Threats Assessment Discussion

210 
FXUS21 KWNC 192009
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT JUNE 19 2018
SYNOPSIS: A BROAD AREA OF HIGH PRESSURE ALOFT IS EXPECTED TO PERSIST OVER THE 
LOWER 48 FOR THE NEXT TWO WEEKS. FRONTAL ACTIVITY IS LIKELY OVER THE CENTRAL 
AND EASTERN U.S. IN THE 3-7 DAY PERIOD, WITH POSSIBLE EXTENSION INTO WEEK-2. 
HEAT IS FORECAST TO BE A CONCERN FOR PARTS OF THE SOUTHERN TIER OF THE COUNTRY 
AND FOR THE NORTHEAST AND UPPER MID-WEST IN WEEK-2. FOR ALASKA, PRECIPITATION 
IS EXPECTED THROUGHOUT THE 3 TO 7 DAY PERIOD ASSOCIATED WITH MID-LEVEL LOW 
PRESSURE, THOUGH LIKELY WILL NOT BE HAZARDOUS.
HAZARDS
HEAVY RAIN ACROSS PORTIONS OF THE GREAT LAKES, THE MIDDLE MISSISSIPPI VALLEY, 
AND THE OHIO VALLEY, FRI, JUN 22.
HEAVY RAIN ACROSS PORTIONS OF THE CENTRAL PLAINS, THE MIDDLE MISSISSIPPI 
VALLEY, THE LOWER MISSISSIPPI VALLEY, AND THE SOUTHERN PLAINS, SAT-MON, JUN 
23-JUN 25.
HEAVY RAIN ACROSS PORTIONS OF THE LOWER MISSISSIPPI VALLEY, THE CENTRAL 
APPALACHIANS, THE TENNESSEE VALLEY, THE MIDDLE MISSISSIPPI VALLEY, THE SOUTHERN 
APPALACHIANS, AND THE OHIO VALLEY, SUN-MON, JUN 24-JUN 25.
EXCESSIVE HEAT ACROSS PORTIONS OF CALIFORNIA AND THE SOUTHWEST, FRI-SUN, JUN 
22-JUN 24.
EXCESSIVE HEAT ACROSS PORTIONS OF THE SOUTHEASTERN QUARTER OF THE CONUS, 
FRI-TUE, JUN 22-JUN 26.
HIGH WINDS ACROSS PORTIONS OF THE CENTRAL PLAINS AND THE SOUTHERN PLAINS, 
SAT-TUE, JUN 23-JUN 26.
HIGH WINDS ACROSS COASTAL PORTIONS OF CALIFORNIA AND THE PACIFIC NORTHWEST, 
SAT-TUE, JUN 23-JUN 26.
MUCH ABOVE NORMAL TEMPERATURES ACROSS PORTIONS OF THE CENTRAL ROCKIES AND THE 
CENTRAL GREAT BASIN, TUE, JUN 26.
SLIGHT RISK OF MUCH ABOVE NORMAL TEMPERATURES FOR PORTIONS OF THE GREAT LAKES, 
THE NORTHEAST, THE UPPER MISSISSIPPI VALLEY, AND THE NORTHERN PLAINS, FRI-TUE, 
JUN 27-JUL 3.
SLIGHT RISK OF EXCESSIVE HEAT FOR PARTS OF THE MIDDLE AND LOWER MISSISSIPPI 
VALLEYS, THE CENTRAL AND SOUTHERN PLAINS, AND THE GREAT LAKES, FRI-SAT, JUN 
27-JUN 28.
SLIGHT RISK OF EXCESSIVE HEAT FOR PARTS OF THE SOUTHWEST, SAT-SUN, JUN 28-JUL 1.
FLOODING POSSIBLE ACROSS PORTIONS OF THE CENTRAL PLAINS, THE LOWER MISSISSIPPI 
VALLEY, THE NORTHERN PLAINS, THE GREAT LAKES, THE NORTHERN ROCKIES, THE MIDDLE 
MISSISSIPPI VALLEY, THE UPPER MISSISSIPPI VALLEY, AND THE SOUTHERN PLAINS.
FLOODING OCCURRING OR IMMINENT ACROSS PORTIONS OF THE MIDDLE MISSISSIPPI 
VALLEY, THE UPPER MISSISSIPPI VALLEY, AND THE NORTHERN PLAINS.
FLOODING LIKELY ACROSS PORTIONS OF THE UPPER MISSISSIPPI VALLEY, THE NORTHERN 
PLAINS, AND THE NORTHERN ROCKIES.
