895
FXUS21 KWNC 121945
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT JULY 12 2023
SYNOPSIS: MULTIPLE DYNAMICAL MODEL ENSEMBLE MEANS FAVORS MID-LEVEL HIGH
PRESSURE ACROSS THE WESTERN CONTIGUOUS U.S. (CONUS) DURING WEEK-2, WITH HIGH
PRESSURE LINGERING ACROSS THE SOUTHEASTERN CONUS AT THE ONSET OF THE PERIOD.
THIS WESTWARD SHIFTED FEATURE COMPARED TO YESTERDAY TRANSLATES TO A SHIFT IN
THE INCREASED LIKELIHOOD FOR EXCESSIVE HEAT FOR MUCH OF THE WEST WITH LINGERING
POTENTIAL ACROSS THE SOUTHEASTERN CONUS AT THE START OF WEEK-2. POSSIBLE
FLOODING IS ANTICIPATED TO CONTINUE FOR 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 THE SOUTHWEST, SOUTHERN ROCKIES,
AND SOUTHERN PLAINS, THU, JUL 20.
MODERATE RISK OF EXCESSIVE HEAT FOR PORTIONS OF THE FOUR CORNERS, NEVADA, AND
THE SOUTHERN PLAINS, THU-FRI, JUL 20-21.
SLIGHT RISK OF EXCESSIVE HEAT FOR PARTS OF THE GULF COAST AND FLORIDA, THU, JUL
20.
SLIGHT RISK OF EXCESSIVE HEAT FOR MUCH OF THE INTERMOUNTAIN WEST AND SOUTHERN
PLAINS, THU-WED, JUL 20-26.
FLOODING POSSIBLE FOR PORTIONS OF NORTHEASTERN SOUTH DAKOTA.
RAPID ONSET DROUGHT RISK FROM PORTIONS OF EASTERN TEXAS TO CENTRAL LOUISIANA.
DETAILED SUMMARY
FOR SATURDAY JULY 15 - WEDNESDAY JULY 19:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR THURSDAY JULY 20 - WEDNESDAY JULY 26: THE GEFS, ECMWF, AND CMCE ENSEMBLE
MEANS INDICATE MID-LEVEL RIDGING SHIFTED WESTWARD COMPARED TO RECENT DAYS, WITH
RIDGING ANTICIPATED TO LINGER ACROSS THE GULF COAST AND SOUTHERN FLORIDA
PENINSULA AT THE ONSET OF WEEK-2. A SLIGHT RISK OF EXCESSIVE HEAT IS POSTED FOR
DAY 8 (JUL 20), PRIMARILY BASED ON WHERE THE ECMWF CALIBRATED SHOWS AT LEAST A
50% CHANCE OF HEAT INDEX VALUES EXCEEDING THE 90TH PERCENTILE CLIMATOLOGICALLY.
THERE IS MULTI-MODEL DEPICTION OF GREATER POSITIVE MID-LEVEL HEIGHTS ACROSS THE
NORTHWESTERN CONUS COMPARED TO YESTERDAY STARTING ON DAY 9 (JUL 21). THIS
FEATURE TRANSLATES TO TEMPERATURE AND HEAT TOOLS SHOWING INCREASED LIKELIHOOD
FOR EXCESSIVE HEAT ACROSS THE NORTHWEST, LIKELY NOT HAVING A SIGNIFICANT
HUMIDITY COMPONENT. A SLIGHT RISK OF EXCESSIVE HEAT IS HIGHLIGHTED ACROSS MUCH
OF THE INTERMOUNTAIN WEST AND SOUTHERN PLAINS THROUGHOUT WEEK-2, WITH THE RISK
FOR THE NORTHWEST LIKELY STARTING BY DAY 9. THE GEFS, ECMWF, AND CMCE PETS SHOW
AT LEAST A 20% CHANCE OF MAXIMUM TEMPERATURES EXCEEDING THE 85TH PERCENTILE AND
95 DEG F ACROSS MUCH OF THESE AREAS (>100 DEG F ACROSS THE SOUTHERN PORTION).
AN EMBEDDED MODERATE RISK (>40% CHANCE) OF EXCESSIVE HEAT IS DESIGNATED FOR
PORTIONS OF THE FOUR CORNERS, NEVADA, AND THE SOUTHERN PLAINS, JUL 20 TO 21,
WHILE A HIGH RISK (>60% CHANCE) IS SPECIFIED FOR PORTIONS OF THE SOUTHWEST,
SOUTHERN ROCKIES, AND SOUTHERN PLAINS JUL 20. THE NATIONAL BLEND OF MODELS
(NBM) INDICATES THE POTENTIAL FOR NEAR RECORD TEMPERATURES (MAXIMUM AND
MINIMUM) MOSTLY FOR NEW MEXICO, TEXAS, THE LOWER MISSISSIPPI VALLEY, AND
FLORIDA. ANTICIPATED HOT, DRY CONDITIONS ACROSS THE SOUTHWESTERN CONUS AND
SOUTHERN PLAINS MAY SUPPORT ENHANCED WILDFIRE RISK, ESPECIALLY WHERE THE
NATIONAL INTERAGENCY FIRE CENTER (NIFC) SHOWS A MODERATE RISK OF SIGNIFICANT
FIRE POTENTIAL AND HIGH RISK TRIGGERS BY THE END OF WEEK-1.
