Prognostic Meteorological Discussion
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FXUS21 KWNC 291916
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT JULY 29 2015

SYNOPSIS: A STATIONARY FRONT IS FORECAST NEAR THE GULF COAST THIS WEEKEND, WITH
THE POTENTIAL FOR SURFACE LOW DEVELOPMENT ACROSS THE NORTHEAST GULF OF MEXICO.
AN AREA OF UPPER-LEVEL LOW PRESSURE NORTH OF THE GREAT LAKES IS EXPECTED TO
RESULT IN A COLD FRONT PROGRESSING SOUTHEAST FROM THE UPPER MISSISSIPPI VALLEY
TO THE NORTHEAST NEXT WEEK. UPPER-LEVEL HIGH PRESSURE IS FORECAST TO WEAKEN
ACROSS THE PACIFIC NORTHWEST FOLLOWING THE WEEKEND. UPPER-LEVEL HIGH PRESSURE
IS EXPECTED TO RETURN TO MAINLAND ALASKA BY EARLY NEXT WEEK.

HAZARDS

HEAVY RAIN ACROSS PARTS OF THE SOUTHEAST, SAT-SUN, AUG 1-2.

MUCH ABOVE-NORMAL TEMPERATURES FOR PARTS OF THE PACIFIC NORTHWEST AND NORTHERN
CALIFORNIA, SAT, AUG 1.

A SLIGHT RISK OF MUCH ABOVE-NORMAL TEMPERATURES FOR PARTS OF THE LOWER
MISSISSIPPI VALLEY AND SOUTHEAST, THU-SUN, AUG 6-9.

ONGOING FLOODING ACROSS PARTS OF THE MIDDLE AND LOWER MISSISSIPPI VALLEY.

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

DETAILED SUMMARY

FOR SATURDAY AUGUST 01 - WEDNESDAY AUGUST 05: A STATIONARY FRONT IS EXPECTED TO
BE THE FOCUS FOR HEAVY RAINFALL (LOCALLY MORE THAN 2 INCHES ON SATURDAY AND
SUNDAY) FROM THE FLORIDA PANHANDLE NORTHEAST TO THE EASTERN CAROLINAS. ALONG
THIS FRONT, MODEL GUIDANCE INDICATES THE POTENTIAL FOR A SURFACE LOW TO DEVELOP
ACROSS THE NORTHEAST GULF OF MEXICO WHICH WOULD ENHANCE RAINFALL AMOUNTS ACROSS
NORTHERN FLORIDA. THE 0Z CANADIAN MODEL ON JULY 29 IS THE MOST AGGRESSIVE WITH
SURFACE LOW DEVELOPMENT BUT IS CURRENTLY AN OUTLIER SOLUTION.



NORTHWEST FLOW ALOFT IS EXPECTED TO PROMOTE A COLD FRONT ENTERING THE UPPER
MISSISSIPPI VALLEY THIS WEEKEND, INCREASING THE POTENTIAL FOR SEVERE
THUNDERSTORMS ACROSS THIS REGION. A SEVERE WEATHER HAZARD IS NOT DEPICTED ON
THE MAP DUE TO LOW CONFIDENCE ON THE EXACT LOCATION AND TIMING OF ORGANIZED
SEVERE WEATHER.



THE POSITION OF THE UPPER-LEVEL RIDGE FAVORS A MODERATE MONSOON FLOW ACROSS THE
SOUTHWEST. THE HEAVIEST RAINFALL (LOCALLY MORE THAN 0.5 INCH WITH INDIVIDUAL
THUNDERSTORMS) IS EXPECTED ACROSS THE HIGHER TERRAIN OF SOUTHERN COLORADO AND
NORTHERN NEW MEXICO. THE HIGHEST RISK OF FLASH FLOODING ACROSS THESE AREAS IS
EXPECTED PRIOR TO THE OUTLOOK PERIOD WHEN RAINFALL AMOUNTS ARE ENHANCED DUE TO
UPSLOPE FLOW.



