325
FXUS02 KWBC 051904
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
200 PM EST SUN FEB 05 2023
VALID 12Z WED FEB 08 2023 - 12Z SUN FEB 12 2023
..GUIDANCE/PREDICTABILITY ASSESSMENT
LATEST GUIDANCE CONTINUES TO EXHIBIT HIGHER-THAN-NORMAL
UNCERTAINTY FOR MUCH OF THE MEDIUM-RANGE PERIOD ESPECIALLY ACROSS
THE EASTERN TWO-THIRDS OF THE COUNTRY. THE MEDIUM-RANGE PERIOD
WILL BEGIN ON WEDNESDAY WITH THE MODELS GENERALLY AGREE THAT THE
SHORTWAVE/UPPER LOW THAT IS FORECAST TO EJECT OUT FROM THE
SOUTHWEST WILL DEVELOP INTO A LOW PRESSURE SYSTEM OVER THE
SOUTHERN PLAINS AND TRACK TOWARD THE NORTHEAST. HOWEVER, MODELS
CONTINUE TO SHOW A GREAT DEAL OF SPREAD REGARDING THE TIMING AND
AMPLITUDE OF THIS SYSTEM THEREAFTER, WITH THE GFS BEING THE
FASTEST, THE CMC BEING QUITE SLOW, WHILE THE ECMWF IS IN BETWEEN
THESE EXTREMES. THE SUBSEQUENT EVOLUTION OF THIS SYSTEM OVER THE
EASTERN U.S./EAST COAST LATER NEXT WEEK WILL BE FURTHER
COMPLICATED BY A SIMULTANEOUS FLOW AMPLIFICATION ACROSS THE U.S.,
WITH A MUCH AMPLIFIED RIDGE OVER THE WESTERN U.S. WHILE A LARGE
CLOSED LOW IS FORECAST TO DEVELOP SOMEWHERE NEAR/OFF THE WEST
COAST WITH A HIGH DEGREE OF UNCERTAINTY WITH ITS POSSIBLE
LOCATION. IN ADDITION, A SHORTWAVE RAPIDLY MOVING ACROSS THE
PACIFIC NORTHWEST ON WEDNESDAY WOULD FURTHER COMPLICATE THE
PATTERN EVOLUTION IN THE EASTERN U.S. LATE NEXT WEEK AS THE WAVE
COULD POSITIVELY REINFORCE A SURGE OF POLAR AIR DOWN THE PLAINS
DURING THE LATTER
PART OF NEXT WEEK, WHICH COULD TRIGGER THE DEVELOPMENT OF A
SMALLER SCALE LOW PRESSURE SYSTEM SOMEWHERE IN THE MID-SOUTH LAT
THIS WEEK AS INDICATED BY THE DETERMINISTIC MODEL SOLUTIONS. THIS
SYSTEM MAY THEN INTERACT WITH RESIDUAL ENERGY ON THE BACK SIDE OF
THE FIRST SYSTEM OFF THE NEW ENGLAND COAST TO FORM ANOTHER LOW
PRESSURE SYSTEM NEAR THE EAST COAST. BY NEXT SUNDAY, MODELS
GENERALLY AGREE THAT THE LOW PRESSURE SYSTEM(S) SHOULD BEGIN TO
MOVE AWAY FROM EAST COAST BUT THE WHEREABOUTS OF THE UPPER LOW
NEAR/OFF THE WEST COAST IS HIGHLY UNCERTAIN.
HE WPC MEDIUM RANGE PRODUCT SUITE THROUGH MEDIUM-RANGE PERIOD WAS
PRIMARILY DERIVED FROM A COMPOSITE BLEND OF 40% FROM THE 00Z
GEFS/00Z & 06Z GFS, 40% FROM TO 00Z ECMWF/EC MEAN, AND 20% FROM
THE 00Z CMC AND CMC MEAN. THE 06Z GEFS WAS NOT INCLUDED DUE TO A
MUCH FASTER NORTHEASTWARD TRACK OF THE LOW FROM THE SOUTH TO THE
GREAT LAKES. AS FOR THE LOW NEAR/OFF THE WEST COAST NEXT WEEKEND,
A SOLUTION BETWEEN THE 00Z GEFS AND THE 00Z EC MEAN WAS ADAPTED,
WHICH PLACES THE SYSTEM NEAR THE SOUTHERN CALIFORNIA COAST BY NEXT
SUNDAY. THIS SOLUTION IS SUPPORTED BY THE LATEST 12Z ECMWF WITH A
FASTER EASTWARD MOTION OF THE SYSTEM.
