Prognostic Meteorological Discussion
Issued by NWS

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FXUS21 KWNC 301943
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT JULY 30 2014

SYNOPSIS: A STATIONARY FRONT IS FORECAST TO SLOWLY DISSIPATE ALONG THE EAST
COAST BY EARLY NEXT WEEK, WHILE A COLD FRONT PROGRESSES FROM THE MIDWEST TO THE
NORTHEAST ON MONDAY AND TUESDAY. AN AREA OF UPPER-LEVEL HIGH PRESSURE IS
EXPECTED TO REMAIN CENTERED OVER THE NORTHWESTERN U.S. DURING THE NEXT WEEK BUT
A WEAK LOW PRESSURE SYSTEM IS FORECAST TO LIFT NORTH FROM THE DESERT SOUTHWEST.
A LARGE AREA OF UPPER-LEVEL LOW PRESSURE IS EXPECTED TO PERSIST ACROSS THE GULF
OF ALASKA.

HAZARDS

MUCH ABOVE-NORMAL TEMPERATURES FOR PARTS OF THE PACIFIC NORTHWEST AND NORTHERN
INTERMOUNTAIN WEST, SAT-TUE, AUG 2-5.

HEAVY RAIN FOR THE COASTAL AREAS OF THE SOUTHERN MID-ATLANTIC AND SOUTHEAST,
SAT-SUN, AUG 2-3.

THE POSSIBILITY OF FLASH FLOODING SHIFTING NORTH FROM THE DESERT SOUTHWEST TO
COLORADO AND UTAH, SAT-TUE, AUG 2-5.

SEVERE DROUGHT FOR PARTS OF THE GREAT PLAINS, SOUTHWEST, PACIFIC NORTHWEST,
GREAT BASIN, AND CALIFORNIA.

DETAILED SUMMARY

FOR SATURDAY AUGUST 02 - WEDNESDAY AUGUST 06: SCATTERED TO NUMEROUS
THUNDERSHOWERS WITH LOCALLY HEAVY RAINFALL ARE EXPECTED ACROSS THE SOUTHWEST
THIS WEEKEND AS MONSOON MOISTURE BECOMES ENHANCED. FLASH FLOODING IS LIKELY TO
REMAIN THE MAJOR HAZARD ACROSS THIS REGION UNTIL THE FLOW BECOMES MORE
WESTERLY. THE 6Z GFS MODEL INDICATES THAT PRECIPITABLE WATER VALUES INCREASE TO
MORE THAN 1 INCH ACROSS THE DESERT SOUTHWEST ON SATURDAY. IN ADDITION TO THE
FLASH FLOODING HAZARD, OUTFLOW FROM THUNDERSTORMS IS CAPABLE OF CAUSING BLOWING
DUST ACROSS SOUTHERN ARIZONA. EARLY NEXT WEEK, THE GFS AND ECMWF MODELS
INDICATE THAT A MID-LEVEL DISTURBANCE AND ENHANCED MOISTURE LIFT NORTH TO THE
CENTRAL ROCKIES WHICH WOULD LIKELY INCREASE THE RISK OF HEAVY RAIN AND FLASH
FLOODING ACROSS COLORADO AND UTAH. THEREFORE, A BROAD AREA OF POSSIBLE FLASH
FLOODING IS POSTED.



ENHANCED LOW-LEVEL CONVERGENCE ALONG A STATIONARY FRONT COUPLED WITH INCREASING
MOISTURE IS EXPECTED TO RESULT IN HEAVY RAINFALL ACROSS COASTAL AREAS OF THE
SOUTHERN MID-ATLANTIC AND SOUTHEAST ON SATURDAY AND SUNDAY.



AN AMPLIFIED RIDGE OVER THE NORTHWESTERN U.S. IS LIKELY TO MAINTAIN MUCH
ABOVE-NORMAL TEMPERATURES THROUGH AT LEAST TUESDAY ACROSS THE INTERIOR PACIFIC
NORTHWEST AND NORTHERN INTERMOUNTAIN WEST. NUMEROUS WILDFIRES CONTINUE TO BURN
ACROSS THESE AREAS ALONG WITH CALIFORNIA, NEVADA, AND UTAH. CURRENTLY, THE
LARGEST WILDFIRE WITH NEARLY 400,000 ACRES BURNED IS LOCATED IN SOUTHEAST
OREGON. A FEW DRY THUNDERSTORMS COULD IGNITE ADDITIONAL WILDFIRES ACROSS THE
NORTHERN GREAT BASIN AND PACIFIC NORTHWEST.



THE COVERAGE OF SHOWERS IS EXPECTED TO INCREASE ACROSS SOUTHERN ALASKA BY EARLY
NEXT WEEK, BUT PRECIPITATION AMOUNTS ARE LIKELY TO REMAIN BELOW HAZARDS
CRITERIA.

FOR THURSDAY AUGUST 07 - WEDNESDAY AUGUST 13: SPREAD AMONGST THE 0Z/6Z GFS
ENSEMBLE MEMBERS BECOMES LARGE ACROSS THE NORTHWESTERN CONUS DURING WEEK-2. A
SLIGHT RISK OF ABOVE-NORMAL TEMPERATURES FOR PARTS OF THE PACIFIC NORTHWEST ON
AUGUST 7 AND 8 ARE POSTED ON THE PROBABILISTIC WEEK-2 HAZARDS OUTLOOK SINCE A
MINORITY OF 0Z/6Z GFS ENSEMBLE MEMBERS MAINTAIN A STRONG UPPER-LEVEL RIDGE
ACROSS THIS REGION.



THE DETERMINISTIC GFS AND ECMWF MODELS FAVOR AN INTENSIFYING AREA OF LOW
PRESSURE ACROSS THE WESTERN BERING SEA EARLY DURING WEEK-2. THIS LOW PRESSURE
DEVELOPMENT SHOULD BE MONITORED FOR POTENTIAL WIND/PRECIPITATION HAZARDS ACROSS
THE ALEUTIANS. MEANWHILE, THE GFS MODEL REMAINS CONSISTENT WITH A TROPICAL
SYSTEM APPROACHING HAWAII BY AUGUST 7.



AS OF 2PM EDT ON WEDNESDAY, AN AREA OF LOW PRESSURE IS LOCATED NEAR 10N/45W.
CONVECTION HAS DECREASED DURING THE PAST 24 HOURS AND THE NATIONAL HURRICANE
CENTER STATES THAT THERE IS A MEDIUM CHANCE FOR TROPICAL FORMATION DURING THE
NEXT 48 HOURS.



BASED ON THE LATEST DROUGHT MONITOR VALID ON JULY 22, SEVERE TO EXCEPTIONAL
DROUGHT CONTINUED TO DECREASE AND NOW COVERS 23.9 PERCENT OF THE CONTINENTAL
U.S.

FORECASTER: BRAD PUGH

$$



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