Prognostic Meteorological Discussion
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FXUS21 KWNC 031918
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT MAY 03 2016

SYNOPSIS: AT THE BEGINNING OF THE FORECAST PERIOD AN MID-LEVEL HIGH PRESSURE IS
SETUP ACROSS THE THE ROCKIES AND PLAINS, WHICH IS EXPECTED TO DEAMPLIFY AND
SHIFT EASTWARD DURING WEEK-1.  A CLOSED MID-LEVEL LOW, TO THE WEST OF THE
AFOREMENTIONED HIGH, IS ANTICIPATED TO OPEN UP LATE IN WEEK-1, NOT BEFORE
BRINGING A WIDE ARRAY OF HAZARDS TO THE WESTERN HALF OF THE CONUS THROUGHOUT
THE WEEK.  FLOW BECOMES INCREASINGLY FLAT DURING WEEK-2, WITH THE PRIMARY FOCUS
BEING A MID-LEVEL HIGH PRESSURE FORECAST TO LIE ACROSS THE WEST COAST INITIALLY
THAT WILL PROGRESS EASTWARD DURING THE PERIOD.  A SERIES OF LOW PRESSURE
FEATURES ARE EXPECTED TO IMPACT SOUTHERN ALASKA THROUGHOUT THE FORECAST PERIOD.

HAZARDS

SEVERE WEATHER FOR THE CENTRAL AND SOUTHERN PLAINS, SAT, MAY 7.

HEAVY RAINFALL FOR SOUTHERN ALASKA AND THE ALASKA PANHANDLE, FRI, MAY 6.

HEAVY PRECIPITATION FOR PORTIONS OF THE SIERRA NEVADAS, FRI-SAT, MAY 6-7.

HEAVY PRECIPITATION FOR THE CENTRAL ROCKIES, FRI-SAT, MAY 6-7.

FLOODING OCCURRING FOR PARTS OF THE CENTRAL U.S., FRI-SAT, MAY 6-7.

FLOODING LIKELY FOR PARTS OF WASHINGTON STATE, FRI-SAT, MAY 6-7.

MUCH ABOVE NORMAL TEMPERATURES FOR THE PACIFIC NORTHWEST, SAT, MAY 7.

CRITICAL FIRE WEATHER CONDITIONS FOR SOUTHEASTERN ARIZONA AND SOUTHWESTERN NEW
MEXICO, FRI, MAY 6.

CRITICAL FIRE WEATHER CONDITIONS FOR SOUTHEASTERN NEW MEXICO, SAT-SUN, MAY 7-8.

HEAVY RAINFALL FOR THE CENTRAL PLAINS, MIDDLE AND LOWER MISSISSIPPI VALLEYS,
SUN-MON, MAY 8-9.

A SLIGHT RISK OF MUCH ABOVE NORMAL TEMPERATURES FOR NEW ENGLAND, WED, MAY 11.

A SLIGHT RISK OF MUCH ABOVE NORMAL TEMPERATURES FOR THE INTERIOR PACIFIC
NORTHWEST, WED-THU, MAY 11-12.

A SLIGHT RISK OF MUCH ABOVE NORMAL TEMPERATURES FOR THE SNAKE RIVER BASIN,
WED-SAT, MAY 11-14.

SEVERE DROUGHT ACROSS PARTS OF CALIFORNIA, THE GREAT BASIN, SOUTHWEST, WYOMING,
SOUTHERN GREAT PLAINS, HAWAII, AND PUERTO RICO.

DETAILED SUMMARY

FOR FRIDAY MAY 06 - TUESDAY MAY 10: THE FOCUS FOR HAZARDS WILL LARGELY BE ON
THE 500-HPA CLOSED LOW INITIALLY FORECAST ACROSS THE WESTERN CONUS EARLY IN
WEEK-1.  HEAVY PRECIPITATION (IN EXCESS OF 1 INCH OF LIQUID OVER 24 HOURS) IS
ANTICIPATED FOR BOTH THE SIERRA NEVADAS AND THROUGHOUT THE CENTRAL ROCKIES ON
FRIDAY, MAY 6 AND SATURDAY, MAY 7 WITH POTENTIAL FOR SNOW AT HIGHER ELEVATIONS.
 AS THE SYSTEM SHIFTS EASTWARD, SPC HAS INTRODUCED A 15% RISK OF SEVERE WEATHER
FOR THE CENTRAL AND SOUTHERN PLAINS ON SUNDAY, MAY 8 ASSOCIATED WITH POTENTIAL
SUPERCELL DEVELOPMENT IN THE CYCLONE`S WARM SECTOR.  THE SEVERE WEATHER THREAT
MAY SHIFT FURTHER EASTWARD WITH THIS SYSTEM ON SUBSEQUENT DAYS, HOWEVER SPC
DOES NOT ISOLATE A SPECIFIC GEOGRAPHIC REGION GIVEN UNCERTAINTIES IN HOW THE
ATTENDANT SYSTEM WILL PROPAGATE.  HEAVY RAINFALL IS FORECAST FOR THE CENTRAL
PLAINS, MIDDLE AND LOWER MISSISSIPPI VALLEYS ON SUNDAY, MAY 8 AND MONDAY, MAY 9
AS THE CYCLONE CONTINUES EASTWARD.



