Prognostic Meteorological Discussion
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FXUS21 KWNC 311930
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT JULY 31 2015

SYNOPSIS: A COLD FRONT IS PREDICTED TO PROPAGATE SOUTHEASTWARD FROM THE
NORTHERN TIER OF THE LOWER 48 STATES AT THE BEGINNING OF THE PERIOD AND EVOLVE
INTO A STATIONARY FRONT, STRETCHING FROM THE CENTRAL PLAINS TO THE MID-ATLANTIC
BY THURSDAY. A SERIES OF COLD FRONTS ARE ANTICIPATED TO ENTER THE PACIFIC
NORTHWEST AND NORTHERN CALIFORNIA DURING THE 3-7 DAY PERIOD. MUCH OF ALASKA IS
EXPECTED TO HAVE A RELATIVELY MILD WEATHER PATTERN DURING DAYS 3 TO 7, WITH
POTENTIAL WARMING ACROSS THE SOUTHERN HALF OF ALASKA AND THE CENTRAL-SOUTHERN
PANHANDLE DURING WEEK-2.

HAZARDS

HEAVY RAIN FOR PARTS OF THE CENTRAL PLAINS, AND THE MIDDLE MISSISSIPPI AND OHIO
VALLEYS, WED, AUG 5.

EXCESSIVE HEAT FOR PARTS OF THE SOUTHEAST, TUE-FRI, AUG 4-7.

FLOODING IS ONGOING OR LIKELY FOR PARTS OF THE MIDDLE AND LOWER MISSISSIPPI
VALLEY.

SEVERE DROUGHT FOR PARTS OF THE WESTERN THIRD OF THE CONUS, SOUTHERN GEORGIA,
SOUTHERN FLORIDA, NORTH CAROLINA AND HAWAII.

SLIGHT CHANCE OF MUCH ABOVE NORMAL TEMPERATURES ACROSS PARTS OF THE CENTRAL AND
SOUTHERN PLAINS, LOWER MISSISSIPPI VALLEY, AND SOUTHEAST, SAT-FRI, AUG 8-14.

SLIGHT CHANCE OF MUCH ABOVE NORMAL TEMPERATURES ACROSS PARTS OF THE SOUTHERN
HALF OF MAINLAND ALASKA AND CENTRAL-SOUTHERN ALASKA PANHANDLE, SAT-FRI, AUG
8-14.

DETAILED SUMMARY

FOR MONDAY AUGUST 03 - FRIDAY AUGUST 07: A COLD FRONT IS EXPECTED TO SINK
SOUTHWARD FROM THE NORTHERN TIER AT THE BEGINNING OF THE PERIOD, DEVELOPING
INTO A STATIONARY FRONT STRETCHING FROM THE CENTRAL PLAINS TO MID-ATLANTIC BY
THURSDAY. THIS FRONT MAY BRING HEAVY RAIN TO PARTS OF THE CENTRAL PLAINS,
MIDDLE MISSISSIPPI, AND OHIO VALLEYS ON WEDNESDAY. THERE IS SIGNIFICANT
UNCERTAINTY REGARDING THE SPECIFIC LOCATIONS EXPECTED TO RECEIVE HEAVY RAIN AND
RAINFALL TOTALS. LOCALIZED AREAS MAY RECEIVE ANYWHERE FROM AN INCH TO THREE
INCHES OF RAINFALL IN A 24-HOUR PERIOD. ADDITIONALLY, ATMOSPHERIC CONDITIONS
MAY BE CONDUCIVE TO SEVERE WEATHER ASSOCIATED WITH THIS FRONT, INITIALLY FOR
PARTS OF THE NORTHEAST AND OHIO VALLEY ON MONDAY AND TUESDAY, FOLLOWED BY THE
CENTRAL AND NORTHERN PLAINS ON TUESDAY AND WEDNESDAY. AT THIS TIME, THE STORM
PREDICTION CENTER HAS NOT HIGHLIGHTED ANY AREAS OF RISK YET, BUT UPDATED
FORECASTS SHOULD BE MONITORED AT WWW.SPC.NOAA.GOV, AS WELL AS LOCAL FORECASTS
AT WWW.WEATHER.GOV.



THE SUBTROPICAL RIDGE IS ANTICIPATED TO EXTEND INTO THE SOUTHEASTERN CONUS,
PROMOTING STRONG, ONSHORE FLOW OFF THE GULF OF MEXICO. THIS PATTERN MAY LEAD TO
EXCESSIVE HEAT ACROSS PARTS OF THE SOUTHEAST TUESDAY TO FRIDAY, AND HEAVY
RAINFALL ACROSS CENTRAL AND EASTERN GULF COAST AREAS THURSDAY AND FRIDAY.
HOWEVER, AN ASSOCIATED HEAVY RAINFALL AREA IS NOT DESIGNATED AT THIS TIME DUE
TO SIGNIFICANT MODEL UNCERTAINTY. DAILY MAXIMUM HEAT INDEX VALUES MAY REACH
GREATER THAN 105 DEG F OVER THESE AREAS.



