Prognostic Meteorological Discussion
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000
FXUS21 KWNC 061842
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT MAY 06 2015

SYNOPSIS: AN AREA OF UPPER-LEVEL LOW PRESSURE IS EXPECTED TO SHIFT EAST FROM
THE WESTERN CONTIGUOUS U.S. EARLY IN THE PERIOD, WHILE AN AREA OF UPPER-LEVEL
HIGH PRESSURE PERSISTS OVER THE WESTERN ATLANTIC. A COLD FRONT IS FORECAST TO
SLOWLY ADVANCE FROM THE GREAT PLAINS THIS WEEKEND TO THE EASTERN U.S. EARLY
NEXT WEEK. A SURFACE LOW PRESSURE SYSTEM IS PREDICTED TO REMAIN NEARLY
STATIONARY NEAR OR OFFSHORE OF THE SOUTHEAST COAST FROM SATURDAY THROUGH
MONDAY. A SURFACE LOW IS EXPECTED TO DEVELOP OVER THE NORTHERN GULF OF ALASKA
JUST PRIOR TO THE START OF THIS HAZARDS OUTLOOK PERIOD.

HAZARDS

SEVERE WEATHER OVER THE GREAT PLAINS SHIFTS EASTWARD INTO THE MISSISSIPPI
VALLEY, SAT-SUN, MAY 9-10.

HEAVY RAIN FROM CENTRAL TEXAS NORTHEASTWARD TO CENTRAL ILLINOIS, SAT-SUN, MAY
9-10.

HEAVY RAIN FOR THE NORTH-CENTRAL PLAINS, SAT-SUN, MAY 9-10.

PERIODS OF HEAVY RAIN IN FAR EASTERN NORTH CAROLINA, SAT-MON, MAY 9-11.

HEAVY RAIN FOR SOUTHERN TEXAS, MON-TUE, MAY 11-12.

HEAVY RAIN FOR WESTERN AND SOUTHERN PORTIONS OF TEXAS, THU, MAY 14.

HEAVY SNOW IN SOUTHEASTERN WYOMING AND NORTH-CENTRAL COLORADO, SAT-SUN, MAY
9-10.

HIGH WINDS FOR PARTS OF THE CENTRAL/SOUTHERN ROCKIES AND CENTRAL/SOUTHERN HIGH
PLAINS, SAT-SUN, MAY 9-10.

FLOODING OCCURRING ALONG THE ALTAMAHA RIVER IN SOUTHEAST GEORGIA.

FLOODING IS POSSIBLE IN EXTREME NORTHEAST KANSAS, SAT-SUN, MAY 9-10.

SEVERE DROUGHT FOR THE NORTHERN, CENTRAL AND SOUTHERN GREAT PLAINS, UPPER
MISSISSIPPI VALLEY, SOUTHWEST, GREAT BASIN, CALIFORNIA, THE PACIFIC NORTHWEST,
AND HAWAII.

DETAILED SUMMARY

FOR SATURDAY MAY 09 - WEDNESDAY MAY 13: DOWNSTREAM OF A STRONG UPPER-LEVEL
TROUGH, ABUNDANT LOW-LEVEL MOISTURE IS LIKELY TO RESULT IN PERIODS OF HEAVY
RAINFALL ACROSS PARTS OF THE GREAT PLAINS THROUGH SUNDAY. UPSLOPE FLOW IS
EXPECTED TO ENHANCE RAINFALL AMOUNTS ACROSS THE NORTH-CENTRAL HIGH PLAINS,
WHILE A SLOW-MOVING DRYLINE AND COLD FRONT INITIATE THUNDERSTORM ACTIVITY ON
SATURDAY AND SUNDAY. RAINFALL AMOUNTS OF 2-3 INCHES ARE EXPECTED ACROSS THE
NORTH-CENTRAL PLAINS, AND FROM CENTRAL TEXAS NORTHEAST TO CENTRAL ILLINOIS,
OVER THE WEEKEND. AS A POTENT SHORTWAVE TROUGH APPROACHES THE CENTRAL AND
SOUTHERN GREAT PLAINS FROM THE FOUR CORNERS REGION, VERTICAL WIND SHEAR AND
INSTABILITY ARE EXPECTED TO BE SUFFICIENT TO SUPPORT SEVERE THUNDERSTORMS ALONG
THE DRYLINE. HIGH WINDS ARE FORECAST BEHIND THE DRYLINE THIS WEEKEND ACROSS
PARTS OF THE CENTRAL AND SOUTHERN HIGH PLAINS. BY MONDAY AND TUESDAY, HEAVY
RAIN (GENERALLY 1-2 INCHES, LOCALLY GREATER) ASSOCIATED WITH THE COLD FRONT, IS
ANTICIPATED TO MOVE ACROSS SOUTHERN TEXAS.



