Prognostic Meteorological Discussion
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FXUS21 KWNC 271835
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT MAY 27 2016

SYNOPSIS: A LOW PRESSURE SYSTEM IS EXPECTED TO AFFECT PARTS OF THE SOUTHEAST
AND SOUTHERN MID-ATLANTIC EARLY IN THE PERIOD. A SURFACE LOW IS EXPECTED TO
TRACK FROM THE NORTHERN GREAT PLAINS TO THE UPPER MISSISSIPPI VALLEY ON MAY 30
AND 31, WHILE THE TRAILING FRONT PROGRESSES INTO THE SOUTHERN GREAT PLAINS ON
JUNE 1 AND 2.  AN AREA OF UPPER-LEVEL HIGH PRESSURE IS LIKELY TO CONTINUE
ACROSS ALASKA THROUGH THE END OF MAY, WITH ONSHORE FLOW INCREASING ACROSS
SOUTHERN ALASKA EARLY IN JUNE. A STRONG AREA OF UPPER-LEVEL HIGH PRESSURE IS
EXPECTED TO BECOME ESTABLISHED ACROSS THE NORTHWESTERN CONUS BY THE BEGINNING
OF JUNE AND PERSIST THROUGH WEEK-2.

HAZARDS

LOCALLY HEAVY RAIN FOR THE EASTERN CAROLINAS, MON-TUE, MAY 30-31.

SEVERE WEATHER FOR PARTS OF THE NORTHERN AND CENTRAL GREAT PLAINS, MON, MAY 30.

LOCALLY HEAVY RAIN FOR PARTS OF THE NORTHERN AND CENTRAL GREAT PLAINS AND
MISSOURI RIVER VALLEY, MON-TUE, MAY 30-31.

LOCALLY HEAVY RAIN SHIFTING SOUTH ACROSS THE CENTRAL AND SOUTHERN GREAT PLAINS,
MON-THU, MAY 30-JUNE 2.

FLOODING IS OCCURRING, IMMINENT, LIKELY, OR POSSIBLE ACROSS PARTS OF THE
CENTRAL AND SOUTHERN GREAT PLAINS, CENTRAL ROCKIES, LOWER MISSOURI RIVER
VALLEY, AND MIDWEST, MON-TUE, MAY 30-31.

MUCH ABOVE-NORMAL TEMPERATURES FOR PARTS OF THE PACIFIC NORTHWEST AND IDAHO,
WED-FRI, JUNE 1-3.

A SLIGHT RISK OF MUCH ABOVE-NORMAL TEMPERATURES FOR MUCH OF THE WESTERN U.S.,
SAT-WED, JUNE 4-8.

A MODERATE RISK OF MUCH ABOVE-NORMAL TEMPERATURES FOR PARTS OF THE PACIFIC
NORTHWEST, IDAHO, AND NORTHERN CALIFORNIA, SAT-MON, JUNE 4-6.

SEVERE DROUGHT ACROSS PARTS OF CALIFORNIA, NEVADA, NORTH-CENTRAL WYOMING, AND
HAWAII.

DETAILED SUMMARY

FOR MONDAY MAY 30 - FRIDAY JUNE 03: ON MAY 27, AN AREA OF LOW PRESSURE IS
BECOMING MORE ORGANIZED A FEW HUNDRED MILES NORTHEAST OF THE BAHAMAS. MODEL
GUIDANCE CONTINUES TO INDICATE THAT THIS LOW PRESSURE SYSTEM WITH A DEEP FEED
OF TROPICAL MOISTURE MOVES INLAND INTO THE EASTERN CAROLINAS DURING THE
MEMORIAL DAY WEEKEND. LOCALLY HEAVY RAIN (MORE THAN 1 INCH PER 24 HOURS) IS
EXPECTED ACROSS THE EASTERN CAROLINAS THROUGH TUESDAY, MAY 31 DUE TO ENHANCED
LOW-LEVEL MOISTURE. LOCALLY HEAVY RAIN MAY ALSO SPREAD NORTH INTO THE
MID-ATLANTIC, BUT MODEL SOLUTIONS VARY ON PRECIPITATION AMOUNTS ACROSS THIS
REGION. AS OF 745AM EDT ON FRIDAY, THE NATIONAL HURRICANE CENTER STATES THAT
THERE IS A 90 PERCENT CHANCE OF TROPICAL CYCLONE FORMATION OFFSHORE OF THE
SOUTHEAST. PLEASE REFER TO THE NATIONAL HURRICANE CENTER FOR THE LATEST UPDATES
ON THIS POTENTIAL TROPICAL OR SUBTROPICAL STORM.



