Prognostic Meteorological Discussion
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FXUS21 KWNC 161908
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT SEPTEMBER 16 2014

SYNOPSIS: THE REMNANT LOW OF FORMER HURRICANE ODILE IS FORECAST TO ENTER THE
SOUTHWEST AND THEN PROGRESS TO THE GREAT PLAINS THIS WEEKEND. SURFACE HIGH
PRESSURE, CENTERED OVER NEW ENGLAND ON FRIDAY MORNING, IS FORECAST TO SHIFT
OFFSHORE OF THE EAST COAST ON SUNDAY. A COLD FRONT IS FORECAST TO PROGRESS FROM
THE GREAT PLAINS ON FRIDAY TO THE EASTERN U.S. BY EARLY NEXT WEEK. AN AREA OF
UPPER-LEVEL LOW PRESSURE IS FORECAST TO PERSIST ACROSS ALASKA DURING THE NEXT
TWO WEEKS.

HAZARDS

FLASH FLOODING POSSIBLE FOR PARTS OF NEW MEXICO, FRI, SEP 19.

HEAVY RAIN SHIFTING SOUTH ACROSS THE CENTRAL AND SOUTHERN GREAT PLAINS,
FRI-SUN, SEP 19-21.

MUCH BELOW-NORMAL TEMPERATURES FOR NORTHERN NEW ENGLAND AND UPSTATE NEW YORK,
FRI MORNING, SEP 19.

SEVERE DROUGHT FOR THE CENTRAL AND SOUTHERN GREAT PLAINS, SOUTHWEST, SOUTHERN
GEORGIA, PACIFIC NORTHWEST, GREAT BASIN, AND CALIFORNIA.

DETAILED SUMMARY

FOR FRIDAY SEPTEMBER 19 - TUESDAY SEPTEMBER 23: THE RISK OF FLASH FLOODING
ACROSS THE DESERT SOUTHWEST IS EXPECTED TO PEAK ON THURSDAY WHEN ANOMALOUS
MOISTURE ASSOCIATED WITH THE REMNANT LOW OF ODILE OVERSPREADS THE REGION. ON
FRIDAY, THE REMNANT LOW IS FORECAST TO EXIT THE DESERT SOUTHWEST BUT HEAVY RAIN
MAY LINGER AND PROLONG THE RISK OF FLASH FLOODING ACROSS THE MOUNTAINS OF NEW
MEXICO. DURING THE WEEKEND, THE DETERMINISTIC GFS AND ECMWF MODELS DIVERGE ON
THE TRACK OF AN UPPER-LEVEL TROUGH. THE GFS MODEL DEPICTS A MUCH WETTER
SOLUTION WITH A CONTINUED RISK OF FLASH FLOODING, WHILE THE ECMWF MODEL
RETROGRADES AN UPPER-LEVEL TROUGH AND PROVIDES A MOSTLY DRY WEEKEND FOR THE
DESERT SOUTHWEST.



A COLD FRONT INTERACTING WITH MID-LEVEL MOISTURE FROM ODILE AND ABUNDANT
LOW-LEVEL MOISTURE FROM THE GULF OF MEXICO IS LIKELY TO BRING HEAVY RAINFALL TO
THE CENTRAL AND SOUTHERN GREAT PLAINS FROM FRIDAY THROUGH SUNDAY. THE 6Z GFS
MODEL INDICATES THAT PRECIPITABLE WATER VALUES INCREASE TO AROUND 2 INCHES
ACROSS THE SOUTHERN GREAT PLAINS BY THIS WEEKEND. SEVERE THUNDERSTORMS COULD
DEVELOP ALONG AND AHEAD OF THE COLD FRONT AS IT CROSSES THE GREAT PLAINS AND
MISSISSIPPI VALLEY, BUT UNCERTAINTY ON SUFFICIENT INSTABILITY PRECLUDES
DESIGNATION OF A SEVERE WEATHER HAZARD AT THIS TIME. EARLY NEXT WEEK, EASTERLY
FLOW AND ANOMALOUS MOISTURE ELEVATE THE THREAT OF HEAVY RAINFALL ACROSS WEST
TEXAS AND THE SOUTHERN HIGH PLAINS. IF A MODEL AGREEMENT ON RAINFALL AMOUNTS
AND LOCATION IMPROVE, THEN A HEAVY RAIN HAZARD WOULD BE POSTED ON LATER
OUTLOOKS.



