Prognostic Meteorological Discussion
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FXUS21 KWNC 281841
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT SEPTEMBER 28 2016

SYNOPSIS: A STATIONARY FRONT IS EXPECTED TO EXTEND FROM THE NORTHERN GULF OF
MEXICO ACROSS NORTHERN FLORIDA TO OFF THE ATLANTIC SEABOARD DURING THE FIRST
SEVERAL DAYS OF THE OUTLOOK PERIOD. WEAK SURFACE LOW PRESSURE INITIALLY IN
INDIANA IS FORECAST TO MOVE SLOWLY NORTHWARD AND EASTWARD DURING THE SAME
PERIOD. IN THE WEST, AN ENERGETIC FRONTAL SYSTEM IS ANTICIPATED TO MOVE ACROSS
THE INTERMOUNTAIN REGION, THE ROCKIES, AND THE NORTHERN AND CENTRAL GREAT
PLAINS DURING THE 3-7 DAY PERIOD. IN THE ALASKA DOMAIN, A FAIRLY STRONG FRONTAL
SYSTEM IS EXPECTED TO MOVE ACROSS THE FAR WESTERN PORTION OF THE STATE,
BRINGING HEAVY PRECIPITATION TO PARTS OF THAT REGION. ELSEWHERE, TROPICAL STORM
MATTHEW IS CURRENTLY MOVING ACROSS THE WINDWARD ISLANDS. THE NATIONAL HURRICANE
CENTER (NHC) PREDICTS MATTHEW WILL CONTINUE WESTWARD ACROSS THE SOUTHERN
CARIBBEAN DURING THE NEXT FEW DAYS, AND STRENGTHEN INTO A HURRICANE. THIS
SYSTEM MAY HAVE A SIGNIFICANT IMPACT ON THE EASTERN GULF COAST STATES OR EAST
COAST STATES EARLY NEXT WEEK, AND SHOULD BE MONITORED CLOSELY.

HAZARDS

HEAVY RAIN FOR SOUTHWESTERN ALASKA, SAT-SUN, OCT 1-2.

FLOODING IS LIKELY, IMMINENT, OR OCCURRING IN PORTIONS OF THE MIDWEST, AND
SOUTHERN TEXAS.

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

DETAILED SUMMARY

FOR SATURDAY OCTOBER 01 - WEDNESDAY OCTOBER 05: A CUT-OFF LOW AT 500-HPA IS
FORECAST TO BE CENTERED OVER THE VICINITY OF INDIANA AND ILLINOIS AT THE START
OF THIS PERIOD. SOON THEREAFTER, THIS LOW IS EXPECTED TO WEAKEN AND LIFT OUT
TOWARDS THE EASTERN GREAT LAKES REGION AND ST. LAWRENCE VALLEY, SIGNALING THE
END OF AN EXTENDED PERIOD OF CLOUDY, COOL, AND WET WEATHER FOR THE MIDWEST AND
NORTHEAST.



FOR THE SECOND HALF OF THIS PERIOD, ATTENTION SHIFTS TO NORTHERN AND CENTRAL
PORTIONS OF THE INTERMOUNTAIN WEST, ROCKIES, AND GREAT PLAINS, AS A VIGOROUS
MID-TROPOSPHERIC TROUGH MOVES ACROSS THE REGION. DETERMINISTIC RUNS OF THE GFS
AND ECMWF MODELS PREDICT HEAVY RAIN ACROSS PORTIONS OF THIS LARGE AREA, AND
POTENTIALLY SOME LIGHT SNOW ACCUMULATIONS ABOVE 6000 FEET IN THE COLD AIR
BEHIND THE UPPER TROUGH AXIS, ESPECIALLY ACROSS EASTERN WYOMING AND
NORTHWESTERN COLORADO. THESE MODELS DEPICT SIGNIFICANT DIFFERENCES IN THE
TIMING AND PLACEMENT OF THE HEAVIER RAIN BANDS, WHICH PRECLUDE THE DESIGNATION
OF A HEAVY RAIN AREA ON THE MAP AT THIS TIME. INSTABILITY IS EXPECTED TO
INCREASE AHEAD OF THE 500-HPA TROUGH ACROSS THE SOUTHERN HALF OF THE GREAT
PLAINS REGION, WHICH IS LIKELY TO INCREASE THE CHANCES FOR STRONG TO SEVERE
THUNDERSTORM ACTIVITY. AT THIS TIME, THERE IS TOO MUCH UNCERTAINTY TO HIGHLIGHT
A SPECIFIC REGION ON THE MAP REGARDING SEVERE WEATHER.



