Prognostic Meteorological Discussion
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FXUS21 KWNC 081935
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EST FEBRUARY 08 2016

SYNOPSIS: A STRONG AREA OF UPPER-LEVEL LOW PRESSURE IS EXPECTED TO REMAIN OVER
THE EASTERN U.S. THROUGH THE NEXT WEEK. ARCTIC SURFACE HIGH PRESSURE IS
FORECAST TO SHIFT SOUTH FROM CANADA THIS WEEKEND. THE WELL-ESTABLISHED AREA OF
UPPER-LEVEL HIGH PRESSURE ACROSS THE WESTERN U.S. IS EXPECTED TO REMAIN STRONG
THROUGH THURSDAY AND THEN GRADUALLY WEAKEN WHEN A LOW PRESSURE SYSTEM MOVES
INLAND FROM THE PACIFIC. AN AREA OF UPPER-LEVEL LOW PRESSURE IS FORECAST TO
PERSIST ACROSS THE ALEUTIANS DURING THE NEXT TWO WEEKS.

HAZARDS

LOCALLY HEAVY, LAKE-EFFECT SNOW DOWNWIND OF THE GREAT LAKES, FRI, FEB 12.

HEAVY SNOW FOR PARTS OF THE CENTRAL AND SOUTHERN APPALACHIANS, FRI, FEB 12.

MUCH BELOW-NORMAL TEMPERATURES FOR THE EASTERN U.S., THU-MON, FEB 11-15.

MUCH BELOW-NORMAL TEMPERATURES FOR THE UPPER MISSISSIPPI VALLEY, GREAT LAKES,
AND MIDWEST, FRI-SAT, FEB 12-13.

FLOODING OCCURRING OR LIKELY ACROSS PARTS OF THE SOUTHEAST AND LOWER
MISSISSIPPI VALLEY.

SEVERE DROUGHT ACROSS PARTS OF THE WESTERN U.S. AND PUERTO RICO.

DETAILED SUMMARY

FOR THURSDAY FEBRUARY 11 - MONDAY FEBRUARY 15: A HIGHLY AMPLIFIED UPPER-LEVEL
TROUGH ACROSS EASTERN NORTH AMERICA IS LIKELY TO RESULT IN A 1044-HPA SURFACE
HIGH SHIFTING SOUTH FROM CANADA INTO THE EASTERN U.S. THIS WEEKEND.
DETERMINISTIC 6Z GFS AND 0Z ECMWF MODEL RUNS ARE IN GOOD AGREEMENT THAT 850-HPA
TEMPERATURES BELOW -24 DEGREES C SHIFT FROM THE GREAT LAKES ON FRIDAY TO THE
MID-ATLANTIC THIS WEEKEND. THE MOST EXTREME ANOMALOUS COLD ACROSS THE UPPER
MISSISSIPPI VALLEY, GREAT LAKES, AND MIDWEST IS FORECAST ON SATURDAY MORNING
WHEN MINIMUM TEMPERATURES OF 0 TO -20 DEGREES F CAN BE EXPECTED. ON SUNDAY
MORNING, SUBZERO MINIMUM TEMPERATURES ARE FORECAST ACROSS THE NORTHEAST WITH
SINGLE DIGITS ABOVE ZERO ACROSS THE MID-ATLANTIC. THESE MINIMUM TEMPERATURES
ARE 20 TO 25 DEGREES F BELOW-NORMAL FOR MID-FEBRUARY. ALTHOUGH WIND SPEEDS ARE
LIKELY TO REMAIN BELOW HAZARDS CRITERIA, GUSTY WINDS OF 15 TO 25 MPH THIS
WEEKEND ARE LIKELY TO CREATE DANGEROUS WIND CHILL VALUES ACROSS THE NORTHEAST
AND MID-ATLANTIC. PRECEDING THIS ARCTIC OUTBREAK, MUCH-BELOW NORMAL
TEMPERATURES (NEGATIVE ANOMALIES OF MORE THAN 12 DEGREES F) ARE ALSO EXPECTED
TO PREVAIL ACROSS PARTS OF THE EASTERN U.S. ON THURSDAY AND FRIDAY.



