Prognostic Meteorological Discussion
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FXUS21 KWNC 041814
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT MAY 04 2016

SYNOPSIS: IN WEEK-1 A SURFACE LOW PRESSURE SYSTEM IS EXPECTED TO BRING AN ARRAY
OF METEOROLOGICAL HAZARDS TO THE WESTERN AND CENTRAL CONUS.  IN THE WAKE OF
THIS SYSTEM DRY AND WINDY CONDITIONS ARE ANTICIPATED ACROSS PARTS OF THE
SOUTHWEST.  AS THE SYSTEM MOVES OUT, A MORE BENIGN WEATHER PATTERN SHOULD SET
UP FOR WEEK-2 WITH TRENDS TOWARDS GENERAL HIGH PRESSURE ACROSS THE WEST AND LOW
PRESSURE ACROSS THE EAST.  THROUGHOUT THE FORECAST PERIOD ALASKA IS ANTICIPATED
TO BE IMPACTED BY A SERIES OF CYCLONES WITH ASSOCIATED IMPACTS DURING WEEK-1
BEFORE MID-LEVEL HIGH PRESSURE BUILDS IN WEEK-2.

HAZARDS

SEVERE WEATHER ACROSS PORTIONS OF THE CENTRAL PLAINS AND THE SOUTHERN PLAINS,
SAT-SUN, MAY 7-8.

HEAVY PRECIPITATION ACROSS PORTIONS OF THE CENTRAL GREAT BASIN AND CALIFORNIA,
SAT-SUN, MAY 7.

HEAVY PRECIPITATION ACROSS PORTIONS OF THE CENTRAL ROCKIES, SAT, MAY 7.

HEAVY RAIN ACROSS PORTIONS OF THE CENTRAL PLAINS, THE MIDDLE MISSISSIPPI
VALLEY, THE LOWER MISSISSIPPI VALLEY, THE SOUTHERN PLAINS, AND THE UPPER
MISSISSIPPI VALLEY, MON-TUE, MAY 9-10.

FLOODING POSSIBLE ACROSS PORTIONS OF WASHINGTON STATE, SAT-SUN, MAY 7-8.

FLOODING POSSIBLE ACROSS PORTIONS OF THE CENTRAL ROCKIES, SAT-SUN, MAY 7-8.

FLOODING OCCURRING OR IMMINENT ACROSS PORTIONS OF THE CENTRAL PLAINS, THE LOWER
MISSISSIPPI VALLEY, THE NORTHERN PLAINS, THE MIDDLE MISSISSIPPI VALLEY, THE
UPPER MISSISSIPPI VALLEY, AND THE SOUTHERN PLAINS, SAT-SUN, MAY 7-8.

HIGH WINDS ACROSS PORTIONS OF THE SOUTHERN PLAINS, SAT, MAY 7.

MUCH ABOVE NORMAL TEMPERATURES ACROSS PORTIONS OF THE PACIFIC NORTHWEST, THE
NORTHERN ROCKIES, AND THE NORTHERN GREAT BASIN, SAT, MAY 7.

MUCH ABOVE NORMAL TEMPERATURES ACROSS PORTIONS OF THE NORTHERN PLAINS, THE
NORTHERN ROCKIES, AND THE NORTHERN GREAT BASIN, SUN, MAY 8.

ENHANCED WILDFIRE RISK ACROSS PORTIONS OF THE THE SOUTHERN ROCKIES AND THE
SOUTHERN PLAINS, SAT-SUN, MAY 7-8.

SLIGHT RISK OF MUCH ABOVE-NORMAL TEMPERATURES FOR PORTIONS OF NEW ENGLAND, THU,
MAY 12.

SLIGHT RISK OF MUCH ABOVE-NORMAL TEMPERATURES FOR NORTHERN CALIFORNIA, THE
CENTRAL GREAT BASIN, THE PACIFIC NORTHWEST, THE NORTHERN ROCKIES, AND THE
NORTHERN GREAT BASIN, THU-SAT, MAY 12-MAY 14.

SEVERE DROUGHT ACROSS THE CENTRAL GREAT BASIN, THE NORTHERN PLAINS, HAWAII, THE
NORTHERN GREAT BASIN, CALIFORNIA, PUERTO RICO, THE SOUTHERN PLAINS, AND THE
SOUTHWEST.

