THE DAY 4/FRIDAY ERO ACROSS
NORTHEAST TEXAS TO OKLAHOMA WHERE GUIDANCE SUGGESTS SOME LOCALLY
ENHANCED TOTALS, OVER A REGION THAT SHOULD ALSO SEE HEAVY RAINFALL
IN THE SHORT RANGE PERIOD. ACTIVITY SHOULD BECOME HEAVIER AND MORE
WIDESPREAD THIS WEEKEND INTO THE MID-MISSISSIPPI
VALLEY/MIDWEST/OHIO VALLEY THOUGH AS THE FRONT MAY BRIEFLY STALL
AND ALLOWS FOR POSSIBLE REPEAT/TRAINING OF STORMS. THERE IS STILL
SOME UNCERTAINTY ON EXACTLY WHERE THE HEAVIEST TOTALS SET UP, BUT
FAIRLY DRY ANTECEDENT CONDITIONS MAY LIMIT THE FLASH FLOOD THREAT
OVERALL, ALLOWING FOR JUST A MARGINAL RISK FOR NOW ON THE DAY
5/SATURDAY ERO. LIGHTER RAIN SHOULD ALSO EXTEND INTO THE GREAT
LAKES/NORTHEAST FROM THE WEEKEND INTO EARLY NEXT WEEK. OUT WEST,
ADDITIONAL PRECIPITATION/HIGHER ELEVATION SNOWS WILL MOVE EASTWARD
ACROSS THE REGION THIS COMING WEEKEND FOLLOWED BY A DRIER TREND AS
THE MOISTURE CONTRIBUTES TO THE ENHANCED RAINFALL AREA FARTHER
EAST. 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 SUPPRTING A
THREAT FOR HEAVY SNOW IN THIS PATTERN FOR THE NORTH-CENTRAL
ROCKIES/PLAINS FRIDAY INTO SATURDAY THAT REMAINS DENOTED IN THE
WPC WINTER WEATHER OUTLOOK.
RENEWED AND AMPLIFIED TROUGHING ACROSS THE WEST WILL CONTINUE A
PROLONGED PERIOD OF BELOW NORMAL TEMPERATURES, WITH DAYTIME HIGHS
15-30 DEGREES BELOW NORMAL (LOCALLY COLDER OVER MONTANA LATE THIS
WEEK) TO SPREAD ACROSS MUCH OF THE INTERIOR WEST AND THE
NORTHERN/CENTRAL PLAINS. BY NEXT MONDAY-TUESDAY, MUCH BELOW NORMAL
TEMPERATURES COULD SINK WELL INTO THE SOUTHERN PLAINS/TEXAS, ALL A
CONSIDERATION FOR HALLOWEEN. A FEW DAILY RECORDS ARE 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. MEANWHILE, WELL ABOVE NORMAL TEMPERATURES
ACROSS THE CENTRAL U.S. AND THE MIDWEST WILL SHIFT EAST AND SETTLE
THIS WEEKEND ACROSS THE EAST/SOUTHEAST AS UPPER RIDGING BUILDS
OVER THIS REGION. 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. AS THE UPPER RIDGING GRADUALLY WEAKENS
AND RETREATS, TEMPERATURES SHOULD MODERATE BACK CLOSER TO NORMAL
ACROSS THE SOUTHEAST AND UP THE EAST COAST INTO NEXT WEEK.
SCHICHTEL/SANTORELLI
HAZARDS:
- HEAVY RAIN ACROSS PORTIONS OF THE SOUTH-CENTRAL U.S., FRI-SUN,
OCT 27-29.
- HEAVY SNOW ACROSS PORTIONS OF THE NORTHERN TO CENTRAL ROCKIES,
SAT-SUN, OCT 28-29.
- FROST/FREEZE ACROSS PORTIONS OF THE CENTRAL/SOUTHERN PLAINS INTO
THE UPPER/MIDDLE MISSISSIPPI VALLEY, SUN-MON, OCT 29-OCT 30.
- HAZARDOUS COLD ACROSS PORTIONS OF THE NORTHERN ROCKIES INTO MUCH
OF THE NORTHERN PLAINS, FRI-SAT, OCT 27-28.
- HAZARDOUS COLD ACROSS PORTIONS OF THE CENTRAL ROCKIES INTO
CENTRAL PLAINS, SUN-TUE, OCT 29-31.
- FLOODING POSSIBLE OVER PORTIONS OF WISCONSIN, FRI-SUN, OCT 27-29.
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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