Analyzed 06Z Wed Feb 21, 2018
Valid 12Z Thu Feb 22, 2018
Valid 18Z Thu Feb 22, 2018
Valid 00Z Fri Feb 23, 2018
Valid 06Z Fri Feb 23, 2018
Valid 12Z Fri Feb 23, 2018
Valid 00Z Sat Feb 24, 2018
Valid 12Z Sat Feb 24, 2018
Valid 12Z Sun Feb 25, 2018
Valid 12Z Mon Feb 26, 2018
Valid 12Z Tue Feb 27, 2018
Valid 12Z Wed Feb 28, 2018
Valid 12Z Thu Mar 01, 2018
+ Short Range Forecast Discussion (Day ½-2½)
+ Medium Range Forecast Discussion (Day 3-7)
Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
302 AM EST Thu Feb 22 2018
Valid 12Z Thu Feb 22 2018 - 12Z Sat Feb 24 2018
...Cold and unsettled weather is expected over the West including
some heavy snow over the Rockies...
...Additional heavy rainfall and widespread concerns for flooding
will persist across parts of the southern Plains, lower
Mississippi Valley and the Ohio Valley...
...Warm temperatures are generally expected to continue across a
large portion of the East...
Much of the West will remain in a cold, active wet pattern through
the end of the week thanks to a series of impulses that will drop
south and reinforce the broad upper level trough of low pressure.
Snow will spread across the Pacific Northwest, Great Basin and to
the Rockies. Snow will be heavy at times across the higher terrain
in northern California, southern Idaho, Nevada, Utah and for
portions of the Central Rockies. The cold airmass in place over
the region will keep afternoon highs generally 10 to 20 degrees
cooler than usual for late February.
The waves of energy will exit the Front Range and track across the
Plains where a quasi-stationary frontal boundary extends from the
Lower Mississippi Valley to the Ohio/Tennessee Valley and
Mid-Atlantic. Multiple rounds of heavy rain is forecast as warm
Gulf moisture advects northward along the boundary. This rainfall
is expected to occur over a broad area already saturated from
prior days of excessive rain. A slight to moderate risk for flash
flooding main stem river flooding will persist through the end of
the week. In the cold sector, scattered to widespread snow will be
possible for portions of the Plains, Midwest and Upper Mississippi
Valley - numerous Winter Weather Advisories are in effect for
Much of the East Coast lies within the warm sector of this system
and will continue to have temperatures topping off in the 70s and
80s, whereas, the central CONUS will be below freezing as much as
10 to 20 degrees below normal.
Regarding the threat of winter weather, there will be the approach
of a wave of low pressure from the Tennessee Valley on Thursday
that will actually interact with sufficient cold air over parts of
the upper Ohio Valley, far northern Mid-Atlantic and interior of
the Northeast for a stripe of some accumulating snow and ice.
Meanwhile, there will also be a swath of accumulating snow and ice
across portions of especially the central Plains, Midwest and
Great Lakes for Thursday and Friday as low pressure rides
northeast up across the region.
