057
FXUS02 KWBC 091900
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
200 PM EST SAT MAR 09 2024
VALID 12Z TUE MAR 12 2024 - 12Z SAT MAR 16 2024
..HEAVY RAINFALL POTENTIAL RETURNS TO THE SOUTH LATE NEXT WEEK
..OVERVIEW
THE MEDIUM RANGE PERIOD STARTS TUESDAY WITH ONE SHORTWAVE MOVING
THROUGH THE CENTRAL U.S. AS THE NEXT ONE ENTERS THE WEST COAST.
AFTER THIS, THE PATTERN LOOKS TO TREND MUCH MORE AMPLIFIED WITH
UPPER RIDGING BUILDING OVER THE EAST COAST ALLOWING FOR THE SECOND
SYSTEM OVER THE WEST TO DIG SOUTHEASTWARD INTO THE SOUTHWEST.
GUIDANCE SHOWS GENERAL AGREEMENT ON A DEEP CLOSED LOW DEVELOPING
OVER THE SOUTHWEST/FOUR CORNERS REGION ON THURSDAY, AND LINGERING
OR ONLY VERY SLOWLY MOVING EASTWARD INTO THE WEEKEND. THIS SHOULD
PROMOTE A PERIOD OF HEAVY RAINFALL POTENTIAL ACROSS PARTS OF THE
SOUTHERN U.S. LATE THIS WEEK. ELSEWHERE, NORTHERN STREAM ENERGY
WILL SLIDE ACROSS THE UPPER MIDWEST/GREAT LAKES LATE WEEK, AS A
STRONG RIDGE SHIFTS OVER THE WEST COAST.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL GUIDANCE IS GENERALLY AGREEABLE ON THE LARGER SCALE PATTERN
THROUGH MUCH OF THE PERIOD, WITH SOME TYPICAL DIFFERENCES IN THE
DETAILS THAT TEND TO INCREASE WITH LEAD TIME. THE 00Z CMC WAS ON
THE SLOWER SIDE WITH THE INITIAL SHORTWAVE MOVING ACROSS THE
CENTRAL U.S. TUESDAY-WEDNESDAY. THEN BY THURSDAY, 00Z AND 06Z GFS
RUNS WERE SHOWING A NOTABLE SHORTWAVE IN THE PLAINS THAT PRODUCES
STRONGER SURFACE LOW PRESSURE THAN THE NON-NCEP GUIDANCE, BUT THE
12Z GFS SEEMS TO BE IN BETTER ALIGNMENT. OVERALL THE 00Z ECMWF
SEEMED TO BE THE BEST PROXY FOR A MIDDLE GROUND SOLUTION AND
FAVORED IT FOR THE FORECAST BLEND. THIS CONTINUES INTO THE LATTER
PART OF NEXT WEEK WHEN LARGER MODEL DIFFERENCES ARISE, PRIMARILY
WITH ENERGY ON THE BACKSIDE OF THE MEAN TROUGH DIGGING SOUTHWARD
TO FORM A SOUTHERN STREAM CLOSED LOW OVER THE SOUTHWEST/FOUR
CORNERS REGION WHILE AT THE SAME TIME NORTHERN STREAM ENERGY
SHIFTS ACROSS THE NORTHERN PLAINS/UPPER GREAT LAKES. MOST
OPERATIONAL AND AI MODELS SHOW STREAM SEPARATION TAKING PLACE,
WITH THE EXCEPTION OF THE 00Z CMC THAT SHOWED PHASING. WITH THE
MAJORITY OF MODELS AND CONTINUITY FAVORING THE STREAM SEPARATION,
THIS FORECAST DID AS WELL. THE 12Z CMC HAS TRANSITIONED TO MORE
STREAM SEPARATION. HOWEVER, THERE IS STILL UNCERTAINTY AMONG
MODELS WITH THE PLACEMENT OF THE SOUTHERN CLOSED LOW AND WITH THE
DEPTH AND POSITION OF THE NORTHERN STREAM TROUGH. AS THE FORECAST
PROGRESSED, TRANSITIONED TOWARD A MODEL BLEND COMPOSED OF HALF
EC/GEFS ENSEMBLE MEANS BY THE DAY 6-7 TIMEFRAME.
