990
FXUS02 KWBC 041902
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
200 PM EST SAT FEB 04 2023
VALID 12Z TUE FEB 07 2023 - 12Z SAT FEB 11 2023
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL GUIDANCE THIS MORNING CONTINUES TO EXHIBIT
HIGHER-THAN-NORMAL UNCERTAINTY FROM MIDWEEK NEXT WEEK ONWARD
ACROSS THE EASTERN TWO-THIRDS OF THE COUNTRY. THE FIRST SYSTEM OF
CONCERN WILL BE ON THE TIMING AND AMPLITUDE OF A SHORTWAVE/UPPER
LOW THAT IS FORECAST TO EJECT OUT FROM THE SOUTHWEST INTO THE
CENTRAL U.S. 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 POTENTIALLY MUCH AMPLIFIED RIDGE OVER THE WESTERN U.S.
WHILE A LARGE CLOSED LOW COULD DEVELOP NEAR/OFF THE WEST COAST.
IN ADDITION, A SHORTWAVE RAPIDLY ENTERING THE PACIFIC NORTHWEST BY
AROUND 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.
THE WPC MEDIUM RANGE PRODUCT SUITE THROUGH MEDIUM RANGE TIME
SCALES WAS PRIMARILY DERIVED FROM A COMPOSITE BLEND OF 40% FROM
THE 06Z GEFS/00Z+06Z GFS, 40% FROM TO 00Z ECMWF/EC MEAN, AND 20%
FROM THE 00Z CMC AND CMC MEAN.
..WEATHER/HAZARD HIGHLIGHTS
EARLY NEXT WEEK ROUNDS OF LIGHT PRECIPITATION WILL PASS OVER
PORTIONS OF THE GREAT LAKES AND THE NORTHEAST REGION WITH
SHORTWAVE PASSAGES AND THE APPROACH OF A LEAD LOW/FRONTAL SYSTEM.
THERE MAY BE LAKE ENHANCEMENT OF THE SNOWFALL FOR THE FAVORED
AREAS DOWNWIND OF THE GREAT LAKES WHICH COULD RESULT IN HIGHER
AMOUNTS THAN SURROUNDING LOCATIONS. MODERATE PRECIPITATION IS
EXPECTED TO OVERSPREAD THE WEST COAST AND INLAND TO THE
INTERMOUNTAIN WEST AND ROCKIES REGION EARLY NEXT WEEK. FOR MOST OF
LOWER COASTAL AREAS THE PRECIPITATION WILL LIKELY FALL AS RAIN AND
THEN TRANSITION TO SNOW FOR THE MID-BASE TO HIGHEST ELEVATIONS;
WITH TYPICAL TERRAIN ENHANCEMENT ACROSS THE COASTAL RANGES AND THE
SIERRA NEVADA. AS THE LOW PRESSURE SYSTEM ADVANCES EASTWARD THE
PRECIPITATION AHEAD OF IT COULD OVERSPREAD THE CENTRAL U.S. THE
DETAILS OF THIS PRECIPITATION INCLUDING PLACEMENT AND
PRECIPITATION TYPE REMAIN UNCERTAIN GIVEN THE MODEL DIFFERENCES.
THE CURRENT FORECAST SHOWS ENHANCED RAINFALL AMOUNTS CENTERED
ACROSS THE SOUTHERN PLAINS FROM NORTHEASTERN TEXAS THROUGH THE
OZARKS FROM LATE TUESDAY INTO WEDNESDAY, WHERE A SLIGHT RISK OF
EXCESSIVE RAINFALL HAS BEEN INTRODUCED OVER THE REGION GIVEN THE
BEST LOW-LEVEL MOISTURE CONVERGENCE AND FAVORABLE RIGHT ENTRANCE
REGION UPPER JET DYNAMICS. THIS WAS SURROUNDED BY A MARGINAL RISK
AREA EXTENDING FROM THE EASTERN TWO-THIRDS OF TEXAS LATE TUESDAY
TO THE MID-MISSISSIPPI VALLEY ON WEDNESDAY AND INTO EARLY
THURSDAY. THE NORTHERN EDGE OF THE PRECIPITATION SHIELD SET TO
SPREAD/SHEAR ACROSS THE EAST LATER NEXT WEEK ALSO MAINTAINS THE
POTENTIAL FOR A SWATH OF SNOW/ICE ACROSS PORTIONS OF THE COOLED
SOUTHERN PLAINS TO MIDWEST AND INTERIOR NORTHEAST. UPSTREAM
EASTERN PACIFIC SYSTEM APPROACH TUESDAY/WEDNESDAY SHOULD OFFER
MODEST SYSTEM AMPLITUDE AND ASSOCIATED MOISTURE/RAINFALL POTENTIAL
ACROSS THE PACIFIC NORTHWEST ALONG WITH TERRAIN/MOUNTAIN SNOWS
INLAND FROM THE NORTHWEST THROUGH THE NORTHERN GREAT
BASIN/ROCKIES. THERE IS THOUGH AN AFOREMENTIONED AND GROWING
GUIDANCE SIGNAL THAT THIS LEADS TO THE AMPLIFICATION OF THE
OVERALL FLOW SIGNIFICANTLY INTO LATER NEXT WEEK ACROSS THE NATION
AND ADJOINING OCEANS, BUT WITH LIMITED PRECIPITATION RE-EMERGENCE
LATER NEXT WEEK 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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