textproduct: Raleigh

WHAT HAS CHANGED

* Widespread frost/freeze conditions are most favored late this weekend Sat through Mon morning of next week.

* Rain chances remain limited Thursday into Friday as the system continues to trend north.

KEY MESSAGES

As of 1245 AM Monday...

1) Thursday through Friday remains the best chance of precipitation, although guidance continues to show limited rainfall.

2) Patchy frost may be possible Tuesday morning, but widespread frost and freeze is expected this coming weekend into early next week.

DISCUSSION

As of 1245 AM Monday...

KEY MESSAGE 1... Thursday through Friday remains the best chance of precipitation, although guidance continues to show limited rainfall.

On the synoptic scale, not much has changed regarding the late week system as the polar jet stream digs south and downstream cyclogenesis occurs Thursday into Friday. A southern stream wave will skirt to our south Wednesday, but only bring mid and high clouds. The suite of ensemble guidance, including machine-learning models/ensembles, continue to favor a northward trend in the surface low. The consensus shows a track across northern VA into New England. This forecast track would offer limited rain chances as the main energy focuses well to the north of central NC. The best chance would ultimately be with the warm front early Thursday and cold front Thursday afternoon and evening. Even with the cold front, ensembles do not show much rainfall, with the 25th to 75th percentile only ranging from a few hundredths to at most three tenths of an inch. The main impact from the system will be the colder air and gusty winds. In fact, northwest wind gusts of 30-35 mph are favored Fri/Sat with a tight pressure gradient.

KEY MESSAGE 2... Patchy frost may be possible Tuesday morning, but widespread frost and freeze is expected this coming weekend into early next week.

Today, a weak dry cold front slides south later today and tonight, with cool high pressure settling in for early Tuesday. While the airmass does cool, it does not appear favorable for widespread frost. Certainly outlying areas will dip into the middle 30s, but most urban areas may only drop into the upper 30s to low 40s. Given that, our confidence was too low to hoist a Frost Advisory. But subsequent shifts may want to reevaluate things with newer guidance.

The better chance of frost/freeze conditions will come this weekend into early next week. In the wake of the departing system, Continental Polar high pressure is forecast to settle in from the TN valley. Corresponding low-level thicknesses drop to between 1300 and 1310m, supportive of low to middle 30s, with outlying areas in the upper 20s. The one limiting factor will be wind gusts. With a tight pressure gradient expected Fri night between the departing low and high pressure ridge to our west, lows in the mid to upper 30s may be the norm with limited freezing temperatures. The better threat appears Sunday and Monday mornings, when the surface high builds east and winds relax.

AVIATION /06Z MONDAY THROUGH FRIDAY/

As of 1245 AM Monday...

VFR conditions are generally expected over the 24 hour TAF period. There is a non-zero chance of some shallow, patchy fog overnight in the south and east. If this does occur the best chances would be at FAY, followed by RWI. However, the chance of this still appears to be low so kept it out of the TAFs. Otherwise, very little to no clouds are expected today. Also, a few infrequent gusts between 15- 18kts may be possible mid-morning into early afternoon.

Outlook: VFR conditions are expected through much of the TAF outlook period. Rain may return Thursday into Friday, bringing the next chance of sub-VFR restrictions. Gusty winds may also be possible Friday after a cold frontal passage.

RAH WATCHES/WARNINGS/ADVISORIES

None.