574  
FXUS21 KWNC 281919  
PMDTHR  
US HAZARDS OUTLOOK  
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD  
300 PM EST FEBRUARY 28 2018  
 
SYNOPSIS: AREAS OF MID-LEVEL LOW PRESSURE ARE FORECAST TO PERIODICALLY SHIFT  
FROM THE PACIFIC NORTHWEST THROUGH THE GREAT LAKES DURING WEEK-1. THIS SCENARIO  
FAVORS SURFACE LOW PRESSURE DEVELOPING OVER THE CENTRAL PLAINS AND LIFTING  
TOWARDS THE GREAT LAKES OVER THE COURSE OF THE WEEK. BEHIND THIS SYSTEM, ARCTIC  
HIGH PRESSURE IS FORECAST TO SAG SOUTHWARD INTO THE WEST, BRINGING WITH IT THE  
POTENTIAL FOR RECORD LOW TEMPERATURES IN PARTS OF THE WEST BY LATE IN WEEK-1 OR  
EARLY IN WEEK-2. MID-LEVEL LOW PRESSURE FORECAST IN THE NORTHEAST PACIFIC  
SUGGESTS AN UNSETTLED PATTERN FOR THE WEST COAST DURING WEEK-2. MULTIPLE  
SURFACE LOW PRESSURE SYSTEMS ARE ANTICIPATED IN THE BERING SEA AND GULF OF  
ALASKA THROUGHOUT THE OUTLOOK PERIOD, BUT NONE ARE CURRENTLY FORECAST TO BE  
PARTICULARLY IMPACTFUL. ALASKA IS ANTICIPATED TO SHIFT INTO A COLDER PATTERN BY  
WEEK-2 AS LOW-LEVEL FLOW INCREASINGLY BECOMES OUT OF THE NORTH AND MID-LEVEL  
LOW PRESSURE BECOMES ESTABLISHED.  
 
HAZARDS  
 
ENHANCED WILDFIRE RISK ACROSS PORTIONS OF THE THE SOUTHERN ROCKIES, THE CENTRAL  
PLAINS, AND THE SOUTHERN PLAINS, SAT, MAR 3.  
 
HIGH WINDS ACROSS PORTIONS OF THE CENTRAL AND SOUTHERN ROCKIES, AND THE CENTRAL  
AND SOUTHERN ROCKIES, SAT-SUN, MAR 3-4.  
 
MUCH BELOW NORMAL TEMPERATURES ACROSS PORTIONS OF THE NORTHERN PLAINS AND THE  
NORTHERN ROCKIES, SUN-WED, MAR 4-7.  
 
MUCH BELOW-NORMAL TEMPERATURES ACROSS PORTIONS OF CALIFORNIA, THE GREAT BASIN,  
THE PACIFIC NORTHWEST, AND THE SOUTHWEST, SUN-MON, MAR 4-5.  
 
HEAVY SNOW ACROSS PORTIONS OF THE UPPER MISSISSIPPI VALLEY AND THE NORTHERN  
PLAINS, MON-TUE, MAR 5-6.  
 
FLOODING OCCURRING OR IMMINENT ACROSS PORTIONS OF THE MISSISSIPPI VALLEY, THE  
TENNESSEE VALLEY, THE GREAT LAKES, THE SOUTHERN PLAINS, AND THE OHIO VALLEY.  
 
FLOODING POSSIBLE ACROSS PORTIONS OF THE MIDDLE MISSISSIPPI VALLEY, THE GREAT  
LAKES, THE OHIO VALLEY, AND THE TENNESSEE VALLEY.  
 
HIGH RISK OF MUCH BELOW-NORMAL TEMPERATURES FOR PORTIONS OF THE NORTHERN  
PLAINS, THU, MAR 8.  
 
MODERATE RISK OF MUCH BELOW-NORMAL TEMPERATURES FOR PORTIONS OF THE NORTHERN  
PLAINS, THU, MAR 8.  
 
SLIGHT RISK OF MUCH BELOW-NORMAL TEMPERATURES FOR PORTIONS OF THE NORTHERN AND  
CENTRAL PLAINS AND THE NORTHERN ROCKIES, THU-FRI, MAR 8-9.  
 
SLIGHT RISK OF MUCH BELOW-NORMAL TEMPERATURES FOR PORTIONS OF THE SOUTHEAST,  
SOUTHERN APPALACHIANS, TENNESSEE VALLEY, AND MID-ATLANTIC, FRI-SAT, MAR 9-MAR  
10.  
 
MODERATE RISK OF HEAVY PRECIPITATION FOR PORTIONS OF CALIFORNIA AND NEVADA,  
THU-FRI, MAR 8-9.  
 
