Prognostic Meteorological Discussion
Issued by NWS

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FXUS21 KWNC 231929
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT AUGUST 23 2016

SYNOPSIS: AT THE START OF THE PERIOD, A FRONTAL SYSTEM IS FORECAST TO STRETCH
FROM AN AREA OF SURFACE LOW PRESSURE OVER EASTERN CANADA SOUTHWESTWARD ACROSS
WESTERN NEW YORK, THE OHIO, TENNESSEE, AND LOWER MISSISSIPPI VALLEYS TO THE
SOUTHERN PLAINS. WEAK SURFACE LOW PRESSURE IS PREDICTED TO FORM OVER THE
SOUTHWEST U.S. AND MOVE NORTH-NORTHEASTWARD TO THE NORTHERN PLAINS. THE FRONT
IS ANTICIPATED TO SLIDE SLOWLY SOUTHEASTWARD AND STALL NEAR THE SOUTHEAST COAST
BY AUG 28. ON AUG 26, A DECAYING FRONTAL ZONE IS PREDICTED NEAR FLORIDA. AS THE
FRONT DISSIPATES, TROPICAL DISTURBANCES ARE FORECAST TO MOVE TOWARDS THE
FLORIDA PENINSULA. SURFACE HIGH PRESSURE OVER THE NORTH-CENTRAL U.S. ON AUG 26
IS ANTICIPATED TO MOVE TOWARDS THE GREAT LAKES AND THEN BUILD OVER THE
NORTHEASTERN PART OF THE NATION. SURFACE HIGH PRESSURE OVER THE GULF OF ALASKA
IN COMBINATION WITH SURFACE LOW PRESSURE MOVING NORTH OF THE STATE LEADS TO
SOUTHWESTERLY FLOW OVER WESTERN ALASKA.

HAZARDS

HEAVY RAIN FOR PARTS OF THE CENTRAL PLAINS AND UPPER AND MIDDLE MISSISSIPPI
VALLEY, FRI-SAT, AUG 26-27.

HEAVY RAIN FOR PARTS OF THE CENTRAL PLAINS AND UPPER AND MIDDLE MISSISSIPPI
VALLEY, SUN-MON, AUG 28-29.

HEAVY RAIN FOR PARTS OF FLORIDA AND THE LOWER MISSISSIPPI VALLEY, SUN-TUE, AUG
28-30.

MUCH ABOVE NORMAL TEMPERATURES FOR PARTS OF THE PACIFIC NORTHWEST, FRI, AUG 26.

MUCH ABOVE NORMAL TEMPERATURES FOR PARTS OF THE OHIO VALLEY AND CENTRAL
APPALACHIANS, SUN AUG 28.

FLOODING POSSIBLE, OCCURRING OR IMMINENT ACROSS PORTIONS OF THE GREAT LAKES,
SOUTHERN PLAINS, AND THE MISSISSIPPI VALLEY.

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

DETAILED SUMMARY

FOR FRIDAY AUGUST 26 - TUESDAY AUGUST 30: WEAK LOW PRESSURE IS FORECAST TO FORM
ON A DECAYING FRONT OVER THE SOUTHWESTERN CONUS AND MOVE NORTHWARD TO THE
NORTHERN PLAINS. THE SURFACE TROUGH ASSOCIATED WITH THIS AREA OF LOW PRESSURE
IS PREDICTED TO MOVE VERY SLOWLY EAST/SOUTHEASTWARD. THIS EVOLUTION LEADS TO
HEAVY RAIN (IN EXCESS OF 1 INCH IN 24 HOURS) FOR PARTS OF THE CENTRAL PLAINS
AND UPPER AND MIDDLE MISSISSIPPI VALLEY AUG 26-27, AND FOR SOUTHERN PORTIONS OF
THESE SAME REGIONS AUG 28-29.

THUNDERSTORMS ARE POSSIBLE OVER THESE AREAS BUT NO ORGANIZED SEVERE WEATHER IS
CURRENTLY ANTICIPATED.



