Prognostic Meteorological Discussion
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2
000
FXUS21 KWNC 041856
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT SEPTEMBER 04 2015

SYNOPSIS: A COLD FRONT IS EXPECTED TO BECOME STATIONARY BY MID-WEEK ACROSS THE
MIDWEST, MIDDLE MISSISSIPPI VALLEY, AND SOUTHERN GREAT PLAINS. A BROAD AREA OF
UPPER-LEVEL LOW PRESSURE IS EXPECTED TO PERSIST THROUGH TUESDAY ACROSS THE
SOUTHEAST. THE REMNANT LOW OF HURRICANE IGNACIO IS FORECAST TO RECURVE
NORTHEAST AND AFFECT THE SOUTHERN ALASKA PANHANDLE EARLY IN THE PERIOD. AN AREA
OF UPPER-LEVEL LOW PRESSURE IS EXPECTED TO GRADUALLY DEVELOP OVER THE
EAST-CENTRAL U.S. DURING THE NEXT WEEK.

HAZARDS

HEAVY RAIN SHIFTING SOUTHEAST ACROSS THE MIDWEST, MIDDLE MISSISSIPPI VALLEY,
AND CENTRAL/SOUTHERN GREAT PLAINS, MON-WED, SEP 7-9.

HEAVY RAIN FOR THE SOUTHERN ALASKA PANHANDLE, MON-TUE, SEP 7-8.

A SLIGHT RISK OF MUCH BELOW-NORMAL TEMPERATURES ACROSS PARTS OF INTERIOR
ALASKA, SAT-MON, SEP 12-14.

SIGNIFICANT RIVER FLOODING LIKELY ALONG THE IOWA RIVER IN EASTERN IOWA.

SIGNIFICANT RIVER FLOODING OCCURRING OR IS IMMINENT ACROSS PARTS OF
WEST-CENTRAL FLORIDA.

SEVERE DROUGHT FOR PARTS OF THE WESTERN THIRD OF THE CONUS, SOUTHEAST, LOWER
MISSISSIPPI VALLEY, OKLAHOMA, TEXAS, AND HAWAII.

DETAILED SUMMARY

FOR MONDAY SEPTEMBER 07 - FRIDAY SEPTEMBER 11: A COLD FRONT IS FORECAST TO
BECOME STATIONARY BY THE MIDDLE PART OF NEXT WEEK AND PROVIDE THE FOCUS FOR
HEAVY RAINFALL (1 TO 3 INCHES, LOCALLY MORE) FROM THE SOUTH-CENTRAL GREAT
PLAINS NORTHEAST TO THE MIDWEST ON MONDAY THROUGH WEDNESDAY. ABUNDANT GULF
MOISTURE, COUPLED WITH SUBTROPICAL MOISTURE FROM THE EAST PACIFIC, IS EXPECTED
TO ENHANCE RAINFALL AMOUNTS ACROSS THESE AREAS. WEAK FLOW ALOFT IS EXPECTED TO
LIMIT THE RISK OF WIDESPREAD SEVERE WEATHER ALONG THE FRONT DURING THIS PERIOD.



A BROAD AREA OF LOW PRESSURE IS LIKELY TO RESULT IN DIURNAL CONVECTION WITH
LOCALLY HEAVY RAIN ACROSS FLORIDA AND THE COASTAL SOUTHEAST THROUGH EARLY NEXT
WEEK. HOWEVER, UNCERTAINTY ON EXACT LOCATION PRECLUDES DESIGNATION OF A HEAVY
RAIN HAZARD.



