Prognostic Meteorological Discussion
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FXUS21 KWNC 031831
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT SEPTEMBER 03 2015

SYNOPSIS: A LOW PRESSURE SYSTEM IS EXPECTED TO EXIT THE NORTHERN GREAT PLAINS
ON SUNDAY, WHILE ITS COLD FRONT PUSHES SLOWLY SOUTHEAST ACROSS THE CENTRAL U.S.
EARLY NEXT WEEK. A BROAD AREA OF UPPER-LEVEL LOW PRESSURE IS EXPECTED TO
PERSIST THROUGH AT LEAST MONDAY ALONG THE SOUTHEAST COAST. THE REMNANT LOW OF
HURRICANE IGNACIO IS FORECAST TO TRACK NORTH AND LIKELY AFFECT THE ALASKA
PANHANDLE NEXT WEEK. AN AREA OF UPPER-LEVEL HIGH PRESSURE IS EXPECTED TO RETURN
NEAR THE WEST COAST DURING THE SECOND WEEK OF SEPTEMBER.

HAZARDS

HEAVY RAIN FOR THE SOUTH-CENTRAL GREAT PLAINS, MIDDLE MISSISSIPPI VALLEY, AND
MIDWEST, MON-WED, SEP 7-9.

MUCH BELOW-NORMAL TEMPERATURES FOR PARTS OF THE GREAT BASIN AND NORTHERN
ROCKIES, SUN, SEP 6.

HIGH WINDS FOR THE NORTHERN HIGH PLAINS, SUN, SEP 6.

HEAVY RAIN FOR THE ALASKA PANHANDLE, TUE, SEP 8.

A SLIGHT RISK OF MUCH BELOW-NORMAL TEMPERATURES ACROSS PARTS OF EASTERN ALASKA,
FRI-MON, SEP 11-14.

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 SUNDAY SEPTEMBER 06 - THURSDAY SEPTEMBER 10: A COLD FRONT IS FORECAST TO
BECOME NEARLY STATIONARY BY THE MIDDLE PART OF NEXT WEEK AND PROVIDE THE FOCUS
FOR HEAVY RAINFALL (1 TO 3 INCHES) FROM THE SOUTH-CENTRAL GREAT PLAINS
NORTHEAST TO THE MIDWEST ON MONDAY THROUGH WEDNESDAY. SUBTROPICAL MOISTURE FROM
THE EAST PACIFIC IS EXPECTED TO ENHANCED RAINFALL AMOUNTS ACROSS THESE AREAS.
SINCE THE FRONT IS LIKELY TO BE MORE PROGRESSIVE FARTHER TO THE NORTH, A HEAVY
RAIN HAZARD IS NOT POSTED FOR THE NORTHERN GREAT PLAINS. SEVERE WEATHER IS ALSO
POSSIBLE ALONG THE COLD FRONT, BUT A LACK OF SUFFICIENT WINDS ALOFT PRECLUDE
DESIGNATION OF A SEVERE WEATHER HAZARD AT THIS TIME.



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



AN ANOMALOUS UPPER-LEVEL TROUGH FOR EARLY SEPTEMBER IS FORECAST TO BRING A
BRIEF PERIOD OF MUCH BELOW-NORMAL TEMPERATURES TO THE INTERIOR WEST DURING THE
LABOR DAY WEEKEND. THE FIRST WIDESPREAD FREEZE IS EXPECTED ACROSS PARTS OF THE
GREAT BASIN AND NORTHERN ROCKIES ON SUNDAY MORNING. IN ADDITION, SNOW IS
POSSIBLE ACROSS ELEVATIONS ABOVE 7,000 FEET THIS WEEKEND ACROSS THE NORTHERN
ROCKIES BUT HAZARDOUS AMOUNTS ARE NOT FORECAST. HIGH WINDS (GUSTS ABOVE 40MPH)
ARE EXPECTED ACROSS THE NORTHERN HIGH PLAINS ON SUNDAY IN THE WAKE OF A STRONG
LOW PRESSURE SYSTEM TRACKING TOWARDS MANITOBA.



AS OF 5AM HST ON THURSDAY, 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 (1 TO 3 INCHES) IS EXPECTED WITH THE REMNANT
LOW PRESSURE SYSTEM WHEN IT REACHES THE ALASKA PANHANDLE ON SEPTEMBER 8.



TROPICAL STORM KEVIN IS EXPECTED TO DISSIPATE WELL 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 WEST TRACK OF THIS POTENTIAL TROPICAL CYCLONE AWAY FROM
NORTH AMERICA WITH THE 0Z/12Z CANADIAN MODEL AN OUTLIER SOLUTION.



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 FRIDAY SEPTEMBER 11 - THURSDAY SEPTEMBER 17: SPREAD AMONG THE 0Z GFS AND 0Z
ECMWF ENSEMBLE MEMBERS BECOMES LARGE ACROSS THE NORTH PACIFIC AND WESTERN NORTH
AMERICA BY WEEK-2, LIKELY DUE IN PART TO THE MULTIPLE TROPICAL CYCLONES ACROSS
THE PACIFIC OCEAN. HOWEVER, ENSEMBLE MEANS ARE IN GOOD AGREEMENT BUILDING A
RIDGE OFFSHORE OF THE WEST COAST DURING WEEK-2. THE EXPECTED LONGWAVE PATTERN
AMONG MODEL SOLUTIONS FAVORS A SLIGHT RISK OF MUCH BELOW-NORMAL TEMPERATURES
ACROSS INTERIOR EASTERN ALASKA. THE EAST PACIFIC IS EXPECTED TO REMAIN ACTIVE
WITH CONTINUED TROPICAL CYCLONE DEVELOPMENT DURING MID-SEPTEMBER.



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

$$




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