247
FXUS02 KWBC 081837
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
137 PM EST THU FEB 08 2024
VALID 12Z SUN FEB 11 2024 - 12Z THU FEB 15 2024
..OVERVIEW
IT GENERALLY REMAINS THE CASE THAT SPLIT FLOW ACROSS THE NATION
INTO EARLY NEXT WEEK FEATURES A NORTHERN STREAM WEAK SHORTWAVE
THROUGH THE GREAT LAKES AND MORE NOTABLY, AN AMPLIFIED UPPER
SHORTWAVE OVER THE SOUTHWEST. THE LATTER WILL SHIFT STEADILY
THROUGH THE SOUTH MONDAY AND TUESDAY ASSOCIATED WITH A DEEPENING
LOW PRESSURE SYSTEM AT THE SURFACE, LEADING INTO POSSIBLE
RE-DEVELOPMENT INTO A COASTAL STORM. THIS WOULD BRING MODERATE TO
HEAVY RAINFALL POTENTIAL TO PARTS OF THE SOUTHEAST/MID-ATLANTIC
AND SNOW ACROSS THE NORTHEAST. AS THIS SYSTEM EXITS OFFSHORE THE
NORTHEAST LATER TUESDAY, THE FLOW BEHIND IT SHOULD BECOME MORE
ZONAL ACROSS MUCH OF THE NATION, WITH A WEAK SHORTWAVE THROUGH THE
NORTHERN TIER WEDNESDAY-NEXT THURSDAY AND A COUPLE OF WEAK
SHORTWAVES INTO THE WEST COAST.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE LATEST GFS/ECMWF/CANADIAN/UKMET SOLUTIONS CONTINUE TO OFFER
REASONABLY GOOD FORECAST CLUSTERING THIS WEEKEND INTO MONDAY. A
MODEL COMPOSITE SEEMS TO OFFER A SOLID FORECAST BASIS ALONG WITH
THE NATIONAL BLEND OF MODELS AND WPC PRODUCT CONTINUITY. FORECAST
SPREAD RAPIDILY INCREASES NEXT WEEK AS MODELS AND ENSEMBLES REMAIN
HIGHLY SENSITIVE TO EMBEDDED SYSTEM AND POTENTIAL STREAM PHASING
UNCERTAINTIES IN COMPLEX AND TRANSITIONAL FLOW. THE MAIN ISSUE IN
THIS TIME FRAME STILL CONCERNS THE POTENTIAL DEVELOPMENT AND TRACK
OF A MAIN SOUTHERN U.S. LOW TO EASTERN U.S./WESTERN ALANTIC
COASTAL STORM BY TUESDAY AND ASSOCIATED INLAND AND MARITIME
IMPACTS. MACHINE LEARNING MODELS STILL OFFER VARIED SOLUTIONS WITH
THIS MAIN SYSTEM IN THIS PERIOD. WPC PRODUCTS HAVE OVER THE PAST
FEW CYCLES TRENDED TO SHOW A SOMEWHAT LESS PROGRESSIVE AND
MODERATELY DEEPER LOW TRACK GIVEN POTENTIAL SUPPORT ALONG WITH A
COMPOSITE TRACK BASED ON ALL GUIDANCE. THIS PLAN MAINTAINS GOOD
WPC PRODUCT CONTINUITY DESPITE RAMPANT RUN-RUN AND MODEL-MODEL
SYSTEM VARIANCES RECENTLY, AND ENSEMBLE MEANS THAT SEEM TOO
PROGRESSIVE GIVEN THE HISTORICAL BIAS OF WELL DEFINED SYSTEMS
WORKING THROUGH AN AT LEAST INITIALLY SEPARATED SOUTHERN STREAM
FLOW.
