510
FXUS21 KWNC 061918
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT JULY 06 2023
SYNOPSIS: MID-LEVEL HIGH PRESSURE PERSISTS OVER THE SOUTHERN AND SOUTHWESTERN
CONTIGUOUS U.S. (CONUS) DURING WEEK-2, LEADING TO THE POTENTIAL FOR EXCESSIVE
HEAT FOR MUCH OF THE SOUTHWESTERN CONUS AND EXTENDING INTO THE SOUTHERN PLAINS.
THERE IS AN INCREASED POTENTIAL FOR HEAVY PRECIPITATION EARLY IN THE PERIOD
ACROSS PORTIONS OF THE CENTRAL PLAINS AND EXTENDING EASTWARD INTO THE MIDDLE
MISSISSIPPI, OHIO, AND TENNESSEE VALLEYS, ALONG A MEAN FRONTAL BOUNDARY.
SNOWMELT SEASON CONTINUES FOR PORTIONS OF THE WEST AFTER EXCEPTIONAL WINTER
ACCUMULATIONS, LEADING TO THE CONTINUED POTENTIAL FOR FLOODING ACROSS PARTS OF
THE CENTRAL SIERRAS IN EASTERN CALIFORNIA, EXTENDING INTO WESTERN NEVADA.
FLOODING IS ALSO POSSIBLE ALONG THE JAMES RIVER IN NORTHEASTERN SOUTH DAKOTA,
WHERE RIVER LEVELS ARE EXPECTED TO REMAIN HIGH LEADING UP TO AND DURING WEEK-2.
CONVERSELY, ABNORMALLY DRY CONDITIONS OVER PORTIONS OF EASTERN TEXAS AND
CENTRAL LOUISIANA INCREASES THE RISK OF RAPID ONSET DROUGHT (ROD).
HAZARDS
HIGH RISK OF EXCESSIVE HEAT FOR PORTIONS OF NEW MEXICO, ARIZONA AND WEST TEXAS,
FRI-MON, JUL 14-17.
MODERATE RISK OF EXCESSIVE HEAT FOR PORTIONS OF THE FOUR CORNERS AND SOUTHERN
PLAINS, FRI-TUE, JUL 14-18.
SLIGHT RISK OF EXCESSIVE HEAT FOR MUCH OF THE SOUTHERN CONUS, FRI-THU, JUL
14-20.
SLIGHT RISK OF HEAVY PRECIPITATION FOR PORTIONS OF THE CENTRAL AND SOUTHERN
PLAINS AND MIDDLE MISSISSIPPI, OHIO, AND TENNESSEE VALLEYS, FRI-SUN, JUL 14-16.
SLIGHT RISK OF PERIODS OF HIGH WINDS FOR PORTIONS OF THE SOUTHERN PLAINS AND
FOUR CORNERS, FRI-THU, JUL 14-20.
FLOODING POSSIBLE FOR PORTIONS OF EASTERN CALIFORNIA, WESTERN NEVADA, AND
NORTHEASTERN SOUTH DAKOTA.
RAPID ONSET DROUGHT RISK ACROSS PORTIONS OF EASTERN TEXAS AND CENTRAL LOUISIANA.
