261
FXUS02 KWBC 141849
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
249 PM EDT THU MAR 14 2024
VALID 12Z SUN MAR 17 2024 - 12Z THU MAR 21 2024
...MULTI-DAY HEAVY RAINFALL EVENT ACROSS THE SOUTH TO COME TO AN
END THIS WEEKEND...
..OVERVIEW
IT OVERALL AGAIN REMAINS THE CASE THAT THE GENERAL FLOW OVER THE
LOWER 48 STATES WILL REMAIN QUITE AMPLIFIED INTO NEXT WEEK AS A
DEEP UPPER LOW MEANDERS OVER THE SOUTHWEST AND AN AMPLIFIED TROUGH
DIVES SOUTH AND EASTWARD THROUGH THE MIDWEST AND EAST. THESE TWO
FEATURES COMBINED WILL CONTINUE TO PROMOTE A MULTI-DAY PERIOD OF
HEAVY RAINFALL POTENTIAL INTO THIS WEEKEND UNDERNEATH ACROSS PARTS
OF THE SOUTHERN U.S., BUT SHOULD COME TO AN END SUNDAY. A LEADING
COLD FRONT WILL ALSO BRING A MUCH COOLER TREND TO MUCH OF THE
EASTERN HALF OF THE LOWER 48, WITH SOME FROST FREEZE CONCERNS
ACROSS THE SOUTH. STRONG RIDGING OFF THE WEST COAST AND INTO THE
NORTHWEST MAY EVENTUALLY BREAK DOWN NEXT WEEK AS SHORTWAVE ENERGY
DROPS INTO/OFFSHORE THE NORTHWEST/WEST COAST, AND THIS MAY
EVENTUALLY WORK TO INTERACT WITH THE STUBBORN SOUTHWEST CLOSED LOW.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE BULK OF LATEST GUIDANCE REMAIN IN REASONABLE AGREEMENT WITH
THE FLOW PATTERN INTO EARLY NEXT WEEK, WITH SOME UNCERTAINTY IN
THE DETAILS AND TIMING OF INDIVIDUAL SYSTEMS, ESPECIALLY SHORTWAVES
THROUGH THE MEAN MIDWEST/EASTERN U.S. UPPER TROUGH POSITION. THE
BIGGEST UNCERTAINTIES ARISE BY ABOUT TUESDAY WITH THE EVOLUTION OF
THE UPPER LOW OVER THE SOUTHWEST. RECENT RUNS OF THE CMC ARE AN
OUTLIER IN SHOWING THE LOW LIFTING NORTHWARD IN FAVOR OF ANOTHER
CUT OFF LOW MOVING IN TOWARDS SOUTHERN CALIFORNIA. THERE IS MINIMAL
SUPPORT FOR THIS SOLUTION AT THIS TIME IN ENSEMBLES. THERE IS
BETTER AGREEMENT IN THE GUIDANCE/ENSEMBLES FOR THE LOW TO MEANDER
IN PLACE AND GRADUALLY WEAKEN BEFORE AN UNCERTAIN SHIFT EASTWARD AS
A SHORTWAVE INTO THE PLAINS BY MID NEXT WEEK, AND THIS SEEMS BEST
SUPPORTED BY MOST MACHINE LEARNING MODELS TOO. THE GFS AND ECMWF
HAVE ALSO TRENDED SOMEWHAT IN BETTER AGREEMENT BACK OVER THE EPAC.
THE WPC FORECAST FOR TONIGHT USED A MAJORITY BLEND OF THE GFS AND
ECMWF (WITH SOME UKMET) THROUGH MONDAY. AFTER THAT, GRADUALLY
INCREASED ENSEMBLE MEAN CONTRIBUTION TO ABOUT 50 PERCENT OF THE
BLEND BY DAY 7, ALONG WITH THE GFS AND ECMWF WHICH SHOWED FAIRLY
GOOD AGREEMENT WITH EACH OTHER THROUGH THE PERIOD.
