Prognostic Meteorological Discussion
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FXUS21 KWNC 261902
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT JULY 26 2016

SYNOPSIS: AT THE BEGINNING OF WEEK-1 A SURFACE LOW PRESSURE CENTER IS EXPECTED
TO BE NEAR CHICAGO WITH AN ASSOCIATED STATIONARY FRONT EXTENDING EASTWARD
ACROSS THE OHIO VALLEY THROUGH THE MID-ATLANTIC, AND A TRAILING COLD FRONT
THROUGH THE CENTRAL PLAINS.  EXPECTATIONS ARE FOR THE COLD FRONT TO SLOWLY PUSH
SOUTH AND EAST OVER THE COURSE OF THE WEEK.  ACROSS THE WESTERN CONUS,
MID-LEVEL HIGH PRESSURE IS FORECAST EARLY IN WEEK-1 THAT IS ANTICIPATED TO
WEAKEN THROUGHOUT THE FORECAST PERIOD.  WEEK-2 FOR THE CONUS IS FORECAST TO BE
DOMINATED BY MID-LEVEL HIGH PRESSURE ACROSS THE CENTRAL PORTION OF THE COUNTRY.
 A COLD FRONT IS EXPECTED TO IMPACT WESTERN AND CENTRAL ALASKA DURING WEEK-1
BEFORE AN ANTICIPATED TRANSITION TO MID-LEVEL HIGH PRESSURE FOR THE FOLLOWING
WEEK.

HAZARDS

HEAVY RAIN ACROSS PORTIONS OF THE CENTRAL APPALACHIANS AND MID-ATLANTIC,
FRI-SAT, JUL 29-JUL 30.

MUCH ABOVE NORMAL TEMPERATURES ACROSS PORTIONS OF THE CENTRAL GREAT BASIN, THE
NORTHERN ROCKIES, CALIFORNIA, THE NORTHERN GREAT BASIN, THE PACIFIC NORTHWEST,
AND THE SOUTHWEST, FRI-SAT, JUL 29-JUL 30.

HEAVY RAIN ACROSS PORTIONS OF WESTERN AND INTERIOR ALASKA, FRI-SAT, JUL 29-JUL
30.

SLIGHT RISK OF MUCH ABOVE-NORMAL TEMPERATURES FOR PORTIONS OF THE CENTRAL
PLAINS, THE NORTHEAST, THE CENTRAL APPALACHIANS, THE NORTHERN PLAINS, THE
MIDDLE MISSISSIPPI VALLEY, THE MID-ATLANTIC, THE UPPER MISSISSIPPI VALLEY, THE
GREAT LAKES, AND THE OHIO VALLEY, WED-FRI, AUG 3-AUG 5.

MODERATE RISK OF MUCH ABOVE-NORMAL TEMPERATURES FOR PORTIONS OF THE NORTHEAST
AND THE GREAT LAKES, WED-THU, AUG 3-AUG 4.

SLIGHT RISK OF MUCH ABOVE-NORMAL TEMPERATURES FOR PORTIONS OF THE SOUTHEAST,
THE MID-ATLANTIC, THE LOWER MISSISSIPPI VALLEY, AND THE SOUTHERN APPALACHIANS,
WED-MON, AUG 3-AUG 8.

SEVERE DROUGHT ACROSS THE MID-ATLANTIC, THE LOWER MISSISSIPPI VALLEY, THE
CENTRAL GREAT BASIN, THE NORTHERN PLAINS, THE TENNESSEE VALLEY, HAWAII, THE
NORTHEAST, CALIFORNIA, THE SOUTHERN APPALACHIANS, THE SOUTHEAST, THE CENTRAL
APPALACHIANS, THE GREAT LAKES, AND THE SOUTHWEST.

DETAILED SUMMARY

FOR FRIDAY JULY 29 - TUESDAY AUGUST 02: AS THE FORECAST PERIOD BEGINS AN
INITIALLY STATIONARY FRONT ACROSS THE MID-ATLANTIC IS EXPECTED TO LIFT SLIGHTLY
NORTHWARD INTO NEW ENGLAND.  HEAVY RAINFALL (EXCEEDING 1" IN 24 HOURS) IS
ANTICIPATED TO ACCOMPANY THE FRONTAL PASSAGE ACROSS THE CENTRAL APPALACHIANS
AND MID-ATLANTIC ON JULY 29-30.  ECMWF PRECIPITATION SOLUTIONS ARE MORE
PROGRESSIVE AND PUSH THE HEAVIEST ACCUMULATIONS OFFSHORE FOR JULY 31 WHILE THE
OPERATIONAL GFS AND GEFS LINGER PRECIPITATION ACROSS THE MID-ATLANTIC.  THE
HAZARD DEPICTED IS IN LINE WITH THE WEATHER PREDICTION CENTER`S GUIDANCE WHICH
APPEARS MORE IN LINE WITH THE EUROPEAN SOLUTIONS.