SNOW LEVELS ARE LIKELY TO FALL AS LOW AS 5,500 FEET THIS WEEKEND AS THE
UPPER-LEVEL TROUGH CROSSES THE CENTRAL ROCKIES. THE AREAS FAVORED TO RECEIVE
HEAVY SNOWFALL AMOUNTS (EXCEEDING 6 INCHES) ARE SOUTHEASTERN WYOMING AND
NORTH-CENTRAL COLORADO. THE 00Z ECMWF SOLUTION IS EVEN MORE BULLISH, WITH
SIGNIFICANTLY HEAVIER SNOW AMOUNTS EXTENDING FARTHER EAST INTO THE NEBRASKA
PANHANDLE, THOUGH THIS SOLUTION APPEARS TO BE MORE OF AN OUTLIER. THE NATIONAL
WEATHER SERVICE FORECAST OFFICE IN CHEYENNE, WYOMING, IS ALSO HIGHLIGHTING THE
POTENTIAL FOR NORTHEASTERLY WINDS AT 35-40 MPH SATURDAY NIGHT AND SUNDAY, WITH
BLIZZARD CONDITIONS POSSIBLE. RESIDENTS IN THIS GENERAL AREA ARE ENCOURAGED TO
STAY TUNED TO THE LATEST DETAILS CONCERNING THIS UPCOMING STORM SYSTEM.



A DISORGANIZED AREA OF SHOWERS AND THUNDERSTORMS CURRENTLY OVER FLORIDA AND THE
BAHAMAS (WEDNESDAY, MAY 6TH) IS ASSOCIATED WITH AN UPPER-LEVEL TROUGH AND A
WEAK SURFACE LOW PRESSURE CENTER. DURING THE NEXT FEW DAYS, CONDITIONS ARE
EXPECTED TO BECOME MORE FAVORABLE FOR SUBTROPICAL OR TROPICAL DEVELOPMENT, AS
THIS SYSTEM HEADS NORTHWARD TOWARDS THE NORTH CAROLINA COAST. BY THE START OF
THE HAZARDS OUTLOOK PERIOD ON SATURDAY, THIS SYSTEM IS FORECAST TO BE LOCATED
FAIRLY CLOSE TO THE NORTH CAROLINA COAST. PERIODS OF HEAVY RAIN ARE PREDICTED
FOR FAR EASTERN NORTH CAROLINA, ALONG WITH THE POSSIBILITY OF RIP CURRENTS AND
BEACH EROSION. THOUGH THE OFFICIAL START OF THE ATLANTIC HURRICANE SEASON IS
JUNE 1ST, SIGNIFICANT SUBTROPICAL (OR TROPICAL) STORMS CAN STILL DEVELOP DURING
MAY, AND THIS PARTICULAR SYSTEM WILL NEED TO BE CLOSELY MONITORED OVER THE NEXT
FEW DAYS. RESIDENTS AND MARINE INTERESTS ALONG THE SOUTHEAST COAST ARE
ENCOURAGED TO KEEP UP WITH THE LATEST INFORMATION REGARDING THIS SYSTEM, FROM
THEIR LOCAL NATIONAL WEATHER SERVICE FORECAST OFFICES.



MODERATE FLOODING ALONG THE ALTAMAHA RIVER IN SOUTHEAST GEORGIA IS EXPECTED TO
CONTINUE INTO THE EARLY STAGES OF THIS OUTLOOK PERIOD. FLOODING IS POSSIBLE IN
EXTREME NORTHEASTERN KANSAS DURING THE EARLY STAGES OF THIS PERIOD.



AN INCREASE IN RAIN AND WINDS CAN BE EXPECTED ACROSS THE ALASKA PENINSULA AS A
SURFACE LOW STRENGTHENS ACROSS THE NORTHERN GULF OF ALASKA. RAINFALL AMOUNTS
AND WIND SPEEDS ARE EXPECTED TO REMAIN BELOW HAZARDS CRITERIA.

FOR THURSDAY MAY 14 - WEDNESDAY MAY 20: THE PREDICTED 500-HPA MEAN CIRCULATION
PATTERN ACROSS THE NORTH AMERICAN DOMAIN IS CHARACTERIZED BY TROUGHS ALONG BOTH
COASTS (THE STRONGER ONE ALONG THE WEST COAST), AND OVER THE ALEUTIANS. RIDGES
ARE ANTICIPATED OVER THE CENTRAL AND EAST-CENTRAL CONUS, AND MOST OF THE ALASKA
MAINLAND, INCLUDING THE PANHANDLE.



AN AREA OF HEAVY RAIN IS FORECAST IN PORTIONS OF WESTERN AND SOUTHERN TEXAS ON
THURSDAY, MAY 14TH, DUE TO A NEARBY COLD FRONT AND AMPLE GULF MOISTURE.



THE MOST RECENT U.S. DROUGHT MONITOR, VALID ON APRIL 28, INDICATES A SLIGHT
INCREASE (TO 20.03 FROM 18.97) IN THE PERCENTAGE OF THE CONUS IN SEVERE TO
EXCEPTIONAL DROUGHT (D2-D4).

FORECASTER: ANTHONY ARTUSA

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