Prognostic Meteorological Discussion
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FXUS21 KWNC 281911
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT JULY 28 2015

SYNOPSIS: UPPER-LEVEL HIGH PRESSURE IS FORECAST TO BUILD ACROSS THE WESTERN
U.S. THIS WEEK, WHILE A STRENGTHENING AREA OF UPPER-LEVEL LOW PRESSURE BECOMES
CENTERED NORTH OF THE GREAT LAKES. A COLD FRONT IS EXPECTED TO BECOME
STATIONARY NEAR THE GULF COAST AND DISSIPATE THIS WEEKEND. ANOTHER COLD FRONT
IS FORECAST TO PROGRESS ACROSS THE GREAT LAKES AND MIDWEST ON SUNDAY AND
MONDAY. UPPER-LEVEL HIGH PRESSURE IS EXPECTED TO RETURN TO MAINLAND ALASKA BY
EARLY NEXT WEEK.

HAZARDS

PERIODS OF HEAVY RAINFALL ACROSS PARTS OF THE SOUTHEAST, FRI-MON, JUL 31-AUG 3.

MUCH ABOVE-NORMAL TEMPERATURES FOR PARTS OF THE PACIFIC NORTHWEST AND NORTHERN
CALIFORNIA, FRI-SAT, JUL 31-AUG 1.

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 FRIDAY JULY 31 - TUESDAY AUGUST 04: MODEL GUIDANCE REMAINS CONSISTENT,
FEATURING AN AMPLIFYING FLOW PATTERN AS 500-HPA HEIGHTS INCREASE (DECREASE)
ACROSS THE WESTERN (EASTERN) U.S. THE FOCUS FOR THE HEAVIEST RAINFALL IS
EXPECTED ALONG A DECAYING FRONT FROM THE FLORIDA PANHANDLE NORTHEAST TO THE
EASTERN CAROLINAS. TOTAL RAINFALL AMOUNTS FROM FRIDAY THROUGH MONDAY COULD
EXCEED 5 INCHES ACROSS THE FLORIDA PANHANDLE. A FEW 0Z GFS ENSEMBLE MEMBERS,
ALONG WITH THE 0Z CANADIAN MODEL, INDICATE SURFACE LOW DEVELOPMENT NEAR THE
GULF COAST. THIS COULD ENHANCE RAINFALL AMOUNTS OVER THE FLORIDA PANHANDLE AND
NORTHEAST FLORIDA. NORTHWEST FLOW ALOFT IS EXPECTED TO PROMOTE ANOTHER COLD
FRONT ENTERING THE UPPER MISSISSIPPI VALLEY THIS WEEKEND WHICH WOULD INCREASE
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.



THE POSITION OF THE UPPER-LEVEL RIDGE AND AVAILABLE MOISTURE FAVOR A LOW TO
MODERATE GRADE MONSOON 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. ALTHOUGH LOCALLY HEAVY
RAIN CAN TRIGGER FLASH FLOODING, THE LACK OF A STRONG MONSOON SIGNAL PRECLUDES
A HEAVY RAIN HAZARD ON THE MAP.



AN AMPLIFIED UPPER-LEVEL RIDGE IS EXPECTED TO MAINTAIN UNSEASONABLY HOT
TEMPERATURES ACROSS PARTS OF THE PACIFIC NORTHWEST AND NORTHERN CALIFORNIA
THROUGH AT LEAST SATURDAY. MUCH ABOVE-NORMAL TEMPERATURES ARE POSTED FOR AREAS
WHERE MAXIMUM TEMPERATURES ARE FORECAST TO AVERAGE 12 DEGREES F OR MORE
ABOVE-NORMAL ON FRIDAY AND SATURDAY. THE HEAT WAVE IS EXPECTED TO PEAK ON
THURSDAY OR FRIDAY WHEN SOME LOCATIONS ACROSS THE PACIFIC NORTHWEST MAY
EXPERIENCE THEIR HOTTEST TEMPERATURE OF THE YEAR SO FAR. MAXIMUM TEMPERATURES
ARE FORECAST TO MODERATE EARLY NEXT WEEK BUT LIKELY REMAIN ABOVE-NORMAL.



FLOODING ALONG THE ILLINOIS RIVER IS FORECAST TO RECEDE THIS WEEK, WHILE
MODERATE FLOODING PERSISTS 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 DEVELOPED DURING THE PAST 24 HOURS ACROSS THE EAST
PACIFIC (16N-128W). THE DEPRESSION IS CURRENTLY EXPECTED TO REMAIN WEAK DUE TO
SHEAR AND DISSIPATE IN 96 HOURS AS IT MOVES INTO MORE STABLE AIR AND COOLER
WATERS. MEANWHILE, A BROAD AREA OF LOW PRESSURE MORE THAN 1,000 MILES SOUTHWEST
OF THE BAJA CALIFORNIA PENINSULA IS LIKELY TO BECOME A TROPICAL CYCLONE BY THE
WEEKEND. THIS SYSTEM SHOULD BE MONITORED AS IT COULD APPROACH HAWAII EARLY NEXT
WEEK.

FOR WEDNESDAY AUGUST 05 - TUESDAY AUGUST 11: DURING WEEK-2, THE GFS AND ECMWF
ENSEMBLE MEANS INDICATE A PERSISTENT UPPER-LEVEL PATTERN FEATURING A RIDGE
(TROUGH) OVER WESTERN (EASTERN) NORTH AMERICA WHICH IS TYPICAL FOR EARLY
AUGUST. THE SLIGHT RISK OF MUCH-ABOVE NORMAL TEMPERATURES ACROSS THE PACIFIC
NORTHWEST IS REMOVED FROM TODAY`S HAZARDS MAP DUE TO TIMING AND SLIGHTLY LOWER
500-HPA HEIGHTS AMONG THE LATEST MODEL SOLUTIONS. THE MOST ANOMALOUS
TEMPERATURES MAY BE OVER THE GREAT LAKES AND EASTERN CORN BELT WHERE AN
UNSEASONABLY STRONG TROUGH IS FORECAST TO RESULT IN BELOW-NORMAL TEMPERATURES
ACROSS THESE AREAS. THE MONSOON IS EXPECTED TO REMAIN AT MODERATE STRENGTH WITH
DAILY CONVECTION ACROSS THE FOUR CORNERS REGION.



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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