973
FXUS02 KWNH 170756
PREEPD
PRELIMINARY EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
255 AM EST SAT JAN 17 2026
VALID 12Z TUE JAN 20 2026 - 12Z SAT JAN 24 2026
...DEEP TROUGHING WILL CAUSE CHILLY BELOW AVERAGE TEMPERATURES IN
THE EASTERN AND NORTHERN U.S. AND LAKE EFFECT SNOW...
..OVERVIEW
A VERY AMPLIFIED PATTERN ALOFT WILL BE IN PLACE AS THE PERIOD
BEGINS TUESDAY, WITH RIDGING OVER THE WEST COAST AND DEEP TROUGHING
OVER THE CENTRAL AND EASTERN U.S., WITH THE LATTER CAUSING BELOW
AVERAGE TEMPERATURES. THIS PATTERN WILL ALSO BE FAVORABLE FOR LAKE
EFFECT SNOW THAT COULD BECOME HEAVY. THE TROUGH MAY BROADEN
WESTWARD MID- AND LATE WEEK WHILE BECOMING SHALLOWER TO THE EAST.
GULF MOISTURE IS FORECAST TO RETURN TO THE SOUTH-CENTRAL U.S. TO
MID-SOUTH WEDNESDAY-THURSDAY, AND THEN THERE IS UNCERTAIN POTENTIAL
FOR SOME WINTRY PRECIPITATION IN THE MIDDLE MISSISSIPPI TO OHIO
VALLEY INTO FRIDAY-SATURDAY.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL GUIDANCE IS IN GOOD AGREEMENT FOR THE LARGE AMPLIFIED TROUGH
FOR AREAS EAST OF THE ROCKIES INTO TUESDAY, WITH RIDGING ATOP THE
WEST COAST. SOME MODEL DISCREPANCIES ARISE WITH SHORTWAVE ENERGIES
WITHIN THE TROUGH PATTERN. BY THURSDAY, THE AIGFS AND EC-AIFS WERE
FARTHER EAST WITH AN EMBEDDED TROUGH AXIS, SHOWING IT ACROSS THE
LOWER GREAT LAKES/OHIO VALLEY RATHER THAN WEST ACROSS THE
MISSISSIPPI VALLEY LIKE MOST DETERMINISTIC MODELS. THIS PATTERN IN
THE AI MODELS YIELDS MORE SURFACE HIGH PRESSURE IN THE MID-SOUTH
AND LESS PRECIPITATION BY THURSDAY. THE 00Z DETERMINISTIC MODELS
HAVE SOMEWHAT TRENDED THIS WAY, WITH IMPLICATIONS ON FUTURE QPF.
THE DETAILS OF SHORTWAVES THAT MAY BRING WINTRY PRECIPITATION TO
THE OHIO VALLEY AND VICINITY FRIDAY-SATURDAY ARE ALSO UNCERTAIN BUT
WITHOUT NOTABLE OUTLIERS THUS FAR.
FARTHER WEST, MODEL SPREAD INCREASES LATER WEEK WITH NORTHERN
STREAM ENERGY DIGGING INTO THE NORTHWEST, PLUS THE POSSIBILITY OF
INTERACTION WITH A SOUTHERN STREAM EASTERN PACIFIC UPPER LOW. THE
NORTHERN STREAM ENERGY HAS TRENDED WEAKER THURSDAY-FRIDAY IN THE
NEW 00Z MODELS, LEADING TO LESS DRAMATIC TROUGHING IN THE WEST
COMPARED TO MODELS LIKE THE 12Z CMC. MULTIPLE AIFS RUNS HAVE BEEN
PARTICULARLY WEAK WITH THIS ENERGY/TROUGHING AND END UP WITH A
RIDGY PATTERN ATOP CALIFORNIA TO THE SOUTHWEST SATURDAY RATHER THAN
TROUGHING. THE OTHER 12Z EC-BASED AI MODELS WERE MORE SIMILAR TO
THE DETERMINISTIC MODELS RATHER THAN THE AIFS THOUGH. SO THE BETTER
CONSENSUS IS FOR SOME TROUGHING IN THE WEST BUT WEAKER. MEANWHILE
WITH THE SOUTHERN STREAM UPPER LOW, THE NEW 00Z ECMWF IS PRETTY
MUCH ALONE IN SHOWING THE ENERGY REACHING NORTHERN MEXICO BY
SATURDAY RATHER THAN STAYING OFFSHORE, SO THE 00Z ECMWF DOES NOT
SEEM FAVORABLE.
THE WPC FORECAST WAS BASED ON A MULTI-MODEL BLEND EARLY IN THE
PERIOD, WITH INCREASING PROPORTIONS OF ENSEMBLE MEANS TO HALF DAY 6
AND MORE DAY 7 GIVEN THE INCREASING SPREAD.