AS OF 5AM HST ON FRIDAY, HURRICANE IGNACIO IS LOCATED NORTH OF THE HAWAIIAN
ISLANDS AND IS FORECAST TO ACCELERATE AND ENTER THE GULF OF ALASKA AS AN
EXTRATROPICAL CYCLONE. HEAVY RAIN, ASSOCIATED WITH THE REMNANT LOW PRESSURE
SYSTEM, REMAINS POSSIBLE ACROSS THE SOUTHERN ALASKA PANHANDLE ON MONDAY AND
TUESDAY. LATE IN THIS PERIOD, HEAVY RAIN COULD RETURN TO THE ALASKA PANHANDLE
BUT LARGE MODEL DIFFERENCES ON TIMING PRECLUDE DESIGNATION OF A HEAVY RAIN
HAZARD BEYOND SEPTEMBER 8.



TROPICAL STORM KEVIN IS EXPECTED TO DISSIPATE SOUTHWEST OF THE BAJA PENINSULA
THIS WEEKEND. MEANWHILE, DIMINISHING WIND SHEAR MAY ALLOW FOR SLOW DEVELOPMENT
OF A TROPICAL CYCLONE OVER THE EAST PACIFIC. THE MODEL CONSENSUS AT THIS TIME
FAVORS A TRACK OF THIS POTENTIAL TROPICAL CYCLONE AWAY FROM NORTH AMERICA.
HOWEVER, THE 0Z CANADIAN MODEL ON SEPTEMBER 4 REMAINS CONSISTENT FEATURING A
TRACK NORTH TOWARDS THE BAJA PENINSULA AT THE END OF THIS PERIOD.



SWELLS, ASSOCIATED WITH HURRICANE JIMENA, ARE FORECAST TO BUILD THIS WEEKEND
ACROSS THE HAWAIIAN ISLANDS. THEREFORE, HIGH SURF IS LIKELY TO AFFECT EAST
FACING SHORES OF KAUAI, OAHU, MOLOKAI, AND THE BIG ISLAND THROUGH EARLY NEXT
WEEK.

FOR SATURDAY SEPTEMBER 12 - FRIDAY SEPTEMBER 18: ALTHOUGH THE 0Z GFS AND 0Z
ECMWF ENSEMBLE MEANS ARE IN REASONABLY GOOD AGREEMENT DURING WEEK-2, SPREAD
AMONG THEIR INDIVIDUAL ENSEMBLE MEMBERS REMAINS LARGE WITH THE POSITION OF AN
UPPER-LEVEL RIDGE NEAR THE WEST COAST. THIS LARGE SPREAD IS LIKELY DUE IN PART
TO THE MULTIPLE TROPICAL CYCLONES ACROSS THE PACIFIC OCEAN. THE EAST PACIFIC IS
EXPECTED TO REMAIN ACTIVE WITH CONTINUED TROPICAL CYCLONE DEVELOPMENT DURING
MID-SEPTEMBER.



THE GFS MODEL CONTINUES TO INDICATE UNSEASONABLY COLD TEMPERATURES ACROSS
EASTERN ALASKA. A SLIGHT RISK OF MUCH-BELOW NORMAL TEMPERATURES IS POSTED FOR
THIS REGION EARLY IN WEEK-2, BUT THE LARGE ENSEMBLE SPREAD LIMITS FORECAST
CONFIDENCE. AN UPPER-LEVEL TROUGH FAVORS BELOW-NORMAL TEMPERATURES ACROSS THE
CENTRAL U.S., BUT MINIMUM TEMPERATURES ARE NOT EXPECTED TO REACH HAZARDOUS
CRITERIA AT THIS TIME.



ACCORDING TO THE U.S. DROUGHT MONITOR MAP, VALID ON SEPTEMBER 1, THE COVERAGE
OF SEVERE TO EXCEPTIONAL DROUGHT (D2 TO D4) INCREASED FROM 18.07 TO 18.72
PERCENT ACROSS THE CONTIGUOUS U.S. SINCE THE PREVIOUS WEEK. THIS INCREASE IS A
RESULT OF THE EXPANDING SHORT-TERM DROUGHT OF SEVERE (D2) INTENSITY ACROSS
PARTS OF EAST TEXAS AND THE LOWER MISSISSIPPI VALLEY.

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.