TROPICAL STORM MATTHEW, WITH PEAK SUSTAINED WINDS OF 60 MPH (AS OF 2PM EDT SEP
28TH), IS MOVING ACROSS THE WINDWARD ISLANDS, HEADING INTO THE SOUTHERN
CARIBBEAN SEA AT 20 MPH. THE OFFICIAL TRACK FROM NHC CONTINUES THIS WESTWARD
MOTION FOR THE NEXT 72 HOURS OVER THE SUFFICIENTLY WARM WATERS OF THE SOUTHERN
CARIBBEAN SEA. THIS WARM WATER, COMBINED WITH LOW ATMOSPHERIC WIND SHEAR,
SHOULD PROVIDE AN ENVIRONMENT THAT IS FAVORABLE FOR INTENSIFICATION, WITH
MATTHEW EXPECTED TO REACH HURRICANE STATUS IN 48 HOURS. BY THE BEGINNING OF
THIS PERIOD, NHC PREDICTS THIS SYSTEM WILL SLOW DOWN AND TAKE A FAIRLY SHARP
TURN TOWARDS THE NORTH, BRINGING MATTHEW CLOSE TO OR OVER JAMAICA. RECENT RUNS
OF THE GFS (6Z AND 12Z) AND THE ECMWF (0Z) TAKE THIS SYSTEM EITHER THROUGH THE
JAMAICA CHANNEL (WHICH SEPARATES JAMAICA FROM HISPANIOLA), OR OVER THE HAITIAN
PENINSULA, THEN NORTHWARD ACROSS THE BAHAMAS. BEYOND THIS TIME, THE MODELS SHOW
SIGNIFICANT DISAGREEMENTS IN THE FORECAST TRACK OF MATTHEW, AND IT IS TOO EARLY
TO TELL WITH ANY CONFIDENCE IF, AND TO WHAT DEGREE, THE UNITED STATES MAY BE
AFFECTED BY THIS SYSTEM. IT IS HIGHLY RECOMMENDED THAT RESIDENTS ACROSS THE
EASTERN GULF COAST REGION AND ALONG THE EAST COAST KEEP A CLOSE EYE ON THE
FUTURE PROGRESS OF MATTHEW.



FLOODING IS LIKELY, IMMINENT, OR OCCURRING IN PORTIONS OF THE MIDWEST AND
SOUTHERN TEXAS FROM OCT 1-3. THIS IS PRIMARILY DUE TO RAIN THAT RECENTLY FELL
ACROSS THESE AREAS.



A CYCLONIC SYSTEM, PRECEDED BY AN EXTENSIVE CORRIDOR OF MOIST, SOUTHERLY FLOW,
IS PREDICTED TO BRING HEAVY RAIN (2 INCHES OR GREATER) TO SOUTHWESTERN ALASKA
ON OCT 1-2. THE DETERMINISTIC 0Z ECMWF AND 6Z GFS RUNS FORECAST IN EXCESS OF 4
INCHES DURING THIS PERIOD ACROSS THE VICINITY OF THE EASTERN ALASKA PENINSULA.

FOR THURSDAY OCTOBER 06 - WEDNESDAY OCTOBER 12: DURING WEEK-2, THE ANTICIPATED
500-HPA FLOW PATTERN FEATURES A POSITIVELY TILTED TROUGH AXIS FROM ABOUT THE
EASTERN DAKOTAS SOUTHWESTWARD TO SOUTHERN CALIFORNIA, A WEAK ANOMALOUS RIDGE
ACROSS THE EASTERN CONUS, A RIDGE OVER MOST OF ALASKA, AND A ZONALLY ELONGATED
TROUGH OVER THE BERING SEA. AT THIS TIME, THE ONLY HAZARDS THAT ARE DEPICTED ON
THE MAP WITH CONFIDENCE ARE THE SEVERE DROUGHT AREAS. TWO AREAS THAT BEAR
WATCHING ARE THE MISSISSIPPI VALLEY/SOUTHERN PLAINS REGION, AND THE EAST COAST
STATES. THE FIRST AREA IS IN REGARD TO THE POSSIBILITY OF HEAVY RAIN AND/OR
STRONG TO SEVERE THUNDERSTORMS, WHILE THE SECOND AREA IS RELATED TO TROPICAL
CYCLONE MATTHEW AND ITS FUTURE TRACK AND INTENSITY.



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 THE
HAWAIIAN ISLANDS IS DESIGNATED WITH SEVERE DROUGHT.

FORECASTER: ANTHONY ARTUSA

$$




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