SEVERE DROUGHT ACROSS THE CENTRAL PLAINS, THE CENTRAL ROCKIES, THE CENTRAL 
GREAT BASIN, THE NORTHERN PLAINS, THE NORTHERN GREAT BASIN, THE SOUTHERN 
ROCKIES, THE MIDDLE MISSISSIPPI VALLEY, CALIFORNIA, THE SOUTHERN PLAINS, AND 
THE SOUTHWEST.
DETAILED SUMMARY
FOR FRIDAY JUNE 22 - TUESDAY JUNE 26: AN UPPER-LEVEL RIDGE OVER THE SOUTHWEST 
IS FORECAST EARLY IN THE PERIOD, BEFORE DEAMPLIFYING AND FLATTENING OVER THE 
WEEKEND. VERY WARM TEMPERATURES ARE EXPECTED OVER THE DESERT SOUTHWEST, 
RESULTANT FROM THIS UPPER-LEVEL PATTERN. CURRENTLY, EXCESSIVE HEAT IS LIKELY 
JUNE 22 TO 24, WHERE TEMPERATURES ARE EXPECTED TO EXCEED 110 DEGREES F. 
TEMPERATURES ARE EXPECTED TO COOL LATER IN THE WEEKEND, AS THE UPPER-LEVEL 
PATTERN BECOMES MORE ZONAL OVER THE U.S. 500 HPA RIDING IS ANTICIPATED TO 
RE-DEVELOP OVER THE SOUTHWEST EARLY NEXT WEEK, INCREASING CHANCES FOR MUCH 
ABOVE NORMAL TEMPERATURES ACROSS PARTS OF THE CENTRAL ROCKIES AND THE CENTRAL 
GREAT BASIN, JUNE 26. MAXIMUM TEMPERATURES ARE EXPECTED TO REACH 12 DEG F ABOVE 
NORMAL, WITH TEMPERATURES REACHING THE 90S (DEG F) AND TRIPLE DIGITS IN 
LOCALIZED AREAS.
AN ACTIVE FRONTAL BOUNDARY IS EXPECTED TO PERSIST THROUGH THE 3-7 DAY PERIOD 
OVER THE EASTERN AND CENTRAL CONUS AND SEVERAL LOW PRESSURE SYSTEMS ARE LIKELY 
TO MOVE ALONG THIS FRONT. THE FRONT IS FORECAST TO PROGRESS SOUTHEASTWARD AS 
THE SURFACE LOW TRACKS NORTHEASTWARD TO THE NORTHEAST OVER THE WEEKEND BRINGING 
HEAVY RAIN TO MANY PARTS OF THE EASTERN HALF OF THE CONUS THROUGHOUT THE 3 TO 7 
DAY PERIOD. LOCALIZED AREAS WITHIN THE PARTS HIGHLIGHTED MAY RECEIVE UP TO ONE 
INCH OR GREATER OF RAINFALL IN A 24-HOUR PERIOD. AS THE COLD FRONT APPROACHES 
THE EAST COAST OF THE CONUS ON JUNE 25, LOCALIZED COASTAL PARTS OF THE 
CAROLINAS MAY RECEIVE HEAVY RAIN, ALTHOUGH THERE ARE SIGNIFICANT MODEL 
DIFFERENCES DELINEATING THIS FEATURE, PRECLUDING AN ADDITIONAL RAIN HAZARD FROM 
BEING INCLUDED AT THIS TIME.
THE 500 HPA HEIGHTS OVER THE SOUTHEAST ARE EXPECTED TO INCREASE TOWARD THE END 
OF THE 3-7 DAY PERIOD. DEW POINTS IN THE LOW TO MID 70'S AND HIGH HUMIDITY 
COINCIDE WITH THE INCREASE IN MID-LEVEL HEIGHTS OVER THE REGION. EXCESSIVE HEAT 
IS FORECAST FOR PARTS OF THE SOUTHEASTERN QUARTER OF THE CONUS, JUNE 22-26; 
HEAT INDEX VALUES ARE LIKELY TO EXCEED 105 DEGREES F.
A SURFACE TROUGH IS PREDICTED TO FORM ACROSS THE GREAT PLAINS THROUGHOUT MOST 
OF THE 3 TO 7 DAY PERIOD. THIS PATTERN MAY SUPPORT INCREASED CHANCES FOR HIGH 
WINDS ACROSS PARTS OF PORTIONS OF THE CENTRAL PLAINS AND THE SOUTHERN PLAINS, 
JUNE 23 TO 26. SOME AREAS MAY EXPERIENCE SUSTAINED WINDS REACHING 30 KNOTS OR 
GREATER.
