423
FXUS02 KWBC 170659
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
158 AM EST THU NOV 17 2022
VALID 12Z SUN NOV 20 2022 - 12Z THU NOV 24 2022
..SYNOPTIC OVERVIEW
A HIGHLY AMPLIFIED UPPER LEVEL FLOW PATTERN WILL BE IN PLACE
ACROSS THE COUNTRY FOR THE WEEKEND WITH A DEEP TROUGH EXTENDING
FROM HUDSON BAY TO THE NORTHEAST. THE DEEP TROUGH IS FORECAST TO
BEGIN LIFTING OUT BY MONDAY AS A MORE ZONAL FLOW PATTERN COMMENCES
ACROSS MUCH OF THE COUNTRY. OUT WEST, A COUPLE OF PACIFIC STORM
SYSTEMS ARE EXPECTED TO MOVE INLAND AS THE UPPER RIDGE AXIS DECAYS
BY SUNDAY AND INTO MONDAY, AND SHOWERS INCREASE IN COVERAGE ACROSS
THE SOUTHERN-TIER STATES BY MIDWEEK AHEAD OF A DEVELOPING STORM
SYSTEM OVER THE PLAINS.
..GUIDANCE AND PREDICTABILITY ASSESSMENT
THE 00Z DETERMINISTIC GUIDANCE CONTINUES TO HAVE AN EXCELLENT
SYNOPTIC SCALE DEPICTION OF THE BROAD UPPER TROUGH OVER THE
EASTERN U.S. THAT WILL LIFT OUT STARTING MONDAY AND THUS HERALDING
A PATTERN CHANGE, WITH MORE QUASI-ZONAL FLOW ACROSS THE NATION FOR
EARLY NEXT WEEK. HOWEVER, MODELS DIFFERENCES BECOME SIGNIFICANT
GOING INTO WEDNESDAY AND BEYOND WITH THE TROUGH DEVELOPING ACROSS
THE PLAINS. THE 12Z ECMWF WAS A MUCH MORE PROGRESSIVE SOLUTION
WITH THE TROUGH/UPPER LOW COMPARED TO THE GFS/CMC, BUT THE LATEST
00Z RUN HAS SHIFTED WEST AND CLOSER TO ITS 00Z RUN YESTERDAY.
TELECONNECTIONS WITH THE POSITIVE HEIGHT ANOMALY OVER NORTHERN
CALIFORNIA SUPPORTED A TROUGH POSITION BETWEEN THE SLOWER CMC/GFS
AND THE SLOWER 00Z ECMWF RUN FROM YESTERDAY, AND NOT AS FAST AS
THE 12Z RUN.
THE WPC FORECAST WAS PRIMARILY BASED ON A MULTI-DETERMINISTIC
MODEL BLEND, INCLUDING THE 00Z AND 12Z RUNS OF THE ECMWF, THROUGH
MONDAY, WITH A GRADUAL INCREASE IN USE OF THE EC AND GEFS MEANS
GOING INTO THE MIDDLE OF NEXT WEEK. FOR THE QPF FORECAST,
PARTICULARLY IN THE VICINITY OF THE GREAT LAKES, THE NBM 4.0 WAS
BLENDED WITH SOME OF THE ECMWF AND GFS TO INCREASE OVERALL TOTALS
ON SUNDAY.
..WEATHER/HAZARD HIGHLIGHTS
WIDESPREAD WELL BELOW AVERAGE TEMPERATURES FOR THIS TIME OF YEAR
ARE EXPECTED ACROSS THE EASTERN HALF OF THE COUNTRY ON SUNDAY AND
ALSO ACROSS MUCH OF SOUTHERN TEXAS, WHERE HIGHS COULD BE ON THE
ORDER OF 15-25 DEGREES BELOW AVERAGE IN SOME CASES. THE EASTERN
U.S. COLD WEATHER IS FORECAST TO MODERATE GOING INTO THE BEGINNING
OF THE WORK WEEK WITH READINGS RETURNING CLOSER TO SEASONAL
AVERAGES. HOWEVER, THE DAKOTAS AND NORTHERN MINNESOTA WILL LIKELY
REMAIN SLIGHTLY BELOW AVERAGE FOR MUCH OF NEXT WEEK, BUT NOT AS
COLD AS WHAT IS EXPECTED DURING THE SHORT RANGE PERIOD.
IN TERMS OF PRECIPITATION, LAKE EFFECT SNOW IS LIKELY TO BE
PERSISTENT DOWNWIND OF THE EASTERN GREAT LAKES THROUGH SUNDAY
NIGHT OWING TO STRONG COLD AIR ADVECTION OVER THE WARMER WATERS,
AND THEN ABATING GOING INTO MONDAY. HEAVY PRECIPITATION IS LIKELY
TO MAKE A RETURN TO WESTERN WASHINGTON AND OREGON WITH MOIST
ONSHORE FLOW EXPECTED, AND THE EXPECTED RAIN/SNOW HAS TRENDED
HIGHER SINCE YESTERDAY. SHOWERS AND SOME THUNDERSTORMS ARE LIKELY
TO GRADUALLY INCREASE IN COVERAGE ACROSS MUCH OF THE SOUTH-CENTRAL
U.S. GOING INTO WEDNESDAY AND THANKSGIVING DAY AS RETURN FLOW FROM
THE GULF OF MEXICO INTERACTS WITH A FRONT AND A SHORTWAVE
DISTURBANCE ALOFT.
HAMRICK
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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