ANOTHER FOCUS FOR HEAT EARLY IN WEEK-1 IS EXPECTED ACROSS MUCH OF THE WEST ON
JULY 29-30 ASSOCIATED WITH A 594-DM RIDGE FORECAST AT 500-HPA.  FORECAST
MAXIMUM TEMPERATURES ARE ANTICIPATED TO BE 8-12 DEGREES F ABOVE NORMAL ON THESE
DATES, WITH EXPECTATIONS OF THE FOCAL REGION SHIFTING NORTH AND EAST ACROSS THE
TWO DAYS.  THE STORM PREDICTION CENTER IS ALSO HIGHLIGHTING ELEVATED FIRE
WEATHER-RELATED RISKS ACROSS THE WEST FOR JULY 29-31, ALTHOUGH AT CRITERIA
BELOW HAZARD DEPICTION.  MARGINAL DRY THUNDERSTORM RISKS ARE FORECAST FOR
PORTIONS OF THE GREAT BASIN ON JULY 29-31, WHILE MARGINAL FIRE WEATHER
CONDITIONS (PROLONGED WARMTH, ELEVATED WINDS, AND LOW HUMIDITY) ARE EXPECTED
FOR PORTIONS OF THE GREAT BASIN AND NORTHERN INTERMOUNTAIN REGION ON JULY 30-31.



RAINFALL IS ALSO FORECAST FOR PORTIONS OF WESTERN ALASKA AND THE INTERIOR BASIN
ON JULY 29-30 ASSOCIATED WITH A COLD FRONT EXPECTED TO SAG SOUTH AND EAST
ACROSS THE STATE.  WHILE WIDESPREAD PRECIPITATION AMOUNTS ARE UNLIKELY TO MEET
ALASKA HAZARDS CRITERIA (2" IN 24 HOURS), ANTECEDENT WET CONDITIONS THAT COULD
LEAD TO FLOODING CONCERNS RESULT IN THIS HAZARD BEING DEPICTED ON THE MAP.
RAINFALL IS LIKELY TO BE ONGOING BEYOND THE HAZARD FORECAST, HOWEVER THE ECMWF
(FURTHER SOUTH) AND GFS (FURTHER NORTH) DIVERGE SUBSTANTIALLY IN REGARDS TO
WHERE THEIR SOLUTIONS FOCUS PRECIPITATION BEYOND THE 30TH.

FOR WEDNESDAY AUGUST 03 - TUESDAY AUGUST 09: SIMILAR THINKING EXISTS TO
YESTERDAY REGARDING WEEK-2 HAZARDS BEING FOCUSED ON HEAT-RELATED EVENTS ACROSS
THE EASTERN CONUS.  500-HPA RIDGING IS FORECAST TO BE FOCUSED ACROSS THE
CENTRAL CONUS DURING THE PERIOD, WITH STRONGEST HEIGHT ANOMALIES EXPECTED
THROUGH THE GREAT LAKES EARLY IN WEEK-2.  THE GEFS IS SLIGHTLY MORE AMPLIFIED
THAN THE ECMWF WITH FORECAST RIDGE AMPLITUDES, YET THE FEATURE IS CONSISTENT
BETWEEN THE TWO.



REFORECAST GUIDANCE FROM THE ECMWF, GFS, AND NAEFS ALL FOCUS ON TWO AREAS OF
WARMTH:  THE FIRST ACROSS THE GREAT LAKES AND VICINITY EARLY IN WEEK-2 AND THE
SECOND ACROSS THE SOUTHEAST FOR MOST OF WEEK-2.  THE GREATEST RISK OF
MUCH-ABOVE NORMAL TEMPERATURES APPEARS TO BE ACROSS THE GREAT LAKES AUGUST 3-4
ASSOCIATED WITH THE STRONGEST 500-HPA HEIGHT ANOMALY FORECASTS, WHILE THE GEFS
PROBABILISTIC EXTREMES TOOL GIVES THIS REGION A 40% CHANCE OF EXCEEDING THE
85TH PERCENTILE OF CLIMATOLOGICAL MAXIMUM TEMPERATURES WHICH IS CONSISTENT WITH
A MODERATE RISK.  A SLIGHT RISK OF MUCH ABOVE-NORMAL TEMPERATURES EXTENDS
THROUGH INTERIOR NEW ENGLAND AND THE UPPER MISSISSIPPI VALLEY FOR AUGUST 3-5
CONSISTENT WITH A 20% CHANCE REFLECTED BY THE GEFS PROBABILISTIC EXTREMES TOOL.
 ACROSS THE SOUTHEAST ANOMALOUS 500-HPA HEIGHTS ARE EXPECTED TO BE WEAKER, BUT
A 20% CHANCE OF EXCEEDING THE 85TH PERCENTILE OF MAXIMUM TEMPERATURES INDICATED
BY THE GEFS PROBABILISTIC EXTREMES TOOL FOR AUGUST 3-8 SUPPORTS A SLIGHT RISK
OF MUCH ABOVE-NORMAL TEMPERATURES.



ACCORDING TO THE U.S. DROUGHT MONITOR (USDM), RELEASED ON JULY 21, SEVERE, OR
GREATER INTENSITY, DROUGHT COVERS 5.68 PERCENT OF THE U.S. DROUGHT MONITOR
AREAS (INCLUDING ALASKA, HAWAII, AND PUERTO RICO), AN INCREASE OF A HALF
PERCENT SINCE THE PREVIOUS WEEK. THIS INCREASE IS DUE TO AN EXPANSION OF
SHORT-TERM SEVERE DROUGHT EAST OF THE ROCKIES.

FORECASTER: DANIEL HARNOS

$$




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