Prognostic Meteorological Discussion
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FXUS21 KWNC 261934
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT AUGUST 26 2014

SYNOPSIS: A SURFACE LOW PRESSURE SYSTEM IS FORECAST TO CROSS THE GREAT LAKES ON
FRIDAY AND SATURDAY, WHILE A TRAILING FRONT PUSHES EAST FROM THE GREAT PLAINS
TO THE MISSISSIPPI VALLEY. DURING THE LABOR DAY WEEKEND, A STRONGER COLD FRONT
IS EXPECTED TO ADVANCE ACROSS THE NORTH-CENTRAL ROCKIES. HURRICANE CRISTOBAL IS
FORECAST TO REMAIN OFFSHORE OF THE EAST COAST, WHILE HURRICANE MARIE WEAKENS
ACROSS THE EAST PACIFIC. A PAIR OF WEAK LOW PRESSURE SYSTEMS ARE EXPECTED TO
AFFECT SOUTHERN ALASKA AND THE ALASKAN PANHANDLE DURING THE NEXT WEEK.

HAZARDS

SIGNIFICANT WAVES FOR THE SOUTHERN CALIFORNIA BEACHES, FRI, AUG 29.

HEAVY RAIN FOR PARTS OF THE GREAT LAKES, FRI-SAT, AUG 29-30.

HEAVY RAIN FOR PARTS OF THE GULF COAST, FRI-SAT, AUG 29-30.

RIVER FLOODING POSSIBLE ACROSS PARTS OF THE MIDWEST.

RIVER FLOODING OCCURRING OR IS IMMINENT ACROSS THE UPPER MISSOURI RIVER VALLEY.

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

DETAILED SUMMARY

FOR FRIDAY AUGUST 29 - TUESDAY SEPTEMBER 02: SIGNIFICANT WAVES ASSOCIATED WITH
HURRICANE MARIE ARE LIKELY ALONG SOUTHERN CALIFORNIA BEACHES THROUGH FRIDAY.
WAVE HEIGHTS ARE EXPECTED TO PEAK ON WEDNESDAY BUT REMAIN HIGH ENOUGH TO
JUSTIFY A SIGNIFICANT WAVE HAZARD ON AUGUST 29. WAVES THIS WEEK ARE EXPECTED TO
BE LARGE ENOUGH TO POTENTIALLY CAUSE STRUCTURAL DAMAGE AND BEACH EROSION. IN
ADDITION, DANGEROUS RIP CURRENTS ARE ANTICIPATED. MINOR COASTAL FLOODING IS
ALSO POSSIBLE FOR LOW LYING AREAS.



A SHORTWAVE TROUGH, ORIGINATING FROM THE WESTERN U.S., IS EXPECTED TO ADVANCE
EAST ACROSS THE GREAT LAKES LATER THIS WEEK. THIS SHORTWAVE TROUGH INTERACTING
WITH ABUNDANT LOW-LEVEL MOISTURE IS FORECAST TO RESULT IN HEAVY RAINFALL (1-3
INCHES, OR MORE) FROM IOWA NORTHEAST TO THE GREAT LAKES ON FRIDAY. DUE TO
RECENT HEAVY RAINFALL, THIS REGION IS VULNERABLE TO FLASH FLOODING AND RIVER
FLOODING. MODEL SOLUTIONS DIFFER ON HOW FAST THE SHORTWAVE TROUGH EXITS THE
GREAT LAKES. ALTHOUGH THUNDERSTORMS ARE FORECAST TO ACCOMPANY THE SHORTWAVE
TROUGH, WEAK FLOW ALOFT IS EXPECTED TO INHIBIT THE RISK OF SEVERE WEATHER.
HEAVY RAIN IS ALSO EXPECTED ACROSS THE CENTRAL/SOUTHERN GREAT PLAINS ON FRIDAY,
BUT A HEAVY RAIN HAZARD IS NOT POSTED SINCE THE HEAVY RAIN WILL LIKELY BE
LOCALIZED.



TROPICAL MOISTURE IS FORECAST TO SPREAD NORTH FROM THE GULF OF MEXICO AND BRING
HEAVY RAIN TO PARTS OF THE GULF COAST ON FRIDAY AND SATURDAY. THE SLOW MOVEMENT
OF THUNDERSTORMS WITH HIGH RAINFALL RATES INCREASES THE POTENTIAL FOR FLASH
FLOODING. THE 0Z GFS MODEL INDICATES THAT PRECIPITABLE WATER VALUES INCREASE TO
NEAR 2.25 INCHES BY FRIDAY ACROSS SOUTHERN LOUISIANA.



AN AMPLIFIED TROUGH IS FORECAST TO ENTER THE PACIFIC NORTHWEST AND MOVE EAST
ACROSS THE NORTHERN ROCKIES DURING THE LABOR DAY WEEKEND. THIS TROUGH IS
EXPECTED TO BRING RELATIVELY COOL TEMPERATURES AND MOSTLY LIGHT PRECIPITATION
TO THE NORTHERN ROCKIES. MAXIMUM TEMPERATURES ARE FORECAST TO AVERAGE AROUND 10
DEGREES F BELOW-NORMAL FROM SUNDAY THROUGH NEXT TUESDAY ACROSS THE NORTHERN
ROCKIES.



HURRICANE CRISTOBAL IS FORECAST TO ACCELERATE NORTHEAST AWAY FROM THE EAST
COAST LATER THIS WEEK. WAVE HEIGHTS ARE EXPECTED TO DECREASE ON FRIDAY ALONG
THE EAST COAST BEACHES. PLEASE REFER TO THE NATIONAL HURRICANE CENTER AT
WWW.NHC.NOAA.GOV FOR THE LATEST STATEMENTS ON CRISTOBAL.



OCCASIONAL RAIN AND GUSTY WINDS ARE EXPECTED TO AFFECT THE ALEUTIANS, SOUTHERN
ALASKA, AND THE ALASKAN PANHANDLE THROUGHOUT THIS PERIOD. HOWEVER, RAINFALL
AMOUNTS AND WIND SPEEDS ARE FORECAST TO REMAIN BELOW HAZARDS CRITERIA.

FOR WEDNESDAY SEPTEMBER 03 - TUESDAY SEPTEMBER 09: THE 0Z GFS AND 0Z ECMWF
ENSEMBLE MEANS INDICATE BELOW (ABOVE)-NORMAL HEIGHTS ACROSS THE WESTERN
(EASTERN) CONUS DURING WEEK-2. THIS LONGWAVE PATTERN IS EXPECTED TO RESULT IN
RELATIVELY COOL TEMPERATURES ACROSS THE NORTHERN ROCKIES AND A CONTINUATION OF
SUMMER WARMTH ACROSS THE EASTERN HALF OF THE U.S.



AS OF 2PM EDT ON TUESDAY, A TROPICAL WAVE IS LOCATED 850 MILES EAST OF THE
LESSER ANTILLES. ENVIRONMENTAL CONDITIONS ARE EXPECTED TO BECOME SLIGHTLY MORE
FAVORABLE FOR TROPICAL CYCLONE DEVELOPMENT LATER IN THE WEEK.



THE MOST RECENT U.S. DROUGHT MONITOR, RELEASED ON AUGUST 21, SHOWS THE
PERCENTAGE OF CONUS IN SEVERE DROUGHT DECREASING VERY SLIGHTLY FROM 22.03% TO
21.62%.

FORECASTER: BRAD PUGH

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