354  
FXUS21 KWNC 221748  
PMDTHR  
US HAZARDS OUTLOOK  
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD  
300 PM EDT SEPTEMBER 22 2017  
 
SYNOPSIS: STRONG MID-LEVEL HIGH PRESSURE IS ANTICIPATED OVER THE EASTERN U.S.,  
WHILE STRONG MID-LEVEL LOW PRESSURE IS EXPECTED OVER THE WEST. A FRONTAL SYSTEM  
OVER THE UPPER MISSISSIPPI VALLEY/GREAT PLAINS/SOUTHWEST U.S. IS FORECAST TO  
MOVE VERY SLOWLY EAST-SOUTHEASTWARD. HURRICANE MARIA IS EXPECTED TO MOVE  
NORTHWARD OVER THE WESTERN ATLANTIC. SURFACE LOW PRESSURE IS FORECAST TO  
DEVELOP OVER THE GULF OF ALASKA. DURING THE BEGINNING TO MIDDLE OF WEEK-2,  
AREAS OF MID-LEVEL LOW PRESSURE ARE ANTICIPATED OVER THE EASTERN U.S. AND  
WESTERN AND CENTRAL MAINLAND ALASKA, WHILE MID-LEVEL HIGH PRESSURE IS EXPECTED  
OVER THE WESTERN U.S. AND SOUTHEASTERN ALASKA. THE MIDDLE TO END OF WEEK-2 IS  
ANTICIPATED TO BE DOMINATED BY A MORE ZONAL PATTERN ACROSS THE LOWER 48 STATES.  
 
HAZARDS  
 
HEAVY RAIN ACROSS PORTIONS OF THE CENTRAL PLAINS AND SOUTHERN PLAINS, MON, SEP  
25.  
 
HEAVY RAIN ACROSS PORTIONS OF THE SOUTHERN PLAINS, TUE-FRI, SEP 26-SEP 29.  
 
HIGH SIGNIFICANT WAVE HEIGHTS FOR COASTAL PORTIONS OF THE MID-ATLANTIC AND THE  
NORTHEAST, WED, SEP 27.  
 
HEAVY RAIN ACROSS PORTIONS OF THE ALASKA PANHANDLE, TUE-WED, SEP 26-SEP 27.  
 
MUCH ABOVE NORMAL TEMPERATURES ACROSS PORTIONS OF THE NORTHEAST, THE CENTRAL  
APPALACHIANS, THE MID-ATLANTIC, THE UPPER MISSISSIPPI VALLEY, THE GREAT LAKES,  
AND THE OHIO VALLEY, TUE-WED, SEP 26-SEP 27.  
 
FLOODING OCCURRING OR IMMINENT ACROSS PORTIONS OF THE SOUTHEAST.  
 
SEVERE DROUGHT ACROSS THE CENTRAL PLAINS, THE NORTHERN PLAINS, HAWAII, THE  
NORTHERN ROCKIES, THE MIDDLE MISSISSIPPI VALLEY, CALIFORNIA, THE UPPER  
MISSISSIPPI VALLEY, AND THE SOUTHERN PLAINS.  
 
DETAILED SUMMARY  
 
FOR MONDAY SEPTEMBER 25 - FRIDAY SEPTEMBER 29: STRONG RIDGING OVER THE  
EAST-CENTRAL CONUS FAVORS MUCH ABOVE NORMAL TEMPERATURES (POSITIVE ANOMALIES  
EXCEEDING 20-24 DEGREES F) ACROSS PORTIONS OF THE NORTHEAST, THE CENTRAL  
APPALACHIANS, THE MID-ATLANTIC, THE UPPER MISSISSIPPI VALLEY, THE GREAT LAKES,  
AND THE OHIO VALLEY, SEP 26-27. DAY TIME MAXIMUM TEMPERATURES ARE EXPECTED IN  
THE UPPER 80'S/LOW 90'S F FOR PARTS OF THESE REGIONS.  
 