DETAILED SUMMARY
FOR SUNDAY JULY 09 - THURSDAY JULY 13:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR FRIDAY JULY 14 - THURSDAY JULY 20: ENSEMBLE MODEL SOLUTIONS FROM THE GEFS,
ECMWF, AND CMCE ALL DEPICT POSITIVE 500-HPA HEIGHT ANOMALIES CENTERED OVER THE
DESERT SOUTHWEST AND FOUR CORNERS IN EXCESS OF 595 DM PERSISTING THROUGHOUT THE
WEEK-2 PERIOD. THERE ARE SIGNIFICANT DIFFERENCES IN THE LOCATION OF THE MEAN
MID-LEVEL RIDGE AXIS AND ITS EVOLUTION DURING WEEK-2. IN SPITE OF THESE
DIFFERENCES, EXCESSIVE HEAT POTENTIAL REMAINS ELEVATED ACROSS MUCH OF THE
SOUTHWESTERN CONUS, EXTENDING INTO THE SOUTHERN PLAINS, ESPECIALLY EARLY IN THE
PERIOD. ECMWF AND GEFS PROBABILISTIC EXTREMES TOOLS (PETS) INDICATE AT LEAST A
60% CHANCE OF MAXIMUM TEMPERATURES EXCEEDING THE 85TH PERCENTILE OF THE
HISTORICAL DISTRIBUTION ACROSS MUCH OF NEW MEXICO, PORTIONS OF ARIZONA, AND
WEST TEXAS, WARRANTING A HIGH RISK OF EXCESSIVE HEAT FOR THESE REGIONS JUL
14-17. THE GEFS, ECMWF, AND CMCE PETS INDICATE AT LEAST A 40% CHANCE OF MAXIMUM
TEMPERATURES EXCEEDING THE 85TH CLIMATOLOGICAL PERCENTILE AND AT LEAST 100 DEG
F FOR MUCH OF THE SOUTHERN PLAINS, EXTENDING ACROSS PARTS OF THE FOUR CORNERS
REGION JUL 14-18, WARRANTING A MODERATE RISK OF EXCESSIVE HEAT FOR THE FOUR
CORNERS AND MUCH OF THE SOUTHERN HIGH PLAINS. ADDITIONALLY, THE PETS INDICATE
AT LEAST A 20% PROBABILITY OF EXCEEDING THE 85TH PERCENTILE FOR MUCH OF THE
SOUTHERN AND SOUTHWESTERN CONUS FOR THE ENTIRE WEEK-2 PERIOD, THUS A SLIGHT
RISK FOR EXCESSIVE HEAT IS POSTED ACROSS MUCH OF THE SOUTHERN TIER FROM THE
PACIFIC TO ATLANTIC COASTS. HOWEVER, IT SHOULD BE NOTED THAT THE MODELS ARE A
BIT CONFLICTED WITH RESPECT TO THE STRENGTH OF THE HEAT SIGNALS IN THE
SOUTHEAST, PARTICULARLY FROM THE CENTRAL GULF COAST TO THE ATLANTIC COASTAL
PLAIN. HEAT POTENTIAL IS INCREASED AT THE START AND LATTER PORTIONS OF WEEK-2,
WITH A BRIEF REPRIEVE DURING THE MIDDLE OF THE PERIOD. AS SUCH, CONFIDENCE IN
THE SLIGHT RISK OF EXCESSIVE HEAT IN THE SOUTHEAST IS SLIGHTLY LOWER THAN FOR
AREAS FARTHER WEST.
AT THE BEGINNING OF WEEK-2 MULTIPLE MODEL SOLUTIONS CONTINUE TO DEPICT
MID-LEVEL TROUGHING OVER THE GREAT LAKES. A MEAN FRONTAL BOUNDARY IS FORECAST
BETWEEN THIS TROUGH AND THE MID-LEVEL RIDGE OVER THE SOUTHWESTERN AND SOUTHERN
CONUS. ALONG THIS MEAN FRONTAL BOUNDARY, THERE IS AN INCREASED POTENTIAL FOR
HEAVY PRECIPITATION, WHICH COULD BE IN THE FORM OF CLUSTERS OF THUNDERSTORMS
(KNOWN AS MESOSCALE CONVECTIVE SYSTEMS, OR MCSS). THEREFORE, A SLIGHT RISK OF
HEAVY PRECIPITATION IS POSTED ACROSS PARTS OF THE CENTRAL AND SOUTHERN PLAINS,
EXTENDING INTO THE MIDDLE MISSISSIPPI, OHIO, AND TENNESSEE VALLEYS JUL 14-16.