ON FRIDAY, STRONG COLD AIR ADVECTION IS EXPECTED TO PROMOTE LOCALLY HEAVY
LAKE-EFFECT SNOW (6 INCHES OR MORE IN 24 HOURS) DOWNWIND OF THE GREAT LAKES.
ALSO, HEAVY SNOW (NEAR 4 INCHES) IS EXPECTED ACROSS PARTS OF THE CENTRAL AND
SOUTHERN APPALACHIANS DUE TO STRONG COLD AIR ADVECTION COUPLED WITH UPSLOPE
FLOW. THE DETERMINISTIC 0Z ECMWF MODEL INDICATES THAT THE AMPLIFYING TROUGH
PROMOTES SURFACE LOW DEVELOPMENT ACROSS THE MID-ATLANTIC ON FRIDAY NIGHT. THIS
LOW PRESSURE SYSTEM POSES A RISK OF MODERATE TO HEAVY SNOW FROM THE
MID-ATLANTIC NORTH TO NEW ENGLAND. HOWEVER, THE DETERMINISTIC 6Z/12Z GFS AND
0Z/12Z CANADIAN MODELS FAVOR OFFSHORE DEVELOPMENT OF THIS SURFACE LOW WITH
LITTLE OR NO SNOW ACROSS THE MID-ATLANTIC AND NORTHEAST. DUE TO THESE LARGE
MODEL DIFFERENCES, A HEAVY SNOW HAZARD IS NOT DEPICTED ON THE MAP FOR THESE
AREAS AT THIS TIME.



THE UPPER-LEVEL RIDGE OVER WESTERN NORTH AMERICA IS FORECAST TO WEAKEN AND
ALLOW THE RETURN OF ONSHORE FLOW TO THE PACIFIC NORTHWEST LATER IN THE WEEK.
PRECIPITATION AMOUNTS ARE NOT EXPECTED TO REACH HAZARDS CRITERIA ACROSS COASTAL
WASHINGTON ON FRIDAY AND SATURDAY.



HEAVY RAINFALL DURING THE PAST FEW WEEKS TRIGGERED MINOR TO MODERATE FLOODING
ALONG THE FOLLOWING RIVERS: ALTAMAHA AND SAVANNAH RIVERS IN GEORGIA, CAPE FEAR
RIVER IN NORTH CAROLINA, EDISTO RIVER IN SOUTH CAROLINA, CHOCTAWHATCHEE RIVER
IN THE FLORIDA PANHANDLE, AND PEARL RIVER IN MISSISSIPPI.



A PERSISTENT AREA OF LOW PRESSURE AND ONSHORE FLOW ARE EXPECTED TO BRING
PERIODS OF INCREASED WINDS AND PRECIPITATION TO COASTAL SOUTHERN ALASKA AND THE
ALASKA PANHANDLE DURING THIS PERIOD. HOWEVER, HAZARDOUS PRECIPITATION AMOUNTS
AND WIND SPEEDS ARE NOT FORECAST ACROSS THESE AREAS.

FOR TUESDAY FEBRUARY 16 - MONDAY FEBRUARY 22: THE 0Z/6Z GFS ENSEMBLE MEAN
MAINTAINS A LONGWAVE PATTERN FEATURING AN UPPER-LEVEL RIDGE (TROUGH) OVER
WESTERN (EASTERN) NORTH AMERICA DURING WEEK-2. HOWEVER, LARGE SPREAD EXISTS
AMONG THE 0Z CANADIAN AND 0Z ECMWF ENSEMBLE MEMBERS ACROSS NORTH AMERICA WITH
THESE MODEL SOLUTIONS SUGGESTING MORE ZONAL FLOW. MODEL GUIDANCE INDICATES THE
POTENTIAL FOR AN IMPACTFUL WINTER WEATHER EVENT ACROSS THE EASTERN U.S. EARLY
IN WEEK-2. HOWEVER, DUE TO LARGE MODEL SPREAD, NO HAZARDS ARE DESIGNATED ON THE
MAP AT THIS TIME.



ACCORDING TO THE U.S. DROUGHT MONITOR VALID ON FEBRUARY 2, THE COVERAGE OF
SEVERE TO EXCEPTIONAL (D2-D4) DROUGHT ACROSS THE 50 U.S. STATES AND PUERTO RICO
DECREASED SLIGHTLY FROM 7.13 PERCENT TO 7.06 PERCENT. SEVERE TO EXCEPTIONAL
DROUGHT IS LIMITED TO THE WESTERN THIRD OF THE CONTIGUOUS U.S. AND PUERTO RICO.

FORECASTER: BRAD PUGH

$$



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