Prognostic Meteorological Discussion
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4
000
FXUS21 KWNC 271825
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT JUNE 27 2017

SYNOPSIS: A COUPLE OF LOW PRESSURE SYSTEMS ARE EXPECTED TO PROGRESS EAST ALONG
A NEARLY STATIONARY FRONT EXTENDING ACROSS THE GREAT LAKES, MIDWEST, AND
CENTRAL GREAT PLAINS DURING THE NEXT WEEK. AN AREA OF UPPER-LEVEL HIGH PRESSURE
IS FORECAST TO BUILD OVER THE HIGH PLAINS BY THE 4TH OF JULY AND THEN EXPAND
EAST DURING WEEK-2. HURRICANE DORA IN THE EAST PACIFIC IS FORECAST TO WEAKEN AS
IT TRACKS NEAR THE 20TH PARALLEL PRIOR TO THIS PERIOD. AN AREA OF UPPER-LEVEL
HIGH PRESSURE IS EXPECTED TO PERSIST OVER EASTERN MAINLAND ALASKA THROUGH THE
FIRST WEEK OF JULY.

HAZARDS

HEAVY RAIN EXTENDING FROM NEW ENGLAND AND THE GREAT LAKES SOUTHWEST TO THE
SOUTHERN GREAT PLAINS, FRI-SAT, JUN 30-JUL 1.

HEAVY RAIN FOR PARTS OF THE NORTHERN AND CENTRAL GREAT PLAINS ALONG WITH THE
MIDWEST, SUN-MON, JUL 2-3.

HEAVY RAIN FOR PARTS OF KODIAK ISLAND, THE KENAI PENINSULA, AND THE PRINCE
WILLIAM SOUND, FRI-SAT, JUN 30-JUL 1.

MUCH ABOVE-NORMAL TEMPERATURES FOR PARTS OF THE NORTHERN AND CENTRAL GREAT
PLAINS, MON-TUE, JUL 3-4.

MUCH ABOVE-NORMAL TEMPERATURES FOR THE UPPER YUKON VALLEY OF ALASKA, MON-TUE,
JUL 3-4.

EXCESSIVE HEAT FOR PARTS OF THE CENTRAL U.S., THU-FRI, JUL 6-7.

SLIGHT RISK OF MUCH ABOVE-NORMAL TEMPERATURES FOR PARTS OF THE CENTRAL AND
EASTERN U.S., WED-MON, JUL 5-10.

SLIGHT RISK OF MUCH ABOVE-NORMAL TEMPERATURES FOR PARTS OF EASTERN MAINLAND
ALASKA, WED-SUN, JUL 5-9.

FLOODING OCCURRING, IMMINENT, OR LIKELY FOR PARTS OF WYOMING, THE MIDWEST, AND
SOUTHEAST.

SEVERE DROUGHT ACROSS CALIFORNIA, HAWAII, THE NORTHERN PLAINS, AND THE
SOUTHWEST.

DETAILED SUMMARY

FOR FRIDAY JUNE 30 - TUESDAY JULY 04: HEAVY RAINFALL AND FLASH FLOODING REMAIN
THE PRIMARY CONCERNS ACROSS THE CENTRAL U.S. THIS WEEK, FOLLOWED BY AN
INCREASING RISK OF A HEAT WAVE DURING EARLY JULY. MODEL GUIDANCE REMAINS
CONSISTENT THAT ABUNDANT LOW-LEVEL MOISTURE WILL DEVELOP ACROSS MUCH OF THE
EASTERN AND CENTRAL U.S. WITH THE DETERMINISTIC 6Z GFS MODEL INDICATING
PRECIPITABLE WATER VALUES INCREASING TO MORE THAN 1.75 INCHES, FOCUSED ALONG A
FRONT. HEAVY RAINFALL (1 TO 3 INCHES, LOCALLY MORE) IS LIKELY ALONG THIS FRONT,
EXTENDING FROM NEW ENGLAND AND THE GREAT LAKES SOUTHWEST TO THE SOUTHERN GREAT
PLAINS ON JUNE 30 AND JULY 1. THE MOST LIKELY AREA FOR HEAVY RAIN IS THEN
EXPECTED TO SHIFT BACK TO THE NORTH ACROSS THE NORTHERN/CENTRAL GREAT PLAINS
AND MIDWEST ON JULY 2 AND 3. THE DEPICTED HEAVY RAIN HAZARDS ARE BASED ON THE
PRECIPITATION FORECASTS FROM THE 6Z GFS AND 0Z ECMWF ENSEMBLE MEANS. GIVEN THE
HIGH MOISTURE CONTENT OF THE ATMOSPHERE, THUNDERSTORMS THROUGHOUT THE CENTRAL
AND EASTERN U.S. WILL BE CAPABLE OF TRIGGERING FLASH FLOODING THIS WEEK. SEVERE
WEATHER, PRIMARILY DAMAGING WIND AND LARGE HAIL, COULD ALSO OCCUR IN THE
STRONGEST THUNDERSTORMS, BUT LOW PREDICTABILITY PRECLUDES A DESIGNATION OF A
SPECIFIC SEVERE WEATHER HAZARD AT THIS TIME.



