Prognostic Meteorological Discussion
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FXUS21 KWNC 162016
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EST JANUARY 16 2017

SYNOPSIS: AN AREA OF UPPER-LEVEL PRESSURE AND ENHANCED ONSHORE FLOW IS LIKELY
TO PERSIST ACROSS THE WESTERN U.S. DURING THE NEXT WEEK, WHILE MULTIPLE LOW
PRESSURE SYSTEMS ADVANCE ACROSS THE CENTRAL AND EASTERN U.S. DURING WEEK-2, A
PATTERN CHANGE IS EXPECTED WITH AN AREA OF UPPER-LEVEL HIGH PRESSURE DEVELOPING
NEAR THE WEST COAST. ARCTIC HIGH PRESSURE IS FORECAST TO REMAIN CENTERED OVER
MAINLAND ALASKA THROUGH THE WEEKEND, WHILE A STRONG SURFACE LOW IS EXPECTED TO
ENTER THE BERING SEA BY EARLY NEXT WEEK.

HAZARDS

PERIODS OF HEAVY PRECIPITATION (RAIN AND HIGH-ELEVATION SNOW) FOR PARTS OF THE
WESTERN U.S., THU-MON, JAN 19-23.

PERIODS OF HIGH WINDS FOR PARTS OF WESTERN U.S. AND SOUTHERN HIGH PLAINS,
THU-MON, JAN 19-23.

SEVERE WEATHER FOR PARTS OF THE SOUTHEAST, SAT, JAN 21.

PERIODS OF HEAVY RAIN FOR PARTS OF THE SOUTHEASTERN U.S., THU-SUN, JAN 19-22.

MUCH BELOW-NORMAL TEMPERATURES FOR PARTS OF MAINLAND ALASKA, THU-SUN, JAN 19-22.

HIGH WINDS FOR THE ALEUTIANS AND ALASKA PENINSULA ON MON, JAN 23.

HEAVY PRECIPITATION (RAIN AND HIGH-ELEVATION SNOW) FOR SOUTHEAST MAINLAND
ALASKA AND THE ALASKA PANHANDLE, TUE-MON, JAN 24-30.

HIGH WINDS FOR SOUTHEAST MAINLAND ALASKA AND THE ALASKA PANHANDLE, TUE-MON, JAN
24-30.

A SLIGHT RISK OF MUCH BELOW-NORMAL TEMPERATURES FOR PARTS OF THE INTERIOR WEST,
TUE-THU, JAN 24-26.

FLOODING LIKELY ACROSS PARTS OF WASHINGTON.

FLOODING OCCURRING ALONG THE MIDDLE MISSISSIPPI RIVER.

SEVERE DROUGHT ACROSS PARTS OF THE EASTERN AND SOUTHERN U.S., GREAT PLAINS,
ARIZONA, CALIFORNIA, AND COLORADO.

DETAILED SUMMARY

FOR THURSDAY JANUARY 19 - MONDAY JANUARY 23: A SERIES OF UPPER-LEVEL TROUGHS,
STRONG ONSHORE FLOW, AND ENHANCED PACIFIC MOISTURE ARE LIKELY TO RESULT IN
PERIODS OF HEAVY PRECIPITATION (RAIN AND HIGH-ELEVATION SNOW) ACROSS SOUTHWEST
OREGON, CALIFORNIA, SOUTHWEST UTAH, AND ARIZONA DURING THIS PERIOD.
DETERMINISTIC MODEL SOLUTIONS INDICATE THAT THE HEAVIEST PRECIPITATION (5 TO 10
INCHES, LIQUID EQUIVALENT) IS LIKELY ACROSS THE OROGRAPHICALLY FAVORED COASTAL
RANGES AND SIERRA MOUNTAINS OF CALIFORNIA. SNOW LEVELS ARE GENERALLY EXPECTED
TO LOWER BY EARLY NEXT WEEK ACROSS THE WESTERN U.S. AS 500-HPA HEIGHTS DECREASE
WITH SNOW LEVELS POTENTIALLY BELOW 5,000 FEET ACROSS ARIZONA ON JAN 23. PERIOD
OF HIGH WINDS (GUSTS ABOVE 50 MPH) ARE ALSO FORECAST ACROSS FROM THE WESTERN
U.S EAST TO THE SOUTHERN HIGH PLAINS DURING THIS PERIOD.



