527
FXUS21 KWNC 231747
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT MAY 23 2013
SYNOPSIS: AT THE START OF THE PERIOD, A LOW PRESSURE CENTER IS FORECAST NEAR
CAPE COD. THE ASSOCIATED COLD FRONT IS PREDICTED TO EXTEND SOUTHWARD FROM THIS
LOW TO THE SOUTHERN ATLANTIC COAST, CONTINUING INLAND AS A STATIONARY FRONT
ACROSS THE INTERIOR GULF COAST STATES, LOWER MISSISSIPPI VALLEY, AND
SOUTH-CENTRAL PLAINS. HIGH PRESSURE IS EXPECTED TO BUILD IN BEHIND THIS FRONT
ACROSS MOST OF THE EASTERN HALF OF THE CONTIGUOUS UNITED STATES. BY THE MIDDLE
OF THE HAZARDS OUTLOOK, ONE FRONTAL SYSTEM IS ANTICIPATED OVER THE
NORTH-CENTRAL STATES, WHILE ANOTHER TRAVERSES THE PACIFIC NORTHWEST. IN ALASKA,
A LOW PRESSURE SYSTEM EXTENDING FROM THE CENTRAL ALEUTIANS TO THE CENTRAL GULF
OF ALASKA IS PREDICTED TO MIGRATE SOUTHEASTWARD TOWARD VANCOUVER AND WASHINGTON
STATE.
HAZARDS
HEAVY RAIN FOR CENTRAL AND WESTERN PORTIONS OF THE CORN BELT, SUN-MON, MAY
26-27.
HIGH WINDS ALONG THE MID-ATLANTIC AND NEW ENGLAND COASTS, SUN, MAY 26.
MUCH ABOVE NORMAL TEMPERATURES FOR THE ALASKA PANHANDLE AND MUCH OF THE EASTERN
MAINLAND, SUN-THU, MAY 26-30.
RIVER FLOODING OCCURRING OR IMMINENT IN NORTHERN NORTH DAKOTA, PARTS OF THE
MIDDLE MISSISSIPPI VALLEY, AND SOUTHEASTERN OKLAHOMA, SUN-MON, MAY 26-27.
RIVER FLOODING LIKELY IN NORTHERN NORTH DAKOTA AND EASTERN IOWA, SUN-MON, MAY
26-27.
RIVER FLOODING POSSIBLE FOR IOWA AND LOWER MICHIGAN, SUN-MON, MAY 26-27.
RIVER FLOODING POSSIBLE ACROSS CENTRAL AND SOUTHWESTERN ALASKA, SUN-THU, MAY
26-30.
RIVER FLOODING POSSIBLE IN WESTERN ALASKA, FRI-THU, MAY 31-JUNE 6.
RIVER FLOODING POSSIBLE IN SOUTHWESTERN ALASKA, FRI-MON, MAY 31-JUNE 3.
SEVERE DROUGHT FOR PARTS OF NORTHERN FLORIDA, GREAT PLAINS, RIO GRANDE VALLEY,
ROCKIES, SOUTHWEST, GREAT BASIN, CALIFORNIA, AND HAWAII.
DETAILED SUMMARY
FOR SUNDAY MAY 26 - THURSDAY MAY 30: AN AREA OF HEAVY RAIN (NEAR 2 INCHES) IS
PREDICTED OVER CENTRAL AND WESTERN SECTIONS OF THE CORN BELT DURING THE FIRST
TWO DAYS OF THIS PERIOD, IN ADVANCE OF A WARM FRONT. THOUGH A MID-TROPOSPHERIC
TROUGH IS FORECAST OVER THE WEST, AND A RIDGE OVER THE CENTRAL CONUS, THERE IS
SIGNIFICANT UNCERTAINTY ASSOCIATED WITH THE ANTICIPATED EVOLUTION OF THE
CIRCULATION PATTERN DURING THIS PERIOD. A MAJOR PROBLEM WITH THIS TYPE OF
500-HPA FLOW PATTERN IS TRYING TO PREDICT THE TIMING OF SHORT-WAVE TROUGHS
EMBEDDED IN SOUTHWESTERLY FLOW. IT IS LARGELY FOR THIS REASON THAT NO SEVERE
WEATHER AREAS OR ENHANCED WILDFIRE AREAS ARE CURRENTLY DESIGNATED ON THE MAP.
IN THE PAST WEEK, ANYWHERE FROM 2-6 INCHES OF RAIN HAVE FALLEN ACROSS NORTHERN
AND SOUTH-CENTRAL PORTIONS OF BOTH THE GREAT PLAINS AND THE MISSISSIPPI VALLEY.
ABOUT 10 FLOOD AREAS ARE HIGHLIGHTED ON THE MAP OVER THE CENTRAL CONUS, DUE TO
THIS RECENT RAIN AND THE EXPECTATION OF MORE RAIN DURING THIS PERIOD.
