734
FXUS02 KWBC 301958
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
358 PM EDT MON OCT 30 2023
VALID 12Z THU NOV 02 2023 - 12Z MON NOV 06 2023
..SYNOPTIC OVERVIEW
AN EXPANSIVE SURFACE HIGH WILL ENCOMPASS MUCH OF THE EASTERN U.S.
THROUGH THIS WEEKEND WITH THE HIGH GRADUALLY WEAKENING THROUGH THE
PERIOD. UNDERNEATH THE HIGH, CALM WINDS AND CLEAR SKIES WILL ALLOW
TEMPERATURES TO DROP LOW ENOUGH FOR WIDESPREAD EARLY MORNING FROST
AND FREEZE CONDITIONS TO FORM MID-WEEK. TEMPERATURES IN THE EAST
WILL MODERATE AS THE HIGH WEAKENS THROUGH THE WEEKEND. COLD
CONDITIONS ARE ALSO IN THE FORECAST FOR THE NORTH-CENTRAL U.S.
WITH A RENEWED SURGE OF COLD AIR EXPECTED TO SURGE INTO THE REGION
EARLY NEXT WEEK. IN THE WEST, A COUPLE LOW PRESSURE SYSTEMS WILL
APPROACH THE COAST THROUGHOUT THE MEDIUM RANGE PERIOD THAT WILL
AIM AN ATMOSPHERIC RIVER AT THE PACIFIC NORTHWEST.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
MODELS ARE IN GENERALLY GOOD AGREEMENT ON THE OVERALL PATTERN WITH
A DEEP UPPER-LEVEL LOW INITIALLY LOCATED NEAR HUDSON BAY IN CANADA
THAT WILL SLOWLY DRIFT NORTHEAST AND A COUPLE OF UPPER-LEVEL
SHORTWAVES/LOWS THAT WILL MOVE DOWN FROM ALASKA TOWARDS THE
PACIFIC NORTHWEST. THERE ARE SOME DIFFERENCES IN TIMING OF
SHORTWAVES MOVING AROUND THE HUDSON BAY LOW AND OF THE
SHORTWAVES/LOWS MOVING INTO THE NORTHWEST. NO MODEL WAS A CLEAR
OUTLIER, THOUGH THE CMC DID STRAY FARTHER AWAY FROM THE SOLUTIONS
OF THE OTHER AVAILABLE GUIDANCE. FOR THIS REASON, THE CMC WAS
GIVEN LESS WEIGHT IN WPCS MODEL BLEND THIS AFTERNOON. WPCS MODEL
BLEND FOR THIS FORECAST PACKAGE IS PURELY DETERMINISTIC FOR THE
FIRST HALF OF THE PERIOD AND ENSEMBLE MEANS WERE INTRODUCED FOR
THE SECOND HALF TO SMOOTH OUT SOME TIMING DIFFERENCES.
..WEATHER/HAZARDS HIGHLIGHTS
SIGNIFICANT RAINFALL HAZARDS ARE NOT EXPECTED FOR MOST OF THE
CONTINENTAL U.S. THROUGH THE END OF THIS WEEK. THE ONLY PLACE
WHERE THERE WILL BE A RISK OF EXCESSIVE RAINFALL LEADING TO FLASH
FLOODING WILL BE IN THE PACIFIC NORTHWEST WITH THE ATMOSPHERIC
RIVER EVENT THAT WILL UNFOLD MID-TO-LATE THIS WEEK. THERE IS A
MARGINAL RISK OF EXCESSIVE RAINFALL ON DAY 4 (THURSDAY) FOR PARTS
OF WESTERN WASHINGTON AND OREGON WHERE A FEW INCHES OF RAINFALL
WILL BE POSSIBLE. LOCALLY HEAVIER RAINFALL ON THE WEST FACING
SLOPES MAY JUST BE ENOUGH TO CAUSE SOME MINOR FLOODING CONCERNS,
ESPECIALLY IN URBAN AND BURN SCAR AREAS. THERE SHOULD BE ENOUGH OF
A LULL ON DAY 5 TO AVOID HAVING A MARGINAL RISK AT THIS TIME, BUT
ANOTHER SURGE OF PACIFIC MOISTURE IS EXPECTED TO ARRIVE OVER THE
WEEKEND.
TEMPERATURES WILL START OFF COLD THURSDAY MORNING WITH POTENTIALLY
RECORD-BREAKING LOW MINIMUM TEMPERATURES FROM THE SOUTH TO THE
MID-ATLANTIC, AND THE CENTRAL AND EASTERN U.S. WILL LIKELY SEE
WIDESPREAD FROST AND FREEZE CONDITIONS. A SLOW MODERATION TREND IN
TEMPERATURES WILL PERSIST THROUGH THE END OF THE WEEK WITH
TEMPERATURES RETURNING TO NEAR NORMAL VALUES BY FRIDAY AND
REACHING SLIGHTLY ABOVE AVERAGE BY SATURDAY. PLEASANTLY MILD
CONDITIONS WILL ALSO RETURN TO THE ROCKIES AND ADJACENT PORTIONS
OF THE CENTRAL AND SOUTHERN PLAINS THIS WEEKEND. HOWEVER, IT
SHOULD CONTINUE TO REMAIN QUITE CHILLY FOR PARTS OF THE NORTHERN
PLAINS AND UPPER MIDWEST WITH HIGHS GENERALLY RANGING FROM THE
UPPER 20S TO LOWER 40S.
HAMRICK/DOLAN
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:
- HEAVY RAIN ACROSS PORTIONS OF NORTHERN CALIFORNIA, AND THE
PACIFIC NORTHWEST, SAT-SUN, NOV 4-NOV
5.
- FLOODING OCCURRING OR IMMINENT ACROSS PORTIONS OF THE UPPER
MISSISSIPPI VALLEY.
- FROST/FREEZE ACROSS PORTIONS OF THE MID-ATLANTIC, THE LOWER
MISSISSIPPI VALLEY, THE CENTRAL
APPALACHIANS, THE TENNESSEE VALLEY, THE MIDDLE MISSISSIPPI VALLEY,
THE NORTHEAST, THE SOUTHERN
APPALACHIANS, THE SOUTHEAST, THE SOUTHERN PLAINS, AND THE OHIO
VALLEY, THU, NOV 2.
- FROST/FREEZE ACROSS PORTIONS OF THE SOUTHEAST, THE SOUTHERN
APPALACHIANS, THE MID-ATLANTIC, THE
NORTHEAST, AND THE CENTRAL APPALACHIANS, THU-FRI, NOV 2-NOV 3.
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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