Prognostic Meteorological Discussion
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FXUS21 KWNC 231849
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT SEPTEMBER 23 2016

SYNOPSIS: AT THE START OF THE PERIOD, A COLD FRONT IS ANTICIPATED TO STRETCH
FROM AN AREA OF SURFACE LOW PRESSURE OVER SOUTH-CENTRAL CANADA SOUTHWARD ACROSS
THE  GREAT LAKES, OHIO AND TENNESSEE VALLEYS, AND THEN SOUTHWESTWARD ACROSS THE
LOWER MISSISSIPPI VALLEY AND SOUTHERN PLAINS. THE NORTHERN PART OF THE FRONT IS
EXPECTED TO MOVE SLOWLY EASTWARD WHILE THE SOUTHERN PORTION OF THE FRONT STALLS
NEAR THE TEXAS GULF COAST. STRONG SURFACE HIGH PRESSURE FORECAST OVER THE GREAT
BASIN SEP 26 WILL CAUSE OFFSHORE WINDS FOR PARTS OF SOUTHERN CALIFORNIA. AN
AREA OF SURFACE LOW PRESSURE IS EXPECTED NEAR THE ALASKA PANHANDLE SEP 26. DEEP
SURFACE LOW PRESSURE IS FORECAST OVER EASTERN RUSSIA/THE BERING SEA ON SEP 30.
DURING WEEK-2, A MODERATE AMPLITUDE FLOW PATTERN IS ANTICIPATED ACROSS MUCH OF
THE U.S. WITH AN AREA OF UPPER-LEVEL LOW PRESSURE EXPECTED OVER THE WEST, AND
UPPER-LEVEL HIGH PRESSURE OVER THE CENTRAL AND EASTERN PARTS OF THE COUNTRY.
UPPER-LEVEL LOW PRESSURE IS FORECAST OVER THE BERING SEA DURING WEEK-2.

HAZARDS

MUCH ABOVE NORMAL TEMPERATURES FOR PARTS OF CENTRAL OREGON AND NORTHERN AND
CENTRAL CALIFORNIA, MON-TUE, SEP 26-27.

HEAVY RAIN ACROSS PARTS OF CENTRAL AND SOUTHERN TEXAS, MON-TUE, SEP 26-27.

CRITICAL FIRE WEATHER FOR PARTS OF SOUTHWESTERN CALIFORNIA, MON, SEP 26.

HEAVY RAIN FOR CENTRAL AND SOUTHERN PARTS OF THE ALASKA PANHANDLE, MON, SEP 26.

FLOODING LIKELY OR OCCURRING FOR PARTS OF THE UPPER AND MIDDLE MISSISSIPPI
VALLEY.

FLOODING POSSIBLE FOR PARTS OF THE SOUTHERN PLAINS.

FLOODING OCCURRING OR IMMINENT FOR PARTS OF NORTHEASTERN NORTH CAROLINA.

SEVERE DROUGHT ACROSS PARTS OF THE EASTERN U.S., MISSOURI RIVER VALLEY, GREAT
PLAINS, NORTHERN ROCKIES, INTERMOUNTAIN WEST, ARIZONA, CALIFORNIA, AND HAWAII.

DETAILED SUMMARY

FOR MONDAY SEPTEMBER 26 - FRIDAY SEPTEMBER 30: AT THE START OF THE PERIOD, LOW
PRESSURE IS FORECAST OVER SOUTH-CENTRAL CANADA. A FRONT ASSOCIATED WITH THIS
AREA OF LOW PRESSURE IS FORECAST TO STRETCH SOUTHWARD FROM THE GREAT LAKES TO
ACROSS THE OHIO AND TENNESSEE VALLEYS, AND THEN SOUTHWESTWARD FROM THE LOWER
MISSISSIPPI VALLEY TO THE SOUTHERN PLAINS. THE FRONT IS EXPECTED TO ACT AS A
FOCUSING MECHANISM FOR SHOWERS AND THUNDERSTORMS LEADING TO HEAVY RAIN (IN
EXCESS OF 1 INCH IN 24 HOURS) FOR PARTS OF CENTRAL AND SOUTHERN TEXAS SEP
26-27. FLOODING IS POSSIBLE FOR PARTS OF SOUTH-CENTRAL TEXAS.



ANTECEDENT RAINFALL LEADS TO FLOODING OCCURRING OR POSSIBLE FOR PARTS OF
NORTHEASTERN NORTH CAROLINA AND PARTS OF THE UPPER AND MIDDLE MISSISSIPPI
VALLEY.