SLIGHT RISK OF HEAVY PRECIPITATION FOR PORTIONS OF CALIFORNIA, OREGON, AND  
NEVADA, THU-MON, MAR 8-12.  
 
MODERATE RISK OF MUCH BELOW-NORMAL TEMPERATURES FOR PORTIONS OF SOUTHWESTERN  
MAINLAND ALASKA, SUN-WED, MAR 11-14.  
 
SLIGHT RISK OF MUCH BELOW-NORMAL TEMPERATURES FOR MUCH OF MAINLAND ALASKA,  
SAT-WED, MAR 10-14.  
 
SEVERE DROUGHT ACROSS THE CENTRAL PLAINS, THE CENTRAL ROCKIES, THE LOWER  
MISSISSIPPI VALLEY, THE CENTRAL GREAT BASIN, THE NORTHERN PLAINS, THE SOUTHERN  
ROCKIES, THE MIDDLE MISSISSIPPI VALLEY, CALIFORNIA, THE SOUTHERN PLAINS, AND  
THE SOUTHWEST.  
 
DETAILED SUMMARY  
 
FOR SATURDAY MARCH 03 - WEDNESDAY MARCH 07: A PAIR OF AMPLIFIED 500-HPA TROUGHS  
ARE FORECAST TO PUSH INTO THE WESTERN U.S. OVER THE COURSE OF WEEK-1. IN  
ASSOCIATION WITH THE FIRST OF THESE PUSHING EASTWARD, LEE CYCLOGENESIS IS  
FORECAST OVER THE CENTRAL PLAINS NEAR THE START OF THE FORECAST PERIOD. MODEL  
GUIDANCE THEN BRINGS THIS SURFACE SYSTEM NORTH TOWARDS THE GREAT LAKES OVER THE  
COURSE OF THE WEEK WHILE FAILING TO SUBSTANTIALLY DEEPEN THE LOW (MINIMUM  
PRESSURE VALUES ABOVE 990 HPA). DESPITE THE MODEST INTENSITY, THE WRAP-AROUND  
REGION ON THE NORTHWESTERN SIDE OF THE SYSTEM COULD YIELD UP TO 6 INCHES OR  
MORE OF HEAVY SNOW FOR THE NORTHERN PLAINS AND UPPER MISSISSIPPI VALLEY ON  
MARCH 5TH AND 6TH. YESTERDAY'S U.S. HAZARDS OUTLOOK FORECAST THE POTENTIAL FOR  
HEAVY RAINS ACROSS THE SOUTHEAST ON THE 5TH AND 6TH, COINCIDENT WITH RECENT  
FLOODING CONCERNS. HOWEVER, THE LATEST GFS, ECMWF, AND CANADIAN MODEL GUIDANCE  
KEEPS 24 HOUR RAINFALL TOTALS ACROSS THIS REGION TO BELOW A HALF INCH, LEADING  
TO THIS RAINFALL HAZARD BEING OMITTED IN THE PRESENT OUTLOOK. THE LACK OF  
MOISTURE AVAILABILITY FROM THE GULF OF MEXICO ALSO APPEARS LIKELY TO LIMIT ANY  
WIDESPREAD SEVERE WEATHER THREAT WITH THE ADVANCING COLD FRONT. ALSO IN  
ASSOCIATION WITH THE AMPLIFIED MID-LEVEL TROUGH IS THE POTENTIAL FOR ENHANCED  
FIRE WEATHER OVER THE SOUTHERN AND CENTRAL PLAINS ON MARCH 3RD AND HIGH WINDS  
ACROSS A SIMILAR REGION ON THE 3RD AND 4TH. WITH THIS SETUP, STRONG MID-LEVEL  
FLOW IS LIKELY TO BE MIXED DOWN TO THE SURFACE, COUPLED WITH LOCALIZED  
DOWNSLOPE EFFECTS TO FURTHER DECREASE LOW-LEVEL HUMIDITY AND RAISE  
TEMPERATURES. THIS SETUP FAVORS WARM, DRY CONDITIONS CONDUCIVE FOR FIRE  
POTENTIAL ON THE 3RD AND 4TH, PARTICULARLY FOR THE HIGHLIGHTED AREA ON THE  
FORECAST GRAPHIC ON THE 3RD.  
 