DETAILED SUMMARY

FOR SATURDAY MAY 07 - WEDNESDAY MAY 11: THE INITIAL 500-HPA FLOW PATTERN IN
WEEK-1 IS EXPECTED TO CONSIST OF HIGH AMPLITUDE FLOW FEATURING AN OMEGA BLOCK
ACROSS THE CONUS HIGHLIGHTED BY CLOSED LOWS ACROSS THE SOUTHWEST AND
MID-ATLANTIC THAT FLANK A RIDGE THROUGH THE SOUTHERN AND CENTRAL PLAINS.  OVER
THE COURSE OF THE WEEK THE PATTERN IS ANTICIPATED TO DEAMPLIFY, PARTICULARLY
OVER THE CENTRAL AND EASTERN CONUS AS THE RIDGE FLATTENS OUT AND THE LOW
TRANSITIONS TO AN OPEN WAVE RESPECTIVELY.  THE DISTURBANCE INITIALLY OVER THE
WESTERN CONUS IS EXPECTED TO BE THE KEY HAZARDS INFLUENCE ON WEEK-1 AS IT
PROGRESSES SLOWLY EASTWARD AND OPENS UP LATE IN THE FORECAST PERIOD.



INITIAL HAZARDS ASSOCIATED WITH THE CYCLONE ACROSS THE WESTERN CONUS ARE
EXPECTED TO BE HEAVY PRECIPITATION (EXCEEDING 1 INCH OF LIQUID EQUIVALENT IN 24
HOURS) ACROSS THE SIERRA NEVADAS AND CENTRAL ROCKIES ON SATURDAY, MAY 7.  THIS
PRECIPITATION WILL LIKELY FALL AS RAIN FOR BOTH REGIONS EXCEPT FOR HIGHER
ELEVATIONS WHERE SNOW POTENTIAL EXISTS.  THE HEAVY PRECIPITATION ACROSS THE
CENTRAL ROCKIES POSSIBLY MAY YIELD LOCALIZED FLOODING CONCERNS FOR THE REGION
ON SATURDAY, MAY 7 AND SUNDAY, MAY 8.  THE SPC HAS INTRODUCED A 15% SEVERE
WEATHER RISK ON SATURDAY, MAY 7 AREA FROM THE CENTRAL PLAINS SOUTHWARD THROUGH
WEST TEXAS ASSOCIATED WITH POTENTIAL SUPERCELL DEVELOPMENT ALONG A DRY LINE
BRINGING PRIMARILY A LARGE HAIL THREAT.  HIGH WINDS IN EXCESS OF 35 MPH ARE
ALSO ANTICIPATED IN THE VICINITY OF THE STOCKTON AND EDWARDS PLATEAUS OF TEXAS
ON SATURDAY, MAY 7 ASSOCIATED WITH THE LOW-LEVEL JET ACTING TO FUEL THE SEVERE
WEATHER.  SPC ANTICIPATES THE 15% CHANCE OF SEVERE WEATHER TO SHIFT EASTWARD ON
SUNDAY, MAY 8 STRETCHING FROM SOUTH-CENTRAL NEBRASKA THROUGH CENTRAL TEXAS,
ONCE MORE ASSOCIATED WITH A DRY LINE SETTING UP ACROSS THIS REGION.  HEAVY
RAINFALL IS FORECAST ACROSS THE MIDDLE AND LOWER MISSISSIPPI VALLEYS BACK
THROUGH EAST TEXAS FOR BOTH MONDAY AND TUESDAY, MAY 9 AND 10 AS THE CYCLONE
CONTINUES EASTWARD.  THIS RAINFALL ACROSS EAST TEXAS AND THE LOWER MISSISSIPPI
VALLEY MAY EXACERBATE ONGOING FLOODING OCCURRING FOR THIS REGION.  HAZARD
IMPACTS FROM THIS LOW-PRESSURE SYSTEM ARE THEREAFTER EXPECTED TO WANE AS THE
SYSTEM LIFTS NORTHWARD TOWARDS CANADA.



BEHIND THE DRY LINE ASSOCIATED WITH THE AFOREMENTIONED CYCLONE, ENHANCED FIRE
WEATHER CONDITIONS ARE EXPECTED ACROSS MUCH OF THE SOUTHWEST FOR DAYS 3 AND 4.
SPC INDICATES A SPECIFIC RISK AREA OF SOUTHEASTERN NEW MEXICO ON SATURDAY AND
SUNDAY MAY 7 AND 8 WHERE WARM AND DRY CONDITIONS ARE EXPECTED IN CONJUNCTION
WITH HIGH WINDS (THAT ARE NOT EXPECTED TO MEET HAZARDOUS CRITERIA).  OUTSIDE OF
THIS SPECIFIC AREA OF ELEVATED FIRE WEATHER RISK, CONDITIONS MAY APPROACH
HAZARDOUS CRITERIA THROUGHOUT CENTRAL AND SOUTHERN NEW MEXICO INTO WEST TEXAS
SUNDAY, MAY 7 THROUGH MONDAY, MAY 9.  ANOMALOUS WARMTH IS ALSO EXPECTED NORTH
OF THE CYCLONE OVER THE WESTERN CONUS EARLY IN WEEK-1.  AREAS THAT MAY SEE MUCH
ABOVE NORMAL TEMPERATURES FOR SATURDAY INCLUDE THE PACIFIC NORTHWEST ON
SATURDAY, MAY 7 WHERE MAXIMUM TEMPERATURES MAY EXCEED CLIMATOLOGY IN EXCESS OF
16 DEGREES FAHRENHEIT.  MELTING SNOWFALL WITH THIS WARMTH COULD POSSIBLY LEAD
TO FLOODING FOR PARTS OF NORTH CENTRAL WASHINGTON ON SATURDAY, MAY 7 AND
SUNDAY, MAY 8.  THIS REGION OF ANOMALOUS WARMTH IS EXPECTED TO SHIFT EASTWARD
ACROSS EASTERN WASHINGTON, NORTHERN IDAHO, AND NORTHWESTERN MONTANA ON SUNDAY,
MAY 8.



