Prognostic Meteorological Discussion
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2
000
FXUS21 KWNC 291847
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT JUNE 29 2015

SYNOPSIS: A FRONTAL BOUNDARY IS EXPECTED TO BE THE FOCAL POINT FOR UNSETTLED
WEATHER ACROSS THE CENTRAL AND EASTERN U.S. DURING THE FIRST SEVERAL DAYS OF
THE PERIOD. UPPER-LEVEL HIGH PRESSURE IS FORECAST TO DOMINATE OVER THE
NORTHWESTERN U.S. EARLY IN THE PERIOD, EXPANDING NORTHWESTWARD TOWARD MAINLAND
ALASKA LATER IN THE PERIOD. PERIODIC UNSETTLED WEATHER IS EXPECTED OVER PARTS
OF THE SOUTHWEST EXTENDING INTO THE CENTRAL ROCKIES, INCREASING IN FREQUENCY
HEADING TOWARD THE MIDDLE OF THE PERIOD.

HAZARDS

MUCH ABOVE-NORMAL TEMPERATURES FOR PARTS OF THE NORTHWEST, INCLUDING NORTHERN
PARTS OF CALIFORNIA AND NEVADA, THU-MON, JUL 2-6.

HEAVY RAIN FOR PARTS OF THE MID-MISSISSIPPI VALLEY, OHIO AND TENNESSEE VALLEYS,
AND THE MID-ATLANTIC, THU-FRI, JUL 2-3.

ENHANCED WILDFIRE RISK FOR PARTS OF MAINLAND ALASKA, THU-MON, JUL 2-13.

EXCESSIVE HEAT FOR PARTS OF THE SOUTHEAST COAST, SAT-MON, JUL 4-6.

SLIGHT RISK FOR MUCH ABOVE-NORMAL TEMPERATURES FOR THE PACIFIC NORTHWEST AND
PARTS OF THE NORTHERN ROCKIES, TUE-MON, JUL 7-13.

MODERATE RISK FOR MUCH ABOVE-NORMAL TEMPERATURES FOR PARTS OF THE INTERIOR
NORTHWEST, TUE-THU, JUL 7-9.

ONGOING, LIKELY, OR POSSIBLE FLOODING ACROSS PARTS OF THE MIDWEST,
MID-MISSISSIPPI VALLEY, AND THE SOUTHERN PLAINS.

SEVERE DROUGHT FOR PARTS OF THE WESTERN THIRD OF THE CONUS, AND SOUTHERN
FLORIDA.

DETAILED SUMMARY

FOR THURSDAY JULY 02 - MONDAY JULY 06: AT THE BEGINNING OF THIS PERIOD, AN
AMPLIFIED UPPER-LEVEL RIDGE IS FORECAST OVER THE WESTERN THIRD OF THE CONUS
WITH A TROUGH DOWNSTREAM CENTERED NEAR THE GREAT LAKES. THIS PATTERN FAVORS
MUCH ABOVE-NORMAL TEMPERATURES ACROSS PARTS OF THE NORTHWEST, INCLUDING
NORTHERN CALIFORNIA FOR THIS ENTIRE PERIOD. SOME OF THESE AREAS MAY EXPERIENCE
TEMPERATURE ANOMALIES OF 24 DEGREES F OR GREATER ABOVE CLIMATOLOGY, WITH
TEMPERATURES REACHING THE TRIPLE DIGITS. BECAUSE OF THE LONG DURATION OF THESE
ANOMALOUSLY WARM TEMPERATURES, PEOPLE OUTDOORS OR WITHOUT AIR CONDITIONING
SHOULD TAKE PRECAUTIONS.



OVER THE SOUTHWESTERN CONUS, A COMBINATION OF REMNANT COLD FRONTS AND INCREASED
MONSOONAL FLOW OUT OF THE SOUTH IS LIKELY TO LEAD TO PERIODS OF LOCALLY HEAVY
RAIN, SPREADING NORTHWARD LATER IN THE PERIOD. WHILE THERE IS NOT SUFFICIENT
CONFIDENCE TO WARRANT A SPECIFIC HAZARD DEPICTION, UPDATED LOCAL FORECASTS
SHOULD BE MONITORED FOR THE INCREASING POTENTIAL OF LOCALIZED HEAVY RAIN AND
FLOODING OVER THE NEXT ONE TO TWO WEEKS.



