775
FXUS02 KWBC 240603
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
202 AM EDT TUE OCT 24 2023
VALID 12Z FRI OCT 27 2023 - 12Z TUE OCT 31 2023
..OVERVIEW
MEAN TROUGHING ACROSS THE WEST WILL DOMINATE THE MEDIUM RANGE
PERIOD (FRIDAY-TUESDAY) AS A COUPLE OF 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.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
THE WPC FORECAST FOR TONIGHT BLENDED THE LATEST OPERATIONAL RUNS
EARLY IN THE PERIOD AND MIXED IN SOME OF THE GEFS/ECENS MEANS
LATER ON TO ACCOUNT FOR DECREASING CONFIDENCE IN EXACT DETAILS
WITHIN AN OVERALL AGREEABLE LARGE SCALE PATTERN. THE MOST NOTABLE
DIFFERENCES IN THE GUIDANCE ARISE THIS WEEKEND WITH THE NEXT
SHORTWAVE AS IT DROPS THROUGH THE WEST. THERE IS STILL PLENTY OF
UNCERTAINTY AND RUN TO RUN VARIABILITY IN THE TIMING AND STRENGTH
OF THIS SYSTEM (SOME MODELS SHOW A CLOSED LOW), AND THE NEW 00Z
GFS RUN FOR TONIGHT CAME IN SIGNIFICANTLY STRONGER/MORE CUT OFF
WITH THE LOW LATE IN THE PERIOD, LINGERING IT OVER THE SOUTHWEST
FOR LONGER, RATHER THAN OPENING UP AND PUSHING EAST LIKE SOME
OTHER GUIDANCE/THE ENSEMBLE MEANS SHOW. THERE ARE ALSO TIMING
DIFFERENCES WITH NORTHERN STREAM ENERGY SKIRTING THE NORTHERN
PLAINS THIS WEEKEND. SYNOPTICALLY SPEAKING THOUGH, CONFIDENCE IN
THE FORECAST IS HIGHER THAN AVERAGE WITH MAINLY JUST THESE SMALLER
SCALE DIFFERENCES IN THE DETAILS TO BE WORKED OUT.
..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 BRIEFLY STALLS 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 FRINGE OF THE
PRECIPITATION SHIELD BUT SPECIFICS REMAIN VERY UNCERTAIN AND
REQUIRE MONITORING.
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. A FEW
DAILY RECORDS ARE POSSIBLE WITHIN THIS COLD AIR MASS. 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 WEAKENS AND RETREATS BACK TO THE SOUTH EARLY
NEXT WEEK, TEMPERATURES SHOULD MODERATE BACK CLOSER TO NORMAL
ACROSS THE SOUTHEAST AND UP THE EAST COAST.
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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