SURFACE HIGH PRESSURE OFF THE COAST OF NORTHWESTERN CONUS FAVORS AN INCREASED 
LIKELIHOOD FOR HIGH WINDS ACROSS COASTAL PARTS OF NORTHERN CALIFORNIA AND THE 
PACIFIC NORTHWEST, JUNE 23 TO 26. LOCALIZED AREAS MAY EXPERIENCE SUSTAINED WIND 
SPEEDS REACHING 30 KNOTS OR GREATER.
WIDESPREAD MID-LEVEL TROUGHING IS EXPECTED FOR ALASKA THROUGH THE 3 TO 7 DAY 
PERIOD. SEVERAL SURFACE LOW PRESSURE SYSTEMS ARE FORECAST TO MOVE OVER THE 
MAINLAND AND PARTS OF THE SOUTHERN COAST; HOWEVER, ALL IMPACTS FROM THESE 
SYSTEMS ARE CURRENTLY FORECAST TO REMAIN BELOW HAZARDOUS CRITERIA.
FOR WEDNESDAY JUNE 27 - TUESDAY JULY 03: AMPLIFIED MID-LEVEL RIDGING IS 
FORECAST TO BUILD ACROSS MUCH OF THE CONUS AT THE BEGINNING OF WEEK-2 AND 
PERSIST THROUGHOUT MOST OF WEEK-2. A SLIGHT RISK OF MUCH ABOVE NORMAL 
TEMPERATURES HAS BEEN FORECAST FOR PORTIONS OF THE GREAT LAKES, THE NORTHEAST, 
THE UPPER MISSISSIPPI VALLEY, AND THE NORTHERN PLAINS, JUNE 27 TO JULY 3, 
ASSOCIATED WITH THIS RIDGING. THE GEFS PROBABILISTIC TOOL PREDICTS A 20%-30% 
CHANCE OF TEMPERATURES SURPASSING THE 85TH CLIMATOLOGICAL PERCENTILE. AREAS OF 
SLIGHT RISK FOR EXCESSIVE HEAT ARE HIGHLIGHTED ACROSS PARTS OF THE MIDDLE AND 
LOWER MISSISSIPPI VALLEYS, THE CENTRAL AND SOUTHERN PLAINS, AND THE GREAT LAKES 
(HEAT VALUES REACHING 105 DEG F OR GRETAER), JUNE 27 TO 28, AND PARTS OF THE 
SOUTHWEST (HEAT VALUES REACHING 100 DEG F OR GREATER), JUNE 28 TO JULY 1.
A SURFACE LOW IS FORECAST TO MOVE OVER THE CENTRAL PLAINS AND INTO THE 
MISSISSIPPI RIVER VALLEY, ALONG THE FRONTAL BOUNDARY FROM THE PREVIOUS PERIOD. 
CURRENTLY, THE GEFS PROBABILISTIC TOOL IS FORECASTING A 20 TO 40 PERCENT CHANCE 
OF RAINFALL TOTALS ACROSS PARTS OF THE CENTRAL AND SOUTHERN PLAINS, MIDDLE AND 
LOWER MISSISSIPPI VALLEY, AND SOUTHEAST SURPASSING THE 85TH PERCENTILE; 
HOWEVER, THE ECMWF TOOL HAS NO INDICATION OF ABOVE NORMAL PRECIPITATION. DUE TO 
THIS DISPARITY IN THE MODEL GUIDANCE, A RISK FOR HEAVY PRECIPITATION HAS NOT 
BEEN FORECAST AT THIS TIME. WE WILL CONTINUE TO WATCH THE EVOLUTION OF THIS 
SYSTEM IN THE MODELS.
THE MID-LEVEL TROUGHING OVER ALASKA IS EXPECTED TO BE ISOLATED TO MAINLY THE 
SOUTH COAST, ALASKA PENINSULA, AND KODIAK ISLAND, WHILE A RIDGE DEVELOPS OVER 
MAINLAND ALASKA. NO HAZARDS ARE IDENTIFIED FOR ALASKA AT THIS TIME.
THE US DROUGHT MONITOR, VALID ON JUNE 12, INDICATES THAT THE COVERAGE OF SEVERE 
TO EXCEPTIONAL DROUGHT DECREASED SLIGHTLY FROM 17.06 PERCENT TO 16.97 PERCENT. 
EXCEPTIONAL DROUGHT REMAINS ENTRENCHED OVER THE FOUR CORNERS REGION. SOME 
IMPROVEMENT IN CONDITIONS IS SEEN IN THE OKLAHOMA PANHANDLE AND INTO 
SOUTHWESTERN KANSAS.
FORECASTER: MELISSA OU 
$$