IN THE WAKE OF THE TROUGH DRIVING THE POTENTIAL FOR THE AFOREMENTIONED SNOW,  
FIRE, AND WIND THREATS, COLD AIR IS LIKELY TO DESCEND OUT OF CANADA AND INTO  
THE WEST. TWO AREAS OF MUCH BELOW-NORMAL TEMPERATURES (MINIMUM TEMPERATURE  
ANOMALIES OF -12 DEGREES F OR GREATER) APPEAR POSSIBLE DURING WEEK-1: THE FIRST  
FOCUSED ON THE GREAT BASIN FOR THE 4TH AND 5TH, AND THE SECOND ACROSS THE  
NORTHERN PLAINS FOR THE 4TH THROUGH 7TH. OVER THE COURSE OF WEEK-1 TEMPERATURES  
APPEAR LIKELY TO MODERATE WEST OF THE ROCKIES AS ANOTHER MID-LEVEL TROUGH  
APPROACHES FROM THE PACIFIC, ALONG WITH A MORE SOUTHERLY COMPONENT TO THE  
LOW-LEVEL FLOW, LEAVING THE ANOMALOUS COLD TO LINGER LONGER OVER THE NORTHERN  
PLAINS WHERE IT APPEARS LIKELY TO EXTEND INTO EARLY WEEK-2.  
 
ALASKA IS FORECAST TO BE IMPACTED BY MULTIPLE SURFACE DISTURBANCES IN THE  
BERING SEA AND GULF OF ALASKA, WITH EACH SYSTEM RELATIVELY WEAK BY ALASKAN  
STANDARDS. GIVEN THE MODEST INTENSITIES FORECAST FOR EACH OF THESE SYSTEMS, NO  
PRECIPITATION, WIND, OR WAVE HAZARDS ARE CURRENTLY ANTICIPATED. THE MUCH  
ABOVE-NORMAL TEMPERATURES HAZARDS THROUGH THE 5TH FROM YESTERDAY'S OUTLOOK HAS  
BEEN DROPPED GIVEN COLDER FORECAST SOLUTIONS BY THE ECMWF RELATIVE TO THE GEFS,  
COUPLED WITH DAILY TEMPERATURES APPEARING LIKELY TO REMAIN BELOW 25 DEGREES F  
THROUGHOUT WEEK-1 ACROSS NORTHWESTERN PARTS OF MAINLAND ALASKA. WHILE  
TEMPERATURES APPEAR LIKELY TO BE HIGHLY ANOMALOUS AT UP TO 35 DEGREES F ABOVE  
NORMAL FROM THE SOUTHERLY FLOW AND LACK OF SEA ICE COVERAGE IN THE BERING SEA,  
NO SPECIFIC HAZARD TO LIFE OR PROPERTY APPEARS LIKELY GIVEN THE COLD  
CLIMATOLOGY THIS TIME OF YEAR.  
 
FOR THURSDAY MARCH 08 - WEDNESDAY MARCH 14: DURING WEEK-2 ANOMALOUS TROUGHING  
IS FAVORED OVER THE PACIFIC AND MID-ATLANTIC STATES. THIS SCENARIO FAVORS  
UNSETTLED WEATHER FOR MUCH OF THE WEST COAST, PARTICULARLY ACROSS CALIFORNIA. A  
MODERATE RISK OF HEAVY PRECIPITATION IS FORECAST FOR MUCH OF NORTHERN  
CALIFORNIA ON THE 8TH AND 9TH, WITH A BROADER REGION ENCOMPASSING PARTS OF  
OREGON, NEVADA, AND MOST OF CALIFORNIA HAVING A SLIGHT RISK OF HEAVY  
PRECIPITATION FROM THE 8TH THROUGH 12TH. THE CALIBRATED ECMWF IS MORE BULLISH  
THAN THE GEFS ON PRECIPITATION ODDS ACROSS THE WEST, WITH LOCALIZED AREAS  
HAVING A BETTER THAN 60% CHANCE OF EXCEEDING THE 85TH CLIMATOLOGICAL PERCENTILE  
OF PRECIPITATION FOR THE 5 DAY PERIOD COMPARED TO THE GEFS WHICH PEAKS AROUND  
30%. ACROSS THE MODERATE RISK AREA DAILY ENSEMBLE MEAN LIQUID EQUIVALENT TOTALS  
ARE GENERALLY AROUND AN INCH FROM BOTH THE GFS AND ECMWF, WITH LOCALLY HIGHER  
VALUES UP TO 2.5 INCHES IN A DAY FROM THEIR DETERMINISTIC RUNS.  
 