A STATIONARY FRONTAL SYSTEM IN COMBINATION WITH WEAK TROPICAL DISTURBANCES
LEADS TO HEAVY RAIN (IN EXCESS OF 1 INCH IN 24 HOURS) FOR PARTS OF SOUTHERN AND
CENTRAL FLORIDA AND THE LOWER MISSISSIPPI VALLEY AUG 28-30. THE EXACT TRACK AND
STRENGTH OF THE TROPICAL DISTURBANCES ARE HIGHLY UNCERTAIN AT THIS TIME AND
ADDITIONAL IMPACTS (HEAVY RAIN, HIGH WINDS, SIGNIFICANT WAVES, BEACH EROSION)
ARE POSSIBLE FOR PARTS OF THE SOUTHEAST, MID-ATLANTIC, AND GULF COASTS. PLEASE
CONSULT THE LATEST ADVISORIES FROM THE NATIONAL HURRICANE CENTER AT
HTTP://WWW.NHC.NOAA.GOV/.



HIGH PRESSURE OVER THE NORTH/CENTRAL CONUS CAUSES SOUTHEASTERLY DOWNSLOPE FLOW
OVER THE PACIFIC NORTHWEST WHICH LEADS TO MUCH ABOVE NORMAL TEMPERATURES
(POSITIVE TEMPERATURE ANOMALIES OF 12-15 DEGREES F) FOR PARTS OF THE REGION AUG
26.



SOUTHERLY FLOW AROUND THE WEST SIDE OF HIGH PRESSURE CENTERED OVER THE
NORTHEAST LEADS TO MUCH ABOVE NORMAL TEMPERATURES (POSITIVE ANOMALIES OF 10-12
DEGREES F) FOR PARTS OF THE OHIO VALLEY AND CENTRAL APPALACHIANS AUG 28.



LOW PRESSURE PASSING NORTH OF ALASKA LEADS TO A LONG FETCH OF SOUTHWESTERLY
FLOW OVER WESTERN PORTIONS OF THE STATE. COASTAL FLOODING AND BEACH EROSION IS
POSSIBLE FOR SOUTHWEST FACING COMMUNITIES OF THE LISBURNE PENINSULA, ESPECIALLY
NEAR KIVALINA AUG 27-29.



ANTECEDENT RAINFALL, IN COMBINATION WITH ADDITIONAL RAINFALL EXPECTED DURING
THE PERIOD LEADS TO FLOODING POSSIBLE, IMMINENT, OR OCCURRING ACROSS PORTIONS
OF THE GREAT LAKES, SOUTHERN PLAINS, AND THE MISSISSIPPI VALLEY.



DESPITE DRY FUELS OVER MUCH OF THE WESTERN CONUS, WIND SPEEDS ARE FORECAST TO
LESSEN SO THAT CRITICAL FIRE WEATHER CONDITIONS ARE NOT CURRENTLY ANTICIPATED
EARLY IN THE PERIOD. LATER IN THE PERIOD, MODEL UNCERTAINTY IS TOO LARGE TO
SPECIFY A HAZARD SHAPE.

FOR WEDNESDAY AUGUST 31 - TUESDAY SEPTEMBER 06: DURING WEEK-2 THE CIRCULATION
PATTERN IS EXPECTED TO FEATURE WEAK TROUGHS OVER THE NORTHEAST AND NORTHWEST
CONUS, AND A RIDGE OVER THE WEST-CENTRAL PART OF THE NATION.



THE ATLANTIC IS SHOWING INCREASED TROPICAL ACTIVITY AND SOME MODELS INDICATE
THE POSSIBILITY OF TROPICAL SYSTEMS NEAR THE EAST COAST OF THE U.S. OR THE GULF
OF MEXICO EARLY IN WEEK-2. THE EXACT EVOLUTION OF ANY TROPICAL SYSTEM IS
EXTREMELY UNCERTAIN THIS FAR OUT SO PLEASE CONSULT THE LATEST ADVISORIES FROM
THE NATIONAL HURRICANE CENTER AT HTTP://WWW.NHC.NOAA.GOV/.





ACCORDING TO THE U.S. DROUGHT MONITOR, THE COVERAGE OF SEVERE OR GREATER
DROUGHT DECREASED TO 7.71 PERCENT FROM 8.20 PERCENT. IMPROVEMENTS WERE REALIZED
ACROSS THE GREAT LAKES, GREAT PLAINS, AND THE LOWER MISSISSIPPI VALLEY.

FORECASTER: RANDY SCHECHTER

$$




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