Prognostic Meteorological Discussion
Issued by NWS

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FXUS21 KWNC 281829
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT JULY 28 2014

SYNOPSIS: A STRONG AREA OF UPPER-LEVEL LOW PRESSURE IS FORECAST TO PERSIST
ACROSS THE EASTERN U.S. INTO THE BEGINNING OF AUGUST, WHILE AN AREA OF
UPPER-LEVEL HIGH PRESSURE REMAINS CENTERED OVER THE WESTERN U.S. A SURFACE LOW
IS EXPECTED TO CROSS MAINLAND ALASKA THIS WEEKEND.

HAZARDS

MUCH ABOVE-NORMAL TEMPERATURES FOR PARTS OF THE PACIFIC NORTHWEST AND NORTHERN
INTERMOUNTAIN WEST, THU-MON, JUL 31-AUG 4.

HEAVY RAIN FOR PARTS OF COLORADO AND NEW MEXICO, THU-FRI, JUL 31-AUG 1.

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

DETAILED SUMMARY

FOR THURSDAY JULY 31 - MONDAY AUGUST 04: AN AMPLIFIED UPPER-LEVEL TROUGH IS
EXPECTED TO RESULT IN A COLD FRONT PROGRESSING UNUSUALLY FAR TO THE SOUTH FOR
THE END OF JULY. BY THURSDAY, A COLD FRONT IS FORECAST TO BECOME STATIONARY
ACROSS NORTH TEXAS AND THE NORTHERN GULF OF MEXICO. UPSLOPE FLOW BEHIND THE
FRONT COUPLED WITH MONSOONAL MOISTURE IS LIKELY TO RESULT IN LOCALLY HEAVY
RAINFALL ACROSS SOUTHEAST COLORADO AND NORTHEAST NEW MEXICO ON THURSDAY AND
FRIDAY. THE MOST LIKELY AREAS FOR FLASH FLOODING WILL BE LOCATIONS THAT RECEIVE
HEAVY RAINFALL PRECEDING THIS PERIOD. MONSOON MOISTURE IS EXPECTED TO MAINTAIN
THE POTENTIAL FOR LOCALLY HEAVY RAIN AND ASSOCIATED FLASH FLOODING ACROSS THE
SOUTHWEST, BUT A HAZARD AREA IS NOT DEFINED AT THIS TIME RANGE.



MAXIMUM TEMPERATURES ARE FORECAST TO AVERAGE 10 TO 15, OR MORE, DEGREES F
BELOW-NORMAL ACROSS THE SOUTHERN GREAT PLAINS THROUGHOUT THIS PERIOD.
MEANWHILE, THE AMPLIFIED RIDGE OVER THE WESTERN U.S. IS LIKELY TO MAINTAIN MUCH
ABOVE-NORMAL TEMPERATURES THROUGH AT LEAST MONDAY 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
PACIFIC NORTHWEST.



A SHORTWAVE TROUGH IS EXPECTED TO ADVANCE SOUTH FROM THE ARCTIC OCEAN AND TRACK
SOUTHWEST ACROSS WESTERN ALASKA TO BRISTOL BAY FROM AUGUST 2-3. LOCALLY HEAVY
PRECIPITATION MAY ACCOMPANY THIS SHORTWAVE TROUGH ACROSS MAINLAND ALASKA, BUT
PRECIPITATION AMOUNTS ARE MOST LIKELY TO REMAIN BELOW HAZARDS CRITERIA.

FOR TUESDAY AUGUST 05 - MONDAY AUGUST 11: SPREAD AMONG THE 0Z GFS ENSEMBLE
MEMBERS INCREASES REGARDING THE AMPLITUDE OF THE RIDGE (TROUGH) OVER THE
WESTERN (EASTERN) U.S. THE LACK OF ANY MAJOR HEAT WAVES EAST OF THE ROCKIES IS
EXPECTED TO CONTINUE INTO EARLY AUGUST.



HOWEVER, A SLIGHT RISK OF ABOVE-NORMAL TEMPERATURES FOR PARTS OF THE PACIFIC
NORTHWEST IS POSTED ON THE PROBABILISTIC WEEK-2 HAZARDS OUTLOOK. THIS WEEK-2
HAZARD AREA AND ITS RISK ARE BASED ON THE POTENTIAL THAT THE UPPER-LEVEL RIDGE
MAY NOT WEAKEN AS QUICKLY AS FORECAST BY THE DETERMINISTIC 12Z GFS MODEL. ALSO,
THIS IS CONSISTENT WITH INCREASING SPREAD AMONG 0Z GFS ENSEMBLE MEMBERS.



A TROPICAL WAVE IS LOCATED SEVERAL HUNDRED MILES SOUTHWEST OF THE CAPE VERDE
ISLANDS. THIS TROPICAL WAVE SHOULD BE MONITORED AS IT COULD BECOME MORE
ORGANIZED ACROSS THE CENTRAL ATLANTIC.



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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