AT THE BEGINNING OF THE HAZARDS OUTLOOK, A COLD FRONT JUST OFF THE EAST COAST
IS EXPECTED TO MOVE SLOWLY OUT TO SEA. A WAVE OF LOW PRESSURE IS FORECAST TO BE
SITUATED ALONG THIS FRONT NEAR CAPE COD. AS THIS LOW DEEPENS, NORTHWESTERLY
WINDS OF 20-30 KNOTS ARE EXPECTED ALONG THE MID-ATLANTIC AND NEW ENGLAND
COASTS, HELPING TO ADVECT UNSEASONABLY CHILLY AIR INTO THE NORTHEAST FOR THE
MEMORIAL DAY WEEKEND.
IN ALASKA, AN AREA OF LOW PRESSURE FROM THE CENTRAL ALEUTIANS TO THE CENTRAL
GULF OF ALASKA IS ANTICIPATED TO TRACK SOUTHEASTWARD TOWARD VANCOUVER ISLAND
AND WASHINGTON STATE. A SURFACE RIDGE OF HIGH PRESSURE IS FORECAST OVER
SOUTHEASTERN PORTIONS OF ALASKA. MUCH ABOVE NORMAL TEMPERATURES ARE PROJECTED
FOR THE PANHANDLE REGION AND A LARGE PORTION OF THE EASTERN MAINLAND. IN
ADDITION, WITH THE EXPECTED CHANGE FROM UNSEASONABLY COLD TO UNSEASONABLY WARM
WEATHER, THERE ARE FLOODING CONCERNS ALONG MAJOR RIVERS (FOR EXAMPLE, THE
YUKON, KUSKOKWIM, AND KOYUKUK RIVERS) IN CENTRAL AND SOUTHWESTERN ALASKA. WITH
SUCH A LATE START TO THE SPRING MELT SEASON, AND A SIGNIFICANTLY HIGHER SUN
ANGLE, IT IS REASONABLE TO EXPECT A SHORT-LIVED BUT FAIRLY INTENSE PERIOD OF
RAPID SNOW MELT AND ICE JAMS IN ALASKA. OF NOTE IS THE VERY RECENT BREAKUP OF
RIVER ICE IN THE TANANA RIVER NEAR NENANA, AK. THIS IS THE LATEST RECORDED
RIVER ICE BREAKUP FOR THE TANANA RIVER SINCE RECORD-KEEPING BEGAN IN 1917. THE
PREVIOUS RECORD WAS SET ON MAY 20, 1964.
FOR FRIDAY MAY 31 - THURSDAY JUNE 06: THE ONLY HAZARDOUS AREAS HIGHLIGHTED ON
THE WEEK 2 MAP AT THIS TIME ARE THE CONTINUING FLOOD AND SEVERE DROUGHT AREAS.
THERE ARE TWO ITEMS WHICH CONTINUE TO BE MONITORED. THE FIRST INVOLVES THE
POTENTIAL FOR MUCH ABOVE NORMAL TEMPERATURES FROM THE CENTRAL HIGH PLAINS
EASTWARD ACROSS THE NORTH-CENTRAL MISSISSIPPI VALLEY AND GREAT LAKES REGION.
HOWEVER, DIFFERING DYNAMICAL MODEL SOLUTIONS MAKE IT UNCLEAR AS TO THE STRENGTH
AND THE DEGREE OF EASTWARD PROGRESSION OF THE UPPER-LEVEL RIDGE OVER THE
CENTRAL CONUS. MOST LOCATIONS WITHIN THE NOTED REGION ARE PREDICTED TO
EXPERIENCE TEMPERATURE ANOMALIES BETWEEN 8-12 DEGREES ABOVE NORMAL, WHICH IS AT
BEST A MARGINAL HAZARD. THE SECOND ITEM INVOLVES THE POSSIBILITY OF A TROPICAL
SYSTEM DEVELOPING OVER THE WESTERN CARIBBEAN AND MOVING NORTHWARD INTO THE GULF
OF MEXICO, AS INDICATED BY CPC'S GLOBAL TROPICS HAZARDS AND BENEFITS OUTLOOK
AT:
HTTP://WWW.CPC.NCEP.NOAA.GOV/PRODUCTS/PRECIP/CWLINK/GHAZARDS/IMAGES/GTH_FULL.PNG
THE RELEASE OF THE U.S. DROUGHT MONITOR THIS MORNING(MAY 23)REVEALS MOSTLY
MINOR ADJUSTMENTS WERE RENDERED TO LAST WEEK'S DROUGHT DEPICTION. THE MORE
SIGNIFICANT CHANGES INCLUDED FURTHER DEGRADATION ACROSS THE SOUTHERN HIGH
PLAINS, AND CONTINUED IMPROVEMENT ACROSS THE NORTH-CENTRAL CONUS. IN ADDITION,
SEVERE TO EXCEPTIONAL (D2-D4) DROUGHT IS AT ITS LOWEST COVERAGE ACROSS THE
CONUS SINCE JUNE 26, 2012 (ABOUT THE TIME WHEN THE FLASH DROUGHT WAS RAMPING UP
LAST YEAR).
FORECASTER: ANTHONY ARTUSA
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