..WEATHER/HAZARDS HIGHLIGHTS
THE WESTERN U.S. REMAINS UNSETTLED FOR THE EARLY PART OF THE
PERIOD AS A COUPLE OF SHORTWAVES BRING ROUNDS OF RAIN AND HIGHER
ELEVATION SNOW, AFFECTING THE PACIFIC NORTHWEST/NORTHERN
CALIFORNIA EASTWARD INTO MUCH OF THE INTERMOUNTAIN WEST ON
TUESDAY, AND SHIFTING MORE INLAND INTO THE ROCKIES WITH TIME. THE
CENTRAL ROCKIES CAN EXPECT THE HIGHEST SNOW AMOUNTS ON WEDNESDAY
AND THURSDAY, WITH SOME UNCERTAINTY WITH HOW MUCH SNOW SPREADS
INTO THE FRONT RANGE URBAN CORRIDOR. SNOW SHOULD CONTINUE INTO
HIGHER ELEVATIONS OF NEW MEXICO FOR THE LATTER PART OF THE WEEK.
FARTHER EAST, RAINFALL WILL BEGIN TO INCREASE IN COVERAGE AND
INTENSITY OVER NORTH-CENTRAL PARTS OF THE PLAINS AND MISSISSIPPI
VALLEY BY WEDNESDAY AS TROUGHING AMPLIFIES OVER THE WEST.
PRECIPITABLE WATER VALUES MAY BE TOO LOW FOR ANY FLOODING CONCERNS
WITH THIS ACTIVITY, AND ANTECEDENT CONDITIONS ARE QUITE DRY, SO
ANY EXCESSIVE RAINFALL THREAT THERE LOOKS TO BE AT SUB-MARGINAL
LEVELS. ON TUESDAY AND WEDNESDAY, CONSIDERABLE CONVECTION IS
LIKELY OVER THE GULF OF MEXICO, WHICH MAY SNEAK INTO THE WEST
COAST OF FLORIDA BY WEDNESDAY, BUT MODEL DIFFERENCES IN AMOUNTS
AND PLACEMENT PRECLUDE ANY AREA IN THE EXCESSIVE RAINFALL OUTLOOK
AT THIS POINT. BUT BY THE LATTER PART OF THE WEEK, MOISTURE
STREAMING AHEAD OF THE CLOSED LOW DEVELOPING OVER THE SOUTHWEST
SHOULD INCREASE THE THREAT FOR HEAVY RAIN AND POTENTIALLY FLASH
FLOODING ACROSS THE LOWER MISSISSIPPI VALLEY/GULF COAST/SOUTHEAST.
AREAS ACROSS THE SOUTH MAY BE MORE SUSCEPTIBLE TO FLOODING WITH
THIS SYSTEM CONSIDERING RECENT HEAVY RAINS. SEVERE WEATHER IS ALSO
A THREAT WITH THIS CONVECTIVE ACTIVITY--THE STORM PREDICTION
CENTER HAS A SEVERE WEATHER AREA DELINEATED FOR PARTS OF THE
SOUTHERN PLAINS ON THURSDAY.
MEAN RIDGING ALOFT OVER THE EAST-CENTRAL AND EASTERN U.S. WILL
SUPPORT AN EXPANDING AREA OF ABOVE NORMAL TEMPERATURES TO THE EAST
OF THE ROCKIES. THE CORE OF WARMEST ANOMALIES SHOULD COVER PARTS
OF THE NORTHERN PLAINS AND UPPER MIDWEST TUESDAY THROUGH
WEDNESDAY, WITH HIGHS POTENTIALLY REACHING 20-30 DEGREES ABOVE
NORMAL. ABOVE NORMAL TEMPERATURES WILL GRADUALLY EXPAND INTO THE
SOUTH AND EAST MID TO LATE NEXT WEEK. OVER THE WEST, THE WET/SNOWY
PATTERN OVER THE NORTHERN-CENTRAL WEST COAST AND EVENTUALLY INTO
THE ROCKIES WILL MAINTAIN MODERATELY BELOW AVERAGE HIGHS AND
NEAR/ABOVE AVERAGE LOWS THROUGH EARLY NEXT WEEK. UPPER TROUGHING
THAT AMPLIFIES INLAND BY WEDNESDAY-THURSDAY SHOULD SPREAD A
BROADER AREA OF COOL DAYTIME HIGHS ACROSS THE WEST, THOUGH
TEMPERATURES SHOULD BEGIN TO REBOUND AGAIN ALONG THE IMMEDIATE
COAST NEXT FRIDAY-SATURDAY AS STRONG RIDGING BUILDS IN ALOFT.
TATE/SANTORELLI
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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