Graphics available at
+ Additional Links
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
116 AM EST THU FEB 22 2018
VALID 12Z SUN FEB 25 2018 - 12Z THU MAR 01 2018
DUE TO TECHNICAL DIFFICULTIES, SOME PRODUCTS MAY NOT BE AVAILABLE
OR UPDATED. PLEASE CHECK ISSUANCE TIMES. WE APOLOGIZE FOR ANY
THE MID-LATITUDE FLOW SHOULD BE IN SOME SORT OF TRANSITIONAL STATE
AS THE PERSISTENT POSITIVE HEIGHT ANOMALY OVER THE WESTERN
ATLANTIC FINALLY BUCKLES. HOWEVER...THE BLOCKING RIDGE EAST OF THE
HAWAIIAN ISLANDS SHOULD CONTINUE WHICH FAVORS A SERIES OF TROUGHS
PUSHING ACROSS THE WESTERN U.S. DURING THE PERIOD. WITHIN THIS
TRAIN OF SHORTWAVES...MANY OF THEM HAVE THE POTENTIAL TO BRING
VAST IMPACTS TO THE REGIONS OF INTEREST. THE LEAD SYSTEM WILL WIND
UP OVER THE UPPER GREAT LAKES ON SUNDAY MORNING BEFORE LIFTING
INTO NORTHERN QUEBEC EARLY NEXT WEEK. ON ITS HEELS...A WELL
ADVERTISED UPPER LOW BARRELS DOWN THE WEST COAST ACCOMPANIED BY
IMPRESSIVELY LOW 1000-500 MB THICKNESS VALUES. THIS PARENT TROUGH
SHOULD OPEN UP WHILE MOVING THROUGH THE DESERT SOUTHWEST AND INTO
THE FOUR CORNERS REGION BY MID-WEEK. THIS COULD LEAD TO THE
FORMATION OF ANOTHER DEEP CYCLONE MOVING TOWARD THE OH VALLEY LATE
IN THE PERIOD. MEANWHILE...ANOTHER SHORTWAVE TAKES SHAPE OVER THE
WEST COAST WHICH MAINTAINS THE VERY REPEATABLE SYNOPTIC PATTERN IN
...MODEL GUIDANCE/UNCERTAINTY ASSESSMENT/PREFERENCES...
AS MENTIONED IN THE HEADER...RESOURCES REMAIN SOMEWHAT SCANT SO
WILL FOCUS ON SOME OF THE MORE MEANINGFUL ISSUES. FIRST OF ALL...A
DEEP SURFACE LOW PRIMED TO PUSH INTO THE UPPER GREAT LAKES ON
SUNDAY MORNING HAS THE POTENTIAL TO BE SUB 980-MB BY 25/1200Z.
CONSIDERING THE PAST FEW RUNS OF THE GFS/ECMWF...THE FORMER HAS
BEEN CONSISTENTLY DEEPER WHICH THE 12Z ECMWF APPEARS TO HAVE
TRENDED TOWARD. DOWNSTREAM RIDGING SHOULD FORCE THIS SHORTWAVE
INTO EASTERN CANADA WHILE MID-LEVEL HEIGHTS BRIEFLY BUILD ACROSS
THE CENTRAL U.S. EARLY MONDAY. THE NEXT SYSTEM IN THE CHAIN WILL
BE IN THE FORM OF A CLOSED LOW WHICH HAS BEEN ADVERTISED FOR A FEW
DAYS NOW. POTENTIAL 1000-500 MB THICKNESSES MAY PUSH INTO THE
530-535 DM RANGE WHICH COULD SPREAD WINTRY PRECIPITATION TO SOME
RATHER LOW ELEVATIONS ALONG THE CA COAST. OVERALL...THE 12Z ECMWF
AND PRECEDING RUNS HAVE BEEN THE MOST STABLE WHILE THE GFS FROM
THE PREVIOUS DAY WAS PERHAPS 24-HOURS SLOWER. THE 00Z GFS SPED UP
FROM ITS PRECEDING RUN WHICH TAKES IT OUT AHEAD OF THE CONSENSUS
SOLUTION EARLY TUESDAY. SUCH DIFFERENCES PROJECT FORWARD WITH SOME
VAST SPREAD WHILE THE SYSTEM ACCELERATES ACROSS THE CENTER OF THE
COUNTRY. BY 01/1200Z...THE 00Z GFS DEPICTS A POTENT SHORTWAVE
CROSSING INTO THE OH VALLEY WHILE THE 12Z ECMWF/CMC ARE BACK
TOWARD THE SOUTHERN/CENTRAL HIGH PLAINS. GIVEN THE STAGNANT RIDGE
OVER THE EASTERN PACIFIC...A THIRD SYSTEM TAKES SHAPE ALONG THE
WEST COAST WITH POSITIONS QUITE VARIABLE AMONG THE OPERATIONAL
WITH THE NON-NCEP GUIDANCE UNAVAILABLE FOR USE IN THE MODEL
BLENDER...HAD TO INCORPORATE THE GFS/GEFS SOLUTIONS AS FIT.