..WEATHER/HAZARDS HIGHLIGHTS
THE PESKY UPPER LOW OVER THE SOUTHWEST SHOULD CONTINUE TO SUPPORT
SOME GENERALLY LIGHT TO MODERATE PRECIPITATION ACROSS THE FOUR
CORNERS REGION, WITH A TERRAIN ENHANCED SNOW THREAT ACROSS THE
HIGHER TERRAIN OF SOUTHWEST COLORADO AND NEW MEXICO THROUGH EARLY
NEXT WEEK. MEANWHILE, MOISTURE STREAMING NORTHWARD AHEAD OF THE LOW
WILL BE INTERACTING WITH A COLD FRONT MOVING THROUGH THE
SOUTHEAST/GULF COAST REGION ON SUNDAY, AND FLORIDA ON MONDAY. FOR
THE EXCESSIVE RAINFALL OUTLOOKS, CONTINUED A MARGINAL RISK ON DAY 4
ALONG THE CENTRAL GULF COAST AS ANOMALOUS MOISTURE AND INSTABILITY
POOL ALONG THE BOUNDARY WHERE THERE SOME INCREASED RISK FOR
TRAINING OF STORMS. THERE MAY BE A LOCALIZED RISK ON DAY 5 AS THE
FRONT MOVES THROUGH FLORIDA, BUT THE FRONT SHOULD BE PROGRESSIVE
ENOUGH AND THE MODEL QPFS DO NOT SUPPORT EVEN A MARGINAL RISK AT
THIS TIME. TO THE NORTH, A SECONDARY COLD FRONT THROUGH THE GREAT
LAKES/NORTHEAST SHOULD BRING SOME LIGHT PRECIPITATION ACROSS THE
REGION. SUFFICIENT COLD AIR AND PROTRACTED WRAP-BACK MOISTURE FEED
MAY COMBINE TO PRODUCE SOME PLOWABLE SNOWS IN WINDY FLOW, WITH MAIN
FOCUS OVER NORTHERN MAINE SUNDAY AS A MAIN SURFACE LOW EXITS AWAY
FROM NEW ENGLAND. WELL UPSTREAM, A COMPLEX LATE PERIOD SYSTEM
WORKING OFFSHORE/INTO THE NORTHWEST MAY BRING SOME LIGHT PRECIP
BACK INTO THAT REGION, POSSIBLY INCREASING SOME INTO NEXT MIDWEEK,
ALBEIT WITH SIGNIFICANT UNCERTAINTY WITH SUPPORT/INTERACTIONS TO
MONITOR IN UPCOMING GUIDANCE CYCLES IN AN OVERALL DRIER PATTERN BY
THEN OVER THE LOWER 48 INTO NEXT WEEK.
TEMPERATURES FROM THE MIDWEST TO THE EAST WILL TREND MUCH COOLER
BY THIS WEEKEND AS STRONG SURFACE HIGH PRESSURE SHIFTS SOUTH AND
EASTWARD. DAYTIME HIGHS FROM THE MID-SOUTH TO SOUTHEAST MAY BE
10-15 DEGREES BELOW NORMAL, WITH SOME FROST/FREEZE CONCERNS FOR
ANY AREAS WHERE SPRING GREEN-UP HAS STARTED AS TEMPERATURES DIP
WELL INTO THE 30S TO NEAR FREEZING ESPECIALLY TUESDAY MORNING.
TEMPERATURES ACROSS THE SOUTHWEST WILL TREND WARMER WITH TIME AS
THE UPPER LOW WEAKENS AND ABOVE NORMAL TEMPERATURES EXPANDING OVER
THE NORTHWEST THIS WEEKEND WILL MOVE INTO THE NORTHERN/CENTRAL
PLAINS AND UPPER MIDWEST BY NEXT TUESDAY-WEDNESDAY.
SANTORELLI/SCHICHTEL
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