A SERIES OF CYCLONES ARE ANTICIPATED TO IMPACT ALASKA THROUGHOUT WEEK-1, YET NO
SPECIFIC HAZARDS ARE DEPICTED AT THIS TIME FOR ALASKA.  HOWEVER, SIGNIFICANT
WAVE HEIGHTS MAY APPROACH 20 FEET FOR THE WESTERN ALEUTIANS ON TUESDAY, MAY 10
ASSOCIATED WITH THE MOST VIGOROUS CYCLONE TO IMPACT THE STATE DURING THIS WEEK.

FOR THURSDAY MAY 12 - WEDNESDAY MAY 18: EARLY IN WEEK-2 THE FORECAST CONUS FLOW
PATTERN EXHIBITS PREDOMINANTLY ZONAL FLOW, WITH WEAK RIDGING FAVORED ACROSS THE
WESTERN CONUS AND TROUGHING THROUGH THE GREAT LAKES.  THROUGHOUT THE COURSE OF
THE WEEK THE PATTERN IS ANTICIPATED TO AMPLIFY SOMEWHAT, ALBEIT NOT THE THE
EXTENT SEEN IN WEEK-1, WITH THE RIDGE AND TROUGH PROPAGATING EASTWARD.  A
500-HPA TROUGH IS EXPECTED TO COME ASHORE OVER THE WESTERN CONUS LATE IN
WEEK-2.  A MID-LEVEL RIDGE IS FORECAST TO AMPLIFY OVER ALASKA DURING THE EARLY
PORTION OF WEEK-2.



PRECIPITATION HAZARDS WERE CONSIDERED FOR BOTH THE TROUGH FORECAST ACROSS THE
GREAT LAKES AROUND SATURDAY, MAY 14 AND TROUGH ACROSS THE WEST LATE IN WEEK-2.
LACK OF CONSENSUS AMONG DYNAMICAL GUIDANCE LED TO THE LACK OF A SPECIFIC HAZARD
BEING DEPICTED FOR EITHER REGION, BUT WILL BE REVISITED IN THE COMING DAYS.



TWO REGIONS HAVE BEEN HIGHLIGHTED FOR A SLIGHT RISK OF MUCH ABOVE NORMAL
TEMPERATURES DURING THE WEEK-2 PERIOD.  THE FIRST IS FOR COASTAL NEW ENGLAND ON
MONDAY, MAY 12 WHERE THE GEFS REFORECAST TOOL DEPICTS PROBABILITIES OF
EXCEEDING THE CLIMATOLOGICAL 85TH PERCENTILE OF MAXIMUM TEMPERATURE EXCEED 30%.
 ALSO HIGHLIGHTED FOR A SLIGHT RISK OF MUCH ABOVE NORMAL TEMPERATURES IS MUCH
OF THE PACIFIC NORTHWEST FOR THURSDAY, MAY 12 THROUGH SATURDAY, MAY 14
ASSOCIATED WITH THE RIDGE BUILDING ACROSS THE WEST THAT COULD PUSH LOWER
ELEVATION TEMPERATURES TO EXCEED 85 FAHRENHEIT.  A SLIGHT RISK REGION OF MUCH
ABOVE NORMAL TEMPERATURES WAS CONSIDERED FOR CENTRAL ALASKA DURING THE FIRST
HALF OF WEEK-2 WHERE A STRONG RIDGE IS EXPECTED TO DEVELOP AND GUIDANCE
SUGGESTS MAXIMUM TEMPERATURES COULD APPROACH RECORD VALUES.  GIVEN THAT RECORD
HIGH TEMPERATURES ARE GENERALLY AT OR BELOW 80 FAHRENHEIT FOR THIS REGION A
LIMITED IMPACT TO LIFE AND PROPERTY WOULD BE ANTICIPATED, AND THUS NO HAZARD IS
SHOWN ON THE MAP.  ALASKA WILL NEED TO BE MONITORED FOR ANY INCREASING RISK OF
ENHANCED FIRE WEATHER CONDITIONS OR SNOW MELT RELATED FLOOD RISKS ASSOCIATED
WITH THIS POSSIBLE WARMTH IN EARLY WEEK-2.



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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