THE APPROACH OF A VIGOROUS SHORTWAVE TROUGH ALONG WITH ADEQUATE LOW-LEVEL
MOISTURE AND INSTABILITY ARE LIKELY TO RESULT IN SEVERE THUNDERSTORMS ACROSS
PARTS OF THE DAKOTAS AND NEBRASKA ON MONDAY, MAY 30. LOCALLY HEAVY RAIN (MORE
THAN 1 INCH PER 24 HOURS) IS EXPECTED TO ACCOMPANY THE SHORTWAVE TROUGH AND THE
ASSOCIATED COLD FRONT AS THEY PROGRESS EAST FROM THE NORTHERN GREAT PLAINS TO
IOWA AND MINNESOTA ON MAY 30 AND 31. DUE TO MODEL DIFFERENCES ON THE SPEED OF
THE SHORTWAVE TROUGH, A SEVERE WEATHER HAZARD IS NOT POSTED BEYOND MAY 30.
PLEASE REFER TO THE STORM PREDICTION CENTER FOR THE LATEST CONVECTIVE OUTLOOKS.



DAILY CONVECTION WITH LOCALLY HEAVY RAIN (MORE THAN 1 INCH PER 24 HOURS) IS
EXPECTED ALONG A COLD FRONT AS IT PROGRESSES SOUTH ACROSS THE CENTRAL AND
SOUTHERN GREAT PLAINS FROM MAY 30 TO JUNE 2. IT SHOULD BE NOTED THAT ABUNDANT
GULF MOISTURE INTERACTING WITH THE TAIL END OF THE FRONT PROVIDES A FAVORABLE
SETUP FOR TORRENTIAL RAINFALL CAPABLE OF TRIGGERING FLASH FLOODING ACROSS TEXAS
ON JUNE 1 AND 2.



RECENT HEAVY RAINFALL HAS RESULTED IN WIDESPREAD MINOR TO MODERATE FLOODING
ACROSS THE CENTRAL CONUS AND IS LIKELY TO CONTINUE INTO NEXT WEEK. FOR EXAMPLE,
MODERATE FLOODING IS FORECAST TO PERSIST ALONG PARTS OF THE NORTH PLATTE RIVER
IN NEBRASKA. ANY HEAVY RAINFALL DURING THE REMAINDER OF MAY INTO THE BEGINNING
OF JUNE COULD EXACERBATE ONGOING FLOODING AND MAY CAUSE ADDITIONAL FLOODING DUE
TO THE ANTECEDENT WETNESS.



AN INCREASE IN 500-HPA HEIGHTS IS LIKELY TO BRING A RAPID WARMING TREND TO THE
WESTERN CONUS DURING THE FINAL DAYS OF MAY. MUCH ABOVE-NORMAL TEMPERATURES
(DEPARTURES OF 15 TO 20 DEGREES F) ARE FORECAST TO BEGIN AFFECTING THE PACIFIC
NORTHWEST ON WEDNESDAY, JUNE 1.



UNSEASONABLY WARM TEMPERATURES ARE LIKELY TO PERSIST ACROSS SOUTHWEST ALASKA AS
RIDGING ALOFT REMAINS DOMINANT THROUGH AT LEAST THE END OF MAY. MODEL GUIDANCE
INDICATES THAT ONSHORE FLOW BEGINS TO BRING AN INCREASE IN RAINFALL ACROSS THE
SOUTHERN HALF OF ALASKA DURING THE BEGINNING OF JUNE.

FOR SATURDAY JUNE 04 - FRIDAY JUNE 10: THE GFS AND ECMWF ENSEMBLE MEANS DEPICT
A STRONG UPPER-LEVEL RIDGE CENTERED ACROSS THE NORTHWESTERN CONUS DURING
WEEK-2. DUE TO THE CONSISTENT SIGNAL AMONG MODEL SOLUTIONS, A MODERATE RISK OF
MUCH ABOVE-NORMAL TEMPERATURES IS POSTED FOR THE INTERIOR PACIFIC NORTHWEST
ALONG WITH PARTS OF IDAHO AND NORTHERN CALIFORNIA FROM JUNE 4 TO 6. THE 6Z GFS
ENSEMBLE MEAN INDICATES TEMPERATURES AVERAGING AS MUCH AS 16 DEGREES F
ABOVE-NORMAL ACROSS THESE AREAS. A SLIGHT RISK OF MUCH ABOVE-NORMAL
TEMPERATURES ARE POSTED FOR THE WESTERN CONUS WHERE THE GEFS REFORECAST TOOL
INDICATES THAT DAILY MAXIMUM TEMPERATURES HAVE AT LEAST A 20 PERCENT CHANCE OF
EXCEEDING THE 85TH PERCENTILE COMPARED TO CLIMATOLOGY.



ACCORDING TO THE U.S. DROUGHT MONITOR, VALID ON MAY 24, SEVERE, OR GREATER
INTENSITY, DROUGHT COVERS 3.69 PERCENT OF THE U.S. DROUGHT MONITOR AREAS
(INCLUDING ALASKA, HAWAII, AND PUERTO RICO), A DECREASE FROM 4.07 PERCENT LAST
WEEK. THIS IS THE LOWEST COVERAGE SINCE OCTOBER 2010.

FORECASTER: BRAD PUGH

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