578
FXUS02 KWBC 132013
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
412 PM EDT FRI OCT 13 2023
VALID 12Z MON OCT 16 2023 - 12Z FRI OCT 20 2023
..OVERVIEW
MOST GUIDANCE SHARES THE GENERAL THEME OF AN AMPLIFIED EASTERN
U.S. TROUGH (WITH POSSIBLE EMBEDDED UPPER LOW) DEPARTING WHILE
PACIFIC TROUGH ENERGY REACHING THE NORTHWEST BY TUESDAY AMPLIFIES
INTO THE CENTRAL U.S. MID-LATE WEEK. THIS LATTER AMPLIFICATION
SHOULD BE IN RESPONSE TO A STRONG EAST-CENTRAL PACIFIC STORM
ORIGINALLY ASSOCIATED WITH CURRENT TYPHOON BOLAVEN HELPING TO
ENHANCE UPPER RIDGING EXPECTED TO BUILD OVER THE WESTERN U.S..
WESTERN ATLANTIC LOW PRESSURE ASSOCIATED WITH THE INITIAL EASTERN
UPPER TROUGH/LOW MAY AFFECT THE EAST COAST TO SOME DEGREE, WHILE A
FRONT REACHING THE WEST COAST EARLY IN THE WEEK MAY BRING A BRIEF
PERIOD OF ENHANCED PRECIPITATION TO THAT REGION. EASTWARD
PROGRESSION OF THIS FRONT SHOULD BRING LIGHTER TOTALS INTO THE
ROCKIES AND PERHAPS SOMEWHAT HEAVIER ACTIVITY OVER PARTS OF THE
CENTRAL U.S. LATER IN THE WEEK. TEMPERATURES OVER THE WEST WILL
TEND TO BE ABOVE NORMAL ASIDE FROM A BRIEF MIDWEEK MODERATION
WHILE MUCH OF THE EAST WILL SEE BELOW NORMAL READINGS ESPECIALLY
DURING EARLY-MID WEEK.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
THERE WAS GOOD ENOUGH AGREEMENT THE FIRST HALF OF THE PERIOD TO
WARRANT A PURELY DETERMINISTIC MODEL BLEND. THERE REMAINS SOME
MINOR DIFFERENCES IN STRENGTH OF A SURFACE LOW OFF THE EAST COAST
EARLY WEEK, THOUGH MODELS HAVE TRENDED FARTHER OFFSHORE THAN
PREVIOUSLY THOUGHT. A BIGGER CHALLENGE HOWEVER REMAINS HOW TO
RESOLVE DIFFERENCES IN SHORTWAVE ENERGY ARRIVING INTO THE CENTRAL
U.S. AROUND MID WEEK. THE ECMWF IS CONSISTENT WITH A LITTLE MORE
PROGRESSIVE/FARTHER NORTH EVOLUTION BOTH ALOFT AND AT THE SURFACE,
WHILE THE CMC CONTINUES TO SHOW THE MOST EXTREME
DIGGING/SOUTHWESTWARD ELONGATION OF THE TROUGH BY NEXT FRIDAY.
NEITHER ARE OUTSIDE THE ENVELOPE OF POSSIBILITIES THOUGH. THE GFS
DIGS AND CLOSES OFF A LOW MORE THAN THE ECMWF DOES, AND SEEMS AT
LEAST AT THIS POINT, THE MOST CONSISTENT WITH THE ENSEMBLE MEANS
AND MOST REASONABLE BASED ON THE STRENGTH OF WHAT IS CURRENTLY
TYPHOON BOLAVEN EVENTUALLY MOVING INTO THE GULF OF ALASKA (AS AN
EXTRA TROPICAL STORM) AND HOW THAT AFFECTS AMPLIFICATION OF THE
PATTERN DOWNSTREAM OVER THE CONUS. ANYWAYS, INCREASING UNCERTAINTY
FOR THE DETAILS IN THIS LATER TIME FRAME LED TO A TRANSITION OF
THE FORECAST TOWARDS THE ENSEMBLE MEANS, WITH SOME CONTRIBUTIONS
FROM THE ECMWF AND GFS. THIS MAINTAINED GOOD CONTINUITY WITH THE
PREVIOUS WPC FORECAST AS WELL.