THE ELEVATED RISK OF DROUGHT DEVELOPMENT IS CONTINUED FOR PARTS OF EAST TEXAS
AND LOUISIANA, DUE TO RECENT (IN SOME CASES RECORD) HEAT IN RECENT WEEKS AND
EXPECTED EXCESSIVE HEAT FORECAST TO PERSIST THROUGH MUCH OF THE WEEK-2 PERIOD.
IN ADDITION, INCREASED CHANCES OF BELOW-NORMAL PRECIPITATION IS FORECAST FOR
THESE SAME AREAS FOR WEEK-2. AS SUCH, A RISK OF RAPID ONSET DROUGHT (ROD) IS
MAINTAINED FROM MUCH OF EASTERN TEXAS TO CENTRAL LOUISIANA.
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. THE
NATIONAL WEATHER SERVICE (NWS) 5-DAY SIGNIFICANT FLOOD OUTLOOK POTENTIAL
INDICATES FLOODING OVER VERMONT AND LIKELY FLOODING ACROSS PARTS OF
MASSACHUSETTS AND CONNECTICUT, WHICH IS LIKELY TO CONTINUE THROUGH WEEK-1 AND
POTENTIALLY INTO AT LEAST PART OF WEEK-2. THE WEATHER PREDICTION CENTER'S (WPC)
7-DAY WEEK-1 PRECIPITATION OUTLOOK INDICATES ANTICIPATED HEAVY RAINFALL FOR
THESE AREAS AND THE CLIMATE PREDICTION CENTER'S (CPC) WEEK-2 OUTLOOK FAVORS LOW
PROBABILITIES OF ABOVE NORMAL PRECIPITATION. DUE TO UNCERTAINTY REGARDING THIS
FLOODING POTENTIAL A RISK AREA FOR WEEK-2 IS NOT DESIGNATED FOR NEW ENGLAND AT
THIS TIME BUT WILL BE MONITORED IN THE UPCOMING DAYS.
THERE IS MULTI-MODEL DEPICTION OF INGREDIENTS THAT ARE CONDUCIVE FOR THE
SOUTHWEST MONSOON ACROSS PORTIONS OF THE FOUR CORNERS INCLUDING FAVORABLE
POSITIONING OF THE MID-LEVEL RIDGE OVER THE FOUR CORNERS AND ENHANCED MOISTURE.
SIMILAR TO YESTERDAY THE ECMWF AND CANADIAN PETS SHOW AT LEAST A 20% CHANCE OF
3-DAY RAINFALL IN THIS REGION EXCEEDING THE 85TH PERCENTILE CLIMATOLOGICALLY,
WITH THE GEFS NOT INDICATING THESE SIGNALS AND LIMITING ENHANCED RAINFALL
FURTHER SOUTH OVER MEXICO. THERE IS TOO MUCH MODEL UNCERTAINTY REGARDING THE
SPECIFICS OF WHERE THE HEAVIEST PRECIPITATION IS ANTICIPATED BUT WILL BE
MONITORED IN THE UPCOMING DAYS.
TROPICAL STORM CALVIN IS CURRENTLY LOCATED SOUTHWEST OF MEXICO AND HAS THE
POSSIBILITY OF TRACKING WESTWARD INTO THE CENTRAL PACIFIC AND APPROACHING THE
HAWAIIAN ISLANDS BY THE START OF WEEK-2. THERE IS A POTENTIAL FOR THIS
DISTURBANCE TO BRING ENHANCED PRECIPITATION AND HIGH WINDS TO SOME AREAS OF THE
ISLANDS, ALTHOUGH THERE IS LESS SUPPORT IN THE PETS REGARDING THE POTENTIAL OF
3-DAY ACCUMULATED PRECIPITATION EXCEEDING THE 85TH PERCENTILE NEAR OR OVER THE
STATE.
NO HAZARDS ARE POSTED FOR ALASKA. NEAR TO ABOVE NORMAL TEMPERATURES AND
PRECIPITATION ARE FAVORED FOR THE WEEK-2 PERIOD FOR THE STATE.
FORECASTER: MELISSA OU
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