..WEATHER/HAZARDS HIGHLIGHTS
SEVERAL DAYS OF LAKE EFFECT AND UPSLOPE FLOW SNOW ARE IN STORE
WITH THE MEAN WESTERLY WIND PATTERN ACROSS THE NORTHEASTERN
QUADRANT OF THE LOWER 48. A CLIPPER SYSTEM COULD SPREAD LIGHT SNOW
TO THE DAKOTAS AND UPPER MIDWEST ON TUESDAY AND ENHANCE GREAT LAKES
SNOW INTO WEDNESDAY, AND THEN POTENTIALLY SPREAD INTO THE INTERIOR
NORTHEAST ON THURSDAY. SNOW IS FORECAST TO BE HEAVIEST IN WESTERN
NEW YORK DOWNWIND OF LAKE ONTARIO FROM THE LAKE EFFECT/ENHANCED
SNOW, AS SEVERAL INCHES OF SNOW PER DAY COULD EVENTUALLY PILE UP TO
1-2 FEET.
LATE TUESDAY AND ESPECIALLY BY WEDNESDAY, GULF MOISTURE IS
FORECAST TO MAKE IT INTO SOUTHERN TEXAS IN PARTICULAR AND POOL
ALONG A FRONT. IT IS UNCERTAIN HOW MUCH INSTABILITY COULD REACH
INLAND, AND SOME MODEL GUIDANCE SHOWS THE INSTABILITY AND THUS
HEAVIEST RAIN RATES REMAINING OFFSHORE. SO WHILE THE TEXAS TO
WESTERN LOUISIANA COAST SHOULD SEE SOME RAIN, HELD OFF FROM ISSUING
AN EXCESSIVE RAINFALL AREA ON THE DAY 5/WEDNESDAY ERO BECAUSE OF
THE UNCERTAINTY AND BECAUSE FLOODING IMPACTS MAY NOT BE LIKELY DUE
TO THE DRY ANTECEDENT CONDITIONS. WILL CONTINUE TO MONITOR.
MODERATE RAIN IS FORECAST TO SPREAD INTO THE ARK-LA-TEX TO LOWER
MISSISSIPPI VALLEY WEDNESDAY AND POSSIBLY ACROSS THE MID-SOUTH
AND/OR SOUTHEAST INTO THURSDAY. THEN INTO FRIDAY-SATURDAY,
PRECIPITATION COULD SPREAD ACROSS THE MID-MISSISSIPPI AND OHIO
VALLEYS, INCLUDING POTENTIAL FOR WINTER WEATHER WITH SNOW AND/OR
ICE. THERE IS AMPLE UNCERTAINTY WITH PRECIPITATION COVERAGE, TYPES,
AND AMOUNTS AT THIS POINT THOUGH, SO STAY TUNED FOR FORECAST
UPDATES. MEANWHILE, AREAS OF THE NORTHWEST COULD SEE INCREASING
PRECIPITATION INTO LATER NEXT WEEK WITH ENERGY ALOFT MOVING
THROUGH.
WELL BELOW AVERAGE TEMPERATURES ARE EXPECTED ACROSS THE EAST-
CENTRAL U.S. TUESDAY, WITH LOWS IN THE SINGLE DIGITS LIKELY
REACHING AS FAR SOUTH AS KENTUCKY AND EAST TO PENNSYLVANIA, AND
LOWS BELOW -10F IN THE UPPER MIDWEST. CHILLY TEMPERATURES SHOULD
TRACK INTO THE EASTERN SEABOARD ON WEDNESDAY WHILE MODERATING. THEN
REPEATED ROUNDS OF REINFORCING TROUGHING ARE FORECAST ACROSS THE
NORTHERN TIER, LEADING TO BELOW AVERAGE TEMPERATURES IN THE
NORTHERN PLAINS TO UPPER MIDWEST BY FRIDAY AND ESPECIALLY SATURDAY,
WHEN EVEN HIGHS MAY STAY UNDER 0F. MEANWHILE, NEAR TO ABOVE
AVERAGE TEMPERATURES ARE FORECAST ACROSS THE WEST INTO MIDWEEK, BUT
WITH UNCERTAINTY AFTER THAT DEPENDENT ON THE PATTERN ALOFT.
TATE
ADDITIONAL 3-7 DAY HAZARD INFORMATION CAN BE FOUND ON THE WPC
MEDIUM RANGE HAZARDS OUTLOOK CHART AT:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
WPC MEDIUM RANGE 500MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,
QUANTITATIVE PRECIPITATION FORECAST (QPF), EXCESSIVE RAINFALL
OUTLOOK (ERO), WINTER WEATHER OUTLOOK (WWO) PROBABILITIES, HEAT
INDICES, AND KEY MESSAGES CAN BE ACCESSED FROM:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST500_WBG.GIF
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST_WBG_CONUS.GIF
HTTPS://WWW.WPC.NCEP.NOAA.GOV/5KM_GRIDS/5KM_GRIDSBODY.HTML
HTTPS://WWW.WPC.NCEP.NOAA.GOV/QPF/DAY4-7.SHTML
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=ERO
HTTPS://WWW.WPC.NCEP.NOAA.GOV/WWD/PWPF_D47/PWPF_MEDR.PHP?DAY=4
HTTPS://WWW.WPC.NCEP.NOAA.GOV/HEAT_INDEX.SHTML
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=OVW
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