AN UPPER-LEVEL RIDGE IS EXPECTED TO STRENGTHEN OVER THE HIGH PLAINS BY EARLY
NEXT WEEK AND BEGIN TO EXPAND EAST ACROSS THE CENTRAL U.S. THEREFORE, MUCH
ABOVE-NORMAL TEMPERATURES (10 DEGREES F OR MORE) ARE FORECAST TO AFFECT THE
NORTHERN AND CENTRAL PLAINS ON JULY 3 AND 4. MAXIMUM TEMPERATURES ARE EXPECTED
TO WARM WELL INTO THE 90S TO NEAR 100 DEGREES F BY JULY 4 ACROSS THIS REGION.
THIS HEAT IS LIKELY TO WORSEN ONGOING DROUGHT CONDITIONS ACROSS EASTERN MONTANA
AND THE DAKOTAS.



ON JUNE 30 AND JULY 1, A LOW PRESSURE SYSTEM WITH ONSHORE FLOW IS EXPECTED TO
BRING HEAVY RAINFALL (LOCALLY MORE THAN 1.5 INCH PER 24 HOURS) ACROSS KODIAK
ISLAND, THE SOUTHEAST KENAI PENINSULA, AND THE PRINCE WILLIAM SOUND. STRONG
RIDGING ALOFT IS EXPECTED TO RESULT IN MUCH ABOVE-NORMAL TEMPERATURES ACROSS
THE YUKON RIVER VALLEY WHERE MAXIMUM TEMPERATURES ABOVE 85 DEGREES F ARE
FORECAST ON JULY 3 AND 4.

FOR WEDNESDAY JULY 05 - TUESDAY JULY 11: THE 6Z GFS AND 0Z ECMWF ENSEMBLE MEANS
AGREE WITH AN AMPLIFIED RIDGE CENTERED OVER THE GREAT PLAINS DURING WEEK-2.
THIS ANOMALOUS RIDGING SUPPORTS A SLIGHT RISK OF MUCH ABOVE-NORMAL TEMPERATURES
FOR PARTS OF THE CENTRAL AND EASTERN U.S. THROUGH AT LEAST JULY 10. THE
OUTLINED SLIGHT RISK AREA IS GENERALLY CONSISTENT WITH THE GEFS REFORECAST TOOL
WHICH FEATURES A BROAD AREA WHERE MAXIMUM TEMPERATURES HAVE A 20 TO 30 PERCENT
CHANCE OF EXCEEDING THE 85TH PERCENTILE COMPARED TO CLIMATOLOGY. ALTHOUGH ONLY
A SLIGHT RISK FOR MUCH ABOVE-NORMAL TEMPERATURES IS POSTED, HEAT INDEX VALUES
MAY EXCEED 105 DEGREES F IN THE MORE HUMID AREAS OF THE CENTRAL AND EASTERN
U.S. BASED ON 850-HPA TEMPERATURES PREDICTED BY THE DETERMINISTIC GFS MODEL,
THE GEFS CALIBRATED HEAT INDEX FORECAST, AND CLIMATOLOGY, AN EXCESSIVE HEAT
HAZARD IS POSTED FOR PARTS OF THE CENTRAL U.S. ON JULY 6 AND 7.



A SLIGHT RISK OF MUCH ABOVE-NORMAL TEMPERATURES IS ALSO POSTED FOR PARTS OF
EASTERN MAINLAND ALASKA THROUGH JULY 9 DUE TO PERSISTENT RIDGING ALOFT. THE
DETERMINISTIC GFS MODEL REMAINS CONSISTENT WITH MAXIMUM TEMPERATURES WARMING TO
NEAR 90 DEGREES F ACROSS THE UPPER YUKON VALLEY EARLY IN WEEK-2.



AN UPPER-LEVEL RIDGE IS FORECAST TO SHIFT SLIGHTLY NORTH TO THE FOUR CORNERS
REGION WHICH WOULD LEAD TO INCREASED MOISTURE ACROSS THE DESERT SOUTHWEST. THIS
INCREASING MOISTURE IS EXPECTED TO RESULT IN MORE CONVECTION AND A HIGHER RISK
OF FLASH FLOODING ACROSS ARIZONA AND NEW MEXICO DURING WEEK-2.



THE U.S. DROUGHT MONITOR VALID ON JUNE 20 SHOWS D2-D4 DROUGHT COVERAGE OVER THE
CONUS NOW AT 2.13%, A SLIGHT INCREASE FROM 1.57% ONE WEEK AGO. THIS INCREASE IS
TIED TO THE EMERGENCE OF SEVERE DROUGHT IN THE NORTHERN PLAINS.

FORECASTER: BRAD PUGH

$$



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.