THE BEST SIGNAL FOR COLD DURING WEEK-2 APPEARS TO BE ACROSS THE NORTHERN  
PLAINS, WHERE BOTH THE DAYS 6-10 GEFS AND ECMWF REFORECAST GUIDANCE DURING DAYS  
6-10 INDICATES A BETTER THAN 80% CHANCE OF BELOW NORMAL TEMPERATURES TO OCCUR  
AS ARCTIC HIGH PRESSURE SAGS SOUTH OUT OF CANADA. A HIGH RISK OF MUCH  
BELOW-NORMAL TEMPERATURES IS FORECAST FOR PORTIONS OF MONTANA AND THE DAKOTAS  
ON THE 8TH; A MODERATE RISK OF MUCH BELOW-NORMAL TEMPERATURES ACROSS A BROADER  
PORTION OF THESE STATES AND NORTHEASTERN WYOMING ALSO ON THE 8TH; AND A SLIGHT  
RISK OF MUCH BELOW-NORMAL TEMPERATURES EXTENDING FROM WESTERN MONTANA THROUGH  
MINNESOTA, DIPPING AS FAR SOUTH AS NORTHERN NEBRASKA ON THE 8TH AND 9TH. THE  
CALIBRATED GEFS GIVES AT LEAST A 60% CHANCE (40% AND 20% CHANCE) OF BEING BELOW  
THE 15TH CLIMATOLOGICAL PERCENTILE FOR THE HIGH (MODERATE AND SLIGHT) RISK  
AREAS. OF PARTICULAR NOTE IS ON THE 8TH ACROSS EASTERN MONTANA THIS TOOL  
INDICATES AT LEAST A 10% CHANCE OF RECORD LOW TEMPERATURES DESPITE THE  
SUBSTANTIAL FORECAST LEAD TIME. ENSEMBLE MEAN TEMPERATURE ANOMALIES OF -16  
DEGREES F OR MORE APPEAR LIKELY FOR THE HIGH RISK REGION, WITH THE COOLING  
LIKELY MAXIMIZED OVERNIGHT BENEATH THE SURFACE HIGH PRESSURE FROM RADIATIONAL  
EFFECTS AND A LACK OF MIXING.  
 
LASTLY OVER THE LOWER-48 STATES, A LATE SEASON FROST IS POSSIBLE FROM THE  
CENTRAL AND SOUTHERN PLAINS THROUGH THE SOUTHEAST ON THE 9TH AND 10TH. A SLIGHT  
RISK OF MUCH BELOW-NORMAL TEMPERATURES EXISTS DUE TO THE ANOMALOUS 500-HPA  
TROUGHING ANTICIPATED IN THE VICINITY. THE CALIBRATED GEFS SUPPORTS AT LEAST A  
20% CHANCE FOR THE HIGHLIGHTED REGION TO DROP BELOW 40 DEGREES F, WHILE ALSO  
GIVING A 20% CHANCE OF THE AREA BEING BELOW THE 15TH CLIMATOLOGICAL PERCENTILE  
ON THESE DATES. ODDS ARE SIMILARLY ENHANCED FOR MORE NORTHERN PARTS OF THE  
HIGHLIGHTED AREA TO DROP BELOW FREEZING OVERNIGHT.  
 
A COOLING TREND IS ANTICIPATED ACROSS ALASKA DURING WEEK-2, WITH MID-LEVEL  
TROUGHING FORECAST TO BECOME ESTABLISHED OVER THE STATE. A MODERATE RISK OF  
MUCH BELOW-NORMAL TEMPERATURES IS FORECAST FOR THE 11TH THROUGH 14TH OVER PARTS  
OF SOUTHWESTERN MAINLAND ALASKA, WITH A SLIGHT RISK ACROSS MUCH OF MAINLAND  
ALASKA FROM THE 10TH THROUGH 14TH. ENSEMBLE MEAN TEMPERATURE ANOMALIES IN THE  
MODERATE RISK AREA APPEAR ON TRACK TO EXCEED -20 DEGREES F, WHILE THE  
CALIBRATED GEFS GIVES A BETTER THAN 40% CHANCE OF BEING BELOW THE 15TH  
CLIMATOLOGICAL PERCENTILE OF MINIMUM TEMPERATURES.  
 
THE U.S. DROUGHT MONITOR, VALID ON FEB 20, 2018 INDICATES A SLIGHT DECREASE IN  
THE COVERAGE OF SEVERE TO EXCEPTIONAL DROUGHT (D2-D4) FROM 18.04% LAST WEEK TO  
17.76% THIS WEEK. A FEW OF THE MORE SUBSTANTIAL REVISIONS MADE TO THE MAP THIS  
WEEK INCLUDE AN INCREASE IN THE D1 COVERAGE OVER OREGON, A DECREASE IN THE D3  
COVERAGE OVER NORTHERN TEXAS, AND THE ADDITION OF D3 COVERAGE OVER THE FOUR  
CORNERS REGION.  
 
FORECASTER: CPC FORECASTER  
 

 
 
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