SOUTHERLY FLOW ON THE REAR SIDE OF HIGH PRESSURE FORECAST TO BUILD OVER THE
GREAT BASIN LEADS TO THE EXPECTATION OF MUCH ABOVE NORMAL TEMPERATURES
(POSITIVE TEMPERATURE ANOMALIES AS MUCH AS 15-20 DEGREES F) FOR PARTS OF
CENTRAL OREGON AND NORTHERN AND CENTRAL CALIFORNIA SEP 26-27. THE AREA OF HIGH
PRESSURE IS ALSO PREDICTED TO LEAD TO ENHANCED OFFSHORE FLOW OVER SOUTHERN
CALIFORNIA. THE POTENTIAL OFFSHORE WINDS, IN COMBINATION WITH A DRY AIR MASS
AND DRY FUELS LEADS TO CRITICAL FIRE WEATHER CONDITIONS FOR PARTS OF SOUTHERN
CALIFORNIA SEP 26.



AN AREA OF LOW PRESSURE FORECAST NEAR THE ALASKA PANHANDLE LEADS TO HEAVY RAIN
(IN EXCESS OF 2 INCHES IN 24 HOURS) FOR PARTS OF THE CENTRAL AND SOUTHERN
ALASKA PANHANDLE SEP 26. AT THE END OF THE ASSESSMENT PERIOD, A DEEP AREA OF
LOW PRESSURE IS PREDICTED OVER EASTERN RUSSIA/THE BERING SEA. SOUTHWESTERLY
FLOW AHEAD OF THIS AREA OF LOW PRESSURE COULD LEAD TO HEAVY RAIN, HIGH WINDS
SIGNIFICANT WAVES, COASTAL FLOODING, AND BEACH EROSION FOR PARTS OF WEST
COASTAL MAINLAND ALASKA. MODEL UNCERTAINTY PRECLUDES THE SPECIFICATION OF
HAZARD SHAPES AT THE CURRENT TIME BUT THIS SITUATION WILL NEED TO BE CAREFULLY
MONITORED.



TROPICAL SYSTEMS KARL AND LISA, CURRENTLY OVER THE TROPICAL ATLANTIC, ARE
EXPECTED TO RECURVE BEFORE GETTING IN CLOSE PROXIMITY TO THE U.S. EAST COAST.
RECENT GFS MODEL SOLUTIONS INDICATE A TROPICAL SYSTEM OVER THE EASTERN PACIFIC
TO BE APPROACHING THE SOUTHWEST CONUS LATE IN THE PERIOD. A MOISTURE SURGE
ASSOCIATED WITH THIS SYSTEM COULD BRING HEAVY RAIN AND LOCALIZED FLOODING TO
PARTS OF THE SOUTHWEST U.S. BUT MODEL UNCERTAINTY PRECLUDES THE SPECIFICATION
OF HAZARD SHAPES AT THE CURRENT TIME. FOR MORE INFORMATION ON THESE SYSTEMS
PLEASE CONSULT THE NATIONAL HURRICANE CENTER AT HTTP://WWW.NHC.NOAA.GOV.

FOR SATURDAY OCTOBER 01 - FRIDAY OCTOBER 07: A TROPICAL WAVE CURRENTLY MOVING
OFF THE WEST COAST OF AFRICA IS FORECAST BY SOME MODELS TO MOVE ACROSS SOUTHERN
PORTIONS OF THE TROPICAL ATLANTIC TOWARDS THE U.S. OR GULF OF MEXICO DURING
THIS PERIOD. FOR MORE INFORMATION ON THIS SYSTEM PLEASE CONSULT THE NATIONAL
HURRICANE CENTER AT HTTP://WWW.NHC.NOAA.GOV.



LOW PRESSURE FORECAST OVER FAR EASTERN RUSSIA/BERING SEA LEADS TO POTENTIAL
STRONG WEST-SOUTHWESTERLY FLOW OVER WESTERN ALASKA OCT 1-OCT 2. HEAVY RAIN,
COASTAL FLOODING, SIGNIFICANT WAVES, AND BEACH EROSION ARE POSSIBLE FOR THE
REGION, BUT MODEL UNCERTAINTY PRECLUDES THE SPECIFICATION OF HAZARD SHAPES AT
THE CURRENT TIME.



DURING WEEK-2 A MODERATELY AMPLIFIED FLOW PATTERN IS FORECAST ACROSS MOST OF
THE CONUS WITH A TROUGH OVER THE WEST AND A RIDGE ANTICIPATED OVER THE CENTRAL
AND EASTERN PARTS OF THE NATION. A TROUGH IS ANTICIPATED OVER THE BERING SEA.



ACCORDING TO THE LATEST U.S. DROUGHT MONITOR (USDM) VALID ON SEPTEMBER 20, THE
COVERAGE OF SEVERE OR GREATER DROUGHT (FOR THE CONUS) INCREASED VERY SLIGHTLY
FROM 7.72 TO 7.76 PERCENT DURING THE PAST WEEK.  LESS THAN 1 PERCENT OF TH
HAWAIIAN ISLANDS IS DESIGNATED WITH SEVERE DROUGHT.

FORECASTER: RANDY SCHECHTER

$$




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