A STRONG MID-LEVEL TROUGH OVER THE WESTERN CONUS, IN COMBINATION WITH A FRONTAL  
SYSTEM FORECAST TO MOVE EAST-SOUTHEASTWARD FROM THE UPPER MISSISSIPPI  
VALLEY/GREAT PLAINS/SOUTHWEST TO THE EAST-CENTRAL CONUS INCREASES THE  
LIKELIHOOD FOR HEAVY RAIN (AMOUNTS OF 3-4 INCHES OVER 48 HOURS) FOR PORTIONS OF  
THE CENTRAL PLAINS AND SOUTHERN PLAINS SEP 25, SHIFTING SOUTHEASTWARD TO THE  
SOUTHERN PLAINS FROM SEP 26 TO 29.  
 
HURRICANE MARIA IS FORECAST TO MOVE NORTHWARD OVER THE WESTERN ATLANTIC. HIGH  
SIGNIFICANT WAVE HEIGHTS (IN EXCESS OF 20 FEET) ARE FORECAST FOR COASTAL  
SECTIONS OF THE MID-ATLANTIC AND NORTHEAST SEP 27. PLEASE CONSULT THE LATEST  
ADVISORIES FROM THE NATIONAL HURRICANE CENTER AT HTTP://WWW.NHC.NOAA.GOV/ FOR  
THE LATEST FORECASTS REGARDING THIS SYSTEM.  
 
SURFACE HIGH PRESSURE IS ANTICIPATED TO BUILD ACROSS THE GREAT BASIN AT THE  
BEGINNING OF THE PERIOD. THIS PATTERN MAY SUPPORT SEVERAL DAYS OF INCREASED  
PROBABILITY FOR WINDY CONDITIONS. HIGH TEMPERATURES, LOW RELATIVE HUMIDITY, AND  
DRY FUELS MAY LEAD TO INCREASED CHANCES FOR WILDFIRE RISK. HOWEVER, DUE TO  
FORECAST SURFACE WIND SPEEDS NOT REACHING CRITICAL CRITERIA, A SPECIFIC AREA IS  
NOT HIGHLIGHTED AT THIS TIME.  
 
RIVER FLOODING IS FORECAST TO CONTINUE FOR PARTS OF FLORIDA DUE TO ANTECEDENT  
RAINFALL FROM HURRICANE IRMA.  
 
A SURFACE LOW PRESSURE SYSTEM IS PREDICTED TO DEVELOP OVER THE GULF OF ALASKA  
EARLY IN THE PERIOD. HEAVY RAIN (AMOUNTS IN EXCESS OF 2 INCHES IN 24 HOURS) IS  
ANTICIPATED ACROSS PORTIONS OF THE ALASKA PANHANDLE SEP 26 TO 27.  
 
FOR SATURDAY SEPTEMBER 30 - FRIDAY OCTOBER 06: THE 6Z DETERMINISTIC GFS  
INDICATES THE POTENTIAL FOR A SURFACE LOW TO DEVELOP OFF THE COAST OF THE  
CAROLINAS BY OCT 1. THIS MODEL SOLUTION THEN INDICATES THE LOW WOULD INTENSIFY  
AND TRACK ALONG THE COAST OF THE MID-ATLANTIC, BRINGING HEAVY RAIN TO COASTAL  
AREAS. HOWEVER, THE 6Z GEFS AND 0Z DETERMINISTIC AND ENSEMBLE ECMWF DOES NOT  
SHOW DEVELOPMENT OF THIS STORM, PRECLUDING ANY RELATED HAZARDS FROM BEING  
DETERMINED AT THIS TIME.  
 
SOME MODEL SOLUTIONS INDICATE THE POSSIBILITY OF TROPICAL ACTIVITY OVER PARTS  
OF THE CARIBBEAN LATE IN THE WEEK-2 PERIOD SO THIS REGION WILL NEED TO BE  
MONITORED.  
 
THE U.S. DROUGHT MONITOR, VALID ON SEP 19, INDICATES THAT SEVERE TO EXCEPTIONAL  
(D2-D4) DROUGHT COVERS 5.60 PERCENT OF THE CONTINENTAL U.S.  
 
FORECASTER: MELISSA OU  
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page