IN THE WAKE OF THIS SYSTEM, AN ENHANCED FIRE WEATHER RISK IS FORECAST FOR PARTS
OF THE SOUTHWEST ON FRIDAY, MAY 6 WHERE WARM TEMPERATURES, DRY CONDITIONS, AND
WINDY (ALTHOUGH NOT MEETING HAZARDOUS CRITERIA) CONDITIONS MAY OCCUR.  THIS
ENHANCED FIRE WEATHER RISK SHIFTS EASTWARD ON SATURDAY, MAY 7 AND SUNDAY, MAY 8
TO SOUTHEASTERN NEW MEXICO.  ELEVATED FIRE WEATHER RISKS ACROSS SOUTHERN NEW
MEXICO AND WESTERN TEXAS MAY OCCUR MONDAY, MAY 9 HOWEVER UNCERTAINTY AMONG
FORECAST GUIDANCE LEADS TO SPC OMITTING A SPECIFIC HAZARD REGION AT THIS TIME.



DAILY MAXIMUM TEMPERATURE ANOMALIES EXCEEDING 16 DEGREES FAHRENHEIT ARE
FORECAST ACROSS THE PACIFIC NORTHWEST FOR SATURDAY, MAY 7 ASSOCIATED WITH
ANOMALOUS RIDGING APPARENT AT 500-HPA TO THE NORTH OF THE CLOSED LOW DETAILED
EARLIER.



A SERIES OF CYCLONES ARE EXPECTED TO IMPACT SOUTHERN ALASKA THROUGHOUT THE
WEEK-1 PERIOD.  THE MOST NOTEWORTHY OF THESE WILL BRING HEAVY RAINFALL IN
EXCESS OF 2 INCHES OVER 24 HOURS TO PARTS OF SOUTHERN ALASKA AND THE ALASKA
PANHANDLE ON FRIDAY, MAY 6.

FOR WEDNESDAY MAY 11 - TUESDAY MAY 17: EARLY IN WEEK-2 A NUMBER OF REGIONS FOR
SLIGHT RISK OF MUCH ABOVE NORMAL TEMPERATURES ARE DEPICTED.  THE FIRST OF THESE
COVERS MUCH OF NEW ENGLAND ON WEDNESDAY, MAY 11 WHERE THE GEFS REFORECAST TOOL
DEPICTS IN EXCESS OF 30% CHANCE OF EXCEEDING THE 85TH PERCENTILE OF MAXIMUM
TEMPERATURE CLIMATOLOGY VALUES AND A GREATER THAN 40% CHANCE OF EXCEEDING 85
DEGREES FAHRENHEIT.  TWO REGIONS ACROSS THE PACIFIC NORTHWEST ARE HIGHLIGHTED
FOR A SLIGHT RISK OF MUCH ABOVE NORMAL TEMPERATURES ASSOCIATED WITH WEAK
RIDGING FORECAST BY DYNAMICAL GUIDANCE.  THE FIRST OF THESE COVERS THE INTERIOR
PACIFIC NORTHWEST WEDNESDAY, MAY 11 AND THURSDAY, MAY 12.  THE SECOND
ENCOMPASSES THE SNAKE RIVER BASIN WEDNESDAY MAY 11 THROUGH SATURDAY MAY 14.
THESE TWO REGIONS BOTH ARE HIGHLIGHTED BY THE GEFS REFORECAST TOOL FOR AT LEAST
A 30% CHANCE OF EXCEEDING THE 85TH CLIMATOLOGICAL PERCENTILE OF HIGH
TEMPERATURE VALUES.



ACCORDING TO THE U.S. DROUGHT MONITOR VALID ON APRIL 26, SEVERE, OR GREATER
INTENSITY, DROUGHT COVERS 5 PERCENT OF THE U.S. DROUGHT MONITOR AREAS WITH A
CONTINUED DECREASE IN COVERAGE DURING THE PAST SIX MONTHS.

FORECASTER: DANIEL HARNOS

$$



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