UTILIZED A COMBINATION OF THE 18Z/12Z GFS WITH THE 18Z GEFS MEAN
THROUGHOUT THE PERIOD WITH A GRADUAL DEDUCTION OF OPERATIONAL
INFLUENCES TOWARD THE DAY 5-7...FEBRUARY 27-MARCH 1...REALM.
UNFORTUNATELY...WITH THE ECMWF SOLUTIONS BEING AROUND 12 TO 18
HOURS SLOWER BY DAY 7...THE MANUAL FORECAST MAY BE TOO QUICK SO
CONFIDENCE IN IT IS VERY LOW.
CONDITIONS WILL GENERALLY REMAIN QUITE MILD FROM THE MS RIVER
EASTWARD...PARTICULARLY ON SUNDAY AND INTO MONDAY MORNING.
RELATIVE TO CURRENT RECORDS...THERE MAY BE SOME OVERNIGHT MINIMA
WHICH BREAK DAILY RECORDS FROM THE MID-SOUTH INTO THE MID-ATLANTIC
ON SUNDAY. EXPECTED LOWS WILL BE ANYWHERE FROM THE MID/UPPER 50S
INTO THE LOWER 60S. SUCH TEMPERATURES WILL RESIDE ANYWHERE FROM 20
TO POSSIBLY 30 DEGREES ABOVE CLIMATOLOGY FOR LATE FEBRUARY.
ANOMALIES SHOULD COME DOWN A BIT AS THE UPPER RIDGE WEAKENS WHILE
UPSTREAM HEIGHTS SEMI-REGULARLY LOWER. OVER THE WESTERN U.S...THE
PERSISTENCE OF UPPER TROUGHING WILL KEEP BELOW AVERAGE
TEMPERATURES IN THE PICTURE ALL THE WAY INTO THE FIRST DAY OF
MARCH. THE SHARPEST DEPARTURES FROM CLIMATOLOGY WILL BE OVER THE
NORTHERN ROCKIES WITH ANOMALIES IN THE 15 TO 20 DEGREE RANGE. THE
WEST COAST IS FORECAST TO ALSO REMAIN CHILLY AS OVERNIGHT LOWS
PUSH BELOW FREEZING IN MANY LOCATIONS.
GIVEN THE INTENSE WAVE OF LOW PRESSURE MOVING INTO THE UPPER GREAT
LAKES ON SUNDAY MORNING...WOULD ANTICIPATE A DEFORMATION ZONE OF
WINTRY PRECIPITATION OVER THE REGION. THIS SHOULD BE IN THE
PROCESS OF EXITING THE REGION WHILE THE TRAILING COLD FRONT WILL
SPREAD RAINFALL ALONG THE ENTIRE EASTERN SEABOARD AS WELL AS ALONG
THE GULF COAST. ACROSS THE WEST COAST...THE UPPER LOW WILL FOCUS
MODERATE/HEAVY RAIN/SNOW OVER WESTERN OR/WA WITH GREATER AMOUNTS
ATTACHED TO THE HIGHER PEAKS OF THE CASCADES. PRECIPITATION SHOULD
SPREAD DOWN THE COAST WITH APPRECIABLY LOW SNOW LEVELS GIVEN THE
MAGNITUDE OF COLD AIR TO WORK WITH. AS THIS SYSTEM BARRELS TOWARD
THE DESERT SOUTHWEST...AMPLE RETURN FLOW IN ADVANCE OF THESE
HEIGHT FALLS WILL BRING WARM ADVECTION RAINFALL TO SECTIONS OF THE
ARKLATEX AND POINTS EASTWARD. THIS COULD BE ACCOMPANIED BY
HYDROLOGIC ISSUES DEPENDING ON THE DEGREE OF RECOVERY OF LOCAL
RIVERS...STREAMS...AND CREEKS FROM THE ONGOING ACTIVITY.
MEANWHILE...UNSETTLED CONDITIONS RETURN TO THE PACIFIC NORTHWEST
WITH THE NEXT SYSTEM PRIMED TO MOVE THROUGH.