THERE IS A POTENTIAL FOR LOCALIZED HEAVY RAINFALL ACROSS PARTS OF THE FOUR
CORNERS REGION ON MONDAY, ASSOCIATED WITH THE SOUTHWEST MONSOON. WARM, MOIST
FLOW ASSOCIATED WITH A SURFACE LOW OVER THE SOUTHERN PLAINS, IN CONJUNCTION
WITH THE PERSISTENT LOW OVER BAJA CALIFORNIA, HAS THE POTENTIAL TO REINVIGORATE
CHANCES FOR HEAVY RAIN TO LOCALIZED AREAS OF THE FOUR CORNERS REGION, CENTRAL
PLAINS, AND MIDDLE MISSISSIPPI VALLEY BY LATE NEXT WEEK INTO NEXT WEEKEND.
SIGNIFICANT MODEL UNCERTAINTY PRECLUDES A SPECIFIC AREA FROM BEING HIGHLIGHTED
AT THIS TIME. INTERESTS IN THESE AREAS SHOULD TAKE CAUTION, SINCE HEAVY RAINS
MAY LEAD TO FLASH FLOODING AND DANGEROUS CONDITIONS, ESPECIALLY IN LOW-LAYING
AREAS BETWEEN CANYONS AND ARROYOS.



AS OF FRIDAY, JULY 31 2PM, HURRICANE GUILLERMO HAS THE POTENTIAL TO HAVE A
TRACK APPROACHING HAWAII, MOST LIKELY REACHING HAWAII AROUND WEDNESDAY. THIS
TROPICAL DISTURBANCE MAY BRING HEAVY RAIN, HIGH WINDS, AND SIGNIFICANT WAVE
HEIGHTS TO PARTS OF HAWAII ON WEDNESDAY AND THURSDAY. UPDATED INFORMATION
REGARDING THIS STORM SHOULD BE MONITORED USING THE NATIONAL HURRICANE CENTER
WEBSITE (HTTP://WWW.NHC.NOAA.GOV).

FOR SATURDAY AUGUST 08 - FRIDAY AUGUST 14: THERE IS RELATIVELY GOOD MODEL
AGREEMENT INDICATING THE BUILDING OF AN AMPLIFIED UPPER-LEVEL RIDGE ACROSS THE
SOUTHERN TIER AND SOUTH-CENTRAL CONUS DURING WEEK-2. THIS PATTERN IS EXPECTED
TO PERSIST FOR THE DURATION OF WEEK-2, FAVORING A SLIGHT RISK OF MUCH ABOVE
NORMAL TEMPERATURES ACROSS PARTS OF THE CENTRAL AND SOUTHERN PLAINS, LOWER
MISSISSIPPI VALLEY, AND SOUTHEAST. THE GEFS REFORECAST TOOL SHOWS THE
POSSIBILITY OF PARTS OF SOUTH-CENTRAL CONUS EXPERIENCING TEMPERATURES GREATER
THAN 100 DEG F.



THE MAJORITY OF MODELS INDICATE THE POSSIBLE DEVELOPMENT OF AN AMPLIFIED RIDGE
OVER PARTS OF MAINLAND ALASKA AND THE ALASKA PANHANDLE. THIS PATTERN SUPPORTS A
SLIGHT RISK OF MUCH ABOVE NORMAL TEMPERATURES FOR PARTS OF THE SOUTHERN HALF OF
MAINLAND ALASKA AND CENTRAL-SOUTHERN ALASKA PANHANDLE DURING THE WEEK-2 PERIOD.
SOME MODELS INDICATE THE POTENTIAL OF AN UPPER-LEVEL SHORTWAVE PROPAGATING
ACROSS SOUTHERN, MAINLAND ALASKA, WHICH WOULD DECREASE THE LIKELIHOOD FOR MUCH
ABOVE NORMAL TEMPERATURES AS WELL AS THE DURATION OF THE EVENT. THE GEFS
REFORECAST TOOL SHOWS A 20% CHANCE OF TEMPERATURES IN THESE HIGHLIGHTED AREAS
REACHING GREATER THAN THE 85TH PERCENTILE, COMPARED TO CLIMATOLOGY.

FORECASTER: MELISSA OU

$$



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