AN AMPLIFIED UPPER-LEVEL RIDGE IS EXPECTED TO MAINTAIN UNSEASONABLY HOT
TEMPERATURES ACROSS PARTS OF THE PACIFIC NORTHWEST AND NORTHERN CALIFORNIA
THROUGH SATURDAY. MUCH ABOVE-NORMAL TEMPERATURES ARE POSTED FOR AREAS WHERE
MAXIMUM TEMPERATURES ARE FORECAST TO AVERAGE 12 DEGREES F OR MORE ABOVE-NORMAL.
MAXIMUM TEMPERATURES ARE FORECAST TO MODERATE EARLY NEXT WEEK AS 500-HPA
HEIGHTS DECREASE. AN EXPANSION OF THE SUBTROPICAL RIDGE EARLY NEXT WEEK MAY
RESULT IN A RETURN OF EXCESSIVE HEAT TO THE LOWER MISSISSIPPI VALLEY AND
SOUTHEAST. RECENT MODEL SOLUTIONS HAVE TRENDED TOWARDS HOTTER TEMPERATURES
ACROSS THESE AREAS FOR AUGUST 3-5.



FLOODING ALONG THE ILLINOIS RIVER IS FORECAST TO RECEDE, WHILE MODERATE
FLOODING PERSISTS THROUGH THE WEEKEND ALONG PARTS OF THE LOWER MISSISSIPPI
RIVER. FOR THE VERY LATEST STREAM AND RIVER FLOODING INFORMATION, PLEASE
CONSULT THE RIVER FORECAST CENTER HOMEPAGE AT:
HTTP://WATER.WEATHER.GOV/AHPS/RFC/RFC.PHP



FOLLOWING A RECENT WET PERIOD, AN INCREASE IN 500-HPA HEIGHTS DURING THE
WEEKEND IS EXPECTED TO RESULT IN A DRYING TREND AND WARMER TEMPERATURES ACROSS
INTERIOR ALASKA. ACCORDING TO THE ALASKA INTERAGENCY COORDINATION CENTER ON
JULY 28, NEARLY 5 MILLION ACRES HAVE BEEN CONSUMED BY WILDFIRES THIS SEASON.
THIS IS IN COMPARISON TO THE YEAR 2004, THE MOST ACTIVE ALASKA WILDFIRE SEASON
ON RECORD (DATING BACK TO 1950), WHEN 6.5 MILLION ACRES BURNED.



TROPICAL DEPRESSION 8-E ACROSS THE EAST PACIFIC IS FORECAST TO DISSIPATE IN 48
HOURS AS IT MOVES INTO MORE STABLE AIR AND COOLER WATERS. MEANWHILE, A LOW
PRESSURE AREA MORE THAN 1,000 MILES SOUTHWEST OF THE BAJA CALIFORNIA PENINSULA
IS MORE ORGANIZED TODAY AND WILL LIKELY BECOME A TROPICAL CYCLONE. THIS SYSTEM
SHOULD BE MONITORED AS IT COULD APPROACH HAWAII NEXT WEEK.

FOR THURSDAY AUGUST 06 - WEDNESDAY AUGUST 12: DURING WEEK-2, THE GFS AND ECMWF
ENSEMBLE MEANS INDICATE A RIDGE CENTERED OVER THE ROCKIES WITH A DOWNSTREAM
TROUGH ACROSS THE NORTHEAST. A SLIGHT PROGRESSION OF THE RIDGE/TROUGH PATTERN
IS APPARENT AMONG TODAY`S ENSEMBLE MEANS. THE SLIGHT RISK OF MUCH ABOVE NORMAL
TEMPERATURES POSTED FOR PARTS OF THE LOWER MISSISSIPPI VALLEY AND SOUTHEAST IS
CONSISTENT WITH THE PREDICTED LONGWAVE PATTERN ALONG WITH GUIDANCE FROM THE
GEFS REFORECAST TOOL. THE MONSOON IS EXPECTED TO REMAIN AT MODERATE STRENGTH
WITH DAILY CONVECTION ACROSS THE FOUR CORNERS REGION. A RELATIVELY DRY, WARM
PATTERN IS EXPECTED TO PERSIST ACROSS MUCH OF ALASKA.



THE MOST RECENT U.S. WEEKLY DROUGHT MONITOR, RELEASED JULY 23, INDICATES A
SLIGHT DECREASE (FROM 17.49 TO 16.74) IN THE PERCENTAGE OF THE CONUS IN SEVERE
TO EXCEPTIONAL DROUGHT (D2-D4) FROM THE PREVIOUS WEEK.

FORECASTER: BRAD PUGH

$$




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