Prognostic Meteorological Discussion
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FXUS21 KWNC 271932
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT APRIL 27 2015

SYNOPSIS: AT THE BEGINNING OF THE OUTLOOK PERIOD, A LOW-PRESSURE SYSTEM IS
FORECAST OVER THE CAROLINA COAST, WITH A PROJECTED NORTHEASTWARD TRACK. AFTER
THAT SYSTEM MOVES OUT, HIGH PRESSURE IS FORECAST OVER MUCH OF THE LOWER 48
STATES FOR THE ENSUING 2-3 DAYS. A WEAK LOW PRESSURE SYSTEM IS FORECAST TO
DEVELOP OVER THE NORTHERN GREAT PLAINS EARLY NEXT WEEK. THROUGH EARLY NEXT
WEEK, MOST OF ALASKA IS LIKELY TO EXPERIENCE SEASONABLE WEATHER AS LOW-PRESSURE
NEAR THE ALEUTIANS IS NOT EXPECTED TO BE PARTICULARLY INTENSE. FORECASTS FOR
NEXT WEEK INDICATE A MORE ACTIVE PATTERN ACROSS THE SOUTHWEST AND GREAT PLAINS.

HAZARDS

HEAVY RAIN FOR THE SOUTHERN MID-ATLANTIC, THU, APR 30.

FLOODING LIKELY ALONG THE GUADALUPE RIVER AT BLOOMINGTON, THU, APR 30.

FLOODING OCCURRING OR IMMINENT FOR PARTS OF THE SOURIS RIVER IN NORTH DAKOTA
DUE TO WATER RELEASE FROM LAKE DARLING.

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

DETAILED SUMMARY

FOR THURSDAY APRIL 30 - MONDAY MAY 04: A MODERATE STRENGTH LOW-PRESSURE SYSTEM
IS FORECAST TO BE OVER THE CAROLINAS AT THE START OF THE OUTLOOK PERIOD. HEAVY
RAINS (1-2 INCHES) ARE LIKELY ALONG AND JUST NORTH OF THE TRACK OF THE
LOW-PRESSURE SYSTEM.  GFS-BASED FORECASTS ARE SLOWER IN PROPAGATING THE
LOW-PRESSURE SYSTEM, AND ACCORDINGLY PRODUCE MORE RAINS FROM THE DELMARVA TO
THE CAROLINAS. IF THE LOW PRESSURE SYSTEM TRACKS CLOSER TO THE COAST, RAINS
COULD EXTEND INTO THE WEEKEND ACROSS PORTIONS OF THE NORTHEAST. ADDITIONALLY,
WITH A MORE WESTWARD TRACK, HIGH WINDS AND COASTAL FLOODING BECOME MORE LIKELY
FOR NEW ENGLAND AND PORTIONS OF LONG ISLAND.



FLOODING IS LIKELY OVER SOUTHEAST TEXAS, ALONG THE GUADALUPE RIVER. RECENT
HEAVY RAINS HAVE DRAMATICALLY INCREASED RUNOFF. FLOODING IN CENTRAL MISSISSIPPI
IS LIKELY TO ABATE BEFORE THE OUTLOOK PERIOD, BUT ANY RAIN BETWEEN NOW THE
START OF THE VALID PERIOD WOULD LIKELY EXACERBATE AND PROLONG THE FLOODING.



A LOW-PRESSURE SYSTEM IS FORECAST DEVELOP OVER THE NORTHERN GREAT PLAINS BY THE
BEGINNING OF NEXT WEEK. AS THE SYSTEM DEEPENS, WINDS ARE LIKELY TO APPROACH
CRITICAL FIRE WEATHER THRESHOLDS, BUT UNCERTAINTY IN THE RELATIVE HUMIDITY
VALUES AND WIND SPEEDS PRECLUDE THE DESIGNATION OF A HAZARD AT THIS TIME.

FOR TUESDAY MAY 05 - MONDAY MAY 11: THE OVERALL PATTERN FOR NEXT WEEK IS LIKELY
TO FEATURE A TROUGH NEAR THE ALEUTIANS AND A TROUGH OVER THE WESTERN HALF OF
THE CONUS, WITH RIDGING FROM THE GREAT PLAINS TO THE EAST COAST. THAT PATTERN
FAVORS ABOVE MEDIAN RAINS FOR MUCH OF THE LOWER 48 STATES.  MEAN TROUGHING
FAVORS ABOVE MEDIAN PRECIPITATION FOR SOUTHERN ALASKA.



EARLY NEXT WEEK, SOME MODELS ARE INDICATING A SHORTWAVE TROUGH MOVING THROUGH
THE PATTERN OVER THE SOUTHWEST. A SHORTWAVE MOVING THROUGH THE SOUTHWEST WOULD
INCREASE THE THREAT FOR SEVERE WEATHER OVER THE SOUTHERN AND CENTRAL GREAT
PLAINS, AS WELL AS INCREASING THE THREAT OF HEAVY RAINS OVER THE GREAT PLAINS.



THE MOST RECENT U.S. DROUGHT MONITOR, VALID ON APRIL 21, INDICATES A VERY
SLIGHT DECREASE (TO 18.97 FROM 19.14 ) IN THE PERCENTAGE OF THE CONUS IN SEVERE
TO EXCEPTIONAL DROUGHT (D2-D4).

FORECASTER: MATTHEW ROSENCRANS

$$




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