Key messages
- 1) High confidence in a strong cold front that will bring
What Has Changed
12Z Aviation Forecast Discussion update.
The severe thunderstorm threat has decreased and trended downward compared to the previous forecast cycles due to lack of surface-based instability, though non-thunderstorm wind gusts threat remains robust.
Key Messages
showers, storms, and gusty winds today.
2) High confidence for a widespread, possible season ending frost/freeze for Saturday night into Sunday morning.
3) Increasing confidence in strong high pressure building across the area promoting dry weather after Saturday and continuing for a long stretch of dry weather into next week.
Discussion
KEY MESSAGE 1...
A deepening surface low is tracking across the Great Lakes and driving due east while dragging a sharp cold front across the area today. The environment will be a high shear and low instability type environment with strong DCAPE and anomously high PWATs. Widespread severe weather is not anticipated however strong forced ascent along the front will allow for heavier shower activity and a few isolated thunderstorms to transport stronger momentum aloft down to the surface. A marginal risk for severe thunderstorms remains to our northeast with isolated damaging winds being the primary threat. Steering flow will be strong enough to force shower or thunderstorm activity along without causing too much in the way of possible flooding issues.
Outside thunderstorm activity strong cold air advection and a tightening pressure gradient will yield widepsread wind gusts of 25 to 35mph across the lowlands and across the higher terrain gusts up to 40mph+ are probable as the front clears out this afternoon. Strong synoptic gusty winds will continue into early Saturday afternoon.
Temperatures will promote a non-diurnal day and after mid morning starting in the upper 60s and 70s temperatures will crash into the 50s from west to east by late afternoon following frontal passage. Residual low-level moisture and upslope northwesterly flow will keep clouds and light showers lingering into Friday night and Saturday morning, especially on the western slopes of the mountains. Cold advection is strong enough that a few snowflakes may mix in at the highest peaks around Snowshoe, WV by daybreak Saturday. Accumulations are not expected at this time as probabilities are lower than 10% of that occurring.
KEY MESSAGE 2...
By Saturday afternoon, precipitation ends and high pressure builds in from the west effectively scouring out clouds and relaxing the pressure gradient. This will set up a very optimal radiational cooling night for Saturday into Sunday morning. With clear skies and decoupling winds along with a cold modified airmass firmly in place, temperatures will be able to plummet significantly. NBM deterministic and probabilistic guidance strongly indicates lows falling into the upper 20s to low 30s across the board.
Probabilities for lower than 32 degrees exceeded 90% for traditional cold spots and sheltered valleys in southeast Ohio and along the mountains. The broader lowlands of the Tri-state area suggests a 60-80% chances of seeing a hard freeze. Therefore, widespread frost and freeze conditions are expected likely ending the growing season for much of the area. Dense freezing river valley fog may also develop in the deeper river basins early Sunday and monday mornings.
After collaboration with neighboring offices we all decided to hold off on a freeze watch for now. Neighbors did not want to go with one just yet so day shift will have to look at it and start a collaboration again. Regardless, we will need headlines for Saturday nights frost/freeze that is expected.
KEY MESSAGE 3...
Headed in to next week probabilities of precipitation near zero continuing an abnormally dry period in the long term as high pressure builds into the region and does not show signs of retreating. As an upper level trough exits to the east a broad mid level ridge and strong surface high pressure migrate from the Midwest to our region. This will yield a steady warming trend bringing daytime highs back to the upper 60s and low 70s by midweek with pleasant dry conditions expected.
Aviation /09Z Friday Through Tuesday/
The main theme with this TAF period is MVFR CIGs progressively lower toward the end of the period to where the mountains sites will likely endure IFR CIGs tonight. The rest of the sites should stay just over IFR but cannot rule out periods of IFR CIGs within rain showers.
Winds will increase and will maintain a gusty status through the period to where wind gusts up to 25kts will be likely through the afternoon with some isolated higher gusts. Shower activity associated with a cold frontal passage will begin in the afternoon and last through the evening. VIS restrictions under shower activity will be likely and as the front shifts through by the mid afternoon a wind shift out of the northwest will take place. Any wind shear should be negated unless the surface winds decrease in intensity which they are forecast not too. Saturday morning fog is not likely due to increased shower activity or cloud coverage and elevated wind speeds.
FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 12Z SATURDAY...
FORECAST CONFIDENCE: Medium.
ALTERNATE SCENARIOS: CIGs may drop even lower this afternoon as frontal passage takes place.
EXPERIMENTAL TABLE OF FLIGHT CATEGORY OBJECTIVELY SHOWS CONSISTENCY OF WFO FORECAST TO AVAILABLE MODEL INFORMATION: H = HIGH: TAF CONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL. M = MEDIUM: TAF HAS VARYING LEVEL OF CONSISTENCY WITH MODELS. L = LOW: TAF INCONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
UTC 1HRLY 10 11 12 13 14 15 16 17 18 19 20 21 EDT 1HRLY 06 07 08 09 10 11 12 13 14 15 16 17 CRW CONSISTENCY M M H H H H H H H H H H HTS CONSISTENCY H H H H H H H H H H H H BKW CONSISTENCY H H H H H H H H H M M M EKN CONSISTENCY L L L M H H H H M M H M PKB CONSISTENCY H H H H H H H H H H H H CKB CONSISTENCY H H H H H H M H H H H H
AFTER 12Z SATURDAY... IFR conditions may linger Friday night, especially in the mountains. Calm winds and clear skies will favor late-night and early-morning dense river valley fog producing LIFR visibility restrictions Sunday, Monday, and Tuesday mornings.
Rlx Watches/Warnings/Advisories
WV...None. OH...None. KY...None. VA...None.
DISCUSSION...JZ AVIATION...JZ