Prognostic Meteorological Discussion
Issued by NWS

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FXUS21 KWNC 211816
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT MAY 21 2015

SYNOPSIS: A SURFACE HIGH PRESSURE CENTER IS FORECAST TO GRADUALLY MOVE OFF THE
EAST COAST, OUT OVER THE WESTERN ATLANTIC. A SURFACE LOW PRESSURE CENTER IS
EXPECTED TO DEVELOP OVER THE CENTRAL HIGH PLAINS, AND TRACK TOWARDS THE WESTERN
GREAT LAKES. VERY WARM AND HUMID SOUTHERLY FLOW IS ANTICIPATED ACROSS
APPROXIMATELY THE SOUTHEAST QUARTER OF THE LOWER 48 STATES, THE OHIO VALLEY,
AND THE MID-ATLANTIC REGION.

HAZARDS

HEAVY RAIN FROM SOUTHERN TEXAS NORTHEASTWARD INTO THE MIDDLE MISSISSIPPI
VALLEY, SUN-MON, MAY 24-25.

MUCH ABOVE-NORMAL TEMPERATURES ARE EXPECTED FOR PARTS OF THE MID-ATLANTIC U.S.,
TUE-THU, MAY 26-28.

FLOODING IS POSSIBLE, IMMINENT, OR OCCURRING IN PARTS OF THE CENTRAL AND
SOUTHERN GREAT PLAINS REGION.

ELEVATED WILDFIRE RISK FOR INTERIOR EASTERN ALASKA, SUN-THU, MAY 24-JUNE 4.

SLIGHT RISK OF MUCH ABOVE-NORMAL TEMPERATURES FOR THE MID-ATLANTIC U.S.,
FRI-SAT, MAY 29-30.

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

DETAILED SUMMARY

FOR SUNDAY MAY 24 - THURSDAY MAY 28: DURING THIS PERIOD, AN UPPER-LEVEL TROUGH
IS FORECAST TO LIFT NORTHEASTWARD OUT OF THE WESTERN CONUS WHILE WEAKENING,
WHILE AN UPPER-LEVEL RIDGE IS FORECAST TO DEVELOP AND PERSIST NEAR THE EAST
COAST. SURFACE LOW PRESSURE ASSOCIATED WITH THE FORMER IS EXPECTED TO MOVE
QUICKLY NORTHEASTWARD TOWARD THE GREAT LAKES, BRINGING HEAVY RAIN IN THE WARM
SECTOR ACROSS A LARGE SECTION OF THE CENTRAL CONUS. PRECIPITATION AMOUNTS OF
2-4 INCHES ARE FORECAST FOR THE AREA DEPICTED ON THE MAP OVER A 2-DAY PERIOD.
GIVEN RECENT HEAVY RAINFALL, AND THE FORECAST FOR ADDITIONAL HEAVY RAIN IN THIS
REGION (ESPECIALLY IN TEXAS AND SOUTHERN OKLAHOMA), SATURATED SOILS WILL
UNDOUBTEDLY LEAD TO FLOODING AREAS. A RELATIVELY SMALL, SEPARATE AREA OF
FLOODING IS ALSO INDICATED IN SOUTHERN COLORADO. DUE TO THE FREQUENT AND OFTEN
RAPID CHANGES IN FLOOD AREAS DESIGNATED ON THE HAZARDS MAP, IT IS RECOMMENDED
THAT RESIDENTS CONSULT THE VERY LATEST INFORMATION AT THE RIVER FORECAST CENTER
(RFC) HOMEPAGE AT HTTP://WATER.WEATHER.GOV/AHPS/RFC/RFC.PHP



STRONG TO SEVERE THUNDERSTORMS MAY DEVELOP DURING THIS PERIOD ACROSS CENTRAL
AND SOUTHERN PORTIONS OF BOTH THE PLAINS AND MISSISSIPPI VALLEY. FAIRLY POOR
RUN-TO-RUN CONTINUITY AMONG VARIOUS DYNAMICAL MODELS, REGARDING THE TIMING OF
INDIVIDUAL SHORT-WAVE FEATURES EXPECTED TO MOVE THROUGH THIS REGION, PRECLUDES
THE DESIGNATION OF A SEVERE WEATHER AREA ON THE MAP AT THIS TIME.



AS AN UPPER-LEVEL RIDGE BUILDS OVER THE SOUTHEAST COAST, HOT AND HUMID
CONDITIONS ARE FORECAST TO RETURN TO PARTS OF THE EASTERN CONUS DURING THE
MIDDLE AND LATTER PARTS OF THE PERIOD. HIGH TEMPERATURES COULD EXCEED 90
DEGREES FOR THREE CONSECUTIVE DAYS OVER THE DEPICTED REGION, FOLLOWING A WARM
FRONTAL PASSAGE ON MONDAY. THE HAZARD IS DEPICTED OVER THE REGION WHERE MAXIMUM
DAYTIME TEMPERATURES ARE FORECAST TO BE GREATER THAN 10 DEGREES ABOVE NORMAL
AND APPROACH OR EXCEED 90 DEGREES.



IN THE EASTERN INTERIOR OF ALASKA, CONTINUED WARM, DRY, AND BREEZY CONDITIONS
FAVOR AN INCREASED CHANCE OF CRITICAL WILDFIRE CONDITIONS THROUGHOUT THIS
PERIOD, AS WELL AS THE ENSUING WEEK-2 PERIOD.

FOR FRIDAY MAY 29 - THURSDAY JUNE 04: THE EXPECTED MID-TROPOSPHERIC FLOW
PATTERN FOR WEEK-2 FEATURES AN AMPLIFIED RIDGE OVER WESTERN CANADA AND ALASKA,
A DEEP TROUGH OVER EASTERN NORTHEASTERN CANADA, AND A ZONALLY-ORIENTED TROUGH
ACROSS THE BERING SEA AND ALEUTIANS. A LESS-AMPLIFIED PATTERN IS PREDICTED OVER
THE CONUS (ESPECIALLY COMPARED TO HIGHER LATITUDES), WITH A TROUGH CENTERED
OVER CALIFORNIA, AND QUASI-ZONAL FLOW DOWNSTREAM OVER THE REMAINDER OF THE
CONUS.



THE ENHANCED RISK OF WILDFIRES NOTED FOR EASTERN INTERIOR ALASKA DURING THE 3-7
DAY PERIOD IS LIKELY TO EXTEND THROUGHOUT MOST, IF NOT ALL, OF WEEK-2. WELL
ABOVE-AVERAGE TEMPERATURES AND BELOW-MEDIAN PRECIPITATION ARE ANTICIPATED
DURING THIS PERIOD, ASSOCIATED WITH THE PREDICTED PERSISTENCE OF AN ANOMALOUS
MID-TROPOSPHERIC RIDGE.



WARM AND HUMID CONDITIONS ARE MORE THAN LIKELY GOING TO PERSIST ACROSS PARTS OF
THE EASTERN CONUS, WHERE A SLIGHT RISK OF MUCH ABOVE-NORMAL TEMPERATURES IS
INDICATED OVER THE MID-ATLANTIC.



THE MOST RECENT U.S. DROUGHT MONITOR, RELEASED TODAY, INDICATES A SUBSTANTIAL
DECREASE (FROM 17.68 TO 15.16) IN THE PERCENTAGE OF THE CONUS IN SEVERE TO
EXCEPTIONAL DROUGHT (D2-D4).

FORECASTER: STEPHEN BAXTER

$$




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