LONG PERIOD SWELLS ASSOCIATED WITH HURRICANE EDOUARD OVER THE ATLANTIC ARE
EXPECTED TO SUBSIDE BY FRIDAY. HOWEVER, ONSHORE WINDS ARE EXPECTED TO MAINTAIN
ELEVATED SEAS AND THE THREAT OF RIP CURRENTS FOR BEACHES ALONG THE SOUTHEAST
COAST THROUGH THE WEEKEND.



AS A STRONG SURFACE HIGH BECOMES CENTERED OVER NEW ENGLAND ON FRIDAY MORNING,
WIDESPREAD FROST OR A LIGHT FREEZE ARE LIKELY FOR NORTHERN NEW ENGLAND AND
UPSTATE NEW YORK. SINCE MINIMUM TEMPERATURES ARE FORECAST TO AVERAGE NEAR 12
DEGREES F BELOW-NORMAL AND THE FREEZE WOULD END THE GROWING SEASON, A
MUCH-BELOW NORMAL TEMPERATURE HAZARD IS POSTED ON TODAY`S MAP.



AN UPPER-LEVEL RIDGE IS EXPECTED TO RESULT IN MAXIMUM TEMPERATURES AVERAGING
AROUND 12 DEGREES F ABOVE-NORMAL ACROSS THE INTERIOR PACIFIC NORTHWEST ON
SUNDAY AND MONDAY. SINCE MAXIMUM TEMPERATURES ARE FORECAST TO REMAIN BELOW 90
DEGREES F, A MUCH-ABOVE NORMAL TEMPERATURE HAZARD IS NOT DEEMED NECESSARY FOR
THIS REGION.



A SERIES OF SURFACE LOWS WITH VARYING INTENSITY ARE EXPECTED TO AFFECT SOUTHERN
ALASKA AND THE ALASKAN PANHANDLE. DUE TO MODEL DIFFERENCE ON TIMING AND
AMOUNTS, A HEAVY PRECIPITATION HAZARD IS NOT POSTED FOR THESE AREAS AT THIS
TIME.

FOR WEDNESDAY SEPTEMBER 24 - TUESDAY SEPTEMBER 30: A LARGE SPREAD AMONG THE 0Z
GFS AND 0Z ECMWF ENSEMBLE MEMBERS PRECLUDES DESIGNATION OF ANY SPECIFIC
HAZARDS, EXPECT ONGOING SEVERE DROUGHT, DURING WEEK-2.



TROPICAL STORM POLO RECENTLY DEVELOPED ACROSS THE EAST PACIFIC. ANOTHER SURGE
OF TROPICAL MOISTURE COULD SPREAD NORTH INTO THE DESERT SOUTHWEST DURING WEEK-2
DEPENDING ON THE TRACK OF THIS SYSTEM.



THE MOST RECENT U.S. DROUGHT MONITOR, RELEASED LAST THURSDAY, INDICATES THE
PERCENTAGE OF THE CONUS IN SEVERE TO EXCEPTIONAL DROUGHT DECREASING FROM THE
PREVIOUS WEEK`S (SEPTEMBER 4) 20.93 PERCENT TO 20.31 PERCENT. THIS IS ALSO DOWN
SUBSTANTIALLY FROM BOTH 2013 AND 2012 AT THIS TIME OF YEAR (32.40 AND 42.48
PERCENT, RESPECTIVELY).

FORECASTER: BRAD PUGH

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