854
FXUS02 KWBC 251900
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
200 PM EST SAT JAN 25 2025
VALID 12Z TUE JAN 28 2025 - 12Z SAT FEB 01 2025
..SOUTH-CENTRAL U.S. HEAVY RAINFALL THREAT WEDNESDAY-SATURDAY
..GENERAL OVERVIEW
THE WPC MEDIUM RANGE FORECAST PERIOD BEGINS ON TUESDAY WITH A VERY
SLOW MOVING CLOSED LOW OVER CALIFORNIA, AND BROAD CYCLONIC FLOW
ALOFT FROM THE NORTHERN PLAINS TO THE NORTHEAST STATES, WITH A
SPLIT UPPER LEVEL FLOW PATTERN IN PLACE FOR THE BEGINNING OF THE
WEEK. THE CLOSED LOW ONLY MAKES IT TO EASTERN NEW MEXICO BY FRIDAY,
WITH A RIDGE AXIS TRYING TO BUILD NORTH AHEAD OF IT ACROSS THE
MIDWEST AND THE SOUTH, A TROUGH REMAINING OVER NEW ENGLAND AND A
SEPARATE TROUGH NEAR THE PACIFIC NORTHWEST. IT APPEARS LIKELY THAT
SURFACE CYCLOGENESIS WILL TAKE PLACE OVER TEXAS IN RESPONSE TO THE
APPROACHING UPPER LOW, AND THIS HAS BECOME INCREASING LIKELY TO FUEL
AN INCREASE IN GULF RETURN FLOW TO FUEL A MULTI-DAY HEAVY RAINFALL
THREAT FOCUS FROM TEXAS TO THE LOWER MISSISSIPPI VALLEY WEDNESDAY-
THROUGH NEXT SATURDAY.
..GUIDANCE/PREDICTABILITY ASSESSMENT
00/06/12 UTC GUIDANCE RUNS GENERALLY OFFERS BETTER THAN NORMAL
FORECAST AGREEMENT AND PREDICTABILITY ACROSS THE CONTINENTAL U.S.
FOR THE BEGINNING TO MID-LATER NEXT WEEK. RECENT GUIDANCE HAS
OVERALL TRENDED SLOWER WITH THE UPPER LOW SLATED TO SLOWLY EJECT
OUT FROM THE SOUTHWESTERN U.S. THROUGH THE SOUTHERN ROCKIES/HIGH
PLAINS, WITH THE ENSEMBLE MEANS GENERALLY A LITTLE FASTER THAN THE
DETERMINISTIC GUIDANCE. THE SURFACE LOW EVOLUTION IS A BIT MORE
UNCERTAIN, BUT THERE IS A TREND FOR THIS TO BE A LITTLE MORE TO THE
SOUTH COMPARED TO PAST FORECASTS. THE WPC PRODUCT SUITE WAS
PRIMARILY DERIVED FROM A GFS/ECMWF/UKMET/CANADIAN MODEL COMPOSITE
FOR TUESDAY INTO EARLY FRIDAY TO PROVIDE BEST SMALLER SCALE DETAIL.
BEYOND THAT, OPTED TO SWITCH TO A BLEND OF GUIDANCE ON THE
SLIGHTLY SLOWER SIDE OF THE FULL ENVELOPE OF SOLUTIONS GIVEN LATEST
GUIDANCE TRENDS AND HISTORICAL NATURE OF CLOSED LOWS/TROUGHS IN A
SEPARATED SOUTHERN STREAM. GUIDANCE USED FOR THIS WAS THE
GFS/CANADIAN AND ECMWF/CANADIAN ENSEMBLE MEANS.
..WEATHER/HAZARDS HIGHLIGHTS
IT REMAINS THE CASE THAT THE EVOLUTION OF THE SOUTHERN PLAINS LOW
PRESSURE SYSTEM STARTING MID-WEEK WILL LIKELY PRODUCE INCREASING
SHOWERS AND THUNDERSTORMS FROM CENTRAL TEXAS TO THE ARKLATEX
REGION, BUT GIVEN MODEL DIFFERENCES WITH RESPECT TO LOCATION AND
MAGNITUDE, NO RISK AREAS ARE CURRENTLY WARRANTED FOR EITHER THE
DAY 4 OR DAY 5 EXCESSIVE RAINFALL OUTLOOKS IN THE INITIAL STAGES OF
RAINFALL DEVELOPMENT. HOWEVER, THIS COULD CHANGE AS SPECIFICS
BECOME CLEARER IN FUTURE OUTLOOKS. LOOKING BEYOND THE DAY 5 PERIOD,
THERE HAS BEEN A GENERAL UPWARD TREND IN EXPECTED RAINFALL TOTALS
COMPARED TO THE PREVIOUS WPC FORECAST OVER THE ARKLATEX REGION TO
THE WESTERN GULF COAST, WITH THE POTENTIAL FOR 2 TO 5+ INCHES FOR
THIS REGION DURING THE THURSDAY TO SATURDAY TIME PERIOD. SOME
STRONG THUNDERSTORMS ARE ALSO POSSIBLE DEPENDING ON HOW THE WARM
SECTOR OF THIS LOW PRESSURE SYSTEM EVOLVES. TRAINING OF ACTIVITY
SEEMS INCREASINGLY LIKELY TO OFFER LOCAL RUNOFF ISSUES TO MONITOR
GIVEN RETURN GULF INFLOW SHOULD PROVIDE AMPLE MOISTURE. THERE IS
ALSO SOME THREAT FOR A SNOW/ICE THREAT ON THE NORTHERN PERIPHERY
OF THIS EXPANDING PRECIPITATION SHIELD GIVEN LINGERING COLD AIR.
ELSEWHERE ACROSS THE NATION, A SWATH OF LIGHT TO MODERATE SNOW IS
LIKELY FROM NORTHERN MINNESOTA TO NORTHERN NEW ENGLAND TUESDAY INTO
WEDNESDAY AS A CLIPPER TYPE LOW PRESSURE SYSTEM CROSSES THE REGION.
LATER IN THE WEEK, RAIN AND MOUNTAIN SNOW IS EXPECTED TO MAKE A
RETURN TO THE PACIFIC NORTHWEST AS THE NEXT SHORTWAVE TROUGH AND
SURFACE COLD FRONT MOVES INTO THE REGION, AND THIS COULD REACH MUCH
OF CALIFORNIA GOING INTO FRIDAY.
MUCH OF THE EAST SHOULD FINALLY BE BACK UP TOWARDS NORMAL
TEMPERATURES EARLY NEXT WEEK, FOLLOWED BY A RETURN TO COLDER
READINGS BY THURSDAY INTO FRIDAY AFTER A COLD FRONT MOVES THROUGH.
ANOMALOUSLY COLD TEMPERATURES ARE EXPECTED ACROSS THE SOUTHWESTERN
U.S. UNDER THE INFLUENCE OF UPPER TROUGHING/CLOSED LOW, WITH SNOW
FOR THE MOUNTAINS OF ARIZONA AND NEW MEXICO.
HAMRICK/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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