..WEATHER/HAZARD HIGHLIGHTS
AN INITIALLY CLOSED SOUTHERN STREAM UPPER TROUGH/LOW WILL EJECT
INTO THE SOUTHERN PLAINS BY MIDWEEK AS A KICKER SHORTWAVE TROUGH
DIGS SOUTHEASTWARD THROUGH THE GREAT BASIN TO SUPPORT SOME
POTENTIAL FOR SNOW THERE INTO THE ROCKIES. DOWNSTREAM, A SURFACE
FRONTAL WAVE OVER TEXAS WITH THE LEAD SYSTEM WILL ORGANIZE, DEEPEN
AND OCCLUDE WHILE LIFTING NORTHEAST INTO THE MIDWEST/OH VALLEY
THURSDAY BEFORE EXITING THROUGH THE NORTHEAST FRIDAY. GULF
MOISTURE INFLOW/INSTABILITY AND SUPPORTIVE UPPER JET/HEIGHT FALLS
WILL COMBINE WITH THE ASSOCIATED FRONTAL SYSTEM TO PRODUCE A SWATH
OF HEAVY RAIN/CONVECTION THIS PERIOD ACROSS THE LOWER/MID MS AND
TN/OH VALLEYS, WITH WIDESPREAD MODERATE RAINS THEN SHEARING ACROSS
THE APPALACHIANS AND EASTERN SEABOARD. THE WPC EXPERIMENTAL DAY 4
EXCESSIVE RAINFALL OUTLOOK (ERO) WILL SHOW A "MARGINAL" THREAT
AREA OVER THE MID MS VALLEY AND VICINITY THROUGH WEDNESDAY, WITH A
NOTICEABLE NORTHEASTWARD SHIFT COMPARED WITH THE PREVIOUS
FORECAST. COLD AIR DRAPED TO THE NORTH OF THE SYSTEM AND SEVERAL
POTENT SHOTS OF CANADIAN AIR COULD TRIGGER A SMALLER SCALE LOW
PRESSURE SYSTEM IN THE WAKE OF THE MAIN SYSTEM, BRINGING A THREAT
OF HEAVY SNOW/ICE ON THE NORTHERN PERIPHERY OF THE EXPANDING
PRECIPITATION SHIELD THIS PERIOD FROM THE CENTRAL PLAINS THROUGH
THE GREAT LAKES, INTERIOR NORTHEAST AND SOUTHERN CANADA. EXPECT
LAKE-EFFECT SNOWS INTO THE WEEKEND GIVEN LINGERING COLD/WINDY FLOW.
UPSTREAM, THERE IS A GROWING GUIDANCE SIGNAL FOR THE AMPLIFICATION
OF THE OVERALL FLOW SIGNIFICANTLY INTO LATER WEEK ACROSS THE
NATION AND ADJOINING ATLANTIC AND PACIFIC OCEANS, BUT WITH LIMITED
PRECIPITATION RE-EMERGENCE OVERALL AT THIS POINT. ORGANIZED RAINS
STAY MAINLY OFF THE WEST COAST THIS PERIOD, WITH SIGNIFICANT
EASTERN PACIFIC STORM DEVELOPMENT HELD JUST OFFSHORE. RENEWED
SHORTWAVE APPROACH OUT FROM THE WEST AND POTENTIALLY THE NORTHERN
STREAM WILL MEANWHILE HELP CARVE OUT AN AMPLIFIED CENTRAL TO
EAST-CENTRAL UPPER TROUGH POSITION LATER WEEK INTO NEXT WEEKEND,
BUT RESPONDING SURFACE SYSTEM DEVELOPMENT DOES NOT SEEM TO HAVE
DEEP MOISTURE INFLOW IN THE WAKE OF THE AFOREMENTIONED LEAD MAIN
SYSTEM, SO EXPECT AN EXPANDING AREA OF OVERALL MODERATE RAINFALL
SIGNATURE WITH A MAIN FOCUS LIKELY TO LIFT FROM THE SOUTHEAST TO
UP THE EAST COAST NEXT WEEKEND WITH MODEST COASTAL LOW GENESIS AND
ATLANTIC INFLOW THAT COULD OFFER A LATE PERIOD INTERIOR SNOW
THREAT OVER THE NORTHEAST TO MONITOR.
KONG/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, EXPERIMENTAL EXCESSIVE RAINFALL
OUTLOOK, WINTER WEATHER OUTLOOK PROBABILITIES AND HEAT INDICES 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
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