Prognostic Meteorological Discussion
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2
000
FXUS21 KWNC 181842
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT SEPTEMBER 18 2014

SYNOPSIS: A PATTERN CHANGE ACROSS NORTH AMERICA IS BECOMING MORE LIKELY AS
NORTH PACIFIC FLOW STRENGTHENS AND AFFECTS THE WEST COAST BY THE MIDDLE PART OF
NEXT WEEK. UPSLOPE FLOW IS EXPECTED ACROSS EASTERN NEW MEXICO AND WEST TEXAS ON
SUNDAY AND MONDAY AS AN AREA OF UPPER-LEVEL LOW PRESSURE TRACKS ACROSS THE
GREAT BASIN AND CENTRAL ROCKIES. A COLD FRONT IS FORECAST TO PROGRESS INTO THE
EASTERN U.S. EARLY IN THE PERIOD, WHILE A SURFACE LOW DEVELOPS NEAR THE EAST
COAST. SURFACE HIGH PRESSURE IS EXPECTED TO BUILD ACROSS ALASKA AS THE NORTH
PACIFIC STORM TRACK SHIFTS SOUTH.

HAZARDS

HEAVY RAIN FOR THE NORTHERN/CENTRAL ALASKA PANHANDLE, SUN, SEP 21.

HEAVY RAIN ACROSS THE SOUTHERN HIGH PLAINS, SUN-MON, SEP 21-22.

FLASH FLOODING POSSIBLE ACROSS THE CENTRAL ROCKIES, SUN, SEP 21.

RIVER FLOODING LIKELY FOR PARTS OF ARIZONA AND NEW MEXICO.

RIVER FLOODING POSSIBLE FOR PARTS OF NEW MEXICO AND WEST TEXAS.

SEVERE DROUGHT FOR THE CENTRAL AND SOUTHERN GREAT PLAINS, SOUTHWEST, SOUTHERN
GEORGIA, PACIFIC NORTHWEST, GREAT BASIN, AND CALIFORNIA.

DETAILED SUMMARY

FOR SUNDAY SEPTEMBER 21 - THURSDAY SEPTEMBER 25: AFTER A COLD FRONT PUSHES
SOUTH, UPSLOPE FLOW AND ANOMALOUS LOW-LEVEL MOISTURE ARE EXPECTED TO MAINTAIN
THE RISK OF HEAVY RAINFALL ACROSS THE SOUTHERN HIGH PLAINS THROUGH AT LEAST
MONDAY. PRECIPITABLE WATER VALUES AROUND 2 INCHES ARE FORECAST ACROSS WEST
TEXAS ON SUNDAY BEFORE DECREASING EARLY NEXT WEEK.



SEVERE THUNDERSTORMS COULD DEVELOP ALONG AND AHEAD OF THE COLD FRONT AS IT
CROSSES THE OHIO VALLEY ON SUNDAY, BUT LIMITED INSTABILITY PRECLUDES
DESIGNATION OF A SEVERE WEATHER HAZARD.



MODEL GUIDANCE REMAINS CONSISTENT THAT A MID-LEVEL TROUGH CROSSES THE CENTRAL
ROCKIES THIS WEEKEND. THIS MID-LEVEL TROUGH ALONG WITH ANOMALOUS LOW-LEVEL
MOISTURE IS EXPECTED TO RESULT IN ISOLATED TO SCATTERED CONVECTION CAPABLE OF
TRIGGERING FLASH FLOODING.



AN UPPER-LEVEL RIDGE IS EXPECTED TO RESULT IN MAXIMUM TEMPERATURES AVERAGING
AROUND 12 DEGREES F ABOVE-NORMAL ACROSS THE INTERIOR PACIFIC NORTHWEST ON
SUNDAY AND MONDAY. SINCE MAXIMUM TEMPERATURES ARE FORECAST TO REMAIN BELOW 90
DEGREES F, A MUCH-ABOVE NORMAL TEMPERATURE HAZARD IS NOT DEEMED NECESSARY FOR
THIS REGION.



NUMEROUS WILDFIRES ARE BURNING ACROSS OREGON AND CALIFORNIA WITH THE LARGEST
WILDFIRE (MORE THAN 125,000 ACRES BURNED) IN SISKIYOU COUNTY OF NORTHERN
CALIFORNIA. DURING THE MIDDLE PART OF NEXT WEEK, THE HIGH RESOLUTION MODELS
INDICATE A TROUGH MOVING ONSHORE INTO THE PACIFIC NORTHWEST WHICH WOULD BRING
MUCH NEEDED RAIN TO THIS REGION. A HEAVY RAIN HAZARD IS NOT POSTED FOR THE
PACIFIC NORTHWEST SINCE THE HIGH RESOLUTION 0Z/6Z GFS MODELS INDICATE RAINFALL
AMOUNTS BELOW HAZARDS CRITERIA.



THE GFS AND CANADIAN MODELS INDICATE LOW PRESSURE DEVELOPMENT OFFSHORE OF THE
CAROLINAS THIS WEEKEND. NO HAZARDOUS WEATHER IS CURRENTLY EXPECTED ALONG THE
EAST COAST SINE THE HEAVIEST RAIN IS FORECAST TO REMAIN OFFSHORE.



A LOW PRESSURE SYSTEM IS EXPECTED TO AFFECT THE ALASKA PANHANDLE ON SUNDAY. A
HEAVY RAIN HAZARD IS POSTED ACROSS THE NORTHERN/CENTRAL ALASKA PANHANDLE WHERE
THE HIGH RESOLUTION 6Z GFS MODEL INDICATES AMOUNTS EXCEEDING 3 INCHES SEPTEMBER
21.

FOR FRIDAY SEPTEMBER 26 - THURSDAY OCTOBER 02: ALTHOUGH LARGE SPREAD AMONG THE
0Z GFS AND 0Z ECMWF ENSEMBLE MEMBERS CONTINUES FOR THE THIRD CONSECUTIVE DAY,
ENSEMBLE MEANS INDICATE A PATTERN CHANGE BY WEEK-2 WITH A TROUGH (RIDGE) OVER
THE WESTERN (EASTERN) CONUS.



THE U.S. DROUGHT MONITOR, VALID ON SEPTEMBER 16, INDICATES THE PERCENTAGE OF
THE CONUS IN SEVERE TO EXCEPTIONAL DROUGHT DECREASED BELOW 20 PERCENT FOR THE
FIRST TIME SINCE JANUARY 2014.

FORECASTER: BRAD PUGH

$$




USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.