Prognostic Meteorological Discussion
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FXUS21 KWNC 021853
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT SEPTEMBER 02 2015

SYNOPSIS: SURFACE HIGH PRESSURE IS PREDICTED TO MOVE FROM EASTERN CANADA INTO
THE EASTERN UNITED STATES WITH A STRONG LOW PRESSURE MOVING THROUGH THE HIGH
PLAINS.  THIS PATTERN FAVORS PRECIPITATION FROM THE SOUTHWESTERN STATES INTO
THE DAKOTAS.  BELOW NORMAL TEMPERATURES ARE FORECAST FOR THE WESTERN STATES
WITH ABOVE NORMAL TEMPERATURES FAVORED FOR THE EASTERN STATES.

HAZARDS

SEVERE DROUGHT FOR PARTS OF THE WESTERN THIRD OF THE CONUS, SOUTHERN GREAT
PLAINS, LOWER MISSISSIPPI VALLEY, SOUTHEAST, AND HAWAII.

FLOODING POSSIBLE FOR PARTS OF WEST-CENTRAL FLORIDA AND IOWA.

HEAVY RAIN FOR SOUTHEASTERN ALASKA, WED-THU, SEP 9-10.

DETAILED SUMMARY

FOR SATURDAY SEPTEMBER 05 - WEDNESDAY SEPTEMBER 09: THIS FORECAST PERIOD IS
EXPECTED TO BEGIN WITH AN UPPER-LEVEL TROUGH AMPLIFYING ALONG THE WEST COAST,
WITH AN UPPER-LEVEL RIDGE FROM EASTERN TEXAS TO THE NORTHERN GULF COAST.  THIS
PATTERN FAVORS BELOW NORMAL TEMPERATURES IN THE WESTERN STATES WITH ABOVE
NORMAL TEMPERATURES IN THE SOUTHEASTERN STATES.  THE GREATEST CHANCE OF
SIGNIFICANT PRECIPITATION EXTENDS ALONG THE WESTERN PERIPHERY OF THE
UPPER-LEVEL HIGH FROM THE MOUNTAINS IN THE SOUTHWEST TO THE HIGH PLAINS AND THE
DAKOTAS.



BY THE END OF THIS PERIOD, MOISTURE FROM THE REMNANTS OF TD 14E SOUTH OF BAJA
CALIFORNIA COULD GET DRAWN INTO THE CONUS, INCREASING THE POTENTIAL AMOUNTS OF
PRECIPITATION IN THE SOUTHWEST.  AT THIS TIME, NO LARGE-SCALE HAZARDS ARE
DENOTED ON THE MAP, BUT LOCALIZED FLOODING IS POSSIBLE IN ANY HEAVY DOWNPOURS
THAT MIGHT OCCUR.



SURFACE LOW PRESSURE IN THE PLAINS COMBINED WITH HIGH PRESSURE IN CANADA IS
EXPECTED TO LEAD TO STRONG NORTHEASTERLY UPSLOPE FLOW FROM IDAHO THROUGH
MONTANA INTO THE DAKOTAS.  WHILE SIGNIFICANT PRECIPITATION IS LIKELY, THE
FORECAST AMOUNTS DO NOT REACH HAZARDOUS CRITERIA, ALTHOUGH SOME LOCALIZED
FLOODING IS POSSIBLE.



IN THE WEST, AS INDIVIDUAL SHORTWAVES ROTATE AROUND THE BASE OF THE TROUGH,
ENHANCED WINDS ARE POSSIBLE, AND GIVEN THE DRY CONDITIONS, AN ENHANCED WILDFIRE
RISK FROM NEVADA INTO UTAH CANNOT BE RULED OUT.  HOWEVER, THERE IS TOO MUCH
MODEL UNCERTAINTY IN REGARDS TO THE MAGNITUDE OF THE SURFACE WINDS, THUS NO
HAZARDS ARE DENOTED ON THE MAP.



NEAR THE END OF THIS FORECAST PERIOD, THE REMNANTS OF HURRICANE IGNACIO ARE
EXPECTED TO MERGE INTO THE MID-LATITUDE WESTERLY FLOW.  AT THIS TIME, MODELS
ARE FORECASTING THE AMPLIFICATION OF AN UPPER-LEVEL TROUGH SOUTH OF THE
ALEUTIANS.  THIS PATTERN FAVORS HEAVY RAIN FOR THE SOUTHEASTERN COAST OF ALASKA
WITH RAINFALL AMOUNTS OF UP TO 5 INCHES OR MORE POSSIBLE.  IN ADDITION, STRONG
WINDS AND HIGH SEAS ARE ALSO POSSIBLE IN THE SAME AREA.

FOR THURSDAY SEPTEMBER 10 - WEDNESDAY SEPTEMBER 16: THE REMNANTS OF IGNACIO ARE
PREDICTED TO CONTINUE TO AFFECT THE SOUTHEASTERN ALASKAN COAST AT THE BEGINNING
OF THIS PERIOD WITH HEAVY RAIN AND POSSIBLE STRONG WINDS AND HIGH SEAS.



ACCORDING TO THE U.S. DROUGHT MONITOR MAP, VALID ON AUGUST 25, THE COVERAGE OF
SEVERE TO EXCEPTIONAL DROUGHT (D2 TO D4) DECREASED FROM 18.21 TO 18.07 PERCENT
ACROSS THE CONTIGUOUS U.S. SINCE THE PREVIOUS WEEK.

FORECASTER: KENNETH PELMAN

$$



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