..WEATHER/HAZARDS HIGHLIGHTS
EXPECT SHORTWAVE ENERGY AND A LEADING COLD FRONT TO BRING A BRIEF
PERIOD OF MODERATE TO HEAVY PRECIPITATION TO THE CENTRAL AND
NORTHERN WEST COAST AROUND MONDAY, WITH HIGHEST TOTALS LIKELY OVER
SOUTHWARD FACING TERRAIN OVER THE PACIFIC NORTHWEST. THERE MAY BE
SUFFICIENT INSTABILITY TO PROMOTE SOME ENHANCED RAINFALL INTENSITY
ON A LOCALIZED BASIS BUT THE COMBINATION OF OBSERVED SOIL
MOISTURE/RECENT RAINFALL/STREAM FLOWS SUGGEST ANY RUNOFF ISSUES
SHOULD BE ISOLATED ENOUGH NOT TO MERIT ANY RISK AREA IN THE DAY 4
(MONDAY) EXCESSIVE RAINFALL OUTLOOK. LIGHTER PRECIPITATION SHOULD
SPREAD ACROSS THE NORTHERN AND PERHAPS CENTRAL ROCKIES AS THE
SHORTWAVE ENERGY AND FRONT CONTINUE EASTWARD. COVERAGE AND
INTENSITY OF RAINFALL SHOULD INCREASE OVER THE CENTRAL U.S. BY
WEDNESDAY-FRIDAY BUT DETAILS BECOME INCREASINGLY UNCLEAR, WITH
VARIOUS POTENTIAL UPPER LEVEL AND SURFACE EVOLUTIONS LEADING TO A
WIDE RANGE OF POSSIBILITIES FOR LOCATION AND MAGNITUDE OF HEAVIEST
RAINFALL. ANOTHER AREA OF MOISTURE COULD REACH NORTHERN PARTS OF
THE PACIFIC NORTHWEST BY LATE NEXT WEEK. EARLY-MID WEEK UPPER
TROUGHING AND POSSIBLE EMBEDDED LOW OVER THE EAST SHOULD PROMOTE
OFFSHORE LOW PRESSURE DEVELOPMENT THAT MAY MAINTAIN BRISK WINDS
FOR A TIME NEAR THE EAST COAST. HOWEVER LATEST TRENDS FOR A WEAKER
AND/OR SOMEWHAT MORE OFFSHORE SYSTEM SHOULD KEEP RAINFALL ON THE
LIGHTER SIDE. THE EASTERN GREAT LAKES INTO THE APPALACHIANS MAY
SEE SOME LIGHT PRECIPITATION AS WELL.
THE AMPLIFIED TROUGH OVER THE EAST EARLY IN THE WEEK WILL SUPPORT
BELOW NORMAL TEMPERATURES OVER MUCH OF THE EASTERN HALF OF THE
COUNTRY EARLY IN THE WEEK, WITH A BROAD AREA OF HIGHS 10-15F BELOW
NORMAL. SIMILAR ANOMALIES FOR MORNING LOWS SHOULD BE CONFINED MORE
TO THE CENTRAL PLAINS ON MONDAY AND THE GULF COAST/FLORIDA REGIONS
TUESDAY-WEDNESDAY. EASTERN U.S. TEMPERATURES SHOULD RETURN CLOSER
TO NORMAL THEREAFTER. THE WESTERN U.S. WILL SEE ABOVE NORMAL
TEMPERATURES FOR MOST OF NEXT WEEK, WITH A BRIEF MIDWEEK LULL
SEPARATING WARMTH AHEAD OF A LEADING PACIFIC COLD FRONT AND THEN A
REBOUND IN TEMPERATURES AS UPPER RIDGING BUILDS OVER THE REGION.
SOME LOCATIONS MAY SEE ONE OR MORE DAYS OF PLUS 10-20F ANOMALIES.
SANTORELLI/RAUSCH
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
HAZARDS:
- FLOODING POSSIBLE ACROSS PORTIONS OF THE SOUTHEAST.
- HEAVY RAIN ACROSS PORTIONS OF THE ALASKA PANHANDLE AND MAINLAND
ALASKA, WED-THU, OCT 18-OCT 19.
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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