THE PETS SUPPORT THIS POTENTIAL, WITH THE ECMWF AND CMCE BOTH INDICATING AT
LEAST A 20% CHANCE OF PRECIPITATION TOTALS EXCEEDING THE 85 CLIMATOLOGICAL
PERCENTILE AND 1 INCH DURING THE FIRST 3 DAYS OF WEEK-2. THE TROUGHING OVER THE
GREAT LAKES IS FORECAST TO DEAMPLIFY TOWARD THE MIDDLE AND LATTER PORTIONS OF
WEEK-2, WHICH WILL ACT TO DIMINISH THE THREAT OF HEAVY PRECIPITATION IN THE
CENTRAL AND EASTERN CONUS.
A SLIGHT RISK OF PERIODS OF HIGH WINDS IS POSTED FOR PARTS OF THE SOUTHERN
PLAINS AND FOUR CORNERS REGION, WHERE GEFS AND ECMWF PETS INDICATE AT LEAST A
20% CHANCE OF WIND SPEEDS EXCEEDING THE 85TH PERCENTILE OF THE HISTORICAL
DISTRIBUTION FOR THE ENTIRE WEEK-2 PERIOD. FIRE RISK REMAINS MODERATE TO VERY
HIGH ACROSS LARGE PORTIONS OF THE SOUTHWESTERN CONUS, WITH THE RISK OF HIGH
WINDS AND EXCESSIVE HEAT ACTING ONLY TO EXACERBATE THAT RISK.
THE RISK OF DROUGHT DEVELOPMENT IS FORECAST TO INCREASE ACROSS PARTS OF EAST
TEXAS AND PARTS OF LOUISIANA, DUE TO RECENT (IN SOME CASES RECORD) HEAT IN
RECENT WEEKS THAT IS FORECAST TO PERSIST THROUGH MUCH OF THE WEEK-2 PERIOD. IN
ADDITION, INCREASED CHANCES OF BELOW-NORMAL PRECIPITATION IS FORECAST FOR THESE
SAME AREAS. AS SUCH, A RISK OF RAPID ONSET DROUGHT (ROD) IS POSTED FOR MUCH OF
EASTERN TEXAS AND CENTRAL LOUISIANA.
SNOWMELT SEASON CONTINUES ACROSS THE WESTERN CONUS AFTER ACCUMULATING A VERY
LARGE AND (IN SOME CASES RECORD-BREAKING) SNOWPACK. THIS HAS RESULTED IN RIVER
FLOODING, ESPECIALLY ACROSS HIGHER ELEVATIONS OF THE CENTRAL SIERRAS IN EASTERN
CALIFORNIA, EXTENDING INTO PARTS OF WESTERN NEVADA. THEREFORE, FLOODING REMAINS
POSSIBLE IN THESE AREAS. ADDITIONALLY, RECENT HEAVY RAINFALL HAS RESULTED IN A
CONTINUATION OF ELEVATED STREAM FLOWS ALONG THE JAMES RIVER IN NORTHEASTERN
SOUTH DAKOTA, LEADING TO AN INCREASED RISK OF FLOODING DURING WEEK-2 FOR SOME
LOCATIONS ALONG THAT BASIN.
NO HAZARDS ARE POSTED FOR ALASKA. HOWEVER, PARTS OF THE YUKON FLATS CONTINUE TO
DRY OUT, WITH SOME LOCATIONS ALREADY FALLING INTO ABNORMAL DRYNESS AND MODERATE
DROUGHT (ACCORDING TO THE U.S. DROUGHT MONITOR). THE ECMWF PET ALSO INDICATES
AT LEAST A 20% CHANCE OF EXCEEDING THE 85TH CLIMATOLOGICAL PERCENTILE AND 80
DEG F ACROSS THESE SAME AREAS DURING WEEK-2. THE ONGOING DRYNESS, COUPLED WITH
THE POTENTIAL FOR ABOVE-NORMAL TEMPERATURES, WILL ACT TO ELEVATE FIRE CONCERNS
FOR SEVERAL OF THESE LOCATIONS.
FORECASTER: ADAM HARTMAN
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