OVER THE CENTRAL AND EASTERN CONUS, A FRONTAL BOUNDARY IS EXPECTED TO FOCUS
LOCALLY HEAVY RAINFALL EXTENDING FROM PARTS OF EASTERN OKLAHOMA EASTWARD
THROUGH THE TENNESSEE VALLY INTO THE MID-ATLANTIC. THE THREAT FOR HEAVY RAIN IS
GREATEST ON THURSDAY AND FRIDAY WHERE THE HAZARD IS DEPICTED, WITH INCREASED
UNCERTAINTY BEYOND THAT, AS THE FRONTAL ZONE IS FORECAST TO SLOWLY MOVE NORTH.
THIS INCREASES ODDS FOR LOCALLY HEAVY RAIN OVER PARTS OF THE MIDWEST AND GREAT
LAKES BY THE END OF THE PERIOD.



TO THE SOUTHEAST OF THE FRONT, HOT AND HUMID CONDITIONS ARE LIKELY, ESPECIALLY
DURING THE MIDDLE AND LATTER PARTS OF THE PERIOD WHEN THE UPPER-LEVEL TROUGH
WEAKENS AND THE FRONTAL ZONE RETREATS NORTHWARD. THE EXCESSIVE HEAT HAZARD IS
DEPICTED AS SUCH DUE TO THE GREATEST LIKELIHOOD OF MAXIMUM HEAT INDEX VALUES
EXCEEDING 105F FOR MULTIPLE DAYS.



WARM AND DRY CONDITIONS ARE ANTICIPATED ACROSS MUCH OF MAINLAND ALASKA,
INCREASING CHANCES FOR WILDFIRE RISK ACROSS PARTS OF THIS AREA DURING THIS
PERIOD AS WELL AS WEEK-2. AN UPPER-LOW IS FORECAST TO IMPACT THE ALASKAN
PANHANDLE AT THE BEGINNING OF THE PERIOD, AND SOME ACTIVE WEATHER IS POSSIBLE
OVER THE ALEUTIANS LATE IN THE PERIOD, THOUGH NEITHER CURRENTLY WARRANTS ANY
ADDITIONAL HAZARDS BEING SPECIFIED.

FOR TUESDAY JULY 07 - MONDAY JULY 13: DURING WEEK-2 THE FORECAST CIRCULATION IS
DOMINATED BY POSITIVE 500-HPA HEIGHT ANOMALIES CENTERED OVER THE GULF OF ALASKA
WITH DOWNSTREAM TROUGHING CENTERED OVER THE GREAT LAKES. THE ENSEMBLE MEANS
INDICATE THAT THE RIDGING OVER THE NORTHEASTERN PACIFIC AND ALASKA IS PART OF A
REX BLOCK AT LEAST EARLY IN THE PERIOD, WITH AN ANOMALOUS TROUGH FORECAST TO
THE SOUTH, JUST OFF THE COAST OF CALIFORNIA. SUCH A PATTERN FAVORS INCREASED
RAINFALL ASSOCIATED WITH MULTIPLE COLD FRONTS EXTENDING FROM THE CENTRAL PLAINS
TO THE NORTHEAST. A COMBINATION OF STALLED COLD FRONTS AND ANOMALOUS SOUTHERLY
FLOW WILL LEAD TO INCREASED CHANCES OF LOCALLY HEAVY RAIN AND FLOODING FOR
PARTS OF THE SOUTHWEST AND GREAT BASIN.



ANOMALOUS RIDGING OVER ALASKA INCREASES THE CHANCES OF DANGEROUS FIRE WEATHER,
AND SO THE HAZARD DEPICTED IN THE 3-7 DAY PERIOD CONTINUES INTO WEEK-2.



WITH PERSISTENT RIDGING FORECAST JUST OFF THE NORTHWEST COAST, A SLIGHT RISK OF
MUCH ABOVE-NORMAL TEMPERATURES CONTINUES THROUGH WEEK-2. WITHIN THAT REGION THE
THREAT OF MUCH ABOVE-NORMAL TEMPERATURES IS MODERATE FOR THE FIRST THREE DAYS
OF THE PERIOD OVER THE INTERIOR PACIFIC NORTHWEST. HOWEVER, THE FORECAST
PATTERN LOOKS POTENTIALLY LESS AMPLIFIED THAN THAT FOR THE 3-7 DAY PERIOD, AS
THE HEIGHT PATTERN EXHIBITS SOME RETROGRESSION AND UNDERCUTTING IS POSSIBLE
LATE IN WEEK-2.



THE MOST RECENT U.S. DROUGHT MONITOR, VALID ON JUNE 23, INDICATES A SMALL
INCREASE (FROM 13.62 TO 14.31) IN THE PERCENTAGE OF THE CONUS IN SEVERE TO
EXCEPTIONAL DROUGHT (D2-D4).

FORECASTER: STEPHEN BAXTER

$$



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