..OVERVIEW AND WEATHER/HAZARDS HIGHLIGHTS
INCREASED MOISTURE RETURN WELL AHEAD OF A MAIN SYSTEM SLATED TO
EXIT EASTWARD FROM THE SOUTHWEST WILL FUEL POTENTIAL FOR HEAVY
RAINFALL FROM THE CENTRAL GULF COAST STATES INTO THE SOUTHEAST
SUNDAY. REPEAT/TRAINING OF ACTIVITY ALONG A FRONTAL BOUNDARY,
COMBINED WITH ANOMALOUS MOISTURE AND SOME INSTABILITY, MAY TRIGGER
A FLASH FLOOD RISK. ACCORDINGLY, A MARGINAL RISK AREA CONTINUES TO
BE HIGHLIGHTED ON THE DAY 4/SUNDAY EXCESSIVE RAINFALL OUTLOOK
(ERO). SUSPECT THE THREAT OVER THE SOUTHEAST MAY LINGER INTO
MONDAY WHOSE DAY 5/ERO NOW SHOWS A SMALL MARGINAL RISK AREA.
ADDITIONALLY, AS THE MAIN LOW PRESSURE STARTS TO DEEPEN ACROSS THE
SOUTH-CENTRAL PLAINS SUNDAY, HEAVY RAINFALL MAY ALSO FOCUS LOCALLY
JUST TO THE NORTH OF THE LOW GIVEN UPPER LEVEL DYNAMICS. LATEST
RUNS OF MODELS HAVE INDICATED SOME SECONDARY QPF MAXES ACROSS
PARTS OF OKLAHOMA. SOME ACCUMULATING SNOWFALL IS ALSO POSSIBLE
ACROSS THE NORTHERN PORTION OF THE PRECIPITATION SHIELD ACROSS THE
CENTRAL PLAINS/MIDDLE MISSISSIPPI VALLEY AS WELL.
AS THE SYSTEM PROGRESSES AND POTENTIALLY REDEVELOPS AS A COASTAL
STORM MONDAY INTO TUESDAY IN A PERIOD WITH UNCERTAIN STREAM
PHASING, HEAVY RAINFALL POTENTIAL SHOULD LIFT NORTHWARD INTO PARTS
OF THE MID-ATLANTIC AND NORTHEAST. INCREASING PROGRESSION SHOULD
LIMIT RUNOFF RISKS OVER MUCH OF THIS BROAD REGION. THERE IS
HOWEVER AN INCREASING POTENTIAL FOR THE SPREAD OF WRAP-BACK
ACCUMULATING SNOWS AND WINDY CONDITIONS ACROSS THE MARGINALLY COOL
APPALACHIANS/INTERIOR NORTHEAST MONDAY AND TUESDAY BEFORE THE
WHOLE SYSTEM WORKS INCREASINGLY OFFSHORE AS A CONTINUED MARITIME
HAZARD. BEHIND THIS SYSTEM, CONDITIONS ACROSS MUCH OF THE CONUS
SHOULD DRY OUT MID NEXT WEEK BESIDES PERIODIC INTRUSIONS FROM THE
PACIFIC TO BRING SOME MODEST PRECIPITATION TO PARTS OF THE
NORTHWEST.
AHEAD OF THE EASTERN U.S. SYSTEM, TEMPERATURES SUNDAY INTO MONDAY
COULD BE 5-15 DEGREES ABOVE AVERAGE, WITH MORNING LOWS EVEN MORE
ANOMALOUSLY WARM GIVEN CLOUDS AND HUMIDITY. THE EAST SHOULD
MODERATE BACK CLOSER TO NORMAL TUESDAY AND BEYOND. IN CONTRAST,
THE SOUTHWEST/CALIFORNIA SHOULD BE COOL WITH UPPER SYSTEM PASSAGE,
ESPECIALLY DAYTIME HIGHS THAT MAY BE 10-15F BELOW NORMAL ON SUNDAY
BEFORE MODERATING. SOME RIDGING IN THE UPPER PATTERN MAY ALSO
SUPPORT ABOVE NORMAL TEMPERATURES ACROSS PARTS OF THE NORTHERN
TIER THROUGH ABOUT WEDNESDAY.
SANTORELLI/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, 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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