ALTHOUGH THE SHORTWAVE TROUGHS, EMERGING FROM THE WESTERN U.S., ARE EXPECTED TO
DAMPEN AS THEY PROGRESS INTO MEAN RIDGING ALOFT OVER THE EASTERN U.S., THERE IS
A SIGNAL FOR HEAVY RAIN ACROSS THE SOUTHEASTERN U.S. DUE TO ABUNDANT LOW-LEVEL
MOISTURE FOR JANUARY. THEREFORE, PERIODS OF HEAVY RAIN ARE FORECAST FROM THE
GULF COAST NORTH TO THE TENNESSEE VALLEY AND SOUTHERN APPALACHIANS FROM JANUARY
19 TO 22. MODEL GUIDANCE INDICATES THAT 96-HOUR TOTAL RAINFALL AMOUNTS COULD
LOCALLY EXCEED 5 INCHES ACROSS THE OUTLINED AREA FOR HEAVY RAIN.



ON JANUARY 21, THE EXIT REGION OF A STRONG MID-LEVEL JET, COINCIDING WITH
MODERATE INSTABILITY AND HIGH LOW-LEVEL MOISTURE, IS EXPECTED TO SUPPORT SEVERE
THUNDERSTORMS ACROSS PARTS OF THE SOUTHEASTERN U.S. THE SEVERE WEATHER HAZARD
AREA FOR THE SOUTHEASTERN U.S. IS EXPECTED TO BE EXTENDED THROUGH JAN 22 IN
SUBSEQUENT OUTLOOKS. THE UNUSUAL ASPECT OF THE STORMINESS ACROSS THE CENTRAL
AND EASTERN U.S. WILL BE THE LACK OF WINTER WEATHER ASSOCIATED WITH THE LOW
PRESSURE SYSTEMS, GIVEN THE ABSENCE OF COLD AIR.



MUCH BELOW-NORMAL TEMPERATURES ARE POSTED FOR MAINLAND ALASKA THROUGH JAN 22,
WHERE THE 6Z GFS ENSEMBLE MEAN INDICATES TEMPERATURES AVERAGING MORE THAN 20
DEGREES F BELOW NORMAL. THE DETERMINISTIC MODELS INDICATE THAT A POTENT LOW
PRESSURE SYSTEM (AROUND 964-HPA) WILL ENTER THE BERING SEA AND BRING HIGH WINDS
(50 KNOTS OR GREATER) TO THE ALEUTIANS AND ALASKA PENINSULA ON JAN 23.

FOR TUESDAY JANUARY 24 - MONDAY JANUARY 30: THE ENSEMBLE MEANS ARE IN GOOD
AGREEMENT AND REMAIN CONSISTENT THAT A MAJOR PATTERN CHANGE OCCURS DURING THE
FINAL WEEK OF JANUARY. AN UPPER-LEVEL RIDGE IS EXPECTED TO BUILD NEAR THE WEST
COAST, RESULTING IN A MUCH DRIER PATTERN FOR THE PACIFIC NORTHWEST AND NORTHERN
CALIFORNIA. MEANWHILE, A FULL LATITUDE TROUGH IS FORECAST TO EXTEND FROM HUDSON
BAY TO THE CENTRAL U.S. THIS LONGWAVE PATTERN IS EXPECTED TO FAVOR A TREND
TOWARDS MORE SEASONAL TEMPERATURES ACROSS THE CENTRAL AND EVENTUALLY THE
EASTERN U.S. LATER IN WEEK-2.



SURFACE HIGH PRESSURE IS EXPECTED TO BECOME CENTERED OVER THE GREAT BASIN EARLY
IN THE WEEK-2 PERIOD. A SLIGHT RISK OF MUCH BELOW-NORMAL TEMPERATURES IS POSTED
FOR PARTS OF THE INTERIOR WEST WHERE STRONG LOW-LEVEL INVERSIONS ARE MOST
LIKELY.



AN UPPER-LEVEL TROUGH, LOCATED SOUTH OF THE ALEUTIANS, FAVORS MULTIPLE LOW
PRESSURE SYSTEMS WITH ONSHORE FLOW AFFECTING SOUTHEAST ALASKA AND THE ALASKA
PANHANDLE DURING WEEK-2. HEAVY PRECIPITATION (RAIN AND HIGH-ELEVATION SNOW WITH
AMOUNTS OF MORE THAN 1.5 INCHES PER 24 HOURS) AND HIGH WINDS (SPEEDS GREATER
THAN 50 KNOTS) ARE POSTED FOR THESE AREAS THROUGHOUT THE PERIOD.



ACCORDING TO THE LATEST U.S. DROUGHT MONITOR (USDM) VALID ON JANUARY 10, THE
COVERAGE OF SEVERE OR GREATER DROUGHT FOR THE CONUS DECREASED FROM 8.63 TO
7.96%. ONE TO TWO CATEGORY IMPROVEMENTS WERE MADE TO THE DROUGHT AREAS ACROSS
PARTS OF CALIFORNIA AND NEVADA FROM THE PREVIOUS